PHASE-MATCHING AND HARMONIC-GENERATION IN BESSEL-GAUSS BEAMS

Conversion efficiencies and far-field profiles for third-order harmoni c generation in an atomic medium irradiated by an intense Bessel-Gauss beam are calculated with an integral method. The calculation takes in to account the nonperturbative variation of the atomic polarizabilitie s. target depletion by photoionization, and the effect of the free ele ctrons. Numerical results are presented for a pump beam of 355-nm wave length and up to 3 x 10(13) W/cm(2) intensity incident on hydrogen. Th ey are compared with equivalent results for a pure Gaussian pump beam. Significant differences are found that originate from the different p hase-matching properties and intensity profile of Bessel-Gauss beams. (C) 1996 Optical Society of America.