RETRACING BEHAVIOR OF THE PHASE-MATCHING ANGLE OF NONLINEAR CRYSTALS IN OPTICAL PARAMETRIC OSCILLATORS

The retracing behavior of the phase-matching angle (RBPA) of many nonl inear optical crystals in optical parametric oscillators (OPO) is repo rted here. The wavelength range of the pump wave and the tuning angle range over which RBPA can occur are obtained. Furthermore, the general ity of this novel and interesting phenomenon is successfully explained by theoretical analysis. We point out that RBPA exists generally in b oth type I and type II OPO's by using either uniaxial or biaxial cryst als.