A compact green Ti:Sapphire astro-comb with 43-GHz repetition frequency

A compact green astro-comb with a 43 GHz repetition rate is developed based on a Ti:sapphire optical frequency comb (OFC) and a mode-selecting cavity. The OFC’s large repetition rate of 1.6 GHz eases the requirements for the mode-selecting cavity. Unnecessary frequency modes of the OFC are suppressed down to 5×10−4 at 535–550 nm using a single mode-selecting cavity with 70 MHz linewidth. The radial velocity precision σ∼1.4m/s is achieved at the high dispersion echelle spectrograph for the Okayama 188 cm telescope of the National Astronomical Observatory of Japan using our astro-comb. With further improvements of the mode-selecting cavity and removal of fiber modal noises, our system will provide a simple, compact, and precise astro-comb setup in the visible wavelength region.