High-pulse-energy, linear optical parametric oscillator with narrow and symmetrical far field

A new method to obtain a narrow and symmetrical far field from a high-pulse-energy optical parametric oscillator (OPO) with a linear resonator has been tested. The OPO employs two identical nonlinear crystals that are cut for type II phase matching, rotated such that their walkoff planes are orthogonal, and separated by a broadband half-wave plate. The OPO has a simple geometry, can be double-pass pumped, is wavelength tunable and operates stably with high conversion efficiency. The method has been demonstrated in a KTP-based OPO pumped at 1064 nm and a BBO-based OPO pumped at 532 nm, with output pulse energies up to 60 mJ and 75 mJ, respectively.