Design of bimetal-coated photonic crystal fiber filter based on surface plasmon resonance

A novel the dual channel bimetal-coated photonic crystal fiber (PCF) single-polarization filter with a high birefringence structure based on surface plasmon resonance (SPR) is proposed and investigated by the finite element method (FEM). The advantages of the filter include high unwanted loss, good extinction ratio characteristics, flexibility in regulating the filtering range, large crosstalk value, as well as broad optical bandwidth. Specifically, the orthogonal two polarized modes can be operated simultaneously at communication wavelengths, and the unwanted losses are up to 591.5 dB/cm and 555.1 dB/cm at 1300 nm, 1570 nm. For a fiber length L of 1000 µm, the crosstalk (CT) values are −492.8 dB and 447.5 dB at 1300 nm and 1570 nm, respectively, corresponding to available optical bandwidths of 258.5 nm and 521.3 nm. The filtering range of the single-polarization filter can be adjusted by varying structural parameters. X-polarized mode filtering range is 1300–1530 nm, while the filtering range of y-polarized mode is 1570–1830 nm.