Tag Archives: Optics

Quantum-accelerated imaging of N stars [CL]

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http://arxiv.org/abs/2104.14600


Imaging point sources with low angular separation near or below the Rayleigh criterion is important in astronomy, \eg, in the search for habitable exoplanets near stars. However, the measurement time required to resolve stars in the sub-Rayleigh region via traditional direct imaging is usually prohibitive. Here we propose quantum-accelerated imaging (QAI) to significantly reduce the measurement time using an information-theoretic approach. QAI achieves quantum acceleration by adaptively learning optimal measurements from data to maximize Fisher information per detected photon. Our approach can be implemented experimentally by linear-projection instruments followed by a single-photon detector array. We estimate the position, brightness and the number of unknown stars $10\sim100$ times faster than direct imaging with the same aperture. QAI is scalable to large number of incoherent point sources and can find widespread applicability beyond astronomy to high-speed imaging, fluorescence microscopy and efficient optical read-out of qubits.

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F. Bao, H. Choi, V. Aggarwal, et. al.
Mon, 3 May 21
40/45

Comments: 12 pages, 4 figures

Intensity correlation speckles as a technique for removing Doppler broadening [CL]

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http://arxiv.org/abs/2104.10200


A method involving intensity correlation measurements is described, which allows for the complete removal of Doppler broadening in the emission of electromagnetic radiation from far-away sources that are inaccessible to conventional Doppler-free measurements. The technique, relying on a correction to g(2) of order N-1, probes the separation between neighboring spectral lines and is also applicable to the elimination of broadening due to collisions (N is the number of emitting particles and g(2) is the second-order field correlation function). Possible applications include a determination of cosmological parameters from red shifts of gravitationally-lensed quasars.

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R. Merlin, N. Green, I. Szapudi, et. al.
Thu, 22 Apr 2021
31/44

Comments: N/A

Photon-Inter-Correlation Optical Communication [IMA]

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http://arxiv.org/abs/2104.08913


The development of modern technology extends human presence beyond cislunar space and onto other planets, which presents an urgent need for high-capacity, long-distance and interplanetary communication. Communication using photons as carriers has a high channel capacity, but the optical diffraction limit in deep space leads to inevitable huge geometric loss, setting an insurmountable transmission distance for existing optical communication technologies. Here, we propose and experimentally demonstrate a photon-inter-correlation optical communication (PICOC) against an ultra-high channel loss. We treat light as a stream of photons, and retrieve the additional information of internal correlation and photon statistics globally from extremely weak pulse sequences. We successfully manage to build high-fidelity communication channel with a loss up to 160dB by separating a single-photon signal embedded in a noise ten times higher. With only commercially available telescopes, PICOC allows establishment of communication links from Mars to Earth communication using a milliwatt laser, and from the edge of the solar system to Earth using a few watts laser.

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Z. Yan, C. Hu, Z. Li, et. al.
Tue, 20 Apr 2021
7/72

Comments: Main Text: 19 pages, 5 figures, 1 table; Supplemental Material: 15 pages, 10 figures

Optimal SMF packing in photonic lanterns: comparing theoretical topology to practical packing arrangements [CL]

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http://arxiv.org/abs/2104.09354


Photonic lanterns rely on a close packed arrangement of single mode fibers, which are tapered and fused into one multi-mode core. Topologically optimal circle packing arrangements have been well studied. Using this, we fabricate PLs with 19 and 37 SMFs showing tightly packed, ordered arrangements with packing densities of 95 % and 99 % of theoretically achievable values, with mean adjacent core separations of 1.03 and 1.08 fiber diameters, respectively. We demonstrate that topological circle packing data is a good predictor for optimal PL parameters.

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J. Davenport, M. Diab, K. Madhav, et. al.
Tue, 20 Apr 2021
17/72

Comments: 10 pages, 10 figures, 2 tables

Kerr spacetime geometric optics for vortex beams [CL]

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http://arxiv.org/abs/2104.06998


We apply the analogy between gravitational fields and optical media in the general relativistic geometric optics framework to describe how light can acquire orbital angular momentum (OAM) when it traverses the gravitational field of a massive rotating compact object and the interplay between OAM and polarization. Kerr spacetimes are known not only to impose a gravitational Faraday rotation on the polarization of a light beam, but also to set a characteristic fingerprint in the orbital angular momentum distribution of the radiation passing nearby a rotating black hole (BH). Kerr spacetime behaves like an inhomogeneous and anisotropic medium, in which light can acquire orbital angular momentum and spin-to-orbital angular momentum conversion can occur, acting as a polarization and phase changing medium for the gravitationally lensed light, as confirmed by the data analysis of M87* black hole.

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F. Tamburini, F. Feleppa, I. Licata, et. al.
Thu, 15 Apr 2021
25/59

Comments: 9 pages, 1 figure

Holographic surface measurement system for the Fred Young Submillimeter Telescope [IMA]

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http://arxiv.org/abs/2103.08429


We describe a system being developed for measuring the shapes of the mirrors of the Fred Young Submillimeter Telescope (FYST), now under construction for the CCAT Observatory. “Holographic” antenna-measuring techniques are an efficient and accurate way of measuring the surfaces of large millimeter-wave telescopes and they have the advantage of measuring the wave-front errors of the whole system under operational conditions, e.g. at night on an exposed site. Applying this to FYST, however, presents significant challenges because of the high accuracy needed, the fact that the telescope consists of two large off-axis mirrors, and a requirement that measurements can be made without personnel present. We use a high-frequency (~300GHz) source which is relatively close to the telescope aperture (<1/100th of the Fresnel distance) to minimize atmospheric effects. The main receiver is in the receiver cabin and can be moved under remote control to different positions, so that the wave-front errors in different parts of the focal plane can be measured. A second receiver placed on the yoke provides a phase reference. The signals are combined in a digital cross-correlation spectrometer. Scanning the telescope provides a map of the complex beam pattern. The surface errors are found by inference, i.e. we make models of the reflectors with errors and calculate the patterns expected, and then iterate to find the best match to the data. To do this we have developed a fast and accurate method for calculating the patterns using the Kirchhoff-Fresnel formulation. This paper presents details of the design and outlines the results from simulations of the measurement and inference process. These indicate that a measurement accuracy of ~3 microns rms is achievable.

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X. Ren, P. Astudillo, U. Graf, et. al.
Tue, 16 Mar 21
45/92

Comments: Proceedings Volume 11445, Ground-based and Airborne Telescopes VIII SPIE Astronomical Telescopes + Instrumentation, 2020, Online Only Conference

Picosecond Laser Ablation of Millimeter-Wave Subwavelength Structures on Alumina and Sapphire [CL]

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http://arxiv.org/abs/2103.06974


We use a 1030 nm laser with 7 ps pulse duration and average power up to 100 W to ablate pyramid-shape subwavelength structures (SWS) on alumina and sapphire. The SWS give an effective and cryogenically robust anti-reflection coating in the millimeter-wave band. We demonstrate average ablation rate of up to 34 mm$^3$/min and 20 mm$^3$/min for structure heights of 900 $\mu$m and 750 $\mu$m on alumina and sapphire, respectively. These rates are a factor of 34 and 9 higher than reported previously on similar structures. We propose a model that relates structure height to cumulative laser fluence. The model depends on the absorption length $\delta$, which is assumed to depend on peak fluence, and on the threshold fluence $\phi_{th}$. Using a best-fit procedure we find an average $\delta = 630$ nm and 650 nm, and $\phi_{th} = 2.0^{+0.5}{-0.5}$ J/cm$^2$ and $2.3^{+0.1}{-0.1}$ J/cm$^2$ for alumina and sapphire, respectively, for peak fluence values between 30 and 70 J/cm$^{2}$. With the best fit values, the model and data values for cumulative fluence agree to within 10%. Given inputs for $\delta$ and $\phi_{th}$ the model is used to predict average ablation rates as a function of SWS height and average laser power.

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Q. Wen, E. Fadeeva, S. Hanany, et. al.
Mon, 15 Mar 21
31/36

Comments: 15 pages, 11 figures, submitted to Optics & Laser Technology

Discrimination between cosmological and stellar phenomena by the intensity interferometry [CL]

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http://arxiv.org/abs/2103.02790


We provide a quantitative theory of discrimination between objects with the same color temperature but having different angular spectrum by intensity interferometry. The two-point correlation function of the black body image with extended angular spectrum has significant differences with a correlation function of a black body with a narrow angular spectrum.

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P. Lerner, N. Miskovsky and P. Cutler
Fri, 5 Mar 21
46/64

Comments: Photonics West, March 6-11, 2021, 11685-38

Optomechanical parametric instabilities simulation in Advanced Virgo [IMA]

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http://arxiv.org/abs/2102.11070


Increasing the laser power is essential to improve the sensitivity of interferometric gravitational wave detectors. However, optomechanical parametric instabilities can set a limit to that power. It is of major importance to understand and characterize the many parameters and effects that influence these instabilities. We perform simulations for the Advanced Virgo interferometer (O3 configuration). In particular we compute mechanical modes losses by combining both on-site measurements and finite element analysis. We also study the influence on optical modes and parametric gains of mirror finite size effects, and mirror deformations due to thermal absorption. We show that these effects play an important role if transverse optical modes of order higher than four are involved in the instability process.

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D. Cohen, A. Allocca, G. Bogaert, et. al.
Tue, 23 Feb 21
68/79

Comments: N/A

Optical design of the laser launch telescope via physical optics theorem for Laser Guide Star Facility [IMA]

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http://arxiv.org/abs/2102.09922


The Laser Guide Star Facility (LGSF), as the most important part of the adaptive optics system of the large ground-based telescope, is aimed to generate multiple laser guide stars at the sodium layer. Laser Launch Telescope is employed to implement this requirement by projecting the Gauss beam to the sodium layer with a small beam size in LGSF system. As the diffraction and interference effects of laser’s long-distance transmission, the conventional optical design based on the geometrical optics mechanism cannot achieve the expected laser propagation. In this paper, we propose a method to design optical system for laser launch telescope based on the physical optics theorem to generate an acceptable light spot at the sodium layer in the atmosphere. Besides, a tolerance analysis method based on physical optics propagation is also demonstrated to be necessitated to optimize the system’s instrumentation performance. The numerical results show that the optical design considering physical optics propagation is highly rewarding and even necessitated in many occasions, especially for laser beam propagation systems.

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Y. Mo, Z. Zhu, Z. Fan, et. al.
Mon, 22 Feb 21
19/51

Comments: N/A

Design of a high throughput telescope based on scanning off-axis Three-Mirror Anastigmat system [IMA]

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http://arxiv.org/abs/2102.09930


High throughput optical system is defined to possess the features of both large field of view (FOV) and high resolution. However, it is full of challenge to design such a telescope with the two conflicting specifications at the same time. In this paper, we propose a method to design a high throughput telescope based on the classical off-axis Three-Mirror Anastigmat (TMA) configuration by introducing a scanning mechanism. We derive the optimum initial design for the TMA system with no primary aberrations through characteristic ray tracing. During the design process, a real exit pupil is necessitated to accommodate the scanning mirror. By gradually increasing the system’s FOV during the optimization procedure, we finally obtained a high throughput telescope design with an F-number of 6, a FOV of 60$^{\circ}$*1.5$^{\circ}$, and a long focal length of 876mm. In addition, the tolerance analysis is also conducted to demonstrate the instrumentation feasibility. We believe that this kind of large rectangle FOV telescope with high resolution has broad future applications in the optical remote sensing field.

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H. Ji, Z. Zhu, H. Tan, et. al.
Mon, 22 Feb 21
48/51

Comments: 12 pages, 9 figures, 7 tables

Optical design of a multi-object fiber-fed spectrograph system for Southern Spectroscopic Survey Telescope [IMA]

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http://arxiv.org/abs/2102.09179


Southern Spectroscopic Survey Telescope (SSST) is a wide-field spectroscopic survey telescope that China plans to build in Chile in the next few years. As an instrument for astronomical spectroscopic survey, the multi-object and fiber-fed spectrograph (MOFFS) is one of the most important scientific instruments for SSST. In this paper, we present a recommended optical design for the MOFFS system based on the Volume Phase Holographic Gratings (VPHG). The whole design philosophy and procedure, including the analytic method to determine the initial structure, optimization procedures of the VPHG and the camera groups, are demonstrated in detail. The numerical results of the final obtained spectrograph show a superior imaging quality and a relatively high transmittance for the whole working waveband and the field of view. The design method proposed in this paper can provide a reference for the design of MOFFS accommodated in spectroscopic survey telescopes.

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Y. Shan, Z. Zhu, H. Tan, et. al.
Fri, 19 Feb 21
42/64

Comments: N/A

A compact green Ti:Sapphire astro-comb with 43-GHz repetition frequency [IMA]

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http://arxiv.org/abs/2101.05926


A compact green astro-comb with 43-GHz repetition rate is developed based on a Ti:Sapphire optical frequency comb (OFC) and a mode-selecting cavity. The OFC’s large repetition rate of 1.6 GHz eases the requirements for the mode-selecting cavity. Unnecessary frequency-modes of the OFC are suppressed down to $5 \times 10^{-4}$ at 535 nm – 550 nm using a single mode-selecting cavity with 70-MHz linewidth. The radial velocity precision $\sigma \sim 1.4$ m/s is achieved at the High Dispersion Echelle Spectrosraph for the Okayama 188-cm telescope of the National Astronomical Observatory of Japan using our astro-comb. With further improvements of the mode-selecting cavity and removal of fiber modal noises, our system will provide a simple, compact, and precise astro-comb setup in visible wavelength region.

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E. Chae, E. Kambe, K. Motohara, et. al.
Mon, 18 Jan 21
26/41

Comments: 10 pages, 7 figures

Hybrid adaptive splines for luminous intensity data regression in I-tables [CL]

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http://arxiv.org/abs/2101.00880


The I-table contains luminous intensity values over the range of angles for the luminaires used in the road lighting in accordance with technical report CIE 121:1996. A limited number of angles causes smoothing of the luminous intensity diagram omitting possible local extremal values which affect the calculations of the photometric parameters such as average illuminance, average luminance, uniformity or treshold increment. The interpolating methods used to calculate the luminous intensity can significantly improve the accuracy of the calculations and redound to more effective and reliable road lighting design. In the paper standard interpolation methods used up to now are compared with newly proposed hybrid adaptive splines. Calculated values of luminous intensity are compared and verified by goniophotometric measurements.

