中文摘要：

领结型多孔光纤具有高双折射的特性,本文基于此设计了一种新型的双芯太赫兹（THz）偏振分束器,采用调整结构法实现了折射率反转匹配耦合,达到偏振分离.仿真结果表明：该偏振分束器在0.5—2.5 THz频率范围内均可实现偏振分离,最小分离长度仅为0.428 cm,且在整个频率范围内分离长度不超过2.5 cm.在2.3 THz,x,y两偏振模的吸收损耗均小于0.35 d B;消光比高达22.9和19.2 d B.此外,与填充法实现折射率反转匹配耦合的双芯THz偏振分束器进行比较,本文设计的偏振分束器实现简单,运行的频率范围更宽,分离长度更短,吸收损耗更低.

英文摘要：

Terahertz（THz） radiation, which is defined as the electromagnetic wave with a frequency ranging from 0.1 THz to 10 THz, has attracted widespread attention in recent years because of its unique possibilities in many fields. Highperformance THz polarization splitter, a key device in THz manipulation, is of great significance for studying the THz devices. In the present paper, a novel dual-core THz polarization splitter is proposed, which is based on porous fiber with near-tie units. The introduction of near-tie units into the fiber core can enhance asymmetry to realize high mode birefringence. And the results show that the porous THz fiber exhibits high birefringence at a level of 10-2over a wide frequency range. An index converse matching coupling（ICMC） method, which exhibits several advantages（such as short splitting length, high extinction ratio, low loss, and broad operation bandwidth）, is used to allow for the coupling of one polarization mode within a broad operation band, while the coupling of the other polarization component is effectively inhibited. The splitting length is equal to one coupling length of x- or y-polarization component for which inter-core coupling occurs, and short splitting length means low transmission loss. Unlike the reported filling method, an adjusting structure method is proposed in the paper to satisfy the condition of index converse matching coupling. The full vector finite element method（FEM）, which is based on the variational principle and the subdivision interpolation, is used to analyze the guiding properties of the proposed THz polarization splitter. The FEM is a widely used numerical method in physical modeling and simulation. Simulation results show that the THz polarization splitter operates within a wide frequency range of 0.5–2.5 THz. The splitting length does not exceed 2.5 cm in the whole frequency range and the minimum is only 0.428 cm. At 2.3 THz, the material absorption losses of x- and y-polarization are both less than 0.35 d B, and the extinction