中国激光, 2020, 47 (9): 0905003, 网络出版: 2020-09-16   

基于涡旋圆偏振光干涉的偏振快速旋转束匀滑方案 下载: 1652次封面文章

Rapid Polarization Rotation Smoothing Scheme Based on Interference of Circularly Polarized Vortex Beamlets
作者单位
四川大学电子信息学院, 四川 成都 610065
摘要
针对高功率激光装置对靶面辐照均匀性和背向散射抑制的要求,提出了一个远场束匀滑方案,该方案利用涡旋圆偏振光的干涉,实现了焦斑均匀性和偏振特性的同步调控。其基本原理是通过对宽带种子光进行选频,使激光集束内的子束出现一定波长差,并采用共轭的螺旋相位板将子光束变换成拓扑荷数相反的拉盖尔-高斯光,进而利用偏振控制器件将其分别变为左旋圆偏振光和右旋圆偏振光,通过这两子束在焦面上的相干叠加即可实现焦斑局部光强和偏振的快速旋转。建立了基于涡旋圆偏振光干涉的偏振旋转物理模型,分析了焦斑的均匀性和偏振特性随子束波长组合、螺旋相位板拓扑荷数和入射激光束参数的变化规律。结果表明,通过合理选取子束波长组合,所提偏振旋转方案可实现局部光强和偏振的快速旋转,且结合传统的光谱色散匀滑方案后,可在改善靶面辐照均匀性的同时对背向散射进行有效抑制。
Abstract
Aiming at the requirement of illumination uniformity and backscattering suppression in laser-driven inertial confinement fusion (ICF) facilities, we propose a polarization rotation (PR) smoothing scheme based on the interference of circularly polarized vortex beamlets, which makes the simultaneous control of intensity and polarization of the focal spot. The basic mechanism is that a conjugate spiral phase plate is first used to transform the beamlets with certain wavelength difference into vortex beams with conjugate helical charges, and then the polarization control plate is used to change the polarization states of the beamlets into counter-rotating ones. Finally, the rapid rotation of both the local intensity and polarization of the focal spot can be realized by means of the interference of the circularly polarized vortex beamlets in the target plane. The physical model of the PR scheme based on the interference of circularly polarized vortex beamlets is established and the variations of illumination uniformity and polarization of the focal spot with the beamlet wavelength, the helical charge of the spiral phase plate, and the parameters of the incident beams are analyzed. The results indicate that the proposed PR scheme can be used to realize the intensity and polarization rotation at a specific rotation frequency by selecting the suitable wavelength combination. When this novel scheme is implemented together with the conventional spectral dispersion smoothing scheme, the smoothing performance can be further improved and the backscattering suppression can be effectively achieved.

黄媛, 张寅瑞, 钟哲强, 张彬, 孙年春. 基于涡旋圆偏振光干涉的偏振快速旋转束匀滑方案[J]. 中国激光, 2020, 47(9): 0905003. Huang Yuan, Zhang Yinrui, Zhong Zheqiang, Zhang Bin, Sun Nianchun. Rapid Polarization Rotation Smoothing Scheme Based on Interference of Circularly Polarized Vortex Beamlets[J]. Chinese Journal of Lasers, 2020, 47(9): 0905003.

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