The operation of nano scale waveguides is based on the principle of total internal reflection or plasmonics. In dielectric waveguides, light is confined within a high-refractive-index core by total internal reflection at the core-cladding interface. In plasmonic waveguides, electromagnetic waves couple with electron oscillations at the surface of a metal, allowing the waves to propagate along the metal-dielectric interface at deeply subwavelength scales.
