A dual cavity Fabry-Perot device for high precision Doppler measurements in astronomy

摘要

We propose a dual cavity Fabry-Perot interferometer as a wavelengthcalibrator and a stability tracking device for astronomical spectrograph. TheFPI consists of two adjoining cavities engraved on a low expansion monoblockspacer. A low-finesse astro-cavity is intended for generating a uniform grid ofreference lines to calibrate the spectrograph and a high-finesse lock-cavity ismeant for tracking the stability of the reference lines using optical frequencystandards. The differential length changes in two cavities due to temperatureand vibration perturbations are quantitatively analyzed using finite elementmethod. An optimized mounting geometry with fractional length changes $\DeltaL/L \approx 1.5\times 10^{-12}$ is suggested. We also identify conditionsnecessary to suppress relative length variations between two cavities wellbelow 10$^{-10}$~m, thus facilitating accurate dimension tracking andgeneration of stable reference spectra for Doppler measurement at 10 cms$^{-1}$level.