Performance analysis of a photonic crystal fiber polarization filter filled with different materials

A compact square photonic crystal fiber polarization filter with high performance is proposed. Two larger holes filled with different metal and fluid are designed to break the strict structure symmetry and forming high birefringence. Four small pores are designed to provide a wider channel for the coupling between defect mode and core mode. Its filtering and coupling characteristics are analyzed by the full vector finite element method. In addition, the properties of PCF filled with different materials are compared and discussed. Different metal materials have different dielectric constants, different optical damping, interband transitions, molecular structure, and physicochemical properties, which make their transmission modes and coupling strength different. The results show that the performance of a PCF filter filled with gold and liquid is the best, which is very suitable for an adjustable PCF polarization filter. The calculation results show that the extinction ratio of the designed filter can reach 5383 dB for a device length of 3 mm; the unwanted fiber loss can reach 2073 dB/cm; and the applicable bandwidth of 2000 nm covers almost the whole communication band. The proposed polarization filter shows large unwanted loss, high extinction ratio, wide bandwidth and coordination, which make it a good candidate for excellent optical fiber filter devices.