http://arxiv.org/abs/1802.06727
In exoplanet interferometry a null of 40~dB is a large step in achieving the ability to directly image an Earth-like planet that is in the habitable zone around a star like our own. Based on the standard procedure at the Australian National University we have created a nulling interferometer that has achieved a 25~dB null in the astronomical L~band under laboratory conditions. The device has been constructed on a 2-dimensional platform of chalcogenide glass: a three layered structure of $Ge_{11.5}As_{24}S_{64.5}$ undercladding, 2~\si{\um} of $Ge_{11.5}As_{24}Se_{64.5}$ core and an angled deposition of $Ge_{11.5}As_{24}S_{64.5}$ as a complete overcladding. Matching simulation from Rsoft and individual results of the MMIs the expected null should produce a null of 40~dB over a bandwidth of 400~nm but due to limitations in mask design and light contamination only a 25~dB extinction can be reliably achieved.
H. Goldsmith, M. Ireland and S. Madden
Tue, 20 Feb 18
17/54
Comments: Only a first draft. Will upload later versions as we go