光纤耦合三角形金柱阵列的等离子体共振

Side-polished Fiber Coupled Plasmon Resonance Based on Triangle Nano-rod Array

为了满足表面等离子体传感器高灵敏度、高线性以及较大测量范围的需求,提出侧边抛磨光纤耦合的三角形纳米金柱阵列等离子体共振传感模型.用有限元法仿真得出侧边抛磨光纤倏逝场激发出三角形纳米金柱的三种等离子体共振模式,分别为传输等离子体、三角形纳米金柱的本征等离子体和柱间等离子体,在传感器透射谱中呈现三个共振波谷.本征等离子体和柱间等离子体均属于局域等离子体,所对应的共振波谷对外界环境折射率的灵敏度较低但具有很高的线性度.传输等离子体对应的波谷随折射率变化灵敏度很高且呈非线性关系,优化后三角形金柱阵列设计中,当折射率为1.38~1.42RIU时,灵敏度高达12 882nm/RIU.该传感结构集成了侧边抛磨光纤的强倏逝场,具有传输等离子体的高灵敏度、局域等离子体的高线性度和大测量动态范围等优点,有重要的研究意义和实用价值.

In order to obtain a high sensitivity,linearity and large dynamic measuring range,aphysical model for a novel surface plasmon resonance sensor coupled by side polished fiber and triangular nano-rod array was proposed.By using Finite Element Method（FEM）,the strong evanescent field escaped from the polished region of the fiber excites three kinds of plasmon resonances,which are Propagating Surface Plasmon Resonance（PSPR）,Intrinsic Surface Plasmon Resonance（ISPR）of the triangular nano-rod,and the Inter-rod Surface Plasmon Resonance（IrSPR）,and correspondingly results in three resonance valleys in the transmission spectra of the sensor.Both the ISPR and the IrSPR are of Localized Surface Plasmon Resonance（LSPR）,and present a relatively low sensitivity while yields in a high linearity to the change of the environment refractive index.On the contrary,the propagating surface plasmon resonance shows a high sensitivity but a nonlinear dependence to the change of refractive index.In the optimized design with a height of 100 nm for the triangular gold nano-rod,a sensitivity up to 12 882nm/RIU is achieved in the range of 1.38~1.42 RIU.The proposed sensing structure utilizing the strong evanescent field of sidepolished fiber,integrates the merit of high sensitivity from propagating surface plasmon resonance,and also the merits of high linearity and large dynamic measuring range from localized surface plasmon resonance.The novel design has important research significance and is believed to developed into an important practical sensing platform.