Photon statistics of a nondegenerate optical parametric oscillator

Photon statistics of light produced by a nondegenerate optical parametric oscillator operating below threshold are calculated. Positive-P representation is used to map quantum dynamics onto a set of classical Langevin equations for the complex field amplitudes associated with the annihilation and creation operators for the field produced by the oscillator. Using a Karhunen Loeve expansion of the resulting stochastic processes the moment generating function for photon counting statistics is obtained.