Ultra-short polarization beam splitter based on rhombic structure dual-core photonic crystal fiber with a central hole filled nematic liquid crystal

Abstract

In this paper, an ultra-short polarization beam splitter (PBS) based on a rhombic structure dual-core photonic crystal fiber (RS-DC-PCF) with a central hole filled nematic liquid crystal (NLC) is proposed. For the RS-DC-PCF, the air holes of different sizes are arranged in a rhombic lattice, and the NLC (E7) is introduced to enhance the birefringence. The full vector–finite element method is used to investigate the coupling and propagation characteristics of the PBS. Moreover, the effects of different structure parameters on the coupling lengths ( C L x , C L y ) and coupling length ratio in the x -polarization and y -polarization directions and the preparation tolerances of different air hole diameters are investigated. And the effects of the temperature and molecule angle of the NLC (E7) on the extinction ratio (ER) are also analyzed. The simulation results show that the ultra-short splitting length of the optimized RS-DC-PCF PBS is 58 µm, the ER is higher than 20 dB in the wavelength range of 1.306 to 1.641 µm, and the bandwidth is up to 335 nm, covering most of the O + E + S + C + L communication bands.