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L. Lipnický, R. Dubnička, J. Petržala, et. al.
Tue, 5 Jan 21
16/82

Comments: N/A

Design and optimization of dihedral angle offsets for the next generation lunar retro-reflectors [IMA]

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http://arxiv.org/abs/2012.13081


Lunar laser ranging (LLR) to the Apollo retro-reflectors, which features the most long-lasting experiment in testing General Relativity theories, has remained operational over the past four decades. To date, with significant improvement of ground observatory conditions, the bottleneck of LLR accuracy lies in the retro-reflectors. A new generation of large aperture retro-reflectors with intended dihedral angle offsets have been suggested and implemented based on NASA’s recent lunar projects to reduce its ranging uncertainty to be less than 1.0 mm. The technique relies on the retro-reflector’s ability to offset its relative angular velocity with regard to a ground LLR observatory (LLRO), so that the LLR accuracy can be ensured along with the larger area of beam reflection. In deployment, solid corner-cube reflectors (CCRs) based on empirical successes of the Apollo 11 and 15 arrays have been selected for the next generation lunar reflectors (NGLRs) due to their stability against heat and dust problems on the Moon. In this work, we present the optical effects in designing the new retro-reflectors given various sets of intended diheral angle offsets (DAOs), and support the design principles with the measurements of of two manufactured NGLRs.

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C. Wu, D. Currie, D. Wellnitz, et. al.
Fri, 25 Dec 20
29/51

Comments: N/A

Design and optimization of dihedral angle offsets for the next generation lunar retro-reflectors [IMA]

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http://arxiv.org/abs/2012.13081


Lunar laser ranging (LLR) to the Apollo retro-reflectors, which features the most long-lasting experiment in testing General Relativity theories, has remained operational over the past four decades. To date, with significant improvement of ground observatory conditions, the bottleneck of LLR accuracy lies in the retro-reflectors. A new generation of large aperture retro-reflectors with intended dihedral angle offsets have been suggested and implemented based on NASA’s recent lunar projects to reduce its ranging uncertainty to be less than 1.0 mm. The technique relies on the retro-reflector’s ability to offset its relative angular velocity with regard to a ground LLR observatory (LLRO), so that the LLR accuracy can be ensured along with the larger area of beam reflection. In deployment, solid corner-cube reflectors (CCRs) based on empirical successes of the Apollo 11 and 15 arrays have been selected for the next generation lunar reflectors (NGLRs) due to their stability against heat and dust problems on the Moon. In this work, we present the optical effects in designing the new retro-reflectors given various sets of intended diheral angle offsets (DAOs), and support the design principles with the measurements of of two manufactured NGLRs.

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C. Wu, D. Currie, D. Wellnitz, et. al.
Fri, 25 Dec 20
19/51

Comments: N/A

Measuring Phase Errors in the Presence of Scintillation [IMA]

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http://arxiv.org/abs/2012.12695


Strong turbulence conditions create amplitude aberrations through the effects of near-field diffraction. When integrated over long optical path lengths, amplitude aberrations (seen as scintillation) can nullify local areas in the recorded image of a coherent beam, complicating the wavefront reconstruction process. To estimate phase aberrations experienced by a telescope beam control system in the presence of strong turbulence, the wavefront sensor (WFS) of an adaptive optics must be robust to scintillation. We have designed and built a WFS, which we refer to as a “Fresnel sensor,” that uses near-field diffraction to measure phase errors under moderate to strong turbulent conditions. Systematic studies of its sensitivity were performed with laboratory experiments using a point source beacon. The results were then compared to a Shack-Hartmann WFS (SHWFS). When the SHWFS experiences irradiance fade in the presence of moderate turbulence, the Fresnel WFS continues to routinely extract phase information. For a scintillation index of $S = 0.55$, we show that the Fresnel WFS offers a factor of $9\times$ gain in sensitivity over the SHWFS. We find that the Fresnel WFS is capable of operating with extremely low light levels, corresponding to a signal-to-noise ratio of only $\mbox{SNR}\approx 2-3$ per pixel. Such a device is well-suited for coherent beam propagation, laser communications, remote sensing, and applications involving long optical path-lengths, site-lines along the horizon, and faint signals.

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J. Crepp, S. Letchev, S. Potier, et. al.
Thu, 24 Dec 20
66/73

Comments: Applications of Adaptive Optics Issue (Published: December 07)

Spectroscopic flat-fields can be used for precision CCD gain and noise tests [IMA]

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http://arxiv.org/abs/2012.09862


One of the basic parameters of a CCD camera is its gain, i.e. the number of detected electrons per output Analogue to Digital Unit (ADU). This is normally determined by finding the statistical variances from a series of flat-field exposures with nearly constant levels over substantial areas, and making use of the fact that photon (Poisson) noise has variance equal to the mean. However, when a CCD has been installed in a spectroscopic instrument fed by numerous optical fibres, or with an echelle format, it is no longer possible to obtain illumination that is constant over large areas. Instead of making do with selected small areas, it is shown here that the wide variation of signal level in a spectroscopic `flat-field’ can be used to obtain accurate values of the CCD gain, needing only a matched pair of exposures (that differ in their realisation of the noise). Once the gain is known, the CCD readout noise (in electrons) is easily found from a pair of bias frames. Spatial stability of the image in the two flat-fields is important, although correction of minor shifts is shown to be possible, at the expense of further analysis.

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J. Robertson
Mon, 21 Dec 20
64/75

Comments: 8 pages, 6 Figures; accepted for publication in PASA

Planar Silicon Metamaterial Lenslet Arrays for Millimeter-wavelength Imaging [IMA]

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http://arxiv.org/abs/2012.08636


Large imaging arrays of detectors at millimeter and submillimeter wavelengths have applications that include measurements of the faint polarization signal in the Cosmic Microwave Background (CMB), and submillimeter astrophysics. We are developing planar lenslet arrays for millimeter-wavelength imaging using metamaterials microlithically fabricated using silicon wafers. This metamaterial technology has many potential advantages compared to conventional hemispherical lenslet arrays, including high precision and homogeneity, planar integrated anti-reflection layers, and a coefficient of thermal expansion matched to the silicon detector wafer. Here we describe the design process for a gradient-index (GRIN) metamaterial lenslet using metal-mesh patterned on silicon and a combination of metal-mesh and etched-hole metamaterial anti-reflection layers. We optimize the design using a bulk-material model to rapidly simulate and iterate on the lenslet design. We fabricated prototype GRIN metamaterial lenslet array and mounted it on a Polarbear/Simons Array 90/150~GHz band transition edge sensor (TES) bolometer detector array with sinuous planar antennas. Beam measurements of a prototype lenslet array agree reasonably well with the model simulations. We plan to further optimize the design and combine it with a broadband anti-reflection coating to achieve operation over 70–350~GHz bandwidth.

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C. McKenney, J. Austermann, J. Beall, et. al.
Thu, 17 Dec 20
5/85

Comments: Presented at SPIE Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X, December 13-18, 2020

Limits on the abundance of millicharged particles bound to matter [CL]

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http://arxiv.org/abs/2012.08169


Millicharged particles (mCPs) are hypothesized particles possessing an electric charge that is a fraction of the charge of the electron. We report a search for mCPs with charges $\gtrsim 10^{-4}~e$ that improves sensitivity to their abundance in matter by roughly two orders of magnitude relative to previous searches. This search reaches abundances predicted for the accumulation of relic dark matter mCPs with masses between 1–100 GeV in terrestrial matter, corresponding to a gap in parameter space that is beyond the reach of previous searches from accelerators, colliders, cosmic-ray experiments, and cosmological constraints. Our results also set a limit on the deviation from zero of the sum of the charges of the proton, neutron and electron at the level of $\sim 3 \times 10^{-19}~e$. While these constraints are two orders of magnitude weaker than the best existing tests of matter neutrality, the sensitivity demonstrated here is sufficient to exceed existing techniques if backgrounds can be further reduced in future searches.

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G. Afek, F. Monteiro, J. Wang, et. al.
Wed, 16 Dec 20
78/93

Comments: 5 pages, 4 figs

Fiber modal noise mitigation by a rotating double scrambler [IMA]

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http://arxiv.org/abs/2012.08116


Fiber modal noise is a performance limiting factor in high-resolution spectroscopy, both with respect to achieving high signal-to-noise ratios or when targeting high-precision radial velocity measurements, with multi-mode fiber-fed high-resolution spectrographs. Traditionally, modal noise is reduced by agitating or “shaking” the fiber. This way, the light propagating in the fiber is redistributed over many different modes. However, in case of fibers with only a limited number of modes, e.g. at near-infrared wavelengths or in adaptive-optics assisted systems, this method becomes very inefficient. The strong agitation that would be needed stresses the fiber and could lead to focal ratio degradation, or worse, to damaging the fiber. As an alternative approach, we propose to make use of a classic optical double scrambler, a device that is already implemented in many high-precision radial-velocity spectrographs, to mitigate the effect of modal noise by rotating the scrambler’s first fiber end during each exposure. Because of the rotating illumination pattern of the scrambler’s second fiber, the modes that are excited vary continuously. This leads to very efficient averaging of the modal pattern at the fiber exit and to a strong reduction of modal noise. In this contribution, we present a prototype design and preliminary laboratory results of the rotating double scrambler.

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G. Raskin, J. Pember, D. Rogozin, et. al.
Wed, 16 Dec 20
93/93

Comments: SPIE Astronomical Telescopes + Instrumentation 2020, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV. arXiv admin note: text overlap with arXiv:1911.08325

Experimental analysis of the achromatic performance of a vector vortex coronagraph [IMA]

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http://arxiv.org/abs/2012.07728


The vector vortex coronagraph is an instrument designed for direct detection and spectroscopy of exoplanets over a broad spectral range. Our team is working towards demonstrating contrast performance commensurate with imaging temperate, terrestrial planets orbiting solar-type stars using the High Contrast Imaging Testbed facility at NASA’s Jet Propulsion Laboratory. To date, the best broadband performance achieved is $\sim$10$^{-8}$ raw contrast over a bandwidth of $\Delta\lambda/\lambda$=10\% in the visible regime (central wavelengths of 550-750 nm), while monochromatic tests yield much deeper contrast ($\sim$10$^{-9}$ or better). In this study, we analyze the main performance limitations on the testbeds so far, focusing on the quality of the focal plane mask manufacturing. We measure the polarization properties of the masks and the residual electric field in the dark hole as a function of wavelength. Our results suggest that the current performance is limited by localized defects in the in the focal plane masks. A new generation of masks is under test that have fewer defects and promise performance improvements.

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G. Ruane, E. Serabyn, C. Prada, et. al.
Tue, 15 Dec 20
31/136

Comments: To appear in SPIE Proceedings Volume 11443, Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave

Electric-quadrupole and magnetic-dipole contributions to the n2+n3 band of carbon dioxide near 3.3 micron [CL]

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http://arxiv.org/abs/2012.07518


The recent detections of electric-quadrupole (E2) transitions in water vapor and magnetic-dipole (M1) transitions in carbon dioxide have opened a new field in molecular spectroscopy. While in their present status, the spectroscopic databases provide only electric-dipole (E1) transitions for polyatomic molecules (H2O, CO2, N2O, CH4, O3), the possible impact of weak E2 and M1 bands to the modeling of the Earth and planetary atmospheres has to be addressed. This is especially important in the case of carbon dioxide for which E2 and M1 bands may be located in spectral windows of weak E1 absorption. In the present work, a high sensitivity absorption spectrum of CO2 was recorded by optical feedback cavity enhanced absorption Spectroscopy (OFCEAS) in the 3.3 micron transparency window of carbon dioxide. The studied spectral interval corresponds to the region where M1 transitions of the n2+n3 band of carbon dioxide were recently identified in the spectrum of the Martian atmosphere. Here, both M1 and E2 transitions of the n2+n3 band were detected by OFCEAS. Using recent ab initio calculations of the E2 spectrum of 12C16O2, intensity measurements of five M1 lines and three E2 lines allow us to disentangle the M1 and E2 contributions. Indeed, E2 intensity values (on the order of a few 10-29 cm per molecule) are found in reasonable agreement with ab initio calculations while the intensity of the M1 lines (including an E2 contribution) agree very well with recent very long path measurements by Fourier Transform spectroscopy. We thus conclude that both E2 and M1 transitions should be systematically incorporated in the CO2 line list provided by spectroscopic databases.

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H. Fleurbaey, R. Grilli, D. Mondelain, et. al.
Tue, 15 Dec 20
49/136

Comments: N/A

Invariants in Interferometry: Geometric Insight into Closure Phases [IMA]

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http://arxiv.org/abs/2012.05254


Closure phase is the phase of a closed-loop product of spatial coherences formed by a $\ge 3$-element interferometer array. Its invariance to element-based phase corruption acquired during propagation and measurement processes, and phase calibration and errors therein, makes it invaluable for interferometric applications that otherwise require high-accuracy phase calibration. However, its understanding has remained mainly mathematical and limited to the aperture plane (Fourier dual of image plane). Here, we lay the foundations for a geometrical insight. We develop and demonstrate a shape-orientation-size (SOS) conservation theorem for images made from a closed triad of elements, in which the relative location of the Null Phase Curves (NPCs) of the three interferometer responses (“fringes”) are preserved, even in the presence of large element-based phase errors, besides overall translation of the fringe pattern. We present two geometric methods to measure the closure phase directly in the image plane (without an aperture-plane view) with a 3-element array and its interference pattern: (i) the closure phase is directly measurable from the positional offset of the NPC of one fringe from the intersection of the other two fringe NPCs, and (ii) the squared closure phase is proportional to the product of the areas enclosed by the triad of array elements and the three fringe NPCs in the aperture and image planes, respectively. We validate this geometric understanding using data observed with the Jansky Very large Array radio telescope. This geometric insight can be potentially valuable to other interferometric applications including optical interferometry. Close parallels exist between interferometric closure phases, structure invariants in crystallography, and phases of Bargmann invariants in quantum mechanics. We generalize these geometric relationships to an N-element interferometer.

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N. Thyagarajan and C. Carilli
Fri, 11 Dec 20
12/75

Comments: 22 pages, 10 captioned figures (12 including sufigures), submitted to Physical Review X. Abstract may be slightly abridged compared to the actual manuscript due to length limitations on arXiv. Comments are welcome!

Image recovery with the solar gravitational lens [CL]

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http://arxiv.org/abs/2012.05477


We report on the initial results obtained with an image convolution/deconvolution computer code that we developed and used to study the image formation capabilities of the solar gravitational lens (SGL). Although the SGL of a spherical Sun creates a greatly blurred image, knowledge of the SGL’s point-spread function (PSF) makes it possible to reconstruct the original image and remove the blur by way of deconvolution. We discuss the deconvolution process, which can be implemented either with direct matrix inversion or with the Fourier quotient method. We observe that the process introduces a “penalty” in the form of a reduction in the signal-to-noise ratio (SNR) of a recovered image, compared to the SNR at which the blurred image data is collected. We estimate the magnitude of this penalty using an analytical approach and confirm the results with a series of numerical simulations. We find that the penalty is substantially reduced when the spacing between image samples is large compared to the telescope aperture. The penalty can be further reduced with suitable noise filtering, which can yield ${\cal O}(10)$ or better improvement for low-quality imaging data. Our results confirm that it is possible to use the SGL for imaging purposes. We offer insights on the data collection and image processing strategies that could yield a detailed image of an exoplanet within image data collection times that are consistent with the duration of a realistic space mission.

