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Yale Astronomy

Single-Lock: A Fabry Perot Frequency Comb

Pushing the radial velocity technique to higher precision requires careful calibration of the stellar spectra. We are building a broadband calibration system called Single-Lock based around a stabilized Fabry-Perot interferometer.

The Fabry-Perot interferometer (FP) is used to filter broadband light and produce a series of peaks with known spacing. Keeping the FP in a temperature and pressure stable envirnoment minimizes drifts of the transmitted peaks. We are adding an additional step in this process by long term drifts of the FP that arise even though it is kept in a stabilized environment.

The reference source for our FP is generated by locking a tunable laser to a hyperfine atomic transition. These transitions occur at known wavelengths, do not drift over time, and provide a narrowband reference for locking. Using saturated absorption spectroscopy, we probe the atomic structure of rubidium and lock our laser to one of its transitions. With the laser locked, a portion of its light is picked off and overlapped with a beam of white light. Both are then fed into the FP to be filtered. This allows us to produce our broadband calibration source while simultaneously locking the FP to the tunable laser.

Laboratory prototype of Single-Lock
Peaks generated from the FP, detected by YDDF