Temperature effects on harmonic generation in laser-irradiated plasmas

Abstract

The generation of second and third harmonics at the oblique incidence of a p-polarized wave on an inhomogeneous plasma (resonance absorption) is studied. The relevant wave equations are solved numerically. First, the dependence of the emitted harmonics on the temperature, the density scale length, and the angle of incidence is investigated for a linear density profile. The strong oscillations of the harmonic emission in a certain temperature range are attributed to the position of the point where the condition for phase matching is fulfilled. In the second part a modified density profile with a caviton is considered, and it is shown that a large enhancement of harmonic emission is possible because of the formation of electrostatic resonant structures. This effect will become important under experimental nonstationary conditions when the density profile is deformed by the ponderomotive force.