Intuitive Analysis of Subwavelength Plasmonic Trench Waveguide

We propose an intuitive and quantitative model to describe the channel plasmon polaritons (CPPs) guided by a subwavelength rectangular groove cut into a metal substrate. The model is built up by considering a multiple scattering process of gap surface plasmons bouncing between the mouth and the bottom of the groove. The model can comprehensively reproduce both the dispersion relations and electromagnetic fields of the CPPs and can also decrease the computational amount compared to full-wave numerical methods. The evolution of the CPP from guided, quasi-guided to evanescent modes with the increase of wavelength is explained with the model.