LONG-TERM STABLE OPERATION AND ABSOLUTE FREQUENCY STABILIZATION OF A DOUBLY RESONANT PARAMETRIC OSCILLATOR

We demonstrate a doubly resonant optical parametric oscillator that op erated on a single mode pair for 18 h without mode hops, and whose out put frequencies can be tuned by almost 10 GHz without mode hops by the tuning of the pump laser frequency. The tuning range is limited by th e available pump tuning range. Active stabilization is used that minim izes the detuning of the parametrically generated waves with respect t o the DRO cavity resonances. Absolute frequency stabilization of the i dler wave is achieved by locking its frequency to an ultra-stable cryo genic reference resonator, using the pump laser frequency as control p arameter. The frequency instability reached is below the 1-kHz level.