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V. Toth and S. Turyshev
Fri, 11 Dec 20
14/75

Comments: 10 pages, 5 figures

Multimaterial Coatings Design via Exhaustive Search for Gravitational Wave Detectors [CL]

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http://arxiv.org/abs/2012.02146


In this work we analyze coatings for gravitational wave detector mirrors obtained by sequencing dielectric layers, with fixed thicknesses, made of three different materials (ternary sequences). Two materials are chosen non-dissipative, i.e. are the standard oxides used in gravitational wave detector coatings technology, the third is a dissipative material. We use the methodology of the exhaustive smart search in the space of sequences to find out the coating design with minimal thermal noise satisfying suitable constraints on transmittance and absorbance. This search has a combinatorial computational complexity and is carried out with a backtracking algorithm. The results obtained show that these ternary sequences can satisfy the optical transmittance and absorbance constraints requested by the mirrors of gravitational wave interferometers, reducing the thermal noise of the coating compared to the standard configuration made of two non-dissipative materials. In all the examined cases the dissipative material is positioned on the bottom of the optimal sequence of the coating layers, close to the substrate. Furthermore, the optimal designs are robust with respect to the uncertainty of the extinction coefficient and have spectral behaviors similar to the quarter wave coatings. Finally, the possibility of further improving performance in terms of thermal noise is demonstrated by considering sequences made of non-quarter wavelength layers.

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V. Pierro, V. Fiumara, F. Chiadini, et. al.
Fri, 4 Dec 20
76/77

Comments: 13 pages, 8 figures, 4 table

Starlight coupling through atmospheric turbulence into few-mode fibers and photonic lanterns in the presence of partial adaptive optics correction [IMA]

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http://arxiv.org/abs/2011.13423


Starlight corrupted by atmospheric turbulence cannot couple efficiently into astronomical instruments based on integrated optics as they require light of high spatial coherence to couple into their single-mode waveguides. Low-order adaptive optics in combination with photonic lanterns offer a practical approach to achieve efficient coupling into multiplexed astrophotonic devices. We investigate, aided by simulations and an experimental testbed, the trade-off between the degrees of freedom of the adaptive optics system and those of the input waveguide of an integrated optic component leading to a cost-effective hybrid system that achieves a signal-to-noise ratio higher than a standalone device fed by a single-mode fiber.

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M. Diab, A. Dinkelaker, J. Davenport, et. al.
Mon, 30 Nov 20
12/117

Comments: 12 pages, 10 figures

X-ray verification of sol-gel resist shrinkage in substrate-conformal imprint lithography for a replicated blazed reflection grating [CL]

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http://arxiv.org/abs/2011.14771


Surface-relief gratings fabricated through nanoimprint lithography (NIL) are prone to topographic distortion induced by resist shrinkage. Characterizing the impact of this effect on blazed diffraction efficiency is particularly important for applications in astrophysical spectroscopy at soft x-ray wavelengths ($\lambda \approx 0.5 – 5$~nm) that call for the mass-production of large-area grating replicas with sub-micron, sawtooth surface-relief profiles. A variant of NIL that lends itself well for this task is substrate-conformal imprint lithography (SCIL), which uses a flexible, composite stamp formed from a rigid master template to imprint nanoscale features in an inorganic resist that cures thermodynamically through a silica sol-gel process. While SCIL enables the production of several hundred imprints before stamp degradation and avoids many of the detriments associated with large-area imprinting in NIL, the sol-gel resist suffers shrinkage dependent on the post-imprint cure temperature. Through atomic force microscopy and diffraction-efficiency testing at beamline 6.3.2 of the Advanced Light Source, the impact of this effect on blaze response is constrained for a $\sim$160-nm-period grating replica cured at 90$^{\circ}$C. Results demonstrate a $\sim$2$^{\circ}$ reduction in blaze angle relative to the master grating, which was fabricated by anisotropic wet etching in $\langle 311 \rangle$-oriented silicon to yield a facet angle close to 30$^{\circ}$.

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J. McCoy, M. Verschuuren, D. Miles, et. al.
Tue, 1 Dec 20
7/108

Comments: 17 pages, 11 figures

Freeform imaging system design with multiple reflection surfaces [CL]

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http://arxiv.org/abs/2011.14802


Reflective imaging systems form an important part of photonic devices such as spectrometers, telescopes, augmented and virtual reality headsets or lithography platforms. Reflective optics provide unparalleled spectral performance and can be used to reduce overall volume and weight. So far, most reflective designs have focused on two or three reflections, while four-reflection freeform designs can deliver a higher light throughput (faster F-number) as well as a larger field-of-view (FOV). However, advanced optical design strategies for four-reflection freeform systems have been rarely reported in literature. This is due to the increased complexity in solution space but also the fact that additional mirrors hinder a cost-effective realization (manufacture, alignment, etc.).
Recently, we have proposed a novel design method to directly calculate the freeform surface coefficients while merely knowing the mirror positions and tilts. Consequently, this method allows laymen with basic optical design knowledge to calculate ‘first time right’ freeform imaging systems in a matter of minutes. This contrasts with most common freeform design processes, which requires considerable experience, intuition or guesswork. Firstly, we demonstrate the effectiveness of the proposed method for a four-mirror high-throughput telescope with 250mm-focal-length, F/2.5 and a wide rectangular FOV of 8.5{\deg} x 25.5{\deg}. In a subsequent step, we propose an effective three-mirror but four-reflection imaging system, which consists of two freeform mirrors and one double-reflection spherical mirror. Compared with common three-mirror and three-reflection imagers, our novel multi-reflection system shows unprecedented possibilities for an economic implementation while drastically reducing the overall volume.

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Y. Nie, D. Shafer, H. Ottevaere, et. al.
Tue, 1 Dec 20
17/108

Comments: 18 pages, 8 figures, submitted to journal

Measurements of Optical Scatter Versus Annealing Temperature for Amorphous Ta2O5 and TiO2:Ta2O5 Thin Films [CL]

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http://arxiv.org/abs/2011.14013


Optical coatings formed from amorphous oxide thin films have many applications in precision measurements. The Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo use coatings of SiO$_2$ (silica) and TiO$_2$:Ta$_2$O$_5$ (titania doped tantala) and post-deposition annealing to 500$^\circ$C to achieve low thermal noise and low optical absorption. Optical scattering by these coatings is a key limit to the detectors’ sensitivity. This paper describes optical scattering measurements for single-layer ion-beam-sputtered thin films on fused silica substrates: two samples of Ta$_2$O$_5$ and two of TiO$_2$:Ta$_2$O$_5$. Using an imaging scatterometer at a fixed scattering angle of 12.8$^\circ$, in-situ changes in the optical scatter of each sample were assessed during post-deposition annealing to 500$^\circ$C in vacuum. The scatter of three of the four coated optics was observed to decrease during the annealing process, by 25-30$\%$ for tantala and up to 74$\%$ for titania-doped tantala, while scatter from the fourth sample held constant. Angle-resolved scatter measurements performed before and after vacuum annealing suggests some improvement in three of four samples. These results demonstrate that post-deposition high-temperature annealing of single-layer tantala and titania-doped tantala thin films in vacuum does not lead to an increase in scatter, and may actually improve their scatter.

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E. Capote, A. Gleckl, J. Guerrero, et. al.
Tue, 1 Dec 20
49/108

Comments: 12 pages, 7 figures, research paper

Rough-Surface Shadowing of Self-Affine Random Rough Surfaces [CL]

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http://arxiv.org/abs/2010.03927


Light scattering from self-affine homogeneous isotropic random rough surfaces is studied using the ray-optics approximation. Numerical methods are developed to accelerate the first-order scattering simulations from surfaces represented as single-connected single-valued random fields, and to store the results of the simulations into a numerical reflectance model. Horizon mapping and marching methods are developed to accelerate the simulation. Emphasis is given to the geometric shadowing and masking effects as a function of surface roughness, especially, to the azimuthal rough-surface shadowing effect.

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H. Parviainen and K. Muinonen
Fri, 9 Oct 20
12/64

Comments: Published in JQSRT 106 (2007)

Modeling optical roughness and first-order scattering processes from OSIRIS-REx color images of the rough surface of asteroid (101955) Bennu [EPA]

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http://arxiv.org/abs/2010.04032


The dark asteroid (101955) Bennu studied by NASA\textquoteright s OSIRIS-REx mission has a boulder-rich and apparently dust-poor surface, providing a natural laboratory to investigate the role of single-scattering processes in rough particulate media. Our goal is to define optical roughness and other scattering parameters that may be useful for the laboratory preparation of sample analogs, interpretation of imaging data, and analysis of the sample that will be returned to Earth. We rely on a semi-numerical statistical model aided by digital terrain model (DTM) shadow ray-tracing to obtain scattering parameters at the smallest surface element allowed by the DTM (facets of \textasciitilde{}10 cm). Using a Markov Chain Monte Carlo technique, we solved the inversion problem on all four-band images of the OSIRIS-REx mission\textquoteright s top four candidate sample sites, for which high-precision laser altimetry DTMs are available. We reconstructed the \emph{a posteriori} probability distribution for each parameter and distinguished primary and secondary solutions. Through the photometric image correction, we found that a mixing of low and average roughness slope best describes Bennu’s surface for up to $90^{\circ}$ phase angle. We detected a low non-zero specular ratio, perhaps indicating exposed sub-centimeter mono-crystalline inclusions on the surface. We report an average roughness RMS slope of $27_{-5}^{\circ+1}$, a specular ratio of $2.6_{-0.8}^{+0.1}\%$, an approx. single-scattering albedo of $4.64_{-0.09}^{+0.08}\%$ at 550 nm, and two solutions for the back-scatter asymmetric factor, $\xi^{(1)}=-0.360\pm0.030$ and $\xi^{(2)}=-0.444\pm0.020$, for all four sites altogether.

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P. Hasselmann, S. Fornasier, M. Barucci, et. al.
Fri, 9 Oct 20
53/64

Comments: 15 pages, 11 figures

Modeling light-controlled actuation of flexible magnetic composite structures using the finite element method (FEM) [CL]

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http://arxiv.org/abs/2009.01510


Photoactive materials hold great promise for a variety of applications. We present a finite element model of light-controlled flexible magnetic composite structure composed of 33.3% Chromium dioxide (CrO2) and 66.7% Polydimethylsiloxane (PDMS) by weight. The structure has a dimension of 8 mm x 2 mm x 100 um and has been previously experimentally studied. Due to the low Curie temperature, the structure acts as an actuator, shows significant deflection under the external magnetic field and relaxation due to laser heating. Thermal and magnetic deflection analysis has been performed using the FEM model. The simulation results show a maximum structural deflection of 6.08 mm (76% of the length of the structure) when subjected to 30 mT magnetic flux density and 160 mW laser power at 303 K (room temperature). We will present the results of the simulation model and comparison to experimental data reproducing the previously observed motion of the (CrO2+PDMS). This model will enable future fracture and fatigue analysis as well as extension to new photoactive geometries.

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A. Jha, M. Li, E. Douglas, et. al.
Fri, 4 Sep 20
-1396/65

Comments: 12 pages, 10 figures, published in Proceedings Volume 11477, Molecular and Nano Machines III; 1147704 (2020), Event: SPIE Organic Photonics + Electronics, 2020, Online Only

Demonstration of an amplitude filter cavity at gravitational-wave frequencies [IMA]

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http://arxiv.org/abs/2008.08094


Quantum vacuum fluctuations fundamentally limit the precision of optical measurements, such as those in gravitational-wave detectors. Injection of conventional squeezed vacuum can be used to reduce quantum noise in the readout quadrature, but this reduction is at the cost of increasing noise in the orthogonal quadrature. For detectors near the limits imposed by quantum radiation pressure noise (QRPN), both quadratures impact the measurement, and the benefits of conventional squeezing are limited. In this paper, we demonstrate the use of a critically-coupled 16m optical cavity to diminish anti-squeezing at frequencies below 90Hz where it exacerbates QRPN, while preserving beneficial squeezing at higher frequencies. This is called an amplitude filter cavity, and it is useful for avoiding degradation of detector sensitivity at low frequencies. The attenuation from the cavity also provides technical advantages such as mitigating backscatter.

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K. Komori, D. Ganapathy, C. Whittle, et. al.
Thu, 20 Aug 20
-1115/48

Comments: 7 pages, 4 figures

Optimal detuning for quantum filter cavities [IMA]

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http://arxiv.org/abs/2008.08086


Vacuum quantum fluctuations impose a fundamental limit on the sensitivity of gravitational-wave interferometers, which rank among the most sensitive precision measurement devices ever built. The injection of conventional squeezed vacuum reduces quantum noise in one quadrature at the expense of increasing noise in the other. While this approach improved the sensitivity of the Advanced LIGO and Advanced Virgo interferometers during their third observing run (O3), future improvements in arm power and squeezing levels will bring radiation pressure noise to the forefront. Installation of a filter cavity for frequency-dependent squeezing provides broadband reduction of quantum noise through the mitigation of this radiation pressure noise, and it is the baseline approach planned for all of the future gravitational-wave detectors currently conceived. The design and operation of a filter cavity requires careful consideration of interferometer optomechanics as well as squeezing degradation processes. In this paper, we perform an in-depth analysis to determine the optimal operating point of a filter cavity. We use our model alongside numerical tools to study the implications for filter cavities to be installed in the upcoming “A+” upgrade of the Advanced LIGO detectors.

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C. Whittle, K. Komori, D. Ganapathy, et. al.
Thu, 20 Aug 20
-1112/48

Comments: N/A

Highly-efficient generation of coherent light at 2128 nm via degenerate optical-parametric oscillation [CL]

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http://arxiv.org/abs/2008.07193


Cryogenic operation in conjunction with new test-mass materials promises to reduce the sensitivity limitations from thermal noise in gravitational-wave detectors. The currently most advanced materials under discussion are crystalline silicon as a substrate with amorphous silicon-based coatings. They require, however, operational wavelengths around 2 $\mathrm\mu$m to avoid laser absorption. Here, we present a light source at 2128 nm based on a degenerate optical parametric oscillator (DOPO) to convert light from a 1064 nm non-planar ring-oscillator (NPRO). We achieve an external conversion efficiency of ($88.3 \pm 1.4$) With our approach, light from the established and existing laser sources can be efficiently converted to the 2 $\mathrm\mu$m regime, while retaining the excellent stability properties.

