Limiting effects of longitudinal optical inhomogeneity of nonlinear crystals on frequency-doubler efficiency

An analysis is made of the influence of the optical inhomogeneity of a nonlinear crystal on the highest possible efficiency of optical doublers pumped by beams with an inhomogeneous transverse distribution. The possibility of optimization of the initial phase mismatch and length of the crystal is considered. A comparison is made of several nonlinear crystals used in doublers and this is done by introducing dimensionless parameters representing the frequency conversion efficiency.