Dielectric slot embedded metal cavity waveguides

We systematically investigate a dielectric slot embedded metal cavity waveguide, which consists of a thin slot embedded in the center of a metal–dielectric–metal (MDM) waveguide. Analytical and numerical calculations are carried out at the telecommunication wavelength λo=1.55 μm and it is shown that introducing the slot simultaneously improves the modal confinement and the propagation distance of the MDM waveguide. It is also shown that a deep subwavelength modal confinement (~10−5(λo/2)2) can be achieved in a form of planar two-dimensional waveguide on a high-index dielectric substrate with most of the field still confined in a slot region. We believe that the slot embedded metal cavity waveguide will help realize ultra-compact optoelectronic devices in various applications of nanophotonics by relaxing the trade-off between the mode area and propagation distance in the MDM waveguide.