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C. Darsow-Fromm, M. Schröder, J. Gurs, et. al.
Tue, 18 Aug 20
-983/70

Comments: To be published in Optics Letters

Single-element dual-interferometer for precision inertial sensing [CL]

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http://arxiv.org/abs/2008.05602


Tracking moving masses in several degrees of freedom with high precision and large dynamic range is a central aspect in many current and future gravitational physics experiments, where laser interferometers have been established as one of the tools of choice. Using sinusoidal phase modulation homodyne interferometry allows a drastic reduction of the complexity of the optical setup, a key limitation of multi-channel interferometry. By shifting the complexity of the setup to the signal processing stage, these measurement schemes enable devices with a size and weight not feasible using conventional techniques. In this paper we present the design of a novel sensor topology based on deep frequency modulation interferometry: the self-referenced single-element dual-interferometer (SEDI) inertial sensor, which takes simplification one step further by accommodating two interferometers in one optic. We show that an inertial sensor with sub-picometer precision for frequencies above 10 mHz, in a package of a few cubic inches, seems feasible with our approach. Moreover we show that by combining two of these devices it is possible to reach sub-picometer precision down to 2 mHz. In combination with the given compactness, this makes the SEDI sensor a promising approach for applications in high precision inertial sensing for both next-generation space-based gravity missions employing drag-free control, and ground-based experiments employing inertial isolation systems with optical readout.

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Y. Yang, K. Yamamoto, V. Huarcaya, et. al.
Fri, 14 Aug 20
-937/70

Comments: 16 pages, 8 figures

The Zwicky Transient Facility: Observing System [IMA]

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http://arxiv.org/abs/2008.04923


The Zwicky Transient Facility (ZTF) Observing System (OS) is the data collector for the ZTF project to study astrophysical phenomena in the time domain. ZTF OS is based upon the 48-inch aperture Schmidt-type design Samuel Oschin Telescope at the Palomar Observatory in Southern California. It incorporates new telescope aspheric corrector optics, dome and telescope drives, a large-format exposure shutter, a flat-field illumination system, a robotic bandpass filter exchanger, and the key element: a new 47-square-degree, 600 megapixel cryogenic CCD mosaic science camera, along with supporting equipment. The OS collects and delivers digitized survey data to the ZTF Data System (DS). Here, we describe the ZTF OS design, optical implementation, delivered image quality, detector performance, and robotic survey efficiency.

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R. Dekany, R. Smith, R. Riddle, et. al.
Thu, 13 Aug 20
-902/67

Comments: 31 pages, 26 figures, 5 tables; published in the Publications of the Astronomical Society of the Pacific

The influence of the electric polarization of hydrogen atoms on the red shift of its spectral lines [GA]

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http://arxiv.org/abs/2008.02645


The Lorentz oscillator system is studied to interpret the spectral lines of hydrogen atoms. The dielectric constant of this system is analyzed, which takes into account the electrical polarization of hydrogen atoms. This dielectric constant gives the red shift of the spectral line and the appearance of the optical spectrum dip. This dip is on the blue side of the spectral position of the shifted line. The value of this red shift and the width of this dip strongly depend on the hydrogen atom concentration and the spectral position of the not shifted line. This red shift increases with an increase in the hydrogen atom concentration.

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V. Severin
Fri, 7 Aug 20
-736/46

Comments: 11 pages, 3 figures

Increased Sensitivity of Higher-Order Laser Beams to Mode Mismatches [CL]

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http://arxiv.org/abs/2007.12564


This manuscript derives mode-mismatch-induced power losses, as a function of mode order, for Hermite-Gauss optical modes. Explicit factors are derived linking mode mismatch losses in a higher order mode to mismatch losses of the fundamental mode. This is particularly relevant for gravitational-wave detectors, where lasers employing higher-order optical modes have been proposed to mitigate thermal noise and quantum-enhanced detectors are very susceptible to losses. This work should inform mode matching and squeezing requirements for \textit{Advanced+} and \textit{Third Generation} detectors.

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A. Jones and A. Freise
Mon, 27 Jul 20
-568/60

Comments: Main text has 6 pages including referances. Two supplementary files are provided, one PDF which is incorperated into the main pdf and one python file. Two figures and one table are contained in the main text

Influence of sensor tilts on bio-inspired polarized skylight orientation determination [CL]

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http://arxiv.org/abs/2007.08987


Many animals such as desert ants, honey bees and locusts have been reported to detect polarized light in the sky as a compass. Inspired by this, several polarized skylight orientation determination approaches have been proposed. However, almost all of these approaches always require polarization sensor pointing to the zenith of the sky dome. So, the influence of sensor tilts (not point to the sky zenith) on bio-inspired polarization orientation determination needs to be analyzed urgently. Aiming at this problem, a polarization compass simulation system is designed based upon solar position model, Rayleigh sky model, and hypothetical polarization imager. Then, the error characteristics of four typical orientation determination approaches are investigated in detail under only pitch tilt condition, only roll tilt condition, pitch and roll tilts condition respectively. Finally, simulation and field experiments all show that the orientation errors of four typical approaches are highly consistent when they are subjected to tilt interference, in addition, the errors are affected by not only the degree of inclination, but also the solar altitude angle and the relative position between the Sun and polarization sensor.

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H. Liang, H. Bai, T. Zhou, et. al.
Mon, 20 Jul 20
-281/85

Comments: N/A

Gravitational wave detectors with broadband high frequency sensitivity [CL]

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http://arxiv.org/abs/2007.08766


The binary neutron star coalescence GW170817 was observed by gravitational wave detectors during the inspiral phase but sensitivity in the 1-5 kHz band was insufficient to observe the expected nuclear matter signature of the merger itself, and the process of black hole formation. This provides strong motivation for improving 1–5 kHz sensitivity which is currently limited by photon shot noise. Resonant enhancement by signal recycling normally improves the signal to noise ratio at the expense of bandwidth. The concept of optomechanical white light signal recycling (WLSR) has been proposed, but all schemes to date have been reliant on the development of suitable ultra-low mechanical loss components. Here for the first time we show demonstrated optomechanical resonator structures that meet the loss requirements for a WLSR interferometer with strain sensitivity below 10$^{-24}$ Hz$^{-1/2}$ at a few kHz. Experimental data for two resonators are combined with analytic models of 4km interferometers similar to LIGO, to demonstrate sensitivity enhancement across a much broader band of neutron star coalescence frequencies than dual-recycled Fabry-Perot Michelson detectors of the same length. One candidate resonator is a silicon nitride membrane acoustically isolated from the environment by a phononic crystal. The other is a single-crystal quartz lens that supports bulk acoustic longitudinal waves. Optical power requirements could prefer the membrane resonator, although the bulk acoustic wave resonator gives somewhat better thermal noise performance. Both could be implemented as add-on components to existing detectors.

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M. Page, M. Goryachev, H. Miao, et. al.
Mon, 20 Jul 20
-279/85

Comments: N/A

A comparison of g(1)(τ), g(3/2)(τ), and g(2)(τ), for radiation from harmonic oscillators in Brownian motion with coherent background [CL]

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http://arxiv.org/abs/2007.06470


We compare the field-field g(1)(\tau), intensity-field g(3/2)(\tau), and intensity-intensity g(2)(\tau) correlation functions for models that are of relevance in astrophysics. We obtain expressions for the general case of a chaotic radiation, where the amplitude is Rician based on a model with an ensemble of harmonic oscillators in Brownian motion. We obtain the signal to noise ratios for two methods of measurement. The intensity-field correlation function signal to noise ratio scales with the first power of |g(1)(\tau)|. This is in contrast with the well-established result of g(2)(\tau) which goes as the square of |g(1)(\tau)|.

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A. Siciak, L. Orozco, M. Fouché, et. al.
Tue, 14 Jul 20
-162/97

Comments: 23 pages, 2 figures, 3 Tables

MEMS Mirror Manufacturing and Testing for Innovative Space Applications [IMA]

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http://arxiv.org/abs/2006.12256


In the framework of the GLARE-X (Geodesy via LAser Ranging from spacE X) project, led by INFN and funded for the years 2019-2021, aiming at significantly advance space geodesy, one shows the initial activities carried out in 2019 in order to manufacture and test adaptive mirrors. This specific article deals with manufacturing and surface quality measurements of the passive substrate of ‘candidate’ MEMS (Micro-Electro-Mechanical Systems) mirrors for MRRs (Modulated RetroReflectors); further publications will show the active components. The project GLARE-X was approved by INFN for the years 2019-2021: it involves several institutions, including, amongst the other, INFN-LNF and FBK. GLARE-X is an innovative R&D activity, whose at large space geodesy goals will concern the following topics: inverse laser ranging (from a laser terminal in space down to a target on a planet), laser ranging for debris removal and iterative orbit correction, development of high-end ToF (Time of Flight) electronics, manufacturing and testing of MRRs for space, and provision of microreflectors for future NEO (Near Earth Orbit) cubesats. This specific article summarizes the manufacturing and surface quality measurements activities performed on the passive substrate of ‘candidate’ MEMS mirrors, which will be in turn arranged into MRRs. The final active components, to be realized by 2021, will inherit the manufacturing characteristics chosen thanks to the presented (and further) testing campaigns, and will find suitable space application to NEO, Moon, and Mars devices, like, for example, cooperative and active lidar scatterers for laser altimetry and lasercomm support.

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A. Bagolini, M. Boscardin, S. Dell’Agnello, et. al.
Tue, 23 Jun 20
58/84

Comments: 9 pages, 5 figures

Development and application of metamaterial-based Half-Wave Plates for the NIKA and NIKA2 polarimeters [IMA]

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http://arxiv.org/abs/2006.12081


CONTEXT.Large field-of-view imaging/polarimetry instruments operating at millimeter and submm wavelengths are fundamental tools to understand the role of magnetic fields (MF) in channeling filament material into prestellar cores providing a unique insight in the physics of galactic star-forming regions. Among other topics, at extra-galactic scales, polarization observations of AGNs will allow us to constrain the possible physical conditions of the emitting plasma from the jets and/or exploring the physics of dust inside supernova remnants. The kilo-pixel NIKA2 camera, installed at the IRAM 30-m telescope, represents today one of the best tools available to the astronomers to produce simultaneous intensity/polarimetry maps over large fields at 260 GHz (1.15 mm). AIMS.The polarization measurement, in NIKA and NIKA2, is achieved by rapidly modulating the total incoming polarization. This allows in the end to safely isolate the small science signal from the large, un-polarized and strongly variable, atmospheric background. METHODS.The polarization modulation is achieved by inserting a fast rotating Half-Wave Plate (HWP) in the optical beam. In order to allow wide field-of-view observations, the plate has to be large, with a diameter exceeding 250 mm. The modulation of the polarized signal, at 12 Hz, requires also the waveplate to be sufficiently light. In addition, this key optical element has to exhibit optimal electromagnetic characteristics in terms of transmission and differential phase-shift. For this purpose, three metamaterial HWPs have been developed using the mesh-filter technology. The knowledge acquired in developing the first two single-band HWPs was used to achieve the more challenging performance requirements of the last dual-band HWP. The first and the third waveplates met the requirements for both the NIKA and NIKA2 instruments. RESULTS.(abridged)

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G. Pisano, A. Ritacco, A. Monfardini, et. al.
Tue, 23 Jun 20
69/84

Comments: Submitted to Astronomy & Astrophysics 12 pages, 28 figures

A universal smartphone add-on for portable spectroscopy and polarimetry: iSPEX 2 [CL]

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http://arxiv.org/abs/2006.01519


Spectropolarimetry is a powerful technique for remote sensing of the environment. It enables the retrieval of particle shape and size distributions in air and water to an extent that traditional spectroscopy cannot. SPEX is an instrument concept for spectropolarimetry through spectral modulation, providing snapshot, and hence accurate, hyperspectral intensity and degree and angle of linear polarization. Successful SPEX instruments have included groundSPEX and SPEX airborne, which both measure aerosol optical thickness with high precision, and soon SPEXone, which will fly on PACE. Here, we present a low-cost variant for consumer cameras, iSPEX 2, with universal smartphone support. Smartphones enable citizen science measurements which are significantly more scaleable, in space and time, than professional instruments. Universal smartphone support is achieved through a modular hardware design and SPECTACLE data processing. iSPEX 2 will be manufactured through injection molding and 3D printing. A smartphone app for data acquisition and processing is in active development. Production, calibration, and validation will commence in the summer of 2020. Scientific applications will include citizen science measurements of aerosol optical thickness and surface water reflectance, as well as low-cost laboratory and portable spectroscopy.

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O. Burggraaff, A. Perduijn, R. Hek, et. al.
Wed, 3 Jun 20
24/83

Comments: 16 pages, 11 figures, SPIE Defense + Commercial Sensing 2020

Integrated Arbitrary Filter with Spiral Gratings: Design and Characterization [IMA]

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http://arxiv.org/abs/2006.00629


We report the design and characterization of a high performance integrated arbitrary filter from 1450 nm to 1640 nm. The filter’s target spectrum is chosen to suppress the night-sky OH emission lines, which is critical for ground-based astronomical telescopes. This type of filter is featured by its large spectral range, high rejection ratio and narrow notch width. Traditionally it is only successfully accomplished with fiber Bragg gratings. The technique we demonstrate here is proven to be very efficient for on-chip platforms, which can bring many benefits for device footprint, performance and cost. For the design part, two inverse scattering algorithms are compared, the frequency domain discrete layer-peeling (f-DLP) and the time domain discrete layer-peeling (t-DLP). f-DLP is found to be superior for the grating reconstruction in terms of accuracy and robustness. A method is proposed to resolve the non-uniformity issue caused by the non-zero layer size in the DLP algorithm. The designed 55-notch filter is 50-mm-long and implemented on a compact Si3N4/SiO2 spiral waveguide with a total length of 63 mm. Experimentally, we demonstrate that the device has a insertion loss as low as 2.5 dB, and that the waveguide propagation loss is as low as 0.10 dB/cm. We are also able to achieve uniform notch depths and 3-dB widths of about 28 dB and 0.22 nm, respectively.

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Y. Hu, S. Xie, J. Zhan, et. al.
Tue, 2 Jun 20
50/90

Comments: 8 pages, 8 figures, accepted for publication in Journal of Lightwave Technology

High-Contrast Integral Field Spectrograph (HCIFS): multi-spectral wavefront control and reduced-dimensional system identification [IMA]

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http://arxiv.org/abs/2005.09753


Any High-contrast imaging instrument in a future large ground-based or space-based telescopes will include an integral field spectrograph (IFS) for measuring broadband starlight residuals and characterizing the exoplanet’s atmospheric spectrum. In this paper, we report the development of a high-contrast integral field spectrograph (HCIFS) at Princeton University and demonstrate its application in multi-spectral wavefront control. Moreover, we propose and experimentally validate a new reduced-dimensional system identification algorithm for an IFS imaging system, which improves the system’s wavefront control speed, contrast and computational efficiency.

