填充ENZ材料的太赫兹高双折射及近零平坦色散微结构光纤北大核心CSCD

为了实现太赫兹波的保偏波导传输,设计了一种含有纤芯缺陷孔和椭圆形包层空气孔的高双折射微结构光纤。通过在包层空气孔中选择性地填充太赫兹近零介电常量(epsilon-nearzero,ENZ)材料,引入了几何结构和材料分布的双重不对称性,破坏了2个偏振基模的简并以获得高双折射特性。应用有限元方法研究了光纤的双折射、损耗和色散等传输特性随结构参数的变化规律。在0.5 THz~2 THz的宽频段范围内获得了大于0.01的高双折射。x和y偏振基模的损耗在0.8 THz附近具有最小值,分别为0.903 dB·cm^(-1)和0.851 dB·cm^(-1)。纤芯缺陷孔可以有效调节色散特性,y偏振基模在1 THz~1.8 THz范围内具有(0±0.054)ps·THz^(-1)·cm^(-1)近零平坦色散特性。光纤的传输特性对ENZ材料的折射率变化不敏感。研究结论为研制太赫兹保偏光纤提供了理论参考。

ENZ material filled microstructured optical fiber with high birefringence and near-zero flattened dispersion at terahertz frequency

The high birefringent microstructured optical fiber (MOF) with small defective holes in fiber core and elliptical cladding air holes was designed for polarization-maintaining waveguide transmission for terahertz wave. By selectively filling the terahertz epsilon-near-zero (ENZ) materials in cladding air holes, the dual asymmetry of the geometric structure and the material distribution was introduced, and the degeneracy of two polarized fundamental modes was broken to obtain the high birefringence. The variation of transmission properties such as birefringence, loss and dispersion with structural parameters was studied by finite element method (FEM). In the wide-band range from 0.5 THz~2 THz, the high birefringence greater than 0.01 was obtained. The loss of the x-polarized and y-polarized fundamental mode has the minimum value around 0.8 THz, which are 0.903 dB·cm?1 and 0.851 dB·cm?1, respectively. The dispersion characteristics can be effctively adjusted by the defective holes in fiber core, and the y-polarized fundamental mode has the near-zero flattened dispersion characteristics of (0±0.054) ps·THz?1·cm?1 in the range of 1 THz~1.8 THz. The transmission characteristics of the designed fiber are insensitive to the refractive index changes of ENZ material. The research conclusions provide theoretical references for the development of terahertz polarization maintaining fiber.