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基于衍射理论,建立了光束经过体布拉格光栅衍射的光束质量分析模型。在考虑入射光束参数和体布拉格光栅参数的情况下,分析任意光束经过体布拉格光栅衍射的光场分布,计算得到二阶矩意义下的束腰和光束质量M2因子,并分析了体布拉格光栅空间周期、入射光束尺寸、光谱线宽和初始入射光束质量M2对衍射光束质量的影响。研究结果表明,衍射光束质量受体布拉格光栅和入射子束共同影响:体布拉格光栅周期越小,其空间色散越严重;入射子束尺寸越大、光谱线宽越宽、初始光束质量越差,衍射后的输出光束质量劣化越明显。该模型给出了衍射后的光束质量表示,可方便快捷地得到不同输入光束衍射后的光束质量。在最高入射功率达千瓦量级时,实验测量了初始M2和光谱线宽两部分贡献对衍射光束质量的结果,并与相应理论分析进行了比较。
Based on the diffraction theory, a beam quality analysis model of the beam diffracted by a Bragg grating is established. Taking into account the incident beam parameters and Bragg grating parameters, the distribution of the light field diffracted by a Bragg grating by any beam is analyzed, and the M2 factor of the beam waist and the beam quality in the second moment is calculated. The Bragg grating space Period, incident beam size, spectral linewidth, and initial incident beam quality M2 on the quality of the diffracted beam. The results show that the Bragg grating and the incident beam have the same effect: the smaller the Bragg grating period, the more serious the spatial dispersion. The larger the incident beam size, the wider the spectral linewidth, the worse the initial beam quality, The more the quality of the diffracted output beam deteriorates. The model shows the quality of the diffracted beam, which makes it easy and fast to obtain the beam quality of different input beams. When the maximum incident power reaches the order of kilowatt, the experimental results show that the initial M2 and the spectral linewidth contribute to the diffracted beam quality, and are compared with the corresponding theoretical analysis.