Coherent beam combining of optical parametric oscillators

We propose a possible way to achieve coherent beam combining (CBC) for the optical parametric process. We point out that the essential difficulty is to lock the phase of an individual wave in the three-wave-mixing process. The phase evolution law in an optical parametric amplifier for both cases of phase matching and quasi-phase matching is studied theoretically. The results indicate that, under the condition of strong pumping, a higher intensity injection signal can lock its phase to be its initial value, while for a weaker injection signal the phases of the signal and idler waves exhibit chaos-like evolution. Based on this understanding, we propose a ring configuration for an optical parametric oscillator (OPO) with the appropriate intensity seed injection. The numerical studies indicate this OPO configuration can achieve phase-locking and wavelength-locking simultaneously. This inspires a possible design to achieve CBC for OPOs.