Phase matching in second harmonic generation

Phase-matching of coupled modes is investigated for the intracavity second harmonic generation in the instability region. In the positive P- representation using numerical solution of Langevin stochastic equations for this system the joint phase distribution function of fundamental and second harmonic modes is calculated. It is shown that for large time and initial vacuum states of both modes the distribution function in the right from bifurcation point has a dip. A removing of the system to the right from the bifurcation point leads to dip's size enhancement. 10 refs