Optimising Single-Frequency Intra-Cavity-Doubled Diamond Raman Lasers

Diamond Raman lasers (DRLs) are a promising approach to generating high power, single-longitudinal mode (SLM) output. While reproducible, long-term SLM operation remains a challenge, SLM performance has been significantly improved by intra-cavity frequency-doubling resulting in side-mode-suppression. However, this introduces two issues have not been discussed thoroughly in the literature. Firstly, combining the forwards and backwards second harmonic (SH) into a single output beam relies on constructive interference, which is affected by dephasing between the fundamental and second harmonic [1]. Secondly, the diamond generally contains some birefringence due to the stress introduced in the growth stage that causes sharp polarisation behaviour around some lithium triborate (LBO) temperatures. Optimisation of these lasers warrants investigation of both effects.