多色光谱色散匀滑技术参数对集束辐照特性的影响

Effects of Parameters in Smoothing of Multi-Color Spectral Dispersion on Laser-Quad Irradiation Characteristics

针对惯性约束聚变装置中多色光谱色散匀滑技术在集束中的运用,提出了对电光调制器、色散光栅和连续相位板(CPP)等主要单元器件进行独立设计和优化的思路。基于这一思路,分别模拟和分析了电光调制器、色散光栅和CPP等单元器件的参数对集束辐照特性的影响。提出了优化的多色光谱色散匀滑方案参数,并仿真了束匀滑参数对激光束纵向成丝特性的影响。结果表明,通过优化不同子束的电光相位调制器和色散光栅参数,可以进一步改善靶面的辐照均匀性。当集束中各子束采用不同的CPPs时,焦斑均匀性得到有效改善,热斑比例明显降低。采用功率谱密度对激光束的光束质量进行分析,结果表明多色光谱色散匀滑方案能有效降低峰值强度,使光强分布更加均匀,从而有利于抑制激光束成丝。

Aimed at the application of smoothing of multi-color spectral dispersion in inertial confinement fusion facilities, an independent design and optimization method for main unit components, including electro-optic modulators, dispersion gratings and continuous phase plates （CPP） and so forth, is proposed. The effects of parameters of electro-optic phase modulators, dispersion gratings and the CPP on the laser-quad irradiation characteristics are simulated and analyzed. The parameters of optimized smoothing of multi-color spectral dispersion are proposed, and the effect of the smoothing parameters on the characteristics of longitudinal filaments of lasers is simulated. Results indicate that the irradiation uniformity on the target surface can be further improved when we optimize the parameters of electro-optical modulator and dispersion grating of different sub-beams. When different CPPs are implemented for different sub-beams in the laser-quad, the focal-spot uniformity can be improved effectively and the proportion of hot spots can be decreased significantly. Moreover, the beam quality of the laser beam is analyzed by the power spectral density. The simulation results show that the smoothing of multi-color spectral dispersion can effectively decrease the peak intensity and make the light intensity distribution more uniform, which is benefit to suppress filaments of laser beams.