Sub-kHz-level relative stabilization of an intracavity doubled   continuous wave optical parametric oscillator using Pound-Drever-Hall scheme
  We report the relative frequency stabilization of an intracavity frequency doubled singly resonant optical parametric oscillator on a Fabry-Perot\'etalon. The red/orange radiation produced by the frequency doubling of the intracavity resonant idler is stabilized using the Pound-Drever-Hall locking technique. The relative frequency noise of this orange light, when integrated from 1 Hz to 50 kHz, corresponds to a standard deviation of 700 Hz. The frequency noise of the pump laser is shown experimentally to be transferred to the non resonant signal beam. 
O. Mhibik, D. Pab{\oe}uf, C. Drag, and F. Bretenaker
physics.optics