圆形螺旋相位板的平面波夫琅和费衍射特性

Properties of the Fraunhofer diffraction of a plane wave by a circular spiral phase plate

摘要:

为了研究圆形螺旋相位板(SPP)对平面波的夫琅和 费衍射特性,基于标量衍射理论给出了圆形SPP对 有限孔径平面波进行夫琅和费衍射时所产生涡旋光束的光强表达式。理论模拟分析了圆 形SPP的拓 扑荷数n、半径R等参数对涡旋光束光强分布的影响,结果表明,当圆形SPP半 径R不变时,随着拓扑荷n的增大,涡旋光束半径逐渐增大,并且光强分布中旁 瓣的比重显著增强；当拓扑荷n不变时,圆形SPP的半径R增 大,产生的涡旋光束半径反而会变小,但涡旋光束的相对形状基本保持不变。基于纯相位空 间光调制器(SLM)实现了圆形SPP对有限孔径平面波的夫琅和费衍射, 并对理论结果进行了实验验证,实验结果与理论分析一致。

Abstract:

For studying the Fraunhofer diffraction properties of a pl ane and finite-radius wave by a circular spiral phase plate (SPP),the analytical expression to describe the light intensity of the vortex beam produced by the Fraunhofer diffraction based on the scalar diffraction theo ry is given.The effects of different parameters on the intensity distribution properties of the vortex beam,such as the topolog ical charge n,the radius R of the circular SPP,are analyzed through theo retical modeling. Theoretical results show that when the radius R of the circular SPP is constant,the radius of the vortex beam would increase with the increasing topological ch arge n,and the proportion of the sidelobes is also enhan ced significantly.However,when the topological charge n is constant,the radius of the vortex beam would decrease with the increasing radiu s of the circular SPP,and the shape of the vortex beam would remain bas ically unchanged.The Fraunhofer diffraction of a plane and finite-radius wave by a circular SPP is achieved with a phase-only spatial light modulator (SLM),and experimental verifications about the above theoretical results are implemented.The experimental results and theoretical analysis are in good agreement.