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Optical Engineering

Zinc sulfide and zinc selenide immersion gratings for astronomical high-resolution spectroscopy: evaluation of internal attenuation of bulk materials in the short near-infrared region
Author(s): Yuji Ikeda; Naoto Kobayashi; Sohei Kondo; Chikako Yasui; Paul J. Kuzmenko; Hitoshi Tokoro; Hiroshi Terada
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Paper Abstract

We measure the internal attenuation of bulk crystals of chemical vapor deposition zinc selenide (CVD-ZnS), chemical vapor deposition zinc sulfide (CVD-ZnSe), Si, and GaAs in the short near-infrared (sNIR) region to evaluate the possibility of astronomical immersion gratings with those high refractive index materials. We confirm that multispectral grade CVD-ZnS and CVD-ZnSe are best suited for the immersion gratings, with the smallest internal attenuation of αatt=0.01 to 0.03 cm-1 among the major candidates. The measured attenuation is roughly in proportion to λ-2, suggesting it is dominated by bulk scattering due to the polycrystalline grains rather than by absorption. The total transmittance in the immersion grating is estimated to be at least >80%, even for the spectral resolution of R=300,000. Two potential problems, the scattered light by the bulk material and the degradation of the spectral resolution due to the gradient illumination in the diffracted beam, are investigated and found to be negligible for usual astronomical applications. Since the remaining problem, the difficulty of cutting grooves on CVD-ZnS and CVD-ZnSe, has recently been overcome by the nanoprecision fly-cutting technique, ZnS and ZnSe immersion gratings for astronomy can be technically realized.

Paper Details

Date Published: 1 August 2009
PDF: 9 pages
Opt. Eng. 48(8) 084001 doi: 10.1117/1.3206734
Published in: Optical Engineering Volume 48, Issue 8
Show Author Affiliations
Yuji Ikeda, Photocoding (Japan)
Naoto Kobayashi, The Univ. of Tokyo (Japan)
Sohei Kondo, The Univ. of Tokyo (Japan)
Chikako Yasui, The Univ. of Tokyo (Japan)
Paul J. Kuzmenko, Lawrence Livermore National Lab. (United States)
Hitoshi Tokoro, Nano-Optics Research Institute (Japan)
Hiroshi Terada, National Astronomical Observatory of Japan/Subaru Telescope (United States)


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