We propose a polarization-insensitive design of a hybrid plasmonic waveguide (HPWG) optimized at the 3.392 µm wavelength which corresponds to the absorption line of methane gas. The waveguide design is capable of providing high mode sensitivity (S_mode) and evanescent field ratio (EFR) for both transverse electric (TE) and transverse magnetic (TM) hybrid modes. The modal analysis of the waveguide is performed via 2-dimension (2D) and 3-dimension (3D) finite element methods (FEMs). At optimized waveguide parameters, S_mode and EFR of 0.94 and 0.704, can be obtained for the TE hybrid mode, respectively, whereas the TM hybrid mode can offer S_mode and EFR of 0.86 and 0.67, respectively. The TE and TM hybrid modes power dissipation of ~3 dB can be obtained for a 20-µm-long hybrid plasmonic waveguide at the 60% gas concentration. We believe that the highly sensitive waveguide scheme proposed in this work overcomes the limitation of the polarization controlled light and can be utilized in gas sensing applications.

我们提出了一种混合等离子体激元波导（HPWG）的对极化不敏感的设计，该优化在3.392 µm波长处进行了优化，该波长对应于甲烷气体的吸收线。波导设计能够为横向电（TE）和横向磁（TM）混合模式提供高模式灵敏度（S_模式）和and逝场比（EFR）。波导的模态分析是通过2维（2D）和3维（3D）有限元方法（FEM）进行的。在优化的波导参数_下，TE混合模式的S_模式和EFR分别为0.94和0.704，而TM混合模式可以提供S_模式和EFR分别为0.86和0.67。对于气体浓度为60％的20 µm长的混合等离子体激元，TE和TM混合模式的功耗可达到〜3 dB。我们相信，这项工作中提出的高灵敏度波导方案克服了偏振控制光的局限性，可用于气体传感应用。