银纳米线-三角片耦合结构发射光的偏振依赖特性  

Polarization Dependence Between Excitation and Emission in Nanowire-Triangular Plate Coupled Structures

作　　者：李圆圆 杨龙坤 李志鹏 Li Yuanyuan;Yang Longkun;Li Zhipeng(Beijing Key Laboratory of Nano-Photonics and Nano-Structure(NPNS),Department of Physics,Capital Normal University,Beijing 100048,China)

机构地区：[1]首都师范大学物理系纳米光子与纳米材料北京市重点实验室,北京100048

出　　处：《中国激光》2023年第1期188-195,共8页Chinese Journal of Lasers

基　　金：国家重点研发计划(2021YFA1400800);北京市自然科学基金(Z190006);国家青年人才支持计划;国家自然科学基金(11704266,11774245)。

摘　　要：银纳米线可以承载传播的表面等离激元,纳米片可以产生局域的表面等离激元,二者形成的耦合结构不但可以将传播光场耦合为局域增强光场,还可以调控光场的偏振态等性质,为纳米光调控提供新的自由度。本团队构建了银纳米线-三角片耦合结构,并发现耦合结构的发射偏振与纳米线-三角片的耦合方式有关:当三角片与纳米线之间是“线”接触耦合时,耦合结构的发射偏振随着激发偏振的旋转而旋转;当二者是“点”接触耦合时,无论激发偏振如何变化,发射偏振角度几乎保持160°不变。进一步,利用时域有限差分法验证了出射偏振对入射偏振的依赖特性。通过计算自由电流密度体积分揭示了纳米线中传播的表面等离激元模式与银纳米线-三角片耦合模式的转化机制,以及不同表面等离激元模式的叠加对发射偏振的调控。这些发现为纳米尺度上的光调控以及在纳米尺度上构建纳米光子器件提供了更多灵活性。Objective Surface plasmon polaritons(SPPs)supported by metallic nanostructures can confine electromagnetic fields at the nanoscale and overcome the diffraction limit.Compared with conventional electronic devices,integrated subwavelength optical devices with high data transmission rates and wide bandwidths provide a promising platform for the development of nanophotonics.In recent decades,various plasmon-based optical elements have been developed,including waveguides,resonators,nanoantennas,multiplexers,and switchers.Polarization-controllable optical elements are important in chip-to-chip interconnects,sensors,and quantum cryptography.Chemically synthesized nanowires have been reported to function as polarization-controllable plasmonic waveguides,where the emission of different SPPs modes relies on the shape of the wire end.Additionally,optical properties sensitive to incident polarization have been observed in coupled nanostructures composed of wires or nanoparticles.For example,the near-field enhancement and far-field emission polarization of coupled junctions can be modulated via incident polarization,through which polarization-dependent routers,modulators,and logic gates have been achieved.Hence,further optimization of coupled waveguides can provide additional flexibility for controlling light polarization at the nanoscale.In this study,we investigated the correlations between the emission and incident polarization of a nanowire-triangular plate coupled structure.The results indicate that the polarization dependence can be modulated by the wire-triangular plate coupling type.The response of the emission polarization to the incident polarization is verified using the finite-difference time-domain(FDTD)method.In theory,by calculating the volume integration of the free current density,the conversion of propagating SPP modes and wire-triangular plate coupled mode can be revealed.The emission mechanism of the coupled structures can be elucidated based on the superposition of different SPP modes.The findings provide

关 键 词：光学材料 表面等离激元 纳米结构 发射 偏振依赖性 

分 类 号：O436[机械工程—光学工程]