The Nonlinear Effect Of Circle Spot Laser Beam In Kerr-Medium

In this dissertation, the transmission of circle spot laser beam in Kerr-medium is investigated with solving nonlinear SchrOdinger equation numerically.The numerical results show that, as the laser beam power is above a certain value, there will be some effects as follows:a) The self-focusing and multilevel focus points are observed, and the focus points are not lie on the axes, but on the circle. The critical power depends upon the radius of the circle spot laser beam.b) The spot splitting and splitting variation are observed in the transmission process. The beam alternates between the self-focusing and spot splitting.c) The beam splitting is observed. As to the beam which has the parameters: the I0 is 250kw/cm2, the radius is 2mm, and the half-width is 0.1mm, it splits into two beams at the second focus point. Its threshold power is related to the radius and the half width of the circle spot. And the beam splitting depends on the intensity distribution at the focus points in the vertical direction.d) The mutual correlation pulse appears in the transmission process.The characterestics of the mutual correlation pulse depends upon the incident laser beam's intensity and its distribution.The mechanism of this mutual correlation is discussed as well.e) The coupling effect appears when the double coaxial circles laser beam passes through the Kerr-medium.And the coupling effect is related with the distance of the double circle spot laser beam. The coupling effect increases the outside circle's self-focusing, and almost has no influence on the inner circle.In addition, we investigate the transmission of the double circle spot laser beam in Kerr-medium cs2 experimentally . In the transmission,as the intensityof the laser beam is above a certain value.we also discovered that: a) the self-focusing of the double circle spot laser beam; b) the spot splitting; and c)the coupling effect between the double coaxial circle; and we also investigate the relationship between the self-focusing and the intensity of the incident laser beam.