Broadband self-phased-locked degenerate continuous-wave optical parametric oscillator

We report on a broadband self-phase-locked operation of a degenerate continuous-wave (cw) optical parametric oscillator (OPO). Pumped at 532 nm in the green, and using a 10-mm-long MgO:PPLN crystal in a fan-out grating design, by controlling the dispersion of the optical cavity, self-phase-locking of the OPO at degeneracy over an extended bandwidth of 3.5 nm is achieved. Phase-locking is validated by radio frequency and f-2f interferometric measurements. Under self-phase-locking, the OPO exhibits improved overall stability, delivering up to 300 mW of output with a passive power stability better than 1.5% rms over 1.8 min, in a Gaussian TEM₀₀ mode profile.