A miniaturized and high-bandwidth polarization filter based on a plasmonic and liquid crystal offset core photonic crystal fiber

Abstract

Miniaturized and broadband polarization-dependent filters with high crosstalk values are extremely desirable for practical applications in the fields of optical communications and sensing. A miniaturized photonic crystal fiber (PCF) with highly broadband polarization filtering properties is proposed in this paper. Two relatively large air holes coated with a gold film on opposite sides of the liquid crystal-filled offset core are introduced in this PCF structure to produce highly broadband polarization-dependent filtering transmissions. The impacts of the filtering properties with variable structural parameters have been studied based on the finite element method. By altering the gold film thickness (t) to be 18.7 nm and 13.8 nm, the proposed broadband polarization filter offers high resonance peaks of 2041.79 dB/cm and 2342.88 dB/cm for y-polarized mode at the wavelengths of 1.31 μm and 1.55 μm, while the corresponding loss for x-polarized one is 0.10 dB/cm and 0.83 dB/cm, respectively. Moreover, the crosstalk of the 100-μm-long PCF polarization filter with t = 18.7 nm and t = 13.8 nm is up to 177.34 dB and 203.43 dB at 1.31 μm and 1.55 μm, respectively. As the fiber length is 100 μm, the bandwidth with the crosstalk less than − 20 dB can be up to 1200 nm, from 1.2 to 2.4 μm. In addition, the proposed broadband and miniaturized PCF filter is not sensitive to the temperature variation and exhibits stable filtering characteristics with the ± 1% fabrication tolerances.