Dispersion characteristics of channel plasmon polariton waveguides with step-trench-type grooves.

We have studied the dispersion characteristics of single-mode channel plasmon polaritons (CPPs) with step-trench-type groove waveguides. From the numerical simulations using the finite-element method, the modal shapes and the complex propagation constants of the CPPs over a wide spectral range were obtained. It is shown that the dispersion characteristics of the step-trench-type CPP waveguide, which is composed of a step trench with a stacking nature, show an intermediate feature between the narrow and broad trenches. The results show that this configuration allows for a well-confined CPP with a moderate propagation loss at the wavelengths investigated.