Initial results from a 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 from our ``green astro-comb'' that has been operating at the HARPS-N spectrograph in the 3.6 m Telescopio Nazionale Galileo (TNG) in the Canary Islands for the past year. The green astro-comb consists of $\sim6000$ lines equally spaced by $\sim20$ 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 $R=100000$ HARPS-N spectrograph. Results from initial investigations with the green astro-comb characterizing the performance of the HARPS-N spectrograph will be presented.