Optical injection locking of a singly resonantcontinuous-wave optical parametric oscillator

We report on experimental realization of optical injection locking of a singly resonant continuous-wave optical parametric oscillator (OPO) based on a thermally induced waveguide in a magnesium-oxide doped periodically poled lithium niobate. An external cavity diode laser is used to control the frequency of the resonant signal output of the OPO at 795 nm. The key to successful injection locking was the improvement of the OPO spatial modes by a special operating condition with a thermally induced waveguide. The phase coherence of injection locking is confirmed by recording a high-contrast interference fringe between the injection laser and the OPO output. High-resolution measurement of the frequency spectrum of the nonresonant idler output by the delayed self-heterodyne technique shows that the spectral linewidth of the OPO is reduced from 4.5 to 0.4 MHz by injection locking. The full locking range is assumed to be less than 1.7 MHz.