Research On Design And Performance Of The Photonic Crystal Fiber Single-polarization Filter Based On Surface Plasmon Resonance

Photonic crystal fiber based on surface plasmon resonance(PCF-SPR)polarization filters have attracted much attention because of their flexible structure design,small size,good filtering effect and wide filtering range.In this paper,three new PCF-SPR filter structures are proposed based on PCF light conduction principle,surface plasma resonance theory and finite element method(FEM).The influence of structural parameters on the performance of PCF-SPR polarization filter is simulated by COMSOL Multiphysics software.Firstly,a single-polarized PCF-SPR filter structure coated with gold film is proposed.The filter can achieve single-channel filtering at a wavelength of 1540 nm,and the loss difference is ideal.The x-polarized core mode loss is 1016.0 d B/cm,while the y-polarized core mode loss is 33.8 d B/cm,and the crosstalk value at a wavelength of 1540 nm is as high as-853.1 d B,and the available optical bandwidth of less than-20 d B is 850 nm.Secondly,a tunable bimetal-coated single-polarization PCF-SPR filter structure is proposed,the orthogonal x-polarized and y-polarized modes can be operated simultaneously at 1310 nm and 1560 nm with y-polarized and x-polarized core mode losses(the unwanted losses)of 544.3 d B/cm and 147.3 d B/cm and corresponding to x-polarized and y-polarized core mode losses are 12.3 d B/cm and 24.0 d B/cm.The crosstalk value of the 1310 nm and 1560 nm are 462.0d B and-107.1d B and the bandwidths are 224 nm and 504 nm.Finally,based on the previous model,a liquid-filled single-polarization PCF-SPR filter structure with two-holes coating is proposed.The filter not only the orthogonal x-polarized and y-polarized modes can be operated simultaneously at 1330 nm and 1570 nm,but also has higher loss peaks and better filtering effect.The x-polarized core mode and the y-polarized core loss are 589.2 d B/cm and 544.8 d B/cm at 1300 nm and 1570 nm,respectively,and corresponding to polarized mode losses are 24.1 d B/cm and 39.8 d B/cm.The crosstalk values are-490.8 d B and 438.7 d B,and the corresponding optical bandwidths are 258 nm and 521 nm.The above three new PCF-SPR polarization filters can achieve good filtering effects,and have improved filter characteristics such as loss,crosstalk,and available optical bandwidth.By adjusting the structural parameters,a larger filtering range can be achieved.With its excellent performance,PCF-SPR polarization filter has broad application prospects.