Highly Confined Photon Transport in Subwavelength Metallic Slot Waveguides

We report experimental realization of subwavelength slot waveguides that exhibit both micrometer-range propagation and high spatial confinement of light. Attention is given to rectangular waveguides with a Si_3N_4 core and Ag cladding; core thicknesses of 50−100 nm and widths of 250 nm − 10 μm are explored. Propagation lengths of ∼5λ are achieved with light confined to lateral and transverse dimensions of ∼λ/5 and ∼λ/2, respectively. This unique combination of light localization and propagation is achieved via interacting surface plasmons, which produce short modal wavelengths and strong field confinement at each metal/dielectric interface.