Power scaling strategy for resonant second-harmonic generation in the visible regime

Abstract

In this paper, we describe external resonant second harmonic generation (SHG) of a multi-axial mode near-infrared (near-IR) source for scaling power in the visible (green) spectral band. By distributing the power across multiple frequencies, we significantly increased the output power obtainable from an ytterbium-doped fibre amplifier before reaching the onset of Stimulated Brillouin Scattering (SBS). Using a near-IR laser with $\sim$9 longitudinal modes and an LBO crystal in a bow-tie cavity configuration, up to 15 W at a wavelength of 532 nm was achieved, with a conversion efficiency of 65% with respect to incident power. We discuss strategies for further up-scaling of output power, including increasing the number of axial modes and optimizing the amplifier configuration. Additionally, we highlight the advantages of our approach compared to previously reported high-power SHG systems, demonstrating its potential for future power scaling.