Nonstationary theory of synchronously pumped femtosecond optical parametric oscillators

Optical parametric oscillators (OPO's) have evolved to operate and be pumpe d by increasingly shorter pulses, so modeling them with a quasi-stationary approximation has become inappropriate. We derive a nonstationary model of an OPO and an optical parametric amplifier that takes into account the firs t-derivative terms of second- and third-order nonlinearity. We have rewritt en this model entirely in the spectral domain. We applied the model to a KT P OPO and found good agreement with a well-characterized experiment. Furthe r calculations were performed with a large diversity of parameters such as reflectivity of the output coupler, length and nonlinear index of refractio n of the nonlinear crystal, length of the resonator, and duration of the pu mp pulse. (C) 2000 Optical Society of America [S0740-3224(00)00605-6]. OCIS codes: 190.4410, 190.4970, 190.7110.