Continuous-wave optical parametric oscillator based on periodically poled KTiOPO₄

We report what is to our knowledge the first demonstration of a continuous-wave optical parametric oscillator (OPO) based on periodically poled KTiOPO₄. The 10-mm-long flux-grown crystal had a quasi-phase-matched period of 9 μm. The pump source was a miniature frequency-doubled Nd:YAG laser, and the threshold power of this doubly resonant device was 51 mW. The OPO was operated near room temperature. The signal and the idler wavelengths could be tuned in the range 1037-1093 nm by variation of the crystal temperature (32-38 °C) and the cavity length. Unlike in other nonlinear crystals, green-induced infrared absorption was not observed up to the highest pumping intensity of ≈4.5 kW/cm².