Design of a Metal-Filled Photonic-Crystal Fiber Polarization Filter Based on Surface Plasmon Resonance at 1.31 and 1.55 $\mu$m

A metal-filled photonic crystal fiber (PCF) polarization filter based on surface plasmon resonance (SPR) is proposed and designed. The structure of the cross-section of a PCF is composed of a hexagonal lattice of air holes, in which an air hole is selectively filled with metal. We realize the polarization filter at the communication wavelengths of 1.31 and 1.55 μm with optimized structural parameters. The losses of the X polarization mode are 25126.44 and 22444.54 dB/m, while the losses of the Y polarization mode are about 1375.81 and 358.62 dB/m at the resonance wavelengths 1.31 and 1.55 μm, respectively. Therefore, the two light polarizations can be clearly separated. When the fiber length is 600 μm, cross-talk is over 20 dB at the communication wavelengths, while the achieved bandwidth is 160 and 200 nm at 1.31 and 1.55 μm, respectively. Furthermore, the distance between the resonance peaks of the two polarizations can reach 267 nm at 1.55 μm, achieving a significantly higher value than previously reported. These results are of great significance for the development of a polarization filter applicable in targeted communication bands.