Terahertz in-fiber polarizer with high polarization loss ratio and low loss using hollow-core anti-resonant fiber

Abstract The high-performance terahertz polarizer is critically required to establish advanced terahertz (THz) communication networks. This work presents a hollow-core anti-resonant fiber polarizer featuring an asymmetric cladding design to achieve both high polarization loss ratio (PLR) and low transmission loss. Semi-circle nested tubes with dual-gradient wall thickness are integrated along one direction to enhance resonant coupling between the x -pol core guided mode and cladding modes, while a three-layer nested anti-resonant structure is employed along the orthogonal direction to ensure ultra-low loss transmission of the y -pol core guided mode (YCGM). The filtering characteristics are analyzed using the powerful finite element method by evaluating geometric parameters. The numerical results show that this fiber polarizer can achieve a maximum PLR of 6.76 × 10 4 at 1.18 THz, with an ultra-low confinement loss of 7.78 × 10 −5 dB m −1 for the YCGM. Meanwhile, a stable bandwidth of 0.13 THz can be obtained, where the PLR exceeds 100. Besides, fabrication tolerance analysis indicates that the device maintains robust performance under a wall thickness deviation of ±2%. We believe that this in-fiber polarizer can be one of the key candidate photonic devices in THz communication, sensing, and other related fields.