PPLN optical parametric oscillator energy scaling capabilities

An investigation of energy scaling of an optical parametric oscillator (OPO) using periodically poled LiNbO₃ (PPLN) is presented. Because PPLN crystals are currently limited to a thickness of 0.5 mm, the pump laser beam must be tightly focused, resulting in high energy flux and limiting peak energy. In an effort to increase the damage threshold of the OPO, the cavity mode was designed with an elliptical cross-section to increase the useful aperture. For a conventionally pumped OPO, maximum output energies approached 400 μJ at a pump energy of 1.15 mJ before crystal surface damage occurred. Using an elliptical OPO cavity mode, output energies up to 1.2 mJ were achieved using 9 mJ of pump energy before the OPO performance began to degrade. We postulate that photorefractive damage within the PPLN crystal limited the performance of the elliptically pumped OPO. The pump energy was increased to more than 30 mJ without observing any surface damage