5 August 2014 A stable and inexpensive wavelength reference for precise wavelength calibration of radial velocity spectrographs
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Abstract
We present a stable, inexpensive wavelength reference, based on a white-light interferometer for the use on current and future (arrays of) diffraction-limited radial velocity (RV) spectrographs. The primary aim of using an interferometer is to obtain a dense sinusoidal wavelength reference with spectral coverage between 450-650 nm. Its basic setup consists of an unbalanced fiber Mach-Zehnder interferometer (FMZI) that creates an interference pattern in the spectral domain due to superposition of phase delayed light, set by a fixed optical path-length difference (OPD). To achieve long-term stability, the interferometer is actively locked to a stable atomic line. The system operates in closed-loop using a thermo-optic modulator as the phase feedback component. We conducted stability measurements by superimposing the wavelength reference with thorium-argon (ThAr) emission lines and found the differential RMS shift to be ~5 m s-1 within 30 minute bins in an experiment lasting 5 hours.
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Tobias Feger, Michael J. Ireland, Joao Bento, Carlos Bacigalupo, "A stable and inexpensive wavelength reference for precise wavelength calibration of radial velocity spectrographs", Proc. SPIE 9147, Ground-based and Airborne Instrumentation for Astronomy V, 914780 (5 August 2014); doi: 10.1117/12.2055674; https://doi.org/10.1117/12.2055674
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