利用二维耦合波理论,分析了超短脉冲激光光束被完全重叠型的局域体全息光栅衍射的时空变化性质,给出了衍射和透射脉冲激光光束沿光栅出射边界的强度时空分布。以LiNbO3晶体为例,数值研究了衍射光脉冲强度沿光栅出射边界的分布和脉冲波形的变化及光栅的总衍射效率受光栅二维尺寸、入射角度、光栅折射率调制度及入射脉冲的脉冲时域半峰全宽等条件的影响而变化的情况。与一维体全息光栅对超短脉冲激光光束衍射的性质,及此光栅对连续光衍射的性质作比较,给出了合理选择光栅参量及入射条件以在光栅出射边界上得到总衍射效率较大且分布较均匀的衍射光脉冲的方法。

Based on the two-dimensional (2D) coupled-wave theory, the temperal and spatial diffraction properties of an overlapping finite size volume holographic grating read by an ultra-short pulsed laser beam are studied. The temporal and spatial distribution of the diffracted and transmitted light intensity along the output boundary of the grating is obtained. Taking LiNbO3 as an example, the effects of the two-dimensional grating size, incident angle, the grating's refractive-index modulation and the pulse width of the input ultra-short laser pulse upon the intensity distributions of the diffracted and transmitted pulsed laser beams along the output boundary of the grating, pulse shaping and the total diffraction efficiency are given. By comparison with the diffraction properties of one-dimensional volume holographic grating read by ultra-short pulsed laser beams and the diffracgtion properties of the grating read by continuous waves, the method of choosing grating parameters and input conditions to obtain the diffracted pulsed laser beams with uniform-distributed pulse and larger total diffraction efficiency is presented.