In this paper, an asymmetric directional coupler (DC) based on a GaAs–CaF₂ hybrid plasmonic waveguide (HPW) and a GaAs nanowire (NW) is designed for the mid-infrared polarization beam splitter (PBS). The mode characteristics of the GaAs–CaF₂ HPW and GaAs NW-based PBS are simulated by using the finite element method (FEM). With the appropriate widths of the HPW and NW, the TE polarization mode in the HPW and NW is phase-matched, whereas the TM polarization mode is phase mismatch. Hence, the TE mode undergoes a strong coupling to the GaAs NW while the TM mode pass through the GaAs–CaF₂ HPW directly. The results show that the PBS achieves the extinction ratio (ER) of 19.78 dB and insertion loss (IL) of 1.64 dB for the TE mode, ER of 7.78 dB and IL of 2.64 dB for the TM mode at the operating wavelength of 3.5 $\mu$m. The PBS based on an asymmetric DC paves the way to achieve integrated waveplates, which has potential applications in the detection and analysis of airborne molecules and the optical communication techniques with large signal transmission capacity.

在本文中，基于 GaAs-CaF ₂混合等离子体波导 (HPW) 和 GaAs 纳米线 (NW)的非对称定向耦合器 (DC)设计用于中红外偏振分束器 (PBS)。GaAs-CaF ₂ HPW 和基于 GaAs NW 的 PBS的模式特性通过使用有限元方法 (FEM) 进行模拟。在 HPW 和 NW 的适当宽度下，HPW 和 NW 中的 TE 偏振模式是相位匹配的，而 TM 偏振模式是相位不匹配。因此，TE 模式与 GaAs NW 发生强耦合，而 TM 模式直接通过 GaAs-CaF ₂ HPW。结果表明，PBS实现了19.78 dB的消光比（ER）和插入损耗（IL) 为 1.64 dB 的 TE 模式，7.78 dB 的ER和2.64 dB 的 TM 模式的IL在 3.5 的工作波长$\mu$米。基于非对称直流的PBS为实现集成波片铺平了道路，在空气分子的检测和分析以及大信号传输容量的光通信技术中具有潜在的应用价值。