Intraresonator generation of second optical harmonic under wave mismatch conditions

A. theoretical analysis is made of the steady-state single-frequency Intraresonator generation of second optical harmonic under wave mismatch conditions. It is assumed that at the fundamental frequency both resonator mirrors are totally reflecting but the second harmonic escapes without hindrance from the resonator. The process of wave amplification in the active medium is described by a system of rate equations and the interaction of waves in the nonlinear medium by a system of reduced equations for the real and imaginary parts of the complex amplitudes. It is assumed that the transverse structure of the waves is homogeneous. An analytic solution of the problem is obtained near the threshold. Numerical solutions are obtained for the case of strong pumping in a wide range of parameters of the problem. It is shown that, in particular, the optimal harmonic generation conditions can be achieved even in the presence of a wave mismatch provided it does not exceed a certain critical value; it is also demonstrated that there is a multitude of optimal regimes. The nonmonotonic nature of the dependence of the optimal length of the nonlinear crystal on the pump rate is established. The results of an experimental investigation of the harmonic generation are in agreement with the theoretical predictions.