Highly sensitive surface plasmon resonance fiber sensor based on triangle gold nano-rod array

In order to obtain a high sensitivity, linearity and large dynamic measuring range, A physical model for a novel surface plasmon resonance sensor coupled by side polished fiber and triangular nano-rod array is proposed and established. 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), presenting a relatively low sensitivity while yields in a high linearity to the change of the refractive index of the surrounding environment. 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 12882 nm/RIU is achieved in the range of 1.38 ~ 1.42 RIU.