Influence of pump source beam quality and OPO cavity resonance regime on output characteristics of mid-infrared ZGP-OPO laser

Abstract

Abstract In this paper, the effect of the pump beam quality on the output results of ZGP-OPO nonlinear conversion pumped by a Q-switched Ho:YLF laser at 2.056 𝜇m wavelength was studied. In the experimental setup, two cavity resonance regimes were applied. First, a U-shape Q-switched resonator at two types of concave-concave and concave-convex structures was investigated. Output energies of 60 and 55 mJ at 24.5 ns of pulse duration were achieved for the resonators mentioned above with double-pass pumping, respectively. In the concave-convex resonator, a far-field beam divergence angle of about 0.7 mrad was recorded, although the conversion efficiency was lower. The maximum conversion efficiency of the linear OPO cavity with a concave-plane structure was recorded. A 30.5 mJ total energy of parametric waves was measured at the PE-DRO resonance regimes pumped by 55 mJ incident energy in the concave-convex resonator at 2056.8 nm Q-switched laser, which corresponds to an optical-to-optical efficiency of 53.5 %. The peak of signal and idler waves are 3779.5 and 4507.6 nm, respectively. The pulse width is about 22.4 ns at the PE-DRO resonance regime