CW and self-pulsating operation of a Tm:YLF 1.91 μm hemispherical laser

Abstract 2 μm lasers are widely employed in LIDAR systems, photomedicine, and as pump sources for OPOs and mid-IR lasers. Tm:YLF is an optimal laser crystal for a 2 μm laser owing to its good mechanical properties, a negative thermo-optic coefficient, and intrinsic birefringence supporting polarized emission. However, many 2 μm lasers have been reported to exhibit unstable operation with a tendency towards self-pulsation (SP). In this paper, we investigate design parameters influencing the temporal output of a compact diode-laser pumped Tm:YLF 1.91 μm laser for stable continuous-wave (CW) and self-pulsating operation. Different sources of perturbation are discussed as main causes for SP. We introduce a novel pulse attenuation parameter, δ , to assess laser stability. We report optical-to-optical slope efficiencies of 35% and 41.5% in stable CW and SP operation, respectively.