For laser inertial confinement fusion (ICF), whether direct or indirect drive, polarization smoothing is critically important. Beyond spatial and temporal dimensions, it provides an additional method for instantaneously achieving focal spot smoothing, and effectively suppresses laser-plasma instabilities (LPI). Currently, the component used to achieve beamlet polarization smoothing is a birefringent wedge (PS crystal) based on large-sized KDP crystal material. This limitation exists because PS crystals have limited production capacity, are extremely expensive, and introduce additional nonlinear effects, severely restricting their engineering applications in ICF.
Addressing the urgent need for large-aperture polarization smoothing components in ICF, this study breaks the constraint of currently requiring extremely expensive large-sized PS crystals with limited laser damage thresholds for 3ω laser polarization smoothing. We innovatively propose a polarization smoothing mechanism based on residual stress birefringence effects in optical fused silica glass, which a material enabling high-quality mass production. This mechanism utilizes intrinsic residual stress independent of external forces or constraints, endowing isotropic fused silica glass with polarization control capabilities.Residual stress is largely uncontrollable, and objective assessment of it remains poorly understood. This study established a residual stress analysis model based on fictive temperature distribution in fused silica, mastered the precise control of residual stress through laser-induced fictive temperature distribution, and developed processes and equipment utilizing CO₂ laser-induced residual stress for random polarization control. The fabricated large-aperture fused silica random polarization components exhibit high laser-damage resistance and compatibility with established devices.This study provides an efficient and economical KDP-free technical solution for the engineering application of sub-beam polarization smoothing.

polarization smoothing,fused silica,fictive temperature,residual stress,laser damage