Mutual quantum fluctuations of modes in the case of two-mode parametric oscillation in a resonator

A quantum solution of the problem of two-mode nondegenerate parametric oscillation in a resonator cavity with an arbitrary Q factor is proposed. It is shown that the existing semiclassical analysis is unsatisfactory. If the signal and idler modes are photodetected independently, the noise level in the normalized spectrum of the difference photocurrent is independent of the parametric gain increment. There are optimal Q factors of the resonator for different frequencies in this spectrum.