Tunable single-polarization bimetal-coated and liquid-filled photonic crystal fiber filter based on surface plasmon resonance.

A bimetal-coated single-polarization photonic crystal fiber (PCF) filter based on surface plasmon resonance (SPR) with a liquid-filled structure is designed and calculated by the finite element method (FEM). The filter has many excellent properties. The y-polarized and x-polarized modes can simultaneously filter at 1310 nm and 1560 nm with unwanted losses 544.3 dB/cm and 147.3 dB/cm, respectively, corresponding to polarized losses as low as 12.3 dB/cm and 24.0 dB/cm. The filtering range can be tuned by adjusting the diameter of the outer air holes (d1), the diameter of the inner air holes (d2), and liquid refractive index n. The filtering ranges of x-polarization and y-polarization are 1550-1990 nm and 1310-1830 nm, respectively. The crosstalk (CT) values are 462.0 dB and -107.1  dB and corresponding available bandwidths are 224 nm and 504 nm at 1310 nm and 1560 nm, respectively.