Phase Diffusion and Quantum Noise in the Optical Parametric Oscillator: A Semiclassical Approach

We calculate by the semiclassical method the noise spectra of a non-degenerate optical parametric oscillator operating above threshold when taking into account two independent diffusion processes on the pump phase and on the signal-idler phase difference. We also show that the phase diffusion processes are important when calculating the quantum noise in an optical parametric oscillator for noise frequencies close to the beat frequency between the signal and idler modes.