Study on the influence of local optical field amplification effect on laser-induced damage of fused silica materials

Fused silica is an important part of optical components in large laser systems. Due to the limitation of manufacturing process, impurities and defects in the optical element would greatly reduce the service life of the optical element, and significantly reduce the final output of the laser performance. Aiming at the modulation effect of the internal defect of the component on the internal optical field of the component, the theoretical, simulation and experimental research are carried out. The results show that in the double-bubble impurity coupling, under the same radius R, when the impurity spacing is 1 lambda, the local optical field amplification has a maximum value. The effect is equivalent to single-bubble modulation with radius 2 R-3 R. There is an extreme point of the modulated optical field between the air and fused silica crossing line for bubble impurities of different radii. The optical field modulation of small radius impurities is distributed behind the bubble impurities, and the modulation effect of large radius impurities is the maximum when the spacing is 2 lambda. The temperature distribution curve of the fused silica element modulated by bubble impurities is consistent with the optical field distribution curve, showing a trend of decreasing slope. The presence of bubble impurities will cause the surface combustion wave of the component to flash and accelerate, and the bubble impurities will increase the generation and expansion rate of the surface combustion wave. This study provides a basis for reducing the uneven distribution of laser energy during the interaction between laser and fused silica, improving the lifetime of the overall optical system, and experimental measurement and analysis.