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H. Sun, A. Goun, S. Redmond, et. al.
Thu, 21 May 20
47/60

Comments: N/A

Methods for coherent optical Doppler orbitography [IMA]

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http://arxiv.org/abs/2005.02546


Doppler orbitography uses the Doppler shift in a transmitted signal to determine the orbital parameters of satellites including range and range-rate (or radial velocity). We describe two techniques for atmospheric-limited optical Doppler orbitography measurements of range-rate. The first determines the Doppler shift directly from a heterodyne measurement of the returned optical signal. The second aims to improve the precision of the first by suppressing atmospheric phase noise imprinted on the transmitted optical signal. We demonstrate the performance of each technique over a 2.2 km horizontal link with a simulated in-line velocity Doppler shift at the far end. A horizontal link of this length has been estimated to exhibit nearly half the total integrated atmospheric turbulence of a vertical link to space. Without stabilisation of the atmospheric effects, we obtained an estimated range rate precision of 17 um/s at 1 s of integration. With active suppression of atmospheric phase noise, this improved by three orders-of-magnitude to an estimated range rate precision of 9.0 nm/s at 1 second of integration, and 1.1 nm/s when integrated over a 60 s. This represents four orders-of-magnitude improvement over the typical performance of operational ground to space X-Band systems in terms of range-rate precision at the same integration time.
The performance of this system is a promising proof of concept for coherent optical Doppler orbitography. There are many additional challenges associated with performing these techniques from ground to space, that were not captured within the preliminary experiments presented here. In the future, we aim to progress towards a 10 km horizontal link to replicate the expected atmospheric turbulence for a ground to space link.

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B. Dix-Matthews, S. Schediwy, D. Gozzard, et. al.
Thu, 7 May 20
8/62

Comments: 10 pages, 6 figures, 1 table

Geometric-Phase Waveplates for Free-Form Dark Hollow beams [CL]

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http://arxiv.org/abs/2005.00733


We demonstrate the possibility to create optical beams with phase singularities engraved into exotic intensity landscapes imitating the shapes of a large variety of diverse plane curves. To achieve this aim, we have developed a method for directly encoding the geometric properties of some selected curve into a single azimuthal phase factor without passing through indirect encryption methods based on lengthy numerical procedures. The outcome is utilized to mould the optic axis distribution of a liquid-crystal-based inhomogeneous waveplate. The latter is finally used to sculpt the wavefront of an input optical gaussian beam via Pancharatnam-Berry phase.

Read this paper on arXiv…

B. Piccirillo, E. Piedipalumbo and E. Santamato
Tue, 5 May 20
44/75

Comments: 11 pages, 6 figures, Published on 21 April 2020 Front. Phys

New method to track length and Differential Wavefront Sensing signals from quadrant photodiodes in heterodyne interferometers with digital PLL readout [CL]

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http://arxiv.org/abs/2005.00003


We propose a new method to track signals from quadrant photodiodes (QPD) in heterodyne interferometers that employ digital phase-locked loops for phase readout. Instead of separately tracking the four segments from the QPD and then combing the results into length and Differential Wavefront Sensing (DWS) signals, this method employs a set of coupled tracking loops that operate directly on the combined length and DWS signals. Benefits are increased Signal-to-Noise Ratio in the loops and the possibility to adapt the loop bandwidths to the different dynamical behaviour of length and DWS signals.

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G. Heinzel and N. Brause
Mon, 4 May 20
17/55

Comments: 9 pages, 4 figures

Simulating Anisoplanatic Turbulence by Sampling Inter-modal and Spatially Correlated Zernike Coefficients [CL]

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http://arxiv.org/abs/2004.11210


Simulating atmospheric turbulence is an essential task for evaluating turbulence mitigation algorithms and training learning-based methods. Advanced numerical simulators for atmospheric turbulence are available, but they require evaluating wave propagation which is computationally expensive. In this paper, we present a propagation-free method for simulating imaging through turbulence. The key idea behind our work is a new method to draw inter-modal and spatially correlated Zernike coefficients. By establishing the equivalence between the angle-of-arrival correlation by Basu, McCrae and Fiorino (2015) and the multi-aperture correlation by Chanan (1992), we show that the Zernike coefficients can be drawn according to a covariance matrix defining the correlations. We propose fast and scalable sampling strategies to draw these samples. The new method allows us to compress the wave propagation problem into a sampling problem, hence making the new simulator significantly faster than existing ones. Experimental results show that the simulator has an excellent match with the theory and real turbulence data.

Read this paper on arXiv…

N. Chimitt and S. Chan
Fri, 24 Apr 20
39/63

Comments: N/A

Numerical solutions for phase noise due to pointing jitter with the LISA telescope [CL]

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http://arxiv.org/abs/2004.04527


The aim of the Laser Interferometer Space Antenna (LISA) is to detect gravitational waves through a phase modulation in long (2.5 Mkm) laser light links between spacecraft. Among other noise sources to be addressed are the phase fluctuations caused by a possible angular jitter of the emitted beam. The present paper follows our preceding one (Vinet et al 2019 Class. Quant. Grav. 36, 205 003) based on an analytical study of the far field phase. We address here a numerical treatment of the phase, to first order in the emitted wavefront aberrations, but without any assumptions on the static bias term. We verify that, in the phase change, the higher order terms in the static mispointing are consistent with the results found in our preceding paper.

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J. Vinet, N. Christensen, N. Dinu-Jaeger, et. al.
Fri, 10 Apr 20
11/56

Comments: N/A

Focal-ratio-degradation (FRD) mitigation in a multimode fiber link using mode-selective photonic lanterns [CL]

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http://arxiv.org/abs/2004.04035


We present a new way to mitigate focal-ratio degradation (FRD) when using optical fibers to transport multimode light. Our approach exploits a custom multicore fiber (MCF) with six dissimilar cores that are single mode at ~1550 nm wavelength and minimally coupled over 7 m. We fabricated adiabatic mode-selective photonic lanterns (PLs) at each end of the MCF to create a fiber link with multimode ports, the PLs coupling each spatial mode of the multimode ports to a specific core of the MCF and vice versa. The PL-MCF-PL link exhibits superior FRD behavior compared to a conventional multimode fiber that also supports 6 modes, because it inhibits the transfer of light from lower-order modes to higher-order modes. These results open up a potentially powerful new approach to mitigate FRD in multimode fiber links, with particular applications in astronomical instruments.

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A. Benoît, S. Yerolatsitis, K. Harrington, et. al.
Thu, 9 Apr 20
41/54

Comments: 9 pages, 12 figures

Control of a Filter Cavity with Coherent Control Sidebands [CL]

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http://arxiv.org/abs/2004.01400


For broadband quantum noise reduction of gravitational wave detectors, frequency dependent squeezed vacuum states realized using a filter cavity is a mature technique and will be implemented in Advanced LIGO and Advanced Virgo from the fourth observation run. To obtain the benefit of frequency dependent squeezing, detuning and alignment of the filter cavity with respect to squeezed vacuum states must be controlled accurately. To this purpose we suggest a new length and alignment control scheme, using coherent control sidebands which are already used to control squeezing angle. Since both squeezed vacuum states and coherent control sidebands have the same mode matching conditions and almost the same frequency, detuning and alignment of the filter cavity can be controlled accurately with this scheme. In this paper, we show the principle of this scheme and its application to a gravitational-wave detector.

Read this paper on arXiv…

N. Aritomi, M. Leonardi, E. Capocasa, et. al.
Mon, 6 Apr 20
4/46

Comments: N/A

Frequency stability of the mode spectrum of broad bandwidth Fabry-Perot interferometers [IMA]

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http://arxiv.org/abs/2003.13770


When illuminated by a white light source, the discrete resonances of a Fabry-Perot interferometer (FP) provide a broad bandwidth, comb-like spectrum useful for frequency calibration. We report on the design, construction and laboratory characterization of two planar, passively stabilized, low finesse (~40) FPs spanning 380 nm to 930 nm and 780 nm to 1300 nm, with nominal free spectral ranges of 20 GHz and 30 GHz respectively. These instruments are intended to calibrate astronomical spectrographs in radial velocity searches for extrasolar planets. By tracking the frequency drift of three widely-separated resonances in each FP we measure fractional frequency drift rates as low as 1 x 10^(-10) / day. However we find that the fractional drift rate varies across the three sample wavelengths, such that the drift of two given resonance modes disagrees with the ratio of their mode numbers. We explore possible causes of this behavior, as well as quantify the temperature and optical power sensitivity of the FPs. Our results demonstrate the advancement of Fabry-Perot interferometers as robust and frequency-stable calibrators for astronomical and other broad bandwidth spectroscopy applications, but also highlight the need for chromatic characterization of these systems.

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J. Jennings, R. Terrien, C. Fredrick, et. al.
Wed, 1 Apr 20
27/83

Comments: 18 pages, 9 figures, submitted to OSA Continuum

Quantum sensing with milligram scale optomechanical systems [CL]

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http://arxiv.org/abs/2003.13906


Probing the boundary between classical and quantum mechanics has been one of the central themes in modern physics. Recently, experiments to precisely measure the force acting on milligram scale oscillators with optical cavities are attracting interest as promising tools to test quantum mechanics, decoherence mechanisms, and gravitational physics. In this paper, we review the present status of experiments using milligram scale optomechanical systems. We compare the feasibility of reaching the quantum regime with a pendulum, torsion pendulum, and optically levitated mirror. Considerations for designing a high $Q$ pendulum, condition for torsion pendulums to have better force sensitivity than pendulums, and constraints in designing optical levitation of a mirror are presented.

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Y. Michimura and K. Komori
Wed, 1 Apr 20
79/83

Comments: 14 pages, 6 figures

Frequency-Dependent Squeezing for Advanced LIGO [IMA]

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http://arxiv.org/abs/2003.13443


The first detection of gravitational waves by the Laser Interferometer Gravitational-wave Observatory (LIGO) in 2015 launched the era of gravitational wave astronomy. The quest for gravitational wave signals from objects that are fainter or farther away impels technological advances to realize ever more sensitive detectors. Since 2019, one advanced technique, the injection of squeezed states of light is being used to improve the shot noise limit to the sensitivity of the Advanced LIGO detectors, at frequencies above $\sim 50$ Hz. Below this frequency, quantum back action, in the form of radiation pressure induced motion of the mirrors, degrades the sensitivity. To simultaneously reduce shot noise at high frequencies and quantum radiation pressure noise at low frequencies requires a quantum noise filter cavity with low optical losses to rotate the squeezed quadrature as a function of frequency. We report on the observation of frequency-dependent squeezed quadrature rotation with rotation frequency of 30Hz, using a 16m long filter cavity. A novel control scheme is developed for this frequency-dependent squeezed vacuum source, and the results presented here demonstrate that a low-loss filter cavity can achieve the squeezed quadrature rotation necessary for the next planned upgrade to Advanced LIGO, known as “A+.”

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L. McCuller, C. Whittle, D. Ganapathy, et. al.
Tue, 31 Mar 20
80/94

Comments: 6 pages, 2 figures, to be published in Phys. Rev. Lett

PSF–NET: A Non-parametric Point Spread Function Model for Ground Based Optical Telescopes [IMA]

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http://arxiv.org/abs/2003.00615


Ground based optical telescopes are seriously affected by atmospheric turbulence induced aberrations. Understanding properties of these aberrations is important both for instruments design and image restoration methods development. Because the point spread function can reflect performance of the whole optic system, it is appropriate to use the point spread function to describe atmospheric turbulence induced aberrations. Assuming point spread functions induced by the atmospheric turbulence with the same profile belong to the same manifold space, we propose a non-parametric point spread function — PSF-NET. The PSF-NET has a cycle convolutional neural network structure and is a statistical representation of the manifold space of PSFs induced by the atmospheric turbulence with the same profile. Testing the PSF-NET with simulated and real observation data, we find that a well trained PSF–NET can restore any short exposure images blurred by atmospheric turbulence with the same profile. Besides, we further use the impulse response of the PSF-NET, which can be viewed as the statistical mean PSF, to analyze interpretation properties of the PSF-NET. We find that variations of statistical mean PSFs are caused by variations of the atmospheric turbulence profile: as the difference of the atmospheric turbulence profile increases, the difference between statistical mean PSFs also increases. The PSF-NET proposed in this paper provides a new way to analyze atmospheric turbulence induced aberrations, which would be benefit to develop new observation methods for ground based optical telescopes.

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P. Jia, X. Wu, Y. Huang, et. al.
Tue, 3 Mar 20
31/68

Comments: Accepted by AJ. The complete code can be downloaded at DOI:10.12149/101014

Direct Multipixel Imaging and Spectroscopy of an Exoplanet with a Solar Gravity Lens Mission [IMA]

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http://arxiv.org/abs/2002.11871


We examined the solar gravitational lens (SGL) as the means to produce direct high-resolution, multipixel images of exoplanets. The properties of the SGL are remarkable: it offers maximum light amplification of ~1e11 and angular resolution of ~1e-10 arcsec. A probe with a 1-m telescope in the SGL focal region can image an exoplanet at 30 pc with 10-kilometer resolution on its surface, sufficient to observe seasonal changes, oceans, continents, surface topography. We reached and exceeded all objectives set for our study: We developed a new wave-optical approach to study the imaging of exoplanets while treating them as extended, resolved, faint sources at large but finite distances. We properly accounted for the solar corona brightness. We developed deconvolution algorithms and demonstrated the feasibility of high-quality image reconstruction under realistic conditions. We have proven that multipixel imaging and spectroscopy of exoplanets with the SGL are feasible. We have developed a new mission concept that delivers an array of optical telescopes to the SGL focal region relying on three innovations: i) a new way to enable direct exoplanet imaging, ii) use of smallsats solar sails fast transit through the solar system and beyond, iii) an open architecture to take advantage of swarm technology. This approach enables entirely new missions, providing a great leap in capabilities for NASA and the greater aerospace community. Our results are encouraging as they lead to a realistic design for a mission that will be able to make direct resolved images of exoplanets in our stellar neighborhood. It could allow exploration of exoplanets relying on the SGL capabilities decades, if not centuries, earlier than possible with other extant technologies. The architecture and mission concepts for a mission to the SGL, at this early stage, are promising and should be explored further.

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S. Turyshev, M. Shao, V. Toth, et. al.
Fri, 28 Feb 20
35/49

Comments: Final Report for the NASA’s Innovative Advanced Concepts (NIAC) Phase II proposal. 79 pages, 47 figures, 5 tables

Polarization loss in reflecting coating [IMA]

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http://arxiv.org/abs/2002.08271


In laser gravitational waves detectors optical loss restricts sensitivity. We discuss polarization scattering as one more possible mechanism of optical losses. Circulated inside interferometer light is polarized and after reflection its plane of polarization can turn a little due to reflecting coating of mirror can have slightly different refraction index along axes $x,\, y$ in plane of mirror surface (optical anisotropy). This anisotropy can be produced during manufacture of coating (elasto-optic effect). This orthogonal polarized light, enhanced in cavity, produces polarization optical loss. Polarization map of mirrors is very important and we propose to measure it. Polarization loss can be important in different precision optical experiments based on usage of polarized light, for example, in quantum speed meter.

