A Novel Polarization Filter Based on Photonic Crystal Fiber with a Single Au-Coated Air Hole and Semi-Hourglass Structure

A polarization filter that has a novel photonic crystal fiber structure of semi-hourglass part and Au-coated film is proposed. We simulated the performance of the structure by the finite element method. The numerical simulation results show that altering the structure parameters and the thickness of Au film can lead to an optimal parameter combination with remarkable features, owing to the semi-hourglass part that induced huge asymmetry factor into the structure. On the one hand, when the thickness of Au film is controlled to be 18.7 nm, we can get the confinement loss 1304.02 dB/cm and 3.96 dB/cm on y-polarization and x-polarization respectively at λ = 1.55 μm. On the other hand, controlling the thickness to 35 nm, the confinement loss on y-polarization and x-polarization is 848.87 dB/cm and 1.31 dB/cm respectively at λ = 1.31 μm. In addition, the bandwidth with crosstalk smaller than − 20 dB is 680 nm and 800 nm at λ = 1.55 μm and 1.31 μm, respectively, when the fiber length is 500 μm. This structure, as a reference, can provide a new idea when designing a photonic crystal fiber structure applied in optical communication and sensor system.