POWER AND SPECTRAL CHARACTERISTICS OF CONTINUOUS-WAVE PARAMETRIC OSCILLATORS - THE DOUBLY TO SINGLY RESONANT TRANSITION

The output power and spectral characteristics of optical parametric oscillators (OPO's) as they evolve from the doubly resonant to the singly resonant regime are examined. By assuming a high-Q signal cavity, we derive approximate analytical solutions of pump depletion and conversion efficiency for OPO's with arbitrary idler Q. Using this set of solutions, we examine in detail amplitude and frequency instabilities of doubly resonant oscillators with low signal loss and arbitrary idler loss. We find that OPO's with weak idler feedback, when operated at a few times above threshold, exhibit improved spectral stability. Experimental results are presented for LiNbO3 and KTP OPO's operating with a fixed low signal loss and various idler losses, including the limiting case of the cw singly resonant oscillator with no idler feedback.