Direct laser frequency comb calibration of an astronomical spectrograph

William Newman; Jake M. Charsley; Jamie Slattery; Toby Mitchell; Kamalesh Dadi; Yuk Shan Cheng; Richard A. McCracken; Derryck T. Reid

doi:10.1117/12.3017977

26 August 2024 Direct laser frequency comb calibration of an astronomical spectrograph

William Newman, Jake M. Charsley, Jamie Slattery, Toby Mitchell, Kamalesh Dadi, Yuk Shan Cheng, Richard A. McCracken, Derryck T. Reid

Author Affiliations +

Proceedings Volume 13100, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI; 131000Q (2024) https://doi.org/10.1117/12.3017977
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Abstract

High-resolution echelle spectrographs are critical for modern astronomy. Determining their wavelength solution is a prerequisite calibration, conventionally performed by illuminating the instrument with a broadband hollow-cathode lamp and cross-referencing the resulting two-dimensional spectrum to an emission-line atlas. Challenging requirements for nextgeneration spectrograph calibration are driving the adoption of laser frequency combs in place of lamps. Laser frequency combs offer an exceptional relative calibration scale, but the task of wavelength-tagging individual comb modes currently makes a spectral-line source essential for absolute calibration. Here, we present a new approach that utilizes a laser frequency comb as the sole calibration light source. An ancillary “spectral shaping” spectrograph can excise an individual comb mode and measure its wavelength, which can then be refined to provide sub-fm accuracy wavelength tagging on a proxy astronomical spectrograph echellogram. In a secondary procedure, a comb mode is isolated for each of the echellogram orders in a single measurement, revealing the free spectral range and allowing the order-to-order relationship to be established. These complementary techniques allow the complete calibration of a spectrograph to be achieved using only a laser frequency comb, eliminating reliance on auxiliary light sources and providing direct access to GPS-referenced accuracy.

Conference Presentation

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

William Newman, Jake M. Charsley, Jamie Slattery, Toby Mitchell, Kamalesh Dadi, Yuk Shan Cheng, Richard A. McCracken, and Derryck T. Reid "Direct laser frequency comb calibration of an astronomical spectrograph", Proc. SPIE 13100, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI, 131000Q (26 August 2024); https://doi.org/10.1117/12.3017977

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