Tunable 30 GHz laser frequency comb for astronomical spectrograph characterization and calibration | CU Experts

The search for Earth-like exoplanets with the Doppler radial velocity; (RV) technique is an extremely challenging and multifaceted precision; spectroscopy problem. Currently, one of the limiting instrumental; factors in reaching the required long-term 10−10 level of; radial velocity precision is the defect-driven subpixel quantum; efficiency (QE) variations in the large-format detector arrays used by; precision echelle spectrographs. Tunable frequency comb calibration; sources that can fully map the point spread function (PSF) across a; spectrograph’s entire bandwidth are necessary for quantifying and; correcting these detector artifacts. In this work, we demonstrate a; combination of laser frequency and mode spacing control that allows; full and deterministic tunability of a 30 GHz electro-optic comb; together with its filter cavity. After supercontinuum generation, this; gives access to any optical frequency across 700–1300 nm. Our specific; implementation is intended for the comb deployed at the Habitable-Zone; Planet Finder (HPF) spectrograph and its near-infrared Hawaii-2RG; array, but the techniques apply to all laser frequency combs (LFCs); used for precision astronomical spectrograph calibration and other; applications that require broadband tuning.

Sekhar P; Kate Kreider M; Fredrick C; Ninan JP; Bender CF; Terrien R; Mahadevan S; Diddams SA

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