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Proceedings Paper

Diamond-machined ZnSe immersion grating for NIR high-resolution spectroscopy
Author(s): Yuji Ikeda; Naoto Kobayashi; Paul J. Kuzmenko; Steve L. Little; Chikako Yasui; Sohei Kondo; Atsushi Minami; Kentaro Motohara
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Paper Abstract

ZnSe immersion gratings (n ~ 2.45) provide the possibility of high-resolution spectroscopy for the near-infrared (NIR) region. Since ZnSe has a lower internal attenuation than other NIR materials, it is most suitable for immersion grating, particularly in short NIR region (0.8 - 1.4 μm). We are developing an extremely high-resolution spectrograph with λ/Δλ = 100, 000, WINERED, customized for the short NIR region, using ZnSe (or ZnS) immersion grating. However, it had been very difficult to make fine grooves on ZnSe substrate with a small pitch of less than 50 μm because ZnSe is a soft/brittle material. We have overcome this problem and successfully machined sharp grooves with fine pitch on ZnSe substrates by nano precision fly-cutting technique at LLNL. The optical testing of the sample grating with HeNe laser shows an excellent performance: the relative efficiency more than 87.4 % at 0.633 μm for a classical grating configuration. The diffraction efficiency when used as an immersion grating is estimated to be more than 65 % at 1μm. Following this progress, we are about to start machining a grating on a large ZnSe prism with an entrance aperture of 23mm × 50mm and the blaze angle of 70°.

Paper Details

Date Published: 25 July 2008
PDF: 9 pages
Proc. SPIE 7018, Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation, 70184R (25 July 2008); doi: 10.1117/12.788113
Show Author Affiliations
Yuji Ikeda, Photocoding (Japan)
Naoto Kobayashi, Institute of Astronomy, Univ. of Tokyo (Japan)
Paul J. Kuzmenko, Lawrence Livermore National Lab. (United States)
Steve L. Little, Lawrence Livermore National Lab. (United States)
Chikako Yasui, Institute of Astronomy, Univ. of Tokyo (Japan)
Sohei Kondo, Institute of Astronomy, Univ. of Tokyo (Japan)
Atsushi Minami, Institute of Astronomy, Univ. of Tokyo (Japan)
Kentaro Motohara, Institute of Astronomy, Univ. of Tokyo (Japan)


Published in SPIE Proceedings Vol. 7018:
Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation
Eli Atad-Ettedgui; Dietrich Lemke, Editor(s)

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