Low-loss hybrid plasmonic modes guided by metal-coated dielectric wedges for subwavelength light confinement.

The optical characteristics of a metal-coated dielectric wedge structure are investigated at a wavelength of 1550 nm. The effects of the metal/gap layers' thicknesses, as well as the dimension of the dielectric wedge on the guided modes' properties, are systematically analyzed. It is revealed that the characteristics of the fundamental quasi-TE and quasi-TM plasmonic modes supported by the configuration demonstrate similar trends against the variation of the metal layer thickness while exhibiting quite different behaviors with the change of the wedge size. By choosing appropriate physical dimensions, both modes could simultaneously achieve low modal loss and subwavelength field confinement, along with reasonable mode power inside the low-index gap region. Investigations on the directional coupling between adjacent identical waveguides indicate that ultralow crosstalk can be enabled by the quasi-TE mode, with the coupling length more than two orders of magnitude larger than that achieved by the plasmonic mode in conventional hybrid counterparts. The presented metal-coated dielectric wedge structures can be employed as important building blocks for a number of integrated nanophotonic components, and could also enable numerous applications at the subwavelength scale.