摘要:
研究了涡旋光束与相位全息光栅不对准时衍射光束的解析特性.利用理论推导的方法得出涡旋光束经相位全息光栅接收后一阶衍射光束的解析表达式.然后通过仿真分析分别得出在发生正常对准、横向偏移、角向倾斜及横向偏移和角向倾斜两者同时出现时衍射光束的质心偏移特性和中心强度变化特性.研究表明：拉盖尔-高斯光束经相位全息光栅衍射后得到的光场表达式为合流超几何函数形式.光束与相位全息光栅间的不对准会引起衍射光束质心的偏移,而且光束质心的偏移量随入射光束偏移距离和偏离角的增加而增加,与入射光束的偏移方向和方位角无关.角向倾斜时,质心的偏移角等于入射光束的方位角,入射光束的拓扑荷和相位全息光栅的分叉数都不影响衍射光束质心的偏移位置.另外还发现：当入射光束的拓扑荷与相位全息光栅的分叉数两者之和为零时,衍射光束的中心强度值会随入射光束的偏移距离和偏离角的增加而逐渐减小;而当两者之和不为零时,由于入射涡旋光束与相位全息光栅不对准使得中心强度值不再为零,这会影响测量结果的正确性.
Abstract:
We study the analytical features of the output beam diffracted from a phase-hologram grating when the incident vortex beam is misaligned with respect to the grating.The analytical representation describing the diffracted beam of the 1st order is derived theoretically.Based on the representation,the central of gravity and the central intensity of the diffracted beam are investigated in the cases of the alignment,lateral displacement,angular tilt and simultaneous lateral misalignment and angular tilt,separately.It is shown that the diffracted beam is described through confluent hypergeometrical function.The misalignment of the incident vortex beam can give rise to the displacement of the beam center of gravity,which is independent of the misalignment direction and azimuth angle.The displacement is more obvious for the lager misalignment.In the case of angular tilt,the direction of beam center of gravity is nearly identical to the misalignment direction,whatever the topological charge of the incident beam and the fork number of the grating are.Besides,if the sum of the topological charge of the incident beam and the fork number of the grating is zero,with radial displacement and deflection angule increasing,the central intensity of the diffracted beam decreases gradually,otherwise,the central intensity is non-zero value any more.That means the misalignment between the phase-hologram grating and the incident vortex beam can influence the measurement of the topological charge of the vortex beam.
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