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S. Vyatchanin
Thu, 20 Feb 20
14/61

Comments: N/A

Light by Light Scattering as a New Probe for Axions [CL]

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http://arxiv.org/abs/2002.06123


We study the impact of virtual axions on the polarization of photons inside a cavity during the interaction of high-power laser pulses. A novel detection scheme for measuring the axion-induced ellipticity signal during the Light-by-Light (LBL) scattering process is investigated. We show that a momentum exchange between photons in a probe laser beam and a high-intensity target beam may lead to a resonance at the physical mass of the axion. Consequently, the resonant enhancement of vacuum birefringence gives rise to a large ellipticity signal. This signal enhancement can be applied in order to discriminate between the axion contribution to LBL scattering and the standard model contribution due to electron-positron pairs. The sensitivity of the scheme is studied for experimentally feasible probe light sources and ultrahigh intensity laser backgrounds. It is shown that this technique has the potential to probe the QCD axion in the mass range $10^{-2} \textrm{eV} \lesssim m_{a} \lesssim 1 \textrm{eV}$. In this region the axion induced signal surpasses the standard model background.

Read this paper on arXiv…

S. Shakeri, D. Marsh and S. Xue
Mon, 17 Feb 20
21/53

Comments: 13 pages, 3 figures

Optical suppression of tilt-to-length coupling in the LISA long-arm interferometer [IMA]

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http://arxiv.org/abs/2002.05669


The arm length and the isolation in space enable LISA to probe for signals unattainable on ground, opening a window to the sub-Hz gravitational-wave universe. The coupling of unavoidable angular spacecraft jitter into the longitudinal displacement measurement, an effect known as tilt-to-length (TTL) coupling, is critical for realizing the required sensitivity of picometer$/\sqrt{\rm{Hz}}$. An ultra-stable interferometer testbed has been developed in order to investigate this issue and validate mitigation strategies in a setup representative of the LISA long-arm interferometer. We demonstrate a reduction of TTL coupling between a flat-top beam and a Gaussian beam via introducing two- and four-lens imaging systems. TTL coupling factors below $\pm 25\,\mu$m/rad for beam tilts within $\pm 300\,\mu$rad are obtained by careful optimization of the system. Moreover we show that the additional TTL coupling due to lateral alignment errors of elements of the imaging system can be compensated by introducing lateral shifts of the detector, and vice versa. These findings help validate the suitability of this noise-reduction technique for the LISA long-arm interferometer.

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M. Chwalla, K. Danzmann, M. Álvarez, et. al.
Fri, 14 Feb 20
25/51

Comments: 11 pages, 10 figures

High-Dynamic-Range Mode-Decomposition for Interferometric Gravitational Wave Detectors and Associated Alignment Considerations [CL]

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http://arxiv.org/abs/2002.04864


Accurate readout of low-power optical higher-order spatial modes is of increasing importance to the precision metrology community. Such devices may prevent mode mismatches from degrading quantum and thermal noise mitigation strategies. Direct mode analysis sensors are a promising technology for real time monitoring of arbitrary higher-order modes. We demonstrate this technology with photo-diode readout to mitigate the typically low dynamic range of CCDs. We experimentally demonstrate the effect of a relative misalignment between the phase-plate and the photo-diode on the readout of higher-order modes, then derive this response. We then compute the residual the effects of the finite photo-diode aperture on the dynamic range and discuss implementation considerations for future sensors.

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A. Jones, M. Wang, C. Mow-Lowry, et. al.
Thu, 13 Feb 20
22/54

Comments: N/A

Astronomical Applications of Multi-Core Fiber Technology [IMA]

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http://arxiv.org/abs/2002.01573


Optical fibers have altered astronomical instrument design by allowing for a complex, often large instrument to be mounted in a remote and stable location with respect to the telescope. The fibers also enable the possibility to rearrange the signal from a focal plane to form a psuedo-slit at the entrance to a spectrograph, optimizing the detector usage and enabling the study of hundreds of thousands of stars or galaxies simultaneously. Multi-core fibers in particular offer several favorable properties with respect to traditional fibers: 1) the separation between single-mode cores is greatly reduced and highly regular with respect to free standing fibers, 2) they offer a monolithic package with multi-fiber capabilities and 3) they operate at the diffraction limit. These properties have enabled the realization of single component photonic lanterns, highly simplified fiber Bragg gratings, and advanced fiber mode scramblers. In addition, the precise grid of cores has enabled the design of efficient single-mode fiber integral field units for spectroscopy. In this paper, we provide an overview of the broad range of applications enabled by multi-core fiber technology in astronomy and outline future areas of development.

Read this paper on arXiv…

N. Jovanovic, R. Harris and N. Cvetojevic
Thu, 6 Feb 20
34/57

Comments: 10 pages, 5 figures, accepted to JSTQE

C-RED 3: A SWIR camera for FSO applications [CL]

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http://arxiv.org/abs/2001.05225


Free space communications (FSO) is interesting for distant applications where high bandwidth is needed while using a fiber is not possible. However these links have to face several issues, and the most important one is the beam scintillation due to the propagation through a turbulent media, the atmosphere. Several mitigation strategies have been developed, but the best way to suppress scintillation is to use adaptive optics, widely used now in astronomy. The main difficulty for FSO is to probe the wavefront fast enough to have a good turbulence correction. This was not possible due to the lack of wavefront sensors working in the SWIR. C-RED 3 is a 640×512 SWIR camera running at 600FPS full frame and has the legacy of all the developments of astronomical infrared fast wavefront sensors on top of specific features for FSO (Low SWaP, Low Cost). We will present the performances of this new camera and demonstrate how it fulfills the needs of FSO adaptive optics.

Read this paper on arXiv…

J. Gach, D. Boutolleau, C. Brun, et. al.
Thu, 16 Jan 20
24/46

Comments: N/A

DEEM, a versatile platform of FRD measurement for highly multiplexed fibre systems in astronomy [IMA]

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http://arxiv.org/abs/1912.11305


We present a new method of DEEM, the direct energy encircling method, for characterising the performance of fibres in most astronomical spectroscopic applications. It’s a versatile platform to measure focal ratio degradation (FRD), throughput, and point spread function (PSF). The principle of DEEM and the relation between the encircled energy (EE) and the spot size were derived and simulated based on the power distribution model (PDM). We analysed the errors of DEEM and pointed out the major error source for better understanding and optimisation. The validation of DEEM has been confirmed by comparing the results with conventional method which shows that DEEM has good robustness with high accuracy in both stable and complex experiment environments. Applications on the integral field unit (IFU) show that the FRD of 50$\mu$m core fibre is substandard for the requirement which requires the output focal ratio to be slower than 4.5. The homogeneity of throughput is acceptable and higher than 85 per cent. The prototype IFU of the first generation helps to find out the imperfections to optimise the new design of the next generation based on the staggered structure with 35$\mu$m core fibres of $N.A.$=0.12, which can improve the FRD performance. The FRD dependence on wavelength and core size is revealed that higher output focal ratio occurs at shorter wavelengths for large core fibres, which is in agreement with the prediction of PDM. But the dependence of the observed data is weaker than the prediction.

Read this paper on arXiv…

Y. Yan, Q. Yan, G. Wang, et. al.
Wed, 25 Dec 19
5/31

Comments: 39 pages, 49 figures, accepted for publication in MNRAS in Feb. 2018

A modified method for determining the FRD and length properties of optical fibres in astronomy [IMA]

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http://arxiv.org/abs/1912.11304


Focal ratio degradation (FRD) is a major contributor to throughput and light loss in a fibre spectroscopic telescope system. We combine the guided mode theory in geometric optics and a well-known model, power distribution model (PDM), to predict and explain the FRD dependence properties. We present a robust method by modifying the energy distribution method (EDM) with \emph{f-intercept} to control the input condition. This method provides a way to determine the proper position of the fibre end on the focal plane to improve energy utilization and FRD performance, which lifts the relative throughput up to 95\% with variation of output focal ratio less than 2\%. And this method can also help to optimize the arrangement of the position of focal-plane plate to enhance the coupling efficiency in a telescope. To investigate length properties, we modified PDM by introducing a new parameter, focal distance \emph{f}, into the original model to make it available for multi-position measurement system. The results show that the modified model is robust and feasible for measuring the key parameter \emph{d}$_0$ to simulate the transmission characteristics. The output focal ratio in the experiment does not follow the prediction trend but shows an interesting phenomenon that the output focal ratio increases at first to the peak, then decreases and remains stable finally with increasing fibre length longer than 15m, which provides a reference for choosing appropriate length of fibre to improve the FRD performance for the design of the fibre system in a telescope.

Read this paper on arXiv…

Y. Yan, G. Wang, W. Sun, et. al.
Wed, 25 Dec 19
28/31

Comments: 21 pages, 40 figures, accepted for publication in MNRAS in Jan. 2017

A modified method for determining the FRD and length properties of optical fibres in astronomy [IMA]

Posted on by

http://arxiv.org/abs/1912.11304


Focal ratio degradation (FRD) is a major contributor to throughput and light loss in a fibre spectroscopic telescope system. We combine the guided mode theory in geometric optics and a well-known model, power distribution model (PDM), to predict and explain the FRD dependence properties. We present a robust method by modifying the energy distribution method (EDM) with \emph{f-intercept} to control the input condition. This method provides a way to determine the proper position of the fibre end on the focal plane to improve energy utilization and FRD performance, which lifts the relative throughput up to 95\% with variation of output focal ratio less than 2\%. And this method can also help to optimize the arrangement of the position of focal-plane plate to enhance the coupling efficiency in a telescope. To investigate length properties, we modified PDM by introducing a new parameter, focal distance \emph{f}, into the original model to make it available for multi-position measurement system. The results show that the modified model is robust and feasible for measuring the key parameter \emph{d}$_0$ to simulate the transmission characteristics. The output focal ratio in the experiment does not follow the prediction trend but shows an interesting phenomenon that the output focal ratio increases at first to the peak, then decreases and remains stable finally with increasing fibre length longer than 15m, which provides a reference for choosing appropriate length of fibre to improve the FRD performance for the design of the fibre system in a telescope.

Read this paper on arXiv…

Y. Yan, G. Wang, W. Sun, et. al.
Wed, 25 Dec 19
18/31

Comments: 21 pages, 40 figures, accepted for publication in MNRAS in Jan. 2017

DEEM, a versatile platform of FRD measurement for highly multiplexed fibre systems in astronomy [IMA]

Posted on by

http://arxiv.org/abs/1912.11305


We present a new method of DEEM, the direct energy encircling method, for characterising the performance of fibres in most astronomical spectroscopic applications. It’s a versatile platform to measure focal ratio degradation (FRD), throughput, and point spread function (PSF). The principle of DEEM and the relation between the encircled energy (EE) and the spot size were derived and simulated based on the power distribution model (PDM). We analysed the errors of DEEM and pointed out the major error source for better understanding and optimisation. The validation of DEEM has been confirmed by comparing the results with conventional method which shows that DEEM has good robustness with high accuracy in both stable and complex experiment environments. Applications on the integral field unit (IFU) show that the FRD of 50$\mu$m core fibre is substandard for the requirement which requires the output focal ratio to be slower than 4.5. The homogeneity of throughput is acceptable and higher than 85 per cent. The prototype IFU of the first generation helps to find out the imperfections to optimise the new design of the next generation based on the staggered structure with 35$\mu$m core fibres of $N.A.$=0.12, which can improve the FRD performance. The FRD dependence on wavelength and core size is revealed that higher output focal ratio occurs at shorter wavelengths for large core fibres, which is in agreement with the prediction of PDM. But the dependence of the observed data is weaker than the prediction.

Read this paper on arXiv…

Y. Yan, Q. Yan, G. Wang, et. al.
Wed, 25 Dec 19
19/31

Comments: 39 pages, 49 figures, accepted for publication in MNRAS in Feb. 2018

A modified method for determining the FRD and length properties of optical fibres in astronomy [IMA]

Posted on by

http://arxiv.org/abs/1912.11304


Focal ratio degradation (FRD) is a major contributor to throughput and light loss in a fibre spectroscopic telescope system. We combine the guided mode theory in geometric optics and a well-known model, power distribution model (PDM), to predict and explain the FRD dependence properties. We present a robust method by modifying the energy distribution method (EDM) with \emph{f-intercept} to control the input condition. This method provides a way to determine the proper position of the fibre end on the focal plane to improve energy utilization and FRD performance, which lifts the relative throughput up to 95\% with variation of output focal ratio less than 2\%. And this method can also help to optimize the arrangement of the position of focal-plane plate to enhance the coupling efficiency in a telescope. To investigate length properties, we modified PDM by introducing a new parameter, focal distance \emph{f}, into the original model to make it available for multi-position measurement system. The results show that the modified model is robust and feasible for measuring the key parameter \emph{d}$_0$ to simulate the transmission characteristics. The output focal ratio in the experiment does not follow the prediction trend but shows an interesting phenomenon that the output focal ratio increases at first to the peak, then decreases and remains stable finally with increasing fibre length longer than 15m, which provides a reference for choosing appropriate length of fibre to improve the FRD performance for the design of the fibre system in a telescope.

Read this paper on arXiv…

Y. Yan, G. Wang, W. Sun, et. al.
Wed, 25 Dec 19
13/31

Comments: 21 pages, 40 figures, accepted for publication in MNRAS in Jan. 2017

DEEM, a versatile platform of FRD measurement for highly multiplexed fibre systems in astronomy [IMA]

Posted on by

http://arxiv.org/abs/1912.11305


We present a new method of DEEM, the direct energy encircling method, for characterising the performance of fibres in most astronomical spectroscopic applications. It’s a versatile platform to measure focal ratio degradation (FRD), throughput, and point spread function (PSF). The principle of DEEM and the relation between the encircled energy (EE) and the spot size were derived and simulated based on the power distribution model (PDM). We analysed the errors of DEEM and pointed out the major error source for better understanding and optimisation. The validation of DEEM has been confirmed by comparing the results with conventional method which shows that DEEM has good robustness with high accuracy in both stable and complex experiment environments. Applications on the integral field unit (IFU) show that the FRD of 50$\mu$m core fibre is substandard for the requirement which requires the output focal ratio to be slower than 4.5. The homogeneity of throughput is acceptable and higher than 85 per cent. The prototype IFU of the first generation helps to find out the imperfections to optimise the new design of the next generation based on the staggered structure with 35$\mu$m core fibres of $N.A.$=0.12, which can improve the FRD performance. The FRD dependence on wavelength and core size is revealed that higher output focal ratio occurs at shorter wavelengths for large core fibres, which is in agreement with the prediction of PDM. But the dependence of the observed data is weaker than the prediction.

