基于表面等离激元交叉耦合作用的纳米金属双缝异常透射现象

Anomalous Transmission Properties of Two Integrated Metallic Nanoslits under Plasmonic Cross Talking Coupling

利用二维时域有限差分方法研究了非对称纳米金属双缝结构在薄隔层情况下对光波的异常透射特性,以及狭缝长度、狭缝数目和入射角度对透射特性的影响.研究发现,该双缝结构中传导的表面等离激元波通过渗透中间隔层材料产生交叉耦合作用,形成对称和反对称耦合模式,导致其透射谱在特定波长位置处形成双共振峰传输和一个透射率为零的透射抑制现象;双缝结构中表面等离激元波交叉耦合作用的本质是其横向电场分量渗入中间隔层材料产生的相互干涉作用,而横向电场分量的初始相位差决定双缝结构中形成的表面等离激元波耦合模式的类型.由于双缝结构的透射极值与各狭缝腔内的法布里-珀罗共振效应密切相关,因此狭缝长度决定透射极值的波长位置,而狭缝数目和入射角度只影响透射峰的传输效率.该双缝结构具备光学滤波和空间分光功能,在新型纳米光子器件领域具有潜在的应用价值.

Two-dimontional the finite-difference time-domain method was adopted to theoretically study the anomalous optical transmission properties of an asymmetric two integrated metallic nanoslits with an ultrathin separation thickness.The influence of the slit length,the slit number and the incident angle on the optical transmission of the proposed structure were also investigated.The results domenstrate that surface plsamon polaritons,propagating inside the two slits,produce a cross-talk coupling effect via penetrating into the metallic separation,and hybridize into symmetric and antisymmetric modes,resluting in two resonant peaks and a nearly-zero dip in the transmission spectrum;the essential physics of the plasmonic cross-talk coupling for the two integrated slits is the interference between the transverse electric fields of surface plsamon polaritons within the seperation material,and the original phase difference of transverse electric fields between the two integrated slits determines the type of the surface plasmon polariton hybird modes inside it.Since the transmission extremums are associated with the Fabry-Perot resonance inside each slit cavity of the two integrated nanoslits structure,the slit length determines the wavelengths of the tranmission peaks and dip,while the slit number and the incident angle of plane wave only influence the effciency of the tranmission peaks.The two integrated nanoslits structure posses the functions of optical filtering and spatial color dispersion,which have implications on the field of new functional nanooptic devices.