Ultra-broadband small-size polarization splitter based on gold-coated dual-core photonic crystal fiber

Abstract In this paper, an ultrashort polarization beam splitter (PBS) for ortho-hexagonal dual-core photonic crystal fiber (OH-DC-PCF) based on a gold-coated film with central holes is proposed. In OH-DC-PCF, air holes are arranged in the ortho-hexagonal lattice with elliptical structures and metal coatings introduced to enhance birefringence. The coupling and propagation characteristics of the transmitted light with the PBS are investigated using the full vector finite element method, and the effects of different structural parameters on the coupling lengths (CL), coupling length ratios (CLR), and extinction ratios (ER) in the x-polarization and y-polarization directions, as well as the effects of the preparation tolerances on the device length and the thickness of the gold film, are explored. The simulation results show that the optimized OH-DC-PCF has an ultrashort splitting length of 16.67 μm, an ER higher than 20 dB over the wavelength range of 0.94–1.97 μm, and a bandwidth of up to 1030 nm, which fully covers the E + S + C + L + U communication band. With ultra-short device length, ultra-wide operating bandwidth and good preparation tolerance, this PBS has great potential for applications in optical fiber communications.