Second optical harmonic generation in nonlinear crystals with a disordereddomain structure

A theory describing the second harmonic generation in nonlinear-optical cry stals with random domains is developed. The theory takes into account the f luctuations of both the phase mismatch and the nonlinear coupling coefficie nt of the interacting waves. It is shown that, in such crystals, the maxima l efficiency of fundamental-to-second harmonic conversion is low, and the d ependence of the average intensity of the second harmonic on the fundamenta l intensity differs considerably from a square law. (C) 2001 MAIK "Nauka/In terperiodica".