中文摘要：

根据菲涅耳衍射积分和拉盖尔高斯光束场强分布，对拉盖高斯光束中的圆孔衍射、单缝衍射和方孔衍射进行了研究，并分析了拉盖高斯光束的相位结构对光束衍射后场分布的影响。拉盖高斯光束的相位奇点落在衍射孔中心时，由螺旋谱计算出拉盖高斯光束通过单缝和方孔衍射后的轨道角动量的弥散程度，从理论上证明了拉盖尔高斯光束通过圆孔衍射后，轨道角动量不发生弥散。

英文摘要：

Based on the Fresnel diffraction integral and Laguerre-Gaussian beam field distribution, the circular aperture diffraction, single slit diffraction and square hole diffraction of Laguerre-Gaussian beam are studied, and the effect of spiral phase structure on the field distribution of the diffracted light beam is analyzed as well. The degree of dispersion of the orbital angular momentum is also calculated using the well-known spiral spectrum, when Laguerre-Gaussian beam passes through a single slit or a square hole in the same case of Laguerre-Gaussian beam phase singularity locating at the center of a diffraction hole. According to the theoretical calculation results, it′s demonstrated that the orbital angular momentum does not disperse when Laguerre-Gaussian beam passes through a circular aperture.