Continuous-wave, dual-cavity, doubly resonant, optical parametric oscillator

We have demonstrated a continuous-wave optical parametric oscillator that uses separate optical cavities to resonate independently the nondegenerate signal and idler frequencies. The three-mirror cavity utilizes the type II phase-matching geometry in lithium triborate, with the orthogonally polarized signal and idler fields separated by an intracavity, dichroic-coated, Brewster-angled beam splitter. This dual-cavity oscillator can overcome mode and cluster hopping effects, which are characteristic of doubly resonant, continuous-wave optical parametric oscillators. We measure a pump power threshold of ≊200 mW and smooth tuning over ≊0.4 GHz. The tuning range is limited by pump resonance effects within the idler cavity.