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

TL;DR

This paper presents a compact green astro-comb with a 43-GHz repetition rate based on a Ti:Sapphire OFC, achieving high mode suppression and radial velocity precision suitable for astronomical spectroscopy.

Contribution

The development of a compact, high-repetition-rate astro-comb with effective mode suppression for visible wavelengths is a novel advancement in astronomical calibration tools.

Findings

Achieved 5×10⁻⁴ mode suppression at 535-550 nm.

Attained 1.4 m/s radial velocity precision.

Demonstrated system's potential for precise astronomical measurements.

Abstract

A compact green astro-comb with 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 $5 \times 10^{-4}$ at 535 nm - 550 nm using a single mode-selecting cavity with 70-MHz linewidth. The radial velocity precision $\sigma \sim 1.4$ m/s is achieved at the High Dispersion Echelle Spectrosraph 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 visible wavelength region.