Read this paper on arXiv…

Y. Yan, Q. Yan, G. Wang, et. al.
Wed, 25 Dec 19
31/31

Comments: 39 pages, 49 figures, accepted for publication in MNRAS in Feb. 2018

Axion Dark Matter Search with Interferometric Gravitational Wave Detectors [CL]

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http://arxiv.org/abs/1912.09123


Axion dark matter differentiates the phase velocities of the circular-polarized photons. In Phys.Rev.Lett. 123 (2019) no.11, 111301, we have proposed a scheme to measure the phase difference by using a linear optical cavity. If the scheme is applied to the Fabry-P\’erot arm of Advanced LIGO-like (Cosmic-Explorer-like) gravitational wave detector, the potential sensitivity to the axion-photon coupling constant, $g_{\text{a}\gamma}$, reaches $g_{\text{a}\gamma} \simeq 8\times10^{-13} \text{GeV}^{-1}\, (4 \times 10^{-14}\text{GeV}^{-1})$ at the axion mass $m \simeq 3\times 10^{-13}$ eV ($2\times10^{-15}$ eV) and remains at around this sensitivity for 3 orders of magnitude in mass. Furthermore, its sensitivity has a sharp peak reaching $g_{\text{a}\gamma} \simeq 10^{-14} \text{GeV}^{-1}\ (8\times10^{-17} \text{GeV}^{-1})$ at $m = 1.563\times10^{-10}$ eV ($1.563\times10^{-11}$ eV). This sensitivity can be achieved without loosing any sensitivity to gravitational waves.

Read this paper on arXiv…

K. Nagano, I. Obata, T. Fujita, et. al.
Fri, 20 Dec 19
39/63

Comments: 4 pages, 2 figures. Based on our previous paper Phys.Rev.Lett. 123 (2019) no.11, 111301. Proceedings for the 16th International Conference on Topics in Astroparticle and Underground Physics, Toyama, September 9-13, 2019

Phasing a deployable sparse telescope [IMA]

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http://arxiv.org/abs/1912.00709


After launching and deploying a sparse space telescope, fine tuning is required to correct for inaccurate initial placement of its elements. We selected unique shapes and locations of these telescope aperture segments, to be able to distinguish between their diffraction patterns, while at the same time having a proper spatial frequency coverage. Then we improved the combined wave front, without measuring it directly: First we correlated each segment’s focal image with its distinctive template, to correct its tilt. Next we interfered them with the other segments, pair by pair, using their limited coherence, to locate their mutual optical path differences. Finally, we optimized the combined focal image for fine alignment.

Read this paper on arXiv…

E. Ribak and B. Levine
Tue, 3 Dec 19
15/90

Comments: 5 pages, 6 figures

Geometrical and physical optics analysis for mm-wavelength refractor telescopes designed to map the cosmic microwave background [IMA]

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http://arxiv.org/abs/1911.13153


We present a compact two-lens HDPE f/1.6 refractor design that is capable of supporting a 28-deg diffraction-limited field of view at 1-mm wavelengths and contrast it to a similar two-lens refractor using silicon lenses. We compare the optical properties of these two systems as predicted by both geometrical and physical optics. The presented analysis suggests that by relaxing telecentricity requirements, a plastic two-lens refractor system can perform comparably to a similar silicon system across a wide field of view and wavelengths up to 1 mm. We show that for both telescope designs, cold stop spillover changes significantly across the field of view in a way that is somewhat inconsistent with Gaussian beam formalism and simple f-number scaling. We present results that highlight beam ellipticity dependence on both pixel location and pixel aperture size — an effect that is challenging to reproduce in standard geometrical optics. We show that a silicon refractor design suffers from larger cross-polarization compared to the HDPE design. Our results address the limitations of solely relying on geometrical optics to assess relative performance of two optical systems. We discuss implications for future refractor designs.

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J. Gudmundsson
Mon, 2 Dec 19
13/91

Comments: 15 pages, 17 figures

Laser-Driven High-Velocity Microparticle Launcher In Atmosphere And Under Vacuum [IMA]

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http://arxiv.org/abs/1911.11572


This paper presents a novel approach to launch single microparticles at high velocities under low vacuum conditions. In an all-optical table-top method, microparticles with sizes ranging from a few microns to tens of microns are accelerated to supersonic velocities depending on the particle mass. The acceleration is performed through a laser ablation process and the particles are monitored in free space using an ultra-high-speed multi-frame camera with nanosecond time resolution. Under low vacuum, we evaluate the current platform performance by measuring particle velocities for a range of particle types and sizes, and demonstrate blast wave suppression and drag reduction under vacuum. Showing an impact on polyethylene, we demonstrate the capability of the experimental setup to study materials behavior under high-velocity impact. The present method is relevant to space applications, particularly to rendezvous missions where velocities range from tens of m/s to a few km/s, as well as to a wide range of terrestrial applications including impact bonding and impact-induced erosion.

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D. Veysset, Y. Sun, S. Kooi, et. al.
Wed, 27 Nov 19
50/59

Comments: 13 pages, 9 figures, keywords: high-velocity launcher; microparticle impact; high-speed imaging; low vacuum; laser-based method; table-top system; ejecta; drag; blast; ballistic limit

Image formation process with the solar gravitational lens [CL]

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http://arxiv.org/abs/1911.03260


We study image formation with the solar gravitational lens (SGL). We consider a point source that is positioned at a large but finite distance from the Sun. We assume that an optical telescope is positioned in the image plane, in the focal region of the SGL. We model the telescope as a convex lens and evaluate the intensity distribution produced by the electromagnetic field that forms the image in the focal plane of the convex lens. We first investigate the case when the telescope is located on the optical axis of the SGL or in its immediate vicinity. This is the region of strong interference where the SGL forms an image of a distant source, which is our primary interest. We derive analytic expressions that describe the progression of the image from an Einstein ring corresponding to an on-axis telescope position, to the case of two bright spots when the telescope is positioned some distance away from the optical axis. At greater distances from the optical axis, in the region of weak interference and that of geometric optics, we recover expressions that are familiar from models of gravitational microlensing, but developed here using a wave-optical treatment. We discuss applications of the results for imaging and spectroscopy of exoplanets with the SGL.

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S. Turyshev and V. Toth
Mon, 11 Nov 19
13/105

Comments: 13 pages, 6 figures

Theoretical Limits of Star Sensor Accuracy [IMA]

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http://arxiv.org/abs/1910.00558


To achieve mass, power, and cost reduction, there is a trend to reduce the volume of many instruments aboard spacecraft, especially for small spacecraft (cubesats or nanosats) with very limited mass, volume and power budgets. With the current trend of miniaturizing spacecraft instruments one could naturally ask if is there a physical limit to this process for star sensors. This paper shows that there is a fundamental limit on star sensor accuracy, which depends on stellar distribution, star sensor dimensions and exposure time. An estimate of such limit is given for our location in the galaxy.

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M. Fialho and D. Mortari
Wed, 2 Oct 19
52/52

Comments: Thoroughly revised and extended version of a chapter of a doctorate thesis published in 2017. Being consireded for publication in a peer reviewed journal

Quantum noise reduction techniques in KAGRA [CL]

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http://arxiv.org/abs/1909.12033


KAGRA is the first large-scale gravitational-wave detector with cryogenic test masses. Its target sensitivity is limited mostly by quantum noise in the observation frequency band owing to the remarkable reduction of thermal noise at cryogenic temperatures. It is thus essential to reduce quantum noise, and KAGRA is designed to implement two quantum noise reduction techniques. KAGRA has already started considering an upgrade plan, in which a few more new quantum noise reduction techniques will be incorporated. In this article, we report the currently implemented quantum noise reduction techniques for KAGRA and those that will be implemented in the near future.

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K. Somiya
Fri, 27 Sep 19
23/64

Comments: 10 pages, 12 figures

LISA Telescope: Phase noise due to pointing jitter [IMA]

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http://arxiv.org/abs/1909.08566


In a space based gravitational wave antenna like LISA, involving long light paths linking distant emitter/receiver spacecrafts, signal detection amounts to measuring the light-distance variationsthrough a phase change at the receiver. This is why spurious phase fluctuations due to various mechanical/thermal effects must be carefully studied. We consider here a possible pointing jitter in the light beam sent from the emitter. We show how the resulting phase noise depends on the quality of the wavefront due to the incident beam impinging on the telescope and due to the imperfections of the telescope itself. Namely, we numerically assess the crossed influence of various defects (aberrations and astigmatisms), inherent to a real telescope with pointing fluctuations.

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J. Vinet, N. Christensen, N. Dinu-Jaeger, et. al.
Thu, 19 Sep 19
5/71

Comments: N/A

New concepts for calibrating non-common path aberrations in adaptive optics and coronagraph systems [IMA]

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http://arxiv.org/abs/1909.05224


Non Common Path Aberrations (NCPA) are often considered as a critical issue in Adaptive Optics (AO) systems, since they introduce bias errors between real wavefronts propagating to the science detectors and those measured by the Wavefront Sensor (WFS). This is especially true when the AO system is coupled to a coronagraph instrument intended for the discovery and characterization of extra-solar planets, because useful planet signals could be mistaken with residual speckles generated by NCPA. Therefore, compensating for those errors is of prime importance and is already the scope of a few theoretical studies and experimental validations on-sky. This communication presents the conceptual optical design of a pseudo-interferometer arrangement suitable to accurate NCPA calibration, based on two WFS cooperating in real-time. The concept is applicable to both classical imaging and spectroscopy assisted by AO, and to high-contrast coronagraphs searching for habitable extra-solar planets. Practical aspects are discussed, such as the choice of WFS and coronagraph types, or specific requirements on additional hardware components, e.g. dichroic beamsplitters

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F. Henault
Thu, 12 Sep 19
29/84

Comments: To appear in Proc. SPIE vol. 11117

Photometric imaging with the solar gravitational lens [IMA]

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http://arxiv.org/abs/1909.03116


We discuss the optical properties of the solar gravitational lens (SGL). We estimate the power of the EM field received by an imaging telescope. Studying the behavior of the EM field at the photometric detector, we develop expressions that describe the received power from a point source as well as from an extended resolved source. We model the source as a disk with uniform surface brightness and study the contribution of blur to a particular image pixel. To describe this process, we develop expressions describing the power received from the directly imaged region of the exoplanet, from the rest of the exoplanet and also the power for off-image pointing. We study the SGL’s amplification and its angular resolution in the case of observing an extended source with a modest size telescope. The results can be applied to direct imaging of exoplanets using the SGL.

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S. Turyshev and V. Toth
Tue, 10 Sep 19
29/80

Comments: 11 pages, 4 figures

Photon vortex generation in quantum level by high-order harmonic synchrotron radiations from spiral moving electrons in magnetic fields [HEAP]

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http://arxiv.org/abs/1908.11545


We explore synchrotron radiations from a spiral moving electron under a uniform magnetic field along z-axis using Landau quantization. We found that this process generates a photon vortex with Bessel wave-function as the eigen-state of the z-component of the total angular momentum and the photon vortices with large angular momenta are generated by high-order harmonic radiations. We also calculate the decay widths and the energy spectra. Under strong magnetic fields as 10^13 G, which are found in astrophysical objects such as magnetars, photon vortices are predominantly generated.

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T. Maruyama, T. Hayakawa, T. Kajino, et. al.
Mon, 2 Sep 19
6/66

Comments: 12 pages, 4 figures

Photon vortex generation in quantum level by high-order harmonic synchrotron radiations from spiral moving electrons in magnetic fields [HEAP]

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http://arxiv.org/abs/1908.11545


We explore synchrotron radiations from a spiral moving electron under a uniform magnetic field along z-axis using Landau quantization. We found that this process generates a photon vortex with Bessel wave-function as the eigen-state of the z-component of the total angular momentum and the photon vortices with large angular momenta are generated by high-order harmonic radiations. We also calculate the decay widths and the energy spectra. Under strong magnetic fields as 10^13 G, which are found in astrophysical objects such as magnetars, photon vortices are predominantly generated.

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T. Maruyama, T. Hayakawa, T. Kajino, et. al.
Mon, 2 Sep 19
41/66

Comments: 12 pages, 4 figures

Vortex fiber nulling for exoplanet observations: conceptual design, theoretical performance, and initial scientific yield predictions [IMA]

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http://arxiv.org/abs/1908.09780


Vortex fiber nulling (VFN) is a method that may enable the detection and characterization of exoplanets at small angular separations (0.5-2 $\lambda/D$) with ground- and space-based telescopes. Since the field of view is within the inner working angle of most coronagraphs, nulling accesses non-transiting planets that are otherwise too close to their star for spectral characterization by other means, thereby significantly increasing the number of known exoplanets available for direct spectroscopy in the near-infrared. Furthermore, VFN targets planets on closer-in orbits which tend to have more favorable planet-to-star flux ratios in reflected light. Here, we present the theory and applications of VFN, show that the optical performance is approximately equivalent for a variety of implementations and aperture shapes, and discuss the trade-offs between throughput and engineering requirements using numerical simulations. We compare vector and scalar approaches and, finally, show that beam shaping optics may be used to significantly improve the throughput for planet light. Based on theoretical performance, we estimate the number of known planets and theoretical exoEarths accessible with a VFN instrument linked to a high-resolution spectrograph on the future Thirty Meter Telescope.

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G. Ruane, D. Echeverri, N. Jovanovic, et. al.
Tue, 27 Aug 19
17/85

Comments: To appear in Proceedings of the SPIE, Techniques and Instrumentation for Detection of Exoplanets IX, Vol. 11117

Scalar vortex coronagraph mask design and predicted performance [IMA]

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http://arxiv.org/abs/1908.09786


Vortex coronagraphs are an attractive solution for imaging exoplanets with future space telescopes due to their relatively high throughput, large spectral bandwidth, and low sensitivity to low-order aberrations compared to other coronagraphs with similar inner working angles. Most of the vortex coronagraph mask development for space applications has focused on generating a polychromatic, vectorial, optical vortex using multiple layers of liquid crystal polymers. While this approach has been the most successful thus far, current fabrication processes achieve retardance errors of 0.1-1.0$^\circ$, which causes a nonnegligible fraction of the starlight to leak through the coronagraph. Circular polarizers are typically used to reject the stellar leakage reducing the throughput by a factor of two. Vector vortex masks also complicate wavefront control because they imprint conjugated phase ramps on the orthogonal circular polarization components, which may need to be split in order to properly sense and suppress the starlight. Scalar vortex masks can potentially circumvent these limitations by applying the same phase shift to all incident light regardless of the polarization state and thus have the potential to significantly improve the performance of vortex coronagraphs. We present scalar vortex coronagraph designs that make use of focal plane masks with multiple layers of dielectrics that (a) produce phase patterns that are relatively friendly to standard manufacturing processes and (b) achieve sufficient broadband starlight suppression, in theory, for imaging Earth-like planets with future space telescopes.

