Induced focusing due to two optical beams counterpropagating in self-defocusing nonlinear media*

In this paper,a research work is done on two optical beams co-propagating in opp osite directions in two-dimensional self-defocusing nonlinear media.Numerical re sults show that the probe beam can be induced to focus due to cross-phase modula tion by the pump beam under certain conditions.We also discuss the effect on the focusing of the probe beam from the four parameters:the specimen length,the ini tial amplitudes of the pump beam and the probe beam,and the initial transversal distance between the centers of the two beams.We find that some of them have opt imum values,which result in the strongest focusing.