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Proceedings Paper • Open Access

Grism and immersion grating for space telescope
Author(s): Noboru Ebizuka; Kiko Oka; Akiko Yamada; Mami Ishikawa; Masako Kashiwagi; Kashiko Kodate; Yasuhiro Hirahara; Shuji Sato; Koji S. Kawabata; Moriaki Wakaki; Shin-ya Morita; Tomoyuki Simizu; Shaohui Yin; Hitoshi Omori; Masanori Iye

Paper Abstract

The grism is a versatile dispersion element for an astronomical instrument ranging from ultraviolet to infrared. Major benefit of using a grism in a space application, instead of a reflection grating, is the size reduction of optical system because collimator and following optical elements could locate near by the grism. The surface relief (SR) grism is consisted a transmission grating and a prism, vertex angle of which is adjusted to redirect the diffracted beam straight along the direct vision direction at a specific order and wavelength. The volume phase holographic (VPH) grism consists a thick VPH grating sandwiched between two prisms, as specific order and wavelength is aligned the direct vision direction. The VPH grating inheres ideal diffraction efficiency on a higher dispersion application. On the other hand, the SR grating could achieve high diffraction efficiency on a lower dispersion application. Five grisms among eleven for the Faint Object Camera And Spectrograph (FOCAS) of the 8.2m Subaru Telescope with the resolving power from 250 to 3,000 are SR grisms fabricated by a replication method. Six additional grisms of FOCAS with the resolving power from 3,000 to 7,000 are VPH grisms. We propose “Quasi-Bragg grism” for a high dispersion spectroscopy with wide wavelength range.

The germanium immersion grating for instance could reduce 1/64 as the total volume of a spectrograph with a conventional reflection grating since refractive index of germanium is over 4.0 from 1.6 to 20 μm. The prototype immersion gratings for the mid-InfraRed High dispersion Spectrograph (IRHS) are successfully fabricated by a nano-precision machine and grinding cup of cast iron with electrolytic dressing method.

Paper Details

Date Published: 21 November 2017
PDF: 8 pages
Proc. SPIE 10568, International Conference on Space Optics — ICSO 2004, 105681M (21 November 2017); doi: 10.1117/12.2308014
Show Author Affiliations
Noboru Ebizuka, RIKEN (Japan)
National Astronomical Observatory (Japan)
Kiko Oka, RIKEN (Japan)
Japan Women's Univ. (Japan)
Akiko Yamada, Japan Women's Univ. (Japan)
Mami Ishikawa, Japan Women's Univ. (Japan)
Masako Kashiwagi, Japan Women's Univ. (Japan)
Kashiko Kodate, Japan Women's Univ. (Japan)
Yasuhiro Hirahara, Nagoya Univ. (Japan)
Shuji Sato, Nagoya Univ. (Japan)
Koji S. Kawabata, Hiroshima Univ. (Japan)
Moriaki Wakaki, Tokai Univ. (Japan)
Shin-ya Morita, RIKEN (Japan)
Tomoyuki Simizu, RIKEN (Japan)
Shaohui Yin, RIKEN (China)
Hitoshi Omori, RIKEN (Japan)
Masanori Iye, National Astronomical Observatory of Japan (Japan)

Published in SPIE Proceedings Vol. 10568:
International Conference on Space Optics — ICSO 2004
Josiane Costeraste; Errico Armandillo, Editor(s)

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