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G. Ruane, D. Mawet, A. Riggs, et. al.
Tue, 27 Aug 19
29/85

Comments: To appear in Proceedings of the SPIE, Techniques and Instrumentation for Detection of Exoplanets IX, Vol. 11117

Light diffusion in birefringent polycrystals and the IceCube ice anisotropy [HEAP]

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http://arxiv.org/abs/1908.07608


The IceCube Neutrino Observatory instruments about 1 km^3 of deep, glacial ice at the geographic South Pole with 5160 photomultipliers to detect Cherenkov light from charged relativistic particles. The experiment pursues a wide range of scientific questions ranging from particle physics such as neutrino oscillations to high-energy neutrino astronomy. Most of these efforts rely heavily on an ever more precise understanding of the optical properties of the instrumented ice. An unexpected light propagation effect, observed by the experiment, is an anisotropic attenuation, which is aligned with the local flow of the ice. The exact cause is still under investigation. In this contribution, the micro-structure of ice as a birefringent polycrystal is explored as the cause for this anisotropy.

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D. Chirkin and M. Rongen
Thu, 22 Aug 19
21/70

Comments: Presented at the 36th International Cosmic Ray Conference (ICRC 2019). See arXiv:1907.11699 for all IceCube contributions

Visible blue-to-red 10 GHz frequency comb via on-chip triple-sum frequency generation [CL]

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http://arxiv.org/abs/1908.05152


A broadband visible blue-to-red, 10 GHz repetition rate frequency comb is generated by combined spectral broadening and triple-sum frequency generation in an on-chip silicon nitride waveguide. Ultra-short pulses of 150 pJ pulse energy, generated via electro-optic modulation of a 1560 nm continuous-wave laser, are coupled to a silicon nitride waveguide giving rise to a broadband near-infrared supercontinuum. Modal phase matching inside the waveguide allows direct triple-sum frequency transfer of the near-infrared supercontinuum into the visible wavelength range covering more than 250 THz from below 400 nm to above 600 nm wavelength. This scheme directly links the mature optical telecommunication band technology to the visible wavelength band and can find application in astronomical spectrograph calibration as well as referencing of continuous-wave lasers.

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E. Obrzud, V. Brasch, T. Voumard, et. al.
Thu, 15 Aug 19
26/69

Comments: N/A

Imaging extended sources with the solar gravitational lens [CL]

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http://arxiv.org/abs/1908.01948


We investigate the optical properties of the solar gravitational lens (SGL) with respect to an extended source located at a large but finite distance from the Sun. The static, spherically symmetric gravitational field of the Sun is modeled within the first post-Newtonian approximation of the general theory of relativity. We consider the propagation of monochromatic electromagnetic (EM) waves near the Sun. We develop, based on a Mie theory, a vector theory of diffraction that accounts for the refractive properties of the solar gravitational field. The finite distance to a point source can be accounted for using a rotation of the coordinate system to align its polar axis with the axis directed from the point source to the center of the Sun, which we call the optical axis. We determine the EM field and study the key optical properties of the SGL in all four regions formed behind the Sun by an EM wave diffracted by the solar gravity field: the shadow, geometric optics, and weak and strong interference regions. Extended sources can then be represented as collections of point sources. We present the power density of the signal received by a telescope in the image plane. Our discussion concludes with considering the implications for imaging with the SGL.

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S. Turyshev and V. Toth
Wed, 7 Aug 19
2/61

Comments: 25 pages, 11 figures

Optimal birefringence distributions for star test polarimetry [IMA]

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http://arxiv.org/abs/1908.02142


Star test polarimetry is an imaging polarimetry technique in which an element with spatially-varying birefringence is placed in the pupil plane to encode polarization information into the point-spread function (PSF) of an imaging system. In this work, a variational calculation is performed to find the optimal birefringence distribution that effectively encodes polarization information while producing the smallest possible PSF, thus maximizing the resolution for imaging polarimetry. This optimal solution is found to be nearly equivalent to the birefringence distribution that results from a glass window being subjected to three uniformly spaced stress points at its edges, which has been used in previous star test polarimetry setups.

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A. Vella and M. Alonso
Wed, 7 Aug 19
58/61

Comments: 15 pages, 7 figures

Testing the near-infrared optical assembly of the space telescope Euclid [IMA]

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http://arxiv.org/abs/1907.12867


Euclid is a space telescope currently developed in the framework of the ESA Cosmic Vision 2015-2025 Program. It addresses fundamental cosmological questions related to dark matter and dark energy. The lens system of one of the two scientific key instruments [a combined near-infrared spectrometer and photometer (NISP)] was designed, built-up and tested at the Max Planck Institute for Extraterrestrial Physics (MPE). We present the final imaging quality of this diffraction-limited optical assembly with two complementary approaches, namely a point-spread function and a Shack-Hartmann sensor-based wavefront measurement. The tests are performed under space operating conditions within a cryostat. The large field of view of Euclid’s wide-angle objective is sampled with a pivot arm, carrying a measurement telescope and the sensors. A sequence of highly accurate movements to several field positions is carried out by a large computer controlled hexapod. Both measurement approaches are compared among one another and with the corresponding simulations. They demonstrate in good agreement a solely diffraction limited optical performance over the entire field of view.

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C. Bodendorf, N. Geis, F. Grupp, et. al.
Wed, 31 Jul 19
59/65

Comments: Proc. SPIE 11116-31, Optics + Photonics (2019)

VUV test of a new polarimeter for spectropolarimetric measurements on board space missions [IMA]

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http://arxiv.org/abs/1907.11549


High-resolution spectropolarimetry is a useful astronomical technique, in particular to study stellar magnetic fields. It has been extensively used in the past but mostly in the visible range. Space missions equipped with high-resolution spectropolarimeters working in the ultra-violet (UV) are now being studied. We propose a concept of a polarimeter working with temporal modulation and allowing to perform Stokes IQUV measurements over the full UV + Visible range. The purpose of this article is to describe the polarimeter concept, two prototypes and the bench developed to perform on ground testing to establish the performances of this new polarimeter.

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M. Gal, M. Pertenais, A. Ariste, et. al.
Mon, 29 Jul 19
30/52

Comments: N/A

Precise and robust optical beam steering for space optical instrumentation [IMA]

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http://arxiv.org/abs/1907.10425


This approach permits much finer adjustments of the beam direction and position when compared to other beam steering techniques of the same mechanical precision. This results in a much increased precision, accuracy and mechanical stability. A precision of better than 5 {\mu}rad and 5 {\mu}m is demonstrated, resulting in a resolution in coupling efficiency of 0.1%. Together with the added flexibility of an additional beam steering element, this allows a great simplification of the design of the fiber coupler, which normally is the most complex and sensitive element on an optical fiber breadboard. We demonstrate a fiber to fiber coupling efficiency of more than 89.8%, with a stability of 0.2% in a stable temperature environment and 2% fluctuations over a temperature range from 10C to 40C over a measurement time of 14 hours. Furthermore, we do not observe any non-reversible change in the coupling efficiency after performing a series of tests over large temperature variations. This technique finds direct application in proposed missions for quantum experiments in space, e.g.where laser beams are used to cool and manipulate atomic clouds.

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G. Drougakis, K. Mavrakis, S. Pandey, et. al.
Thu, 25 Jul 19
19/72

Comments: 12 pages,6 Figures , 17 References

Coronagraphic phase diversity through residual turbulence: performance study and experimental validation [IMA]

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http://arxiv.org/abs/1907.07038


Quasi-static aberrations in coronagraphic systems are the ultimate limitation to the capabilities of exoplanet imagers both ground-based and space-based. These aberrations – which can be due to various causes such as optics alignment or moving optical parts during the observing sequence – create light residuals called speckles in the focal plane that might be mistaken for a planets. For ground-based instruments, the presence of residual turbulent wavefront errors due to partial adaptive optics correction causes an additional difficulty to the challenge of measuring aberrations in the presence of a coronagraph. In this paper, we present an extension of COFFEE, the coronagraphic phase diversity, to the estimation of quasi-static aberrations in the presence of adaptive optics-corrected residual turbulence. We perform realistic numerical simulations to assess the performance that can be expected on an instrument of the current generation. We perform the first experimental validation in the laboratory which demonstrates that quasistatic aberrations can be corrected during the observations by means of coronagraphic phase diversity.

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O. Herscovici-Schiller, J. Sauvage, L. Mugnier, et. al.
Wed, 17 Jul 19
49/75

Comments: This is a pre-copyedited, author-produced PDF of an article accepted for publication in the Monthly Notices of the Royal Astronomical Society following peer review

Astro2020: Astrophotonics White Paper [IMA]

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http://arxiv.org/abs/1907.05904


Astrophotonics is the application of versatile photonic technologies to channel, manipulate, and disperse guided light from one or more telescopes to achieve scientific objectives in astronomy in an efficient and cost-effective way. The developments and demands from the telecommunication industry have driven a major boost in photonic technology and vice versa in the last 40 years. The photonic platform of guided light in fibers and waveguides has opened the doors to next-generation instrumentation for both ground- and space-based telescopes in optical and near/mid-IR bands, particularly for the upcoming extremely large telescopes (ELTs). The large telescopes are pushing the limits of adaptive optics to reach close to a near-diffraction-limited performance. The photonic devices are ideally suited for capturing this AO-corrected light and enabling new and exciting science such as characterizing exoplanet atmospheres. The purpose of this white paper is to summarize the current landscape of astrophotonic devices and their scientific impact, highlight the key issues, and outline specific technological and organizational approaches to address these issues in the coming decade and thereby enable new discoveries as we embark on the era of extremely large telescopes.

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P. Gatkine, S. Veilleux, J. Mather, et. al.
Tue, 16 Jul 19
84/89

Comments: Astro2020 APC white paper, Submitted to the National Academy of Sciences for Astro2020 Decadal Survey, 9 pages (excluding references) and 3 figures

An optical lock-in camera for advanced gravitational wave interferometers [IMA]

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http://arxiv.org/abs/1907.05224


Knowledge of the intensity and phase profiles of spectral components in a coherent optical field is critical for a wide range of high-precision optical applications. One of these is interferometric gravitational wave detectors, which rely on such fields for precise control of the experiment. Here we demonstrate a new device, an \textit{optical lock-in camera}, and highlight how they can be used within a gravitational wave interferometer to directly image fields at a higher spatial and temporal resolution than previously possible. This improvement is achieved using a Pockels cell as a fast optical switch which transforms each pixel on a sCMOS array into an optical lock-in amplifier. We demonstrate that the optical lock-in camera can image fields with 2~Mpx resolution at 10~Hz with a sensitivity of -62~dBc when averaged over 2s.

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H. Cao, D. Brown, P. Veitch, et. al.
Fri, 12 Jul 19
9/67

Comments: N/A

On observational cosmology with radiometers based on novel whispering-gallery mode resonators technology [IMA]

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http://arxiv.org/abs/1907.04145


The fundamentals of the whispering gallery mode (WGM) resonators are well established in the literature, with several successful proof-of-concept experiments. One remarkable benefit of this technology is the room-temperature operation. This characteristic could be used to build a new generation of radiometers that do not need to be cooled down to cryogenic temperatures to reach high sensitivities. In this article, a study of the viability of technological transfer is undertaken, beginning with a brief review of the theoretical background that will be applied and leading to a proposal for a novel spectro-polarimeter design. Simulations for a radiometer based on WGM resonance are analyzed and compared with a state-of-the-art heterodyne receivers. The results are then discussed

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J. Miguel-Hernández and R. Hoyland
Wed, 10 Jul 19
46/53

Comments: 13pages, 4 figs

Moving black holes: energy extraction, absorption cross-section and the ring of fire [CL]

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http://arxiv.org/abs/1906.10140


We consider the interaction between a plane wave and a (counter-moving) black hole. We show that energy is transferred from the black hole to the wave, giving rise to a negative absorption cross-section. Moving black holes absorb radiation and deposit energy in external radiation. Due to this effect, a black hole hole of mass M moving at relativistic speeds in a cold medium will appear to be surrounded by a bright “ring” of diameter 3\sqrt{3}GM/c^2 and thickness GM/c^2.

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V. Cardoso and R. Vicente
Wed, 26 Jun 19
33/68

Comments: 6 pages, 3 figures

Novel signatures of dark matter in laser-interferometric gravitational-wave detectors [IMA]

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http://arxiv.org/abs/1906.06193


Dark matter may induce apparent temporal variations in the physical “constants”, including the electromagnetic fine-structure constant and fermion masses. In particular, a coherently oscillating classical dark-matter field may induce apparent oscillations of physical constants in time, while the passage of macroscopic dark-matter objects (such as topological defects) may induce apparent transient variations in the physical constants. In this paper, we point out several new signatures of the aforementioned types of dark matter that can arise due to the geometric asymmetry created by the beam-splitter in a two-arm laser interferometer. These new signatures include dark-matter-induced time-varying size changes of a freely-suspended beam-splitter and associated time-varying shifts of the main reflecting surface of the beam-splitter that splits and recombines the laser beam, as well as time-varying refractive-index changes in the freely-suspended beam-splitter and time-varying size changes of freely-suspended arm mirrors. We demonstrate that existing ground-based experiments already have sufficient sensitivity to probe extensive regions of unconstrained parameter space in models involving oscillating scalar dark-matter fields and domain walls composed of scalar fields. In the case of oscillating dark-matter fields, Michelson interferometers $-$ in particular, the GEO600 detector $-$ are especially sensitive. The sensitivity of Fabry-Perot-Michelson interferometers, including LIGO, VIRGO and KAGRA, to oscillating dark-matter fields can be significantly increased by making the thicknesses of the freely-suspended Fabry-Perot arm mirrors different in the two arms. We also discuss how small-scale Michelson interferometers could be used to perform resonant narrowband searches for oscillating dark-matter fields with enhanced sensitivity to dark matter.

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H. Grote and Y. Stadnik
Mon, 17 Jun 19
30/53

Comments: 16 pages, 4 figures

Standardized spectral and radiometric calibration of consumer cameras [CL]

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http://arxiv.org/abs/1906.04155


Consumer cameras, particularly onboard smartphones and UAVs, are now commonly used as scientific instruments. However, their data processing pipelines are not optimized for quantitative radiometry and their calibration is more complex than that of scientific cameras. The lack of a standardized calibration methodology limits the interoperability between devices and, in the ever-changing market, ultimately the lifespan of projects using them. We present a standardized methodology and database (SPECTACLE) for spectral and radiometric calibrations of consumer cameras, including linearity, bias variations, read-out noise, dark current, ISO speed and gain, flat-field, and RGB spectral response. This includes golden standard ground-truth methods and do-it-yourself methods suitable for non-experts. Applying this methodology to seven popular cameras, we found high linearity in RAW but not JPEG data, inter-pixel gain variations >400% correlated with large-scale bias and read-out noise patterns, non-trivial ISO speed normalization functions, flat-field correction factors varying by up to 2.79 over the field of view, and both similarities and differences in spectral response. Moreover, these results differed wildly between camera models, highlighting the importance of standardization and a centralized database.

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O. Burggraaff, N. Schmidt, J. Zamorano, et. al.
Tue, 11 Jun 19
8/60

Comments: 27 pages, 11 figures, accepted for publication in Optics Express