Formation of self-focusing filaments in harmonic generation under conditions of coherent two-photon interaction between optical pulses and resonant media

A theoretical analysis is made of the influence of a transverse inhomogeneity of a plane wave on third harmonic generation under conditions of coherent two-photon interaction with resonant media. It is found that self-focusing filaments are formed in a distance equal to the two-photon absorption length and that the harmonic generation efficiency is enhanced considerably under these conditions.