An ultra-high extinction ratio broadband photonic crystal fiber splitter designed for the terahertz band

• We designed and analyzed a photonic crystal fiber polarization beam splitter consisting of a cyclic olefin copolymer as a base material by introducing a central air hole to increase the asymmetry of the structure. Excellent polarization beam splitting performance was achieved. • The cladding pores are arranged in a simple periodic arrangement, which makes the preparation process more maneuverable and cost-effective compared to compact pore structures, while retaining high optical properties. • At a length of 29.50688 mm, the extinction ratio is as high as −324.257 dB. • It has an ultra-bandwidth of 0.19 THz in the operating frequency range of 0.47 THz to 0.66 THz. Terahertz (THz) polarization beam splitters (PBS) are valuable for applications in areas such as wireless high-speed communications and terahertz imaging. In this paper, a dual-core terahertz photonic crystal fiber (PCF) polarization beam splitter is proposed to achieve short length, high extinction ratio and wide bandwidth. This PBS has a cyclic olefin copolymer (COC) as the base material, and the dual-core structure is realized by introducing a central air hole. Performance analysis, conducted using the finite element method, reveals that the proposed PBS achieves a minimum length of 29.50688 mm, a bandwidth of 0.19 THz between 0.47 THz and 0.66 THz, and a maximum extinction ratio of −324.257 dB at an incident light frequency of 0.54 THz, where the two polarization modes are nearly completely separated. In addition, the PBS exhibits good manufacturing tolerances with a structural error of ± 1 %. These excellent properties indicate that THz PCF-PBS has great potential for applications in terahertz-band optical communication, optical sensing and optoelectronic detection.