design of a compact and broadband polarization filter based on a liquid crystal-filled and gold-coated photonic crystal fiber

A compact and broadband polarization-dependent filter of a simple hexagonal gold-coated pcf with liquid crystal infiltrating is proposed, and its polarization filtering properties are investigated by using the finite element method. the design of two gold-coated holes filled with liquid crystal can significantly improve the crosstalk in a 0.8–2.4-μm wavelength range, where the core-guided modal loss in the x polarization is far higher than the one in the y polarization. the confinement losses of the core modes for the x and y polarizations are 314.29 db/cm and 0.11 db/cm at 0.8 μm, 1439.64 db/cm and 1.89 db/cm at 1.31 μm, and 1124.6 db/cm and 2.83 db/cm at 1.55 μm, respectively. the suggested 100-μm-long single polarization filter has an ultra-broadband bandwidth of 1600 nm, from 0.8 to 2.4 μm, with high crosstalk better than 20 db. moreover, by adjusting the gold layer thickness between 25 and 30 nm, the bandwidth remains close to 1600 nm with a small wavelength shift, making this broadband polarization filter widely used in broadband communication systems.