Sub-ns OPO based on PPKTP with 1 mJ idler energy at 2.8 μm

Recently we demonstrated that periodically-poled oxide materials can be employed in short cavity, singly-resonant optical parametric oscillators (OPOs), with very low thresholds and high conversion efficiency. We demonstrated sub-ns pulse durations down to ~250 ps for the signal and idler pulses of 1-10 kHz OPOs based on periodically-poled KTiOPO₄ (PPKTP) and pumped at 1064 nm. However, with maximum idler energies of 110 and 50 μJ near 2.8 μm obtained with the 1-ns and 500-ps pump pulse sources, respectively, the energy scaling capability of thick PPKTP remained unexploited. Here we extend these results to the millijoule energy range for the idler by utilizing the full crystal aperture with a powerful pump source specially designed for this purpose.