8 August 2016 Cryogenic performance of high-efficiency germanium immersion grating
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Abstract
Immersion gratings will play important roles for infrared astronomy in the next generation. We have been developing immersion gratings with a variety of kinds of materials and have succeeded in fabricating a high-efficiency germanium (Ge) immersion grating with both a reflection coating on the grating surface and an AR coating on the entrance surface. The grating will be installed in a K-, L-, and M-bands (2-5μm) high-resolution (R=80,000) spectrograph, VINROUGE, which is a prototype for the TMT MIR instrument. In this paper, we report the preliminary results on the evaluation of the Ge immersion grating. We confirmed that the peak absolute diffraction efficiency was in the range of 70-80%, which was as expected from the design, at both room and cryogenic temperatures.
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Yuki Sarugaku, Yuji Ikeda, Sayumi Kaji, Naoto Kobayashi, Takashi Sukegawa, Takayuki Arasaki, Sohei Kondo, Kenshi Nakanishi, Chikako Yasui, Hideyo Kawakita, "Cryogenic performance of high-efficiency germanium immersion grating", Proc. SPIE 9906, Ground-based and Airborne Telescopes VI, 990637 (8 August 2016); doi: 10.1117/12.2233626; https://doi.org/10.1117/12.2233626
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