High-pulse-energy high-efficiency mid-infrared generation based on KTA optical parametric oscillator

A high-energy, high-efficiency mid-infrared KTA OPO at 3.47 mu m intracavity pumped by a Nd:YAG laser is presented. The maximum output energy is 31 mJ at the repetition rate of 10 Hz with a V-shaped cavity, corresponding to the absolute optical-to-optical conversion efficiency of 4.76% from the diode and the photon conversion efficiency of 87% from the fundamental to mid-infrared energy. The pulse width is 5.8 ns at the maximum output energy and the peak power reaches higher than 5 MW. The line width of the mid-infrared wave is about 1.1 nm (or 0.9 cm(-1) in wave number). The output energy demonstrates good stability. To our knowledge, these are the highest pulse energy and conversion efficiency of mid-infrared OPOs using bulk nonlinear crystals in the 3-5 mu m range.