Propagation characteristics of a high-power broadband laser beam passing through a nonlinear optical medium with defects

Xueqiong Chen,Jixiong Pu,Guowen Zhang,Jianqiang Zhu,Xiaoyan Li,Ziyang Chen

doi:10.1017/hpl.2013.22

Abstract

AbstractThe intensity distributions of a high-power broadband laser beam passing through a nonlinear optical medium with defects and then propagating in free space are investigated based on the general nonlinear Schrödinger equation and the split-step Fourier numerical method. The influences of the bandwidth of the laser beam, the thickness of the medium, and the defects on the light intensity distribution are revealed. We find that the nonlinear optical effect can be suppressed and that the uniformity of the beam can be improved for a high-power broadband laser beam with appropriate wide bandwidth. It is also found that, under the same incident light intensity, a thicker medium will lead to a stronger self-focusing intensity, and that the influence of defects in the optical elements on the intensity is stronger for a narrowband beam than for a broadband beam.

Highlights

The self-focusing of a laser beam is a basic physical phenomenon in nonlinear optics, and it has been the focus of several investigations[1,2,3,4]
By.comparing.Figure.2.with.Figure.5,.we find that the propagation characteristic of a broadband beam passing through a nonlinear medium with defects is different from that for a broadband beam passing through a nonlinear medium without defects
It is seen that the transverse intensity distribution is asymmetric, and when the incident laser beam is of narrowband type, there exist many spikes

Summary

Introduction

The self-focusing of a laser beam is a basic physical phenomenon in nonlinear optics, and it has been the focus of several investigations[1,2,3,4]. The nonlinear effect makes the whole.intensity.distribution.of.the.laser.change..Jokipii et al presented solutions for reduction or elimination of catastrophic self-focusing in a medium[5]. Beckwitt et al.[6] used cascade quadratic nonlinearity to compensate self-focusing. Another factor influencing the intensity is defects in the optical elements[7,8]. The presence of defects may lead to a more complex intensity distribution and worse beam quality, and may even cause small-scale self-focusing which may damage optical elements[9,10]. Increasing attention has been paid to broadband technology in high-power lasers: for example, the formation of a hot image from phase defects in high-power broadband laser beams[13], parametric characteristics of a broadband

Theory

The case of a nonlinear medium without defects

The case of a nonlinear medium with defects

Conclusions