文章提出一种光子晶体光纤(PCF),通过调整结构，改变包层缺陷中微型空气孔的排列方式、孔大小和孔孔间隔实现折射率匹配耦合，达到单模单偏振传输的目的。采用全矢量有限元法仿真建模，结果表明，当包层缺陷中微型空气孔直径为27.7 μm、孔孔间隔为38 μm，且采用三角晶格排列时，在0.719～1 THz范围内，偏振损耗比>100，实现了单模单偏振传输，此时y偏振基模的传输损耗最低为2.4e-3 dB/km。与填充法实现折射率匹配耦合相比，调整结构可以获得更大的偏振损耗比479，更低的传输损耗2.4e-3 dB/km以及更宽的带宽0.281 THz。

In this paper, a kind of THz single-polarization single-mode PCF is proposed. The dependence of refractive index matching coupling on several parameters (diameter of the micro air holes d3, lattice constant Λ3, lattice shapes in cladding) are investigated with a full-vector Finite Element Method (FEM). Simulation results show that the best-optimized parameters of fiber are supposed to be d3=27.7 μm, Λ3=38 μm and triangular lattice. The fiber exhibits large polarization-dependent loss ratio (>100) and wide bandwidth (0.281 THz). The polarization-dependent loss ratio will be larger than 100 when the frequency is higher than 0.719 THz, and single-polarization single-mode transmission is realized. At the frequency of 0.95 THz, the polarization-dependent loss ratio reaches the maximum of 479 and the confinement loss is 2.4e-3 dB/km. Compared with the liquid filling method, the structural adjustment method achieves larger polarization-dependent loss radio, lower confinement loss, and wider bandwidth.