Tunable Characteristics of Wedge Plasmonic Waveguide with Thin Metallic Layers

In this study, we propose a mechanism for tuning the modal characteristics of a wedge plasmonic waveguide. The wedge plasmonic waveguide is composed of a thin metallic layer deposited on a wedge-shaped dielectric waveguide. The tuning mechanism is based on controlling the surface plasmon polariton (SPP) mode at the interface between the metal layer and the dielectric waveguide instead of controlling the SPP mode at the interface between the wedge-shaped metal layer and the surrounding media. This mechanism is performed by modulating the effective refractive index of the dielectric waveguide using a closely coupled tuning waveguide. The numerically investigated results show that the propagation length of the device can be tuned more than 100%; this characteristic has not been explored yet in previous studies. The effective mode area with deep-subwavelength size is almost kept constant while tuning the propagation length. This study offers new insights into tailoring the modal characteristics of plasmonic waveguides based on controlling the mode property at the interface between the metal layer and the dielectric waveguide. This study is also a guideline for developing active plasmonic devices such as tunable nanoscale lightwave guiding waveguides and THz optic modulators.