Ultra-Uniform Field Distribution in a Finite-Width Metal-Dielectric-Metal Waveguide

We investigate the propagation characteristics of the fundamental surface plasmon polariton (SPP) mode of a finite-width metal-dielectric-metal waveguide. By changing the refractive index or the thickness of the dielectric layer of the waveguide, the SPP mode can be transformed from a mode confined in the dielectric layer into a mode confined around the metal corners. There always exists a condition at which the mode field distribution in the dielectric layer becomes almost perfectly uniform along the direction parallel to the metal layers, and this condition is insensitive to the width of the waveguide. It is also possible to obtain an ultra-uniform field distribution by controlling the refractive index of a different dielectric placed on both sides of the waveguide. The waveguide can be used as a basic structure for the realization of nanosized photonic devices and sensors. © 2012 Springer Science+Business Media, LLC.