基于等离激元超表面的径向和角向偏振矢量光束的产生

Generation of radially and azimuthally polarized vector vortex beams based on plasmonic metasurfaces

为满足信息大容量和快速传输处理的需求,小型平面化集成光学器件正逐渐代替传统的大体积折射器件,可在亚波长尺度进行光波操控的超表面结构为微纳光子学器件设计和相关物理现象的研究提供了全新途径.该文设计了一种由正交纳米缝对组成的表面等离激元(surface plasmon polariton, SPP)超表面,实现了径向和角向偏振矢量涡旋光束的产生.利用惠更斯-菲涅尔原理从理论上推导出螺旋超表面中心区域的表面等离激元光场表达式,并利用时域有限差分法(FDTD)进行了模拟计算.实验搭建显微成像系统采集的SPP光强分布图样与FDTD模拟和理论计算结果吻合得很好,验证了利用该超表面获得径向和角向矢量涡旋光束的可行性.

In order to meet the needs of large capacity and fast transmission and processing of information,small planar integrated optical devices are gradually replacing the traditional large-volume refractive devices.The metasurface that can manipulate light waves in sub-wavelength scale provides a new way for designing nano-device engineering and studying related physical phenomena.A plasmonic metasurface composed of orthogonal nano-slit pairs to generate radially and azimuthally polarized vector vortex beam was designed in this paper.Based on the Huygens-Fresnel principle,the wavefield expressions of the surface plasmon polariton(SPP)in the central point area of the metasurface were derived theoretically.The results were validated by performing finite-difference time-domain simulations(FDTD).In addition,this paper used a microscopic imaging system to collect the intensity pattern of the SPP field.The experimental doughnut-shaped radially and azimuthally polarized vector vortex was consistent with the theoretical and simulated results.