Green Astro-comb for exoplanet searches at HARPS-N

Astro-combs, a combination of a laser frequency comb, a coherent wavelength shifting mechanism (such as a doubling crystal and photonic crystal fiber), and a mode-filtering Fabry-Perot cavity, are promising tools that enable searches for Earth-like extra-solar planets (exoplanets) and the direct observation of the accelerating expansion of the universe. In this talk, We will present recent results of tests of our ``green astro-comb'' operating at the HARPS-N spectrograph in the 3.6 m Telescopio Nazionale Galileo (TNG) in the Canary Islands. The green astro-comb consists of $\sim$6000 lines equally spaced by $\sim$20 GHz in the 500 nm - 600 nm optical band and is derived from a 1-GHz Ti:Sapphire comb laser, a custom tapered photonic crystal fiber that spectrally shifts the comb lines to the visible, and two mode-filtering Fabry-Perot cavities that increase the line spacing to match the R=100,000 HARPS-N spectrograph. The green astro-comb was recently installed and tested at HARPS-N. Results from initial investigations with the green astro-comb at HARPS-N will be presented.