Single-frequency optical parametric oscillator

An optical parametric oscillator operating on a single longitudinal mode of its resonator is described. Using KTP as the nonlinear optical material and a grazing-incidence-grating resonator, single-frequency linewidths of 0.02 cm−1 are achieved. The device, pumped at 532 nm, was tuned over 0.7–0.9 μm (signal branch) and 1.3–2.2 μm (idler branch), and operated with up to 3 mJ of output corresponding to an external photon conversion efficiency of 12%.