Conical Third-Harmonic Generation in Normally Dispersive Media

Abstract

It is shown, both theoretically and experimentally, that in normally dispersive media under tight-focusing conditions third harmonic is generated by six-wave mixing rather than via common third-order frequency tripling. Though far-field pattern of third-harmonic signal was an axially symmetric ring for a wide range of the material wave vector mismatch and laser beam focusing conditions, in some cases the generation of more complex beams has been found possible. Results of simulations of the proposed model qualitatively correspond well with experimental data for the calculated values of third- and fifth-order nonlinear susceptibilities of sodium.