Single-polarization terahertz hollow-core anti-resonant fiber with ultra-high polarization loss ratio

A terahertz-band single-polarization (SP) hollow-core anti-resonant fiber (HC-ARF) based on asymmetric cladding structures is proposed. In the Y axis direction, the mixed nested structure based on circular and elliptical tubes is used to suppress the loss of the Y-polarized fundamental mode (YPFM). The X axis cladding structure is composed of an outer circular tube with gradient wall thickness and two inner circular tubes which can enhance the transmission loss of the X-polarized fundamental mode (XPFM). The numerical analysis results demonstrate that the losses of XPFM and YPFM are 1.05 dB/m and 3.1 × 10−5 dB/m, respectively, at 1 THz. The ultra-high polarization loss ratio (PLR) of 33 727 is achieved. Meanwhile, the PLR can be maintained greater than 100 in the range of 0.96–1.04 THz and 1.115–1.125 THz. The excellent performance of the designed HC-ARF further expands its application potential in the terahertz-band.