基于SPPs-CDEW混合模式的亚波长单缝多凹槽结构全光二极管  

All-optical diode of subwavelength single slit with multi-pair groove structure based on SPPs-CDEW hybrid model

作　　者：祁云平[1] 南向红[1] 摆玉龙[1] 王向贤[2] 

机构地区：[1]西北师范大学物理与电子工程学院,兰州730070 [2]兰州理工大学理学院,兰州730050

出　　处：《物理学报》2017年第11期270-281,共12页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61367005;41461078)资助的课题~~

摘　　要：全光二极管是集成光子回路上最基本的光子器件,如何有效增强全光二极管的单向透射性,提高消光比一直是学者们研究的重点.当前,利用表面等离极化激元(surface plasmon polaritons,SPPs)和复合衍射衰逝波(composite diffracted evanescent wave,CDEW)的亚波长金属微纳结构构建全光二极管器件还鲜有研究.因此,开发出一种可调制的全光二极管,对未来制备复杂的光子回路具有重要意义.本文提出了一种基于SPPs-CDEW混合模式设计全光二极管的方法和结构,该结构结合纳米缝中的类法布里-珀罗共振效应,利用结构参数对SPPs进行调控,实现了光束单向透过的功能.首先,利用理论推导和有限元算法分析了单缝-对称双凹槽纳米结构的透射增强现象,提出了透射增强和削弱的物理机理.其次,计算出规约化透射率随单狭缝和凹槽对之间距离变化的远场透射谱,给出的理论和数值计算结果符合得很好.最后,通过此透射谱精确确定凹槽的位置和数量,得出上表面对称分布五对增强透射凹槽、下表面六对抑制透射凹槽的最优全光二极管结构,有效增强了全光二极管的单向透射性,提高了消光比,最大消光比可以达到38.3 dB,即正向透射率是反向透射率的6761倍,比已有文献提高了14.6 dB,并在850 nm左右有70 nm宽的工作波长带宽(>20 dB).本文提出的光二极管结构简单,宽带宽工作,易于集成,耦合效率高,研究结果对光学信号传输、集成光回路、超分辨率光刻等相关领域具有潜在的应用价值.All-optical diode is the most basic photonic device in integrated optical clrcmts. It is o1： great slgnmcance w develop a modulated optical diode for preparing complex optical circuits in the near future. However, there are few studies on constructing all-optical diodes in subwavelength metal micro-nano structured devices based on the hybrid model of surface plasmon polaritons （SPPs） and composite diffracted evanescent wave （CDEW）. in fact, most of the researches have been focusing on how to effectively enhance the unidirectional nonreciprocal transmission of the optical diode and improve the extinction ratio. According to SPPs-CDEW hybrid states, in this paper we put forward a novel method of designing an optical diode and its structure. The structure consists of a subwavelength single micro-nano slit surrounded by symmetric multi-pair grooves on a silver film. First of all, on the basis of the single slit structure of the silver film, the pairs of the groove structures are etched on both sides of the silver film： the positions and quantities of the grooves on the top and bottom surfaces are asymmetric. Then combining with an effect similar to Fabry-Perot resonance effect inside the micro-nano slit, the function of beam unidirectional transmission is achieved by controlling SPPs through changing the geometric parameters of the structure. Furthermore, in order to realize unidirectional nonreciprocal transmission, by means of theoretical derivation and the finite element method （FEM）, in this paper we analyze the transmission enhancement phenomenon of single slit-symmetric pair of groove micro-nano structure, discuss the physical mechanisms of transmission enhancement and weakening, and also give the far field transmission spectrum of the normalized transmission changing with the distance between slit and pair grooves. The results obtained from the rigorous theoretical formula are in excellent agreement with the numerical results obtained by using FEM. Finally, as the position and number of the pai

关 键 词：全光二极管 表面等离子体极化激元 非互易导通 消光比 

分 类 号：TN31[电子电信—物理电子学]