PROPAGATION EFFECTS IN HIGH-ORDER HARMONIC-GENERATION IN RARE-GASES

We study the role of propagation effects in high-order harmonic-generation experiments. The phase-matching integrals are calculated in the weak-field limit by taking into account the dispersion of the rare-gas medium at each harmonic frequency and the absorption of the harmonics. The refractive indices of the rare gases are deduced from a calculation of the dynamic polarizabilities within the framework of many-body perturbation theory and the random phase approximation. We also study the influence of the ionization of the gaseous medium and the presence of free electrons on the harmonic conversion efficiency by numerically integrating the propagation equation. These results are compared with experimental data. © 1990 Optical Society of America.