Impact of Spatial Filter Parameters on Output Beam Performance in High-Power Laser System: A Comprehensive Analysis

Spatial filters are critical components in high-power laser systems for improving laser performance, removing high-spatial-frequency components which experience high nonlinear gain, thereby ensuring safe operation under high fluence conditions. Based on free-space propagation models and nonlinear B-integral theory, this paper systematically investigates the relationship between the output beam modulation and the pinhole size of spatial filters under various operating conditions. First, the influence of wavefront perturbances on beam performance is illustrated, revealing that surface errors impose constraints on the allowable pinhole size. Furthermore, based on a high-power laser system of 4+2 multi-pass amplification prototype, the nonlinear gain and beam modulation along its propagation path are analyzed. This analysis yields insights into output beam quality under the influence of multiple factors. Finally, the study clarifies the evolution of output beam performance in relation to optical surface errors, the B-integral value, and spatial filter pinhole size. Based on these results, the ultimate output capability of the high-power laser system is discussed. This work provides a theoretical basis for optimizing the pinhole size of spatial filters and guarantees safe operation of high-power laser systems.

空间滤波器（spatial filter）是高功率激光系统中用于提升激光性能的核心组件，其可滤除具有高非线性增益的高空间频率分量，从而确保系统在高注量工况下安全运行。本文基于自由空间传输模型（free-space propagation models）与非线性B积分理论，系统研究了不同工况下空间滤波器的输出光束调制与针孔尺寸之间的关联规律。首先，本文阐述了波前扰动（wavefront perturbances）对光束性能的影响，揭示出光学面形误差会对允许针孔尺寸施加约束。此外，本文以4+2多程放大原型高功率激光系统为研究对象，分析了其传输路径上的非线性增益与光束调制特性，厘清了多因素影响下的输出光束质量演化规律。最后，本研究明确了输出光束性能随光学面形误差、B积分值以及空间滤波器针孔尺寸的变化规律，并基于上述研究结果探讨了高功率激光系统的极限输出性能。本研究为空间滤波器针孔尺寸的优化提供了理论依据，同时为高功率激光系统的安全运行提供了保障。