Theoretical and experimental investigations on idler-resonant intracavity KTA OPO pumped by a dual-loss-modulated Q-switched laser with AOM and Ta2NiS5 nanosheets.

Ta2NiS5 nanosheets were fabricated and analyzed for their microstructures and nonlinear optical responses. As a saturable absorber (SA), Ta2NiS5 was integrated into an idler-resonant KTiOAsO4 (KTA)-based intracavity optical parametric oscillator (IOPO) pumped by a dual-loss-modulated Q-switched YVO4/Nd:YVO4 laser. At an incident pump power of 18.9 W and an acousto-optic modulator (AOM) modulation rate of 4 kHz, the maximum output powers of 467 mW for the signal wave and 228 mW for the idler wave were achieved, corresponding to an overall optical-to-optical conversion efficiency of 3.68%. Remarkably, the shortest measured pulse widths of 872 ps for the signal wave and 2.86 ns for the idler wave were obtained, corresponding to the highest peak powers of 392 kW and 57.6 kW for the signal and idler waves, respectively. In comparison to the IOPO pumped by a singly Q-switched YVO4/Nd:YVO4 laser (SIOPO) with an AOM, the IOPO pumped by a doubly Q-switched YVO4/Nd:YVO4 laser (DIOPO) with an AOM and a Ta2NiS5 SA can generate signal and idler waves with significantly shorter pulse widths and higher peak powers. Additionally, the coupled rate equations for the idler-resonant DIOPO were given. The numerical simulations exhibited remarkable consistency with the experimental results. [ABSTRACT FROM AUTHOR]