Nonstationary theory of synchronously pumped femtosecond optical parametric oscillators

Optical parametric oscillators (OPO’s) have evolved to operate and be pumped 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 first-derivative terms of second- and third-order nonlinearity. We have rewritten this model entirely in the spectral domain. We applied the model to a KTP OPO and found good agreement with a well-characterized experiment. Further calculations were performed with a large diversity of parameters such as reflectivity of the output coupler, length and nonlinear index of refraction of the nonlinear crystal, length of the resonator, and duration of the pump pulse.