Abstract

Eimerl¹ has presented a map of harmonic generation efficiency as a function of nonlinear drive and beam dephasing. While useful as a conceptual guideline, this type of analysis is limited by the implicit assumption that the beams involved are both temporally and spatially uniform, i.e., that they are continuous-plane waves. Most beams used in practice have spatially nonuniform (approximately Gaussian, in many cases) profiles. In addition, the need to achieve high nonlinear drives usually requires the pump beams to be pulsed in time, often with crudely Gaussian profile in time. The uniform-beam model predicts a rapid decline in conversion efficiency as the nonlinear drive is increased beyond a certain value; experiments with nonuniform beams typically do not exhibit this behavior. The present work extends the conversion efficiency theory to beams with arbitrary super-Gaussian profiles in both space and time. The resulting total energy conversion efficiencies are presented as maps in the drive-dephasing plane, with the beam profiles collapsed into a single additional parameter. As this beam nonuniformity parameter is increased the maps clearly show that the efficiency roll-off tends to disappear, corresponding with the experimentally observed data.

© 1991 Optical Society of America