基于经典耦合波理论, 分析了透射型体Bragg光栅的衍射特性, 建立了透射型体Bragg光栅的设计体系。采用带有调制的超高斯光束, 对高功率激光系统的近场滤波进行了理论模拟, 采用软化因子、近场调制度、近场对比度分析了输出光束的近场质量, 采用功率谱密度函数分析了近场滤波对不同空间频率的滤除能力。研究结果表明, 近场滤波对0.3~2.0 mm-1的中、高频调制具有显著的滤除作用。

Diffraction characteristic of transmitting volume Bragg grating is analyzed with classical coupled wave theory, and the design method of transmitting volume Bragg grating is built. The near-field filtering effect is simulated with modulated super-Gaussian beam. The softening factor, near-field modulation and near-field contrast are used to analyze the beam quality. The power spectral density is used to describe the evolution of spatial frequency. The results show that the spatial frequencies from 0.3 mm-1 to 2.0 mm-1 are clean out with the near-field filtering, but the filtering effect is limited by the beam diffraction sidelobes of transmitting volume Bragg grating.