Polarization singularities in the metal-insulator-metal surface plasmon polariton waveguide

We investigate the polarization singularities in the metal-insulator-metal (MIM) plasmonic waveguide structure. It turns out that there exist $L$-line and $C$-point polarization singularities for the antisymmetric plasmonic mode in the MIM plasmonic waveguide. These polarization singularities have unique properties because they exist on a subwavelength plane parallel to the direction of propagation of light along the core. We believe that our findings can expand the understanding of polarization distributions in nanoscale plasmonic structures.