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Proceedings Paper

Fiber mode scrambler experiments for the Subaru Infrared Doppler Instrument (IRD)
Author(s): M. Ishizuka; T. Kotani; J. Nishikawa; M. Tamura; T. Kurokawa; T. Mori; T. Kokubo
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Paper Abstract

We report the results of fiber mode scrambler experiments for the Infra-Red Doppler instrument (IRD) on the Subaru 8.2-m telescope. IRD is a near infrared, high-precision radial velocity (RV) instrument to search for exoplanets around M dwarfs. It is a fiber-fed, high-resolution (R~70000) spectrograph with an Echelle grating and a state-of-the art laser frequency comb. Expected precision of RV measurements is 1m/s. To achieve 1m/s accuracy, we must reduce modal noise, which is intensity instability of light at the end of multimode fibers. Modal noise is caused by interference of finite number of propagating modes of light. This noise can cause false RV signals, which reduce the accuracy of RV measurements. A mode scrambler is a mechanism to reduce modal noise. However, the best mode scrambler system at near infrared wavelengths is still unknown. Thus, we tested many kinds of mode scramblers, various length fibers, a double scrambler, and octagonal fibers, as static scramblers. We also tested dynamic scramblers, which make output uniform by moving optical fibers dynamically. We report the effects of these mode scramblers.

Paper Details

Date Published: 12 August 2016
PDF: 8 pages
Proc. SPIE 9912, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II, 99121Q (12 August 2016); doi: 10.1117/12.2232166
Show Author Affiliations
M. Ishizuka, The Univ. of Tokyo (Japan)
T. Kotani, National Astronomical Observatory of Japan (Japan)
Astrobiology Ctr. (Japan)
J. Nishikawa, National Astronomical Observatory of Japan (Japan)
Astrobiology Ctr. (Japan)
M. Tamura, The Univ. of Tokyo (Japan)
National Astronomical Observatory of Japan (Japan)
Astrobiology Ctr. (Japan)
T. Kurokawa, Tokyo Univ. of Agriculture and Technology (Japan)
T. Mori, Tokyo Univ. of Agriculture and Technology (Japan)
T. Kokubo, Tokyo Univ. of Agriculture and Technology (Japan)


Published in SPIE Proceedings Vol. 9912:
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II
Ramón Navarro; James H. Burge, Editor(s)

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