Design and characterization of a thermally stabilized fiber Fabry–Perot etalon as a wavelength calibrator for high-precision spectroscopy

Filtering light from a broadband source with a Fabry–Perot etalon generates comb-like peaks in the spectral domain that can serve as calibration reference for precise Doppler shift detection on astronomical spectrographs. Fiber Fabry–Perot etalons are small in size and easily aligned optically. In application, high thermal sensitivity of the fiber core material requires a highly stable temperature control system. Here, we report on the design, characterization, and thermal performance of a fiber Fabry–Perot etalon-based calibrator system insensitive to environmental temperature perturbation, aimed as a reference for m ⋅ s − 1 precision radial velocity measurements. A fast and simple method to estimate the etalon finesse and a dual-loop approach to achieve sub-millikelvin temperature fluctuation are proposed and demonstrated.