Quadrature frequency conversion

A technique for frequency conversion of high-power lasers is described which uses two crystals for each conversion step rather than one. The two crystals are oriented so that the waves generated in them are orthogonally polarized. The conversion efficiency of these quadrature arrangements is much less sensitive to laser pulse nonuniformities than that in single-crystal methods. Consequently, very high conversion efficiency is possible for typically nonuniform laser pulses. Realization of the quadrature concept for all types of nonlinear optical processes are described. Data taken on second harmonic generation of Gaussian pulses shows that very high (internal) conversion efficiency is possible ( > 95 percent) over a substantial range of input energy.