Chinese Journal of Lasers, Vol. 47, Issue 9, 0905003 (2020)
Rapid Polarization Rotation Smoothing Scheme Based on Interference of Circularly Polarized Vortex Beamlets
Huang Yuan, Zhang Yinrui, Zhong Zheqiang, Zhang Bin*, and Sun Nianchun
- College of Electronics and Information Engineering, Sichuan University, Chengdu, Sichuan 610065, China
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.
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