Narrow-bandwidth low-divergence optical parametric oscillator for nonlinear frequency-conversion applications

We describe the design and operation of a pulsed optical parametric oscillator (OPO) system suitable for nonlinear frequency conversion. The OPO system, which uses a type-I β-barium borate (BBO) crystal as the nonlinear medium, is tunable from 0.435 to 2.3 μm. It possesses linewidths that are less than 0.2 cm−1 and beam divergences of less than 0.5 mrad. We report frequency-doubling efficiencies of the output of this OPO system. Maximum doubling efficiencies obtained are 18.5% with BBO and 28% with potassium dihydrogen phosphate.