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arXiv · 2408.02627

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

Pooja Sekhar·Molly Kate Kreider·Connor Fredrick·Joe P Ninan·Chad F Bender·Ryan Terrien·Suvrath Mahadevan·Scott A Diddams
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Abstract

The search for earth-like exoplanets with the Doppler radial velocity 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 sub-pixel quantum efficiency 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 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 spectrograph and its near-infrared Hawaii-2RG array, but the techniques apply to all laser frequency combs used for precision astronomical spectrograph calibration and other applications that require broadband tuning.

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Pooja Sekhar, Molly Kate Kreider, Connor Fredrick, Joe P Ninan, Chad F Bender, Ryan Terrien, Suvrath Mahadevan, Scott A Diddams. 2024-08-05. Tunable 30 GHz laser frequency comb for astronomical spectrograph characterization and calibration. https://arxiv.org/abs/2408.02627

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