Design of a compressed hexagonal dual-core photonic crystal fiber polarization beam splitter with a liquid crystal filled air hole

A compressed hexagonal dual-core photonic crystal fiber (CH-DC-PCF) polarization beam splitter (PBS) with a liquid crystal filled air hole is designed. The designed CH-DC-PCF has different sizes of air holes, which are arranged in a compressed hexagonal structure in the cladding region and introduce the birefringence. In addition, the nematic liquid crystal is filled into the central air hole to enhance the beam splitting effect. To obtain a shorter PBS, the structure parameters of the CH-DC-PCF are optimized by the finite element method. The simulation results show that the length of the proposed CH-DC-PCF PBS is 109.5 μm, and the corresponding extinction ratio (ER) reaches the first peak value of 86.07 dB at wavelength 1.494 μm, then 63.14 dB at wavelength 1.55 μm, and the second peak value of 83.35 dB at wavelength 1.553 μm. Moreover, the ER is higher than 20 dB in the wavelength range of 1.402 to 1.682 μm, so the bandwidth of the PBS is up to ∼280 nm, covering the S + C + L + U communication band.