Generation of the third harmonic in isotropic media under self-interaction conditions

An analysis is made of frequency addition in isotropic media under self-interaction conditions. An analytic solution is obtained for strong focusing conditions. The optimal position of a constriction of a Gaussian beam is shown to be governed by the ratio of linear and nonlinear contributions to the phase mismatch and by a phase shift resulting from focusing. A study is made of a change in the distribution of the intensity of the output radiation under the influence of Kerr nonlinearities.