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在产生涡旋光束过程中,固体激光器所输出的光束中心很难与螺旋相位板的中心完全对准,实际出射的光束为离轴涡旋光束.在衍射理论的基础上,对离轴涡旋光束的传输进行了研究,推导了离轴涡旋光束传输一段距离后电场和光强的解析表达式.研究表明,与理想的涡旋光束不同,离轴涡旋光束具有非对称性的光强分布,在传输过程中光斑除了展宽外,涡旋暗核还会发生移动.拓扑电荷数的大小只影响到光束的展宽,拓扑电荷数为正时,暗核沿着逆时针切线方向移动;拓扑电荷数为负时,暗核沿着顺时针的切线方向移动,该结果对长距离探测涡旋光束的对准问题起到指导作用.
During the generation of vortex beam, the center of the beam output by the solid-state laser is hard to be perfectly aligned with the center of the spiral phase plate, and the actual beam is an off-axis vortex beam.Based on the diffraction theory, The propagation of the beam is studied and the analytical expression of the electric field and the intensity of the off-axis vortex beam is deduced.The results show that the intensity of the off-axis vortex beam is asymmetric with that of the ideal vortex beam In the transmission process, the vortex dark nucleus will move except for the broadening of the beam width. The size of the topological charge only affects the beam broadening. When the topological charge number is positive, the dark nucleus moves counterclockwise and tangential. When the charge is negative, the dark nucleus moves in a clockwise tangential direction, and the result instructs the alignment of the long-range detection vortex beam.