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基于非线性耦合波方程分析了神光II升级系统中束匀滑技术对三次谐波转换过程的影响。模拟结果显示:400μm焦斑所采用的连续相位板将引起1.4%左右的效率下降,近场对比度增加量约为0.02,均在可接受范围内;但当焦斑达到800μm时将会引起6%左右的效率下降,并导致近场对比度增加近0.05,无法兼容目前系统设计,必须进一步优化连续相位板设计方案;而谱色散匀滑技术引入光谱展宽达到60GHz时将引起5%左右的效率下降,且会引发明显的时间纹波扰动;但是谱色散匀滑引入的空间角谱扫描并不会明显影响谐波转换效率,因此在高通量运行时,需要适当减小调制带宽以提高谐波转换效率和系统的稳定性。
Based on the nonlinear coupled wave equation, the influence of beam smoothing technology on the third harmonic conversion process in SG upgrade system is analyzed. The simulation results show that the continuous phase plate used in the 400μm focal spot will cause the efficiency decrease of about 1.4% and the increase of the near-field contrast about 0.02, all within the acceptable range; however, when the focal spot reaches 800μm, it will cause 6% And the near-field efficiency is reduced, and the near-field contrast is increased by nearly 0.05, which can not be compatible with the current system design. Therefore, the continuous phase plate design scheme must be further optimized; while the spectral chromatic dispersion smoothing technique leads to about 5% And will lead to obvious time ripple disturbance. However, the spectral angular spread introduced by spectral dispersion and smoothing does not significantly affect the harmonic conversion efficiency. Therefore, in high-throughput operation, it is necessary to reduce the modulation bandwidth appropriately to improve the harmonic conversion Efficiency and system stability.