Long-range dielectric-loaded surface plasmon-polariton waveguides.

A waveguiding configuration for surface plasmon polaritons (SPPs) featuring simultaneously a tight mode confinement and long propagation (several millimeters) at telecom wavelengths is proposed and analyzed using the finite-element method. The configuration represents a long-range dielectric-loaded SPP waveguide (LR-DLSPPW), in which a thin and narrow metal stripe is sandwiched between a square dielectric ridge and a dielectric film supported by a low-index substrate. Considering optical polymers, for example, we calculated that a 15-nm-thick and 500-nm-wide gold stripe placed on a 460 nm thick medium-index (1.49) layer supported by a low-index (1.34) substrate and topped by a 850 × 850 nm(2) high-index (1.535) ridge supports a fundamental LR-DLSPPW mode having width of 1.6 μm and propagating over 3.1 mm at the wavelength λ = 1.55 μm. The proposed configuration allows for easy connection to electrodes enabling, e.g., thermo- or electro-optic control, and is technologically simple being compatible with planar fabrication using UV-lithography.