亚波长光栅负折射透镜的柱矢量光束聚焦特性  

Focusing Properties of Cylindrical Vector Beams Through Subwavelength Grating Lenses with Negative Refractive Indices

作　　者：刘山峰 袁沭娟 孙钰淇 杨茜[1] 刘扬眉 刘宁[1] 陆云清[1] 许吉[1] Liu Shanfeng;Yuan Shujuan;Sun Yuqi;Yang Qian;Liu Yangmei;Liu Ning;Lu Yunqing;Xu Ji(College of Electronic and Optical Engineering&College of Microelectronics,Nanjing University of Posts and Telecommunications,Nanjing,Jiangsu 210023,China)

机构地区：[1]南京邮电大学电子与光学工程学院微电子学院

出　　处：《光学学报》2019年第11期37-42,共6页Acta Optica Sinica

基　　金：国家自然科学基金(11404170,61505083)

摘　　要：研究亚波长负折射光栅透镜的柱矢量光束聚焦效应,探索并分析光栅的材料、几何参数等对聚焦效果的影响。亚波长光栅的-1级衍射效应可实现等效负折射现象,结合等光程原理可设计出聚焦平凹镜。利用柱对称坐标系下的有限元算法,分析不同材料折射率、不同等效负折射率、不同预设焦距对实际聚焦效果的影响。结果表明:材料折射率能影响聚焦场的能量效率;等效负折射率为-1时,焦点尺寸最小;预设焦距越小,焦点尺寸越小。聚焦场中纵向电场的比例是影响聚焦场横向尺寸的决定性因素。因此,合理设定光栅负折射率、材料折射率,优化负折射光栅平凹镜设计,能够获得优化的聚焦效果。本工作为柱矢量光束聚焦场调控及相关领域的微纳结构设计提供了参考。In this study, we analyze the focusing properties of the cylindrical vector beams through a subwavelength grating lens with a negative refractive index and the effects of grating material and geometric parameters on the focusing properties. Here, the equivalent negative refraction can be attributed to the subwavelength grating′s diffraction order of-1, and the focusing plane-concave lens can be designed using the equivalent optical path method. Further, we use the finite element method in a cylindrical-symmetric coordinate system to simulate and analyze the effects of different material refractive indices, equivalent negative refractive indices, and predetermined focal lengths on the focusing properties. The results denote that the material refractive index significantly affects the energy efficiency of the focal field, the focus size is minimized by an equivalent negative refractive index of-1, and the short predetermined focal lengths yield small focus sizes. The proportion of longitudinal electric-field components in the focal field is the main factor that determines its lateral size. Therefore, the optimum focusing effect can be obtained by selecting an appropriate negative refractive index of the grating and a material refractive index and optimizing the design of the plane-concave lens of the negative refractive grating. This study provides a reference for modulating the focal field of cylindrical vector beams and designing micro/nanostructured devices in related fields.

关 键 词：光栅 亚波长结构 透镜 柱矢量光束 负折射 聚焦 

分 类 号：O436[机械工程—光学工程]