PHASE-MATCHING EFFECTS IN HARMONIC-GENERATION AND NONLINEAR-OPTICAL FREQUENCY MIXING IN THE PLASMA OF OPTICAL-BREAKDOWN

We experimentally and theoretically study the influence of phase-match ing effects on the generation of harmonics of Nd:YAG-laser radiation a nd on nonlinear-optical frequency mixing in a low-temperature plasma o f optical breakdown. It is demonstrated that the efficiency of optical frequency conversion in a laser-produced plasma considerably depends on phase-matching conditions. The dependence of the phase-matching int egral on parameters of focusing is numerically investigated with allow ance for one-photon absorption for various processes of optical freque ncy mixing in plasma media with model distributions of the electron de nsity.