Design of a compact and broadband terahertz polarization splitter based on gradient dual-core photonic crystal fiber

摘要

We report a broadband polarization splitter based on polyethylene photonic crystal fiber with microstructured dual refractive index gradient cores. These dual cores consist of a properly optimized arrangement of air holes such that for individual fibers x-polarized modes have large effective indices difference, while this index difference is almost zero for their y-polarized modes, leading to efficient coupling between the y-polarized modes. We have shown that by proper optimization of gradience created in the arrangement of air holes, efficient polarization splitting can be achieved for a broad range of terahertz frequencies. Device length and extinction ratio have been calculated numerically for the proposed configuration. Device length of similar to 1.96 to similar to 60 cm was found to be appropriate for frequencies in the 0.4-1.0 THz range to have high extinction ratios: -38 to -49 dB and -15 to -23 dB for the x and y polarizations, respectively. The bending loss for the proposed design is quite low: similar to 0.05 dB/m at 1 THz for the bend radius of 1 cm. These results suggest that a compact, low-loss, and broadband polarization splitter with very high extinction ratios can be achieved by wrapping the fiber around a small mandrel. (C) 2020 Optical Society of America