Experimental Research Of Small-scale Self-focusing Of Broadband Laser

"Broadband"and"Nonlinearity"are two key techniques in the field of intense laser technology. It is very important to reveal the characteristic of nonlinear small-scale self-focusing of broadband laser experimentally, and it is also of great theoretical and practical significance for the development of high-power laser system. In this paper, by setting up the experimental platform, we further study on the dynamic propagation process of small-scale self-focusing of the broadband laser experimentally, which is on the basis of using analytical and numerical method to study the law of small-scale self-focusing of broadband laser. The main research results are listed below:Firstly, we build a theoretical model for ultrashort pulse propagating in nonlinear media, and then, based on algorithm of the slip step Fourier, we establish a numerical simulation program to solve the theoretical model. We simulate two propagation processes, one is that the effects of chirp on the small-scale self-focusing of ultrashort lasers pulse under the condition of single silk diffraction modulation, and the other is that the dynamic propagation process of small-scale self-focusing of ultrashort lasers pulse under the condition of cross silks diffraction modulation. The numerical simulation is in good agreement with the experimental results.Secondly, the effects of chirp on the small-scale self-focusing of ultrashort lasers pulse under the condition of diffraction modulation and the dynamic propagation process of small-scale self-focusing are both experimental studied. On the one hand, the modulation growth which is induced by the small-scale self-focusing becomes slowly when the pulse's chirp increases. At the same time, the input average power also added. On the other hand, under a certainty spatial silk diffraction modulation, the dynamic evolutionary process of ultashort pulse's small-scale self-focusing with the increasing of input average power is obtained. We find that, first, modulation increase occurs at some particular position. It not infinitely increases, but appears new modulation increase in other place. Then the modulation increase slow down, in the end, these increases begin to compete with each other and bring the laser pulse split into filamentation.