Understanding the beam self-cleaning behavior of ultrashort laser pulse filamentation  

作　　者：See Leang Chin 

机构地区：[1]Department of Physics, Engineering Physics and Optics & Center for Optics, photonics and Laser (COPL), Laval University, Quebec, Canada G1K 7P4

出　　处：《Science China(Technological Sciences)》2007年第4期413-421,共9页中国科学（技术科学英文版）

基　　金：Supported by the National Natural Science Foundation of China (Grant No. 60637020)

摘　　要：In this paper we report a recent study on the beam self-cleaning behavior occurred during the ultrashort laser pulse filamentation process. The propagation of a Gaussian beam with distorted beam profile is numerically simulated based on the nonlinear wave equation. Our results demonstrate that when the power is not too high so that multiple filaments are not yet induced, the intensity perturbation con-tained in the initial beam profile could be treated as high order spatial modes su-perpositioning on a fundamental mode. Then the self-focusing of the laser beam acts as a spatial filter. It focuses the fundamental mode toward the propagation axis, and produces a fundamental mode profile at the self-focus. While the strong diffraction of higher order modes could not be counteracted by the self-focusing. Therefore their propagation is mainly governed by the divergence without de-stroying the high profile quality at the self-focal region. These lead to the observa-tion of beam profile self-cleaning behavior.In this paper we report a recent study on the beam self-cleaning behavior occurred during the ultrashort laser pulse filamentation process. The propagation of a Gaussian beam with distorted beam profile is numerically simulated based on the nonlinear wave equation. Our results demonstrate that when the power is not too high so that multiple filaments are not yet induced, the intensity perturbation contained in the initial beam profile could be treated as high order spatial modes superpositioning on a fundamental mode. Then the self-focusing of the laser beam acts as a spatial filter. It focuses the fundamental mode toward the propagation axis, and produces a fundamental mode profile at the self-focus. While the strong diffraction of higher order modes could not be counteracted by the self-focusing. Therefore their propagation is mainly governed by the divergence without destroying the high profile quality at the self-focal region. These lead to the observation of beam profile self-cleaning behavior.

关 键 词：FILAMENTATION ULTRASHORT PULSE SELF-CLEANING 

分 类 号：TN241[电子电信—物理电子学]