Induced Focusing of Two Laser Beams in Cubic Quintic NonlinearMedia

Abstract

This paper presents an investigation of induced focusing of two laser beams(i.e., a pump beam and another probe beam) in a medium possessing cubicquintic nonlinearity. Third and fifth order nonlinear susceptibilities in presenceof two interacting waves have been evaluated. These susceptibilities are thenemployed to derive two coupled nonlinear Schrödinger equations. Variationalformalism has been employed to derive relevant equations which governdifferent characteristics of propagating beams. Extensive numerical simulationhas been performed to investigate the influence of the pump beam on thepropagation characteristics of the probe beam. Among several important.ndings, most noteworthy one is that a very weak probe beam can be guidedand focused with a pump beam even if its power is well below threshold valueof focusing of the pump beam alone. It has been found that induced focusing ofthe probe beam is more effective when its wavelength is smaller and initialbeam width larger than the corresponding quantities of the pump. The roles offifth order nonlinear coefficient on induced focusing have been investigated.Particularly, it has been established that even an initially defocusing pump canfocus a very weak probe.