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Proceedings Paper

Development of compact and ultra-high-resolution spectrograph with multi-GHz optical frequency comb
Author(s): Mamoru Endo; Takashi Sukegawa; Alissa Silva; Yohei Kobayashi
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Paper Abstract

In recent years, a calibration method for an astronomical spectrograph using an optical frequency comb (OFC) with a repetition rate of more than ten GHz has been developed successfully [1-5]. But controlling filtering cavities that are used for thinning out longitudinal modes precludes long term stability. The super-mode noise coming from the fundamental repetition rate is an additional problem. We developed a laser-diode pumped Yb:Y2O3 ceramic oscillator, which enabled the generation of 4-GHz (maximum repetition rate of 6.7 GHz) pulse trains directly with a spectrum width of 7 nm (full-width half-maximum, FWHM), and controlled its optical frequency within a MHz level of accuracy using a beat note between the 4-GHz laser and a 246-MHz Yb-fiber OFC. The optical frequency of the Yb-fiber OFC was phase locked to a Rb clock frequency standard. Furthermore we also built a table-top multi-pass spectrograph with a maximum frequency resolution of 600 MHz and a bandwidth of 1 nm using a large-size high-efficiency transmission grating. The resolution could be changed by selecting the number of passes through the grating. This spectrograph could resolve each longitudinal mode of our 4-GHz OFC clearly, and more than 10% throughput was obtained when the resolution was set to 600 MHz. We believe that small and middle scale astronomical observatories could easily implement such an OFC-calibrated spectrograph.

Paper Details

Date Published: 28 July 2014
PDF: 6 pages
Proc. SPIE 9147, Ground-based and Airborne Instrumentation for Astronomy V, 91477Y (28 July 2014); doi: 10.1117/12.2055788
Show Author Affiliations
Mamoru Endo, The Univ. of Tokyo (Japan)
Exploratory Research for Advanced Technology (Japan)
Takashi Sukegawa, Canon Inc. (Japan)
Alissa Silva, The Univ. of Tokyo (Japan)
Exploratory Research for Advanced Technology (Japan)
Yohei Kobayashi, The Univ. of Tokyo (Japan)
Exploratory Research for Advanced Technology (Japan)


Published in SPIE Proceedings Vol. 9147:
Ground-based and Airborne Instrumentation for Astronomy V
Suzanne K. Ramsay; Ian S. McLean; Hideki Takami, Editor(s)

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