Spiking in pump enhanced idler resonant optical parametric oscillators

We report on time-resolved measurements of the output power of an idler resonant optical parametric oscillator (OPO) with resonator internal pump power enhancement. The experiments are performed with a two-mirror, pump and an idler resonant OPO based on a RbTiOAsO4 (RTA) crystal, pumped with a single-frequency Ti:sapphire laser. When the length of the OPO cavity is piezoelectrically tuned through pump resonance, we observe a strong transient spiking in the output of the signal wave with a repetition rate of about 7 MHz. This spiking was also observed in the pump power transmitted by the OPO cavity. The observed transient spiking is in agreement with the predictions of a numerical analysis based on the equations of motion for the intracavity electric fields. This analysis also indicates the possibility to obtain pulsed operation of an OPO with a cavity resonant for the cw pump and the idler wave, by Q-switching the idler cavity loss. (C) 1998 Elsevier Science B.V.