Dual-core negative curvature fiber-based terahertz polarization beam splitter with ultra-low loss and wide bandwidth

Rui-Hua Liu,Zhan-Qiang Hui,Dong-Dong Han,Li-Ming Gao,Wei Wang

doi:10.7498/aps.71.20211650

Abstract

A novel terahertz polarization beam splitter (PBS) with low loss and large bandwidth based on double core negative curvature fiber is designed. The device takes copolymers of cycloolefin as the substrate, and 12 circular tubes with embedded tubes are evenly distributed along the circumference. The fiber core is divided into two cores through two groups of circumscribed small clad tubes symmetrical up and down. The finite-difference time-domain (FDTD) method is used to analyze its guide mode properties. The effects of various structural parameters on its beam splitting characteristics are investigated in detail, and the extinction ratio (ER), bandwidth and transmission loss of the PBS are analyzed. The simulation results show that when the incident light frequency is 1THz and the beam splitter length is 6.224 cm, the ER of <i>x</i>-polarized light reaches 120.8 dB, the bandwidth with ER above 20 dB is 0.024 THz, the ER of <i>y</i>-polarized light reaches 63.74 dB, the bandwidth with ER above 20 dB is 0.02THz, and the total transmission loss is as low as 0.037 dB/cm. Tolerance analysis shows that the PBS can still maintain good performance under the ±1% deviation of structural parameters.

Highlights

接着分析参数 r2 对耦合特性的影响. 图 3 为固定参数 r1 = 380 μm, r3 = 174.1 μm, L = 810 μm, t = 90 μm, r2 分别为 156, 160, 164 μm 时耦合长度和 CLR 随频率变化的曲线图. 可以看出, x 偏振光和 y 偏振光的耦合长度的变化趋势与图 2(a) 类似, 耦合长度比 CLR 的变化趋势与图 2(b) 类似. 分析认为, r2 的增大导致双芯间的耦合“桥梁”变小, 耦合作用的强弱和折射率差均发生改变, 耦合作用的强弱和折射率差的大小共同影响耦合长度的大小. 因此 x 偏振和 y 偏振的耦合长度出现图 3 中所示变化, 且不同的 r2 下具有不同的耦合长度. 在 1 THz 处, 当 r2 = 160 μm 时, CLR = 2, 因此选取 r2 的最优参数为 160 μm
Opt. 59 1974 [44] Zhu Y F, Chen M Y, Wang H, Yao H B, Zhang Y K, Yang J

Summary

Poyut Poxut

消光比的绝对值越大, 分束特性越好. 在实际应用中, 一般认为偏振分束器消光比的绝对值大于 20 dB 时, 即实现较好分束. 因此, 偏振分束器的消光比的绝对值大于 20 dB 所覆盖的频率范围被定义为其工作带宽. 在实际应用中, 一般认为偏振分束器消光比的绝对值大于 20 dB 时, 即实现较好分束. 因此, 偏振分束器的消光比的绝对值大于 20 dB 所覆盖的频率范围被定义为其工作带宽. 对于太赫兹负曲率光纤来说, 限制损耗 (confinement loss, CL) 和有效材料吸收损耗 (effective material loss, EML) 也是需要考虑的, 二者统称为总传输损耗. 一般用限制损耗 αCL 来表示光子晶体光纤对太赫兹波的限制能力, 可根据有效折射率的虚部计算得到 [33]: αCL =.

Lx m

Effective index

Optimal parameter