摘要
利用惠更斯-菲涅耳衍射积分以及叉形光栅的透射率函数,推导出了涡旋光束经叉形光栅衍射后的解析表达式。详细研究了涡旋光束通过携带拓扑电荷数l的叉形光栅后的光强分布和拓扑电荷数。结果表明,中心零级光斑和入射涡旋光束的拓扑电荷数m相同;随着衍射级数n的变化,衍射光斑的拓扑电荷数变为nl+m。当满足nl+m=0时,该n级光斑中心为平面波形的亮斑,在此光斑两侧随着衍射级数的改变,衍射光斑的空心半径逐渐增大。根据平面波光斑所在位置的级数n以及叉形光栅携带的拓扑电荷数l,由nl+m=0可确定入射涡旋光束的拓扑电荷数m。将计算结果与实验结果做了比较,发现两者基本吻合。
Based on the Huygens-Fresnel integral and the transmittance function of the fork-shaped grating,analytical expression of a vortex beam passing through a fork-shaped grating is derived.The diffraction characteristics of vortex beams by a fork-shaped grating embedded with topological charge l are studied in great detail.It is shown that the topological charge of the center spot of the diffracted beam is the same as that of the incident vortex beam,and that the topological charge of the nth diffracted beam is nl＋m with different diffraction order n.The nth diffracted beam spot is plane wave when it satisfies nl＋m=0.While on both sides of the plane wave spot,the doughnut radius of the diffracted beam spot increases as the diffraction order n changes.According to nl＋m=0,the topological charge of the incident vortex beam can be detected through the order n of the plane wave spot and the topological charge l embedded in the fork-shaped grating.The results are compared with the experimental results and it is found that they are both in good agreement.
出处
《中国激光》
EI
CAS
CSCD
北大核心
2011年第3期57-63,共7页
Chinese Journal of Lasers
基金
国家自然科学基金(60977068
10874125)资助课题
关键词
衍射
涡旋光束
叉形光栅
拓扑电荷数
diffraction
vortex beam
fork-shaped grating
topological charge
