Hybrid long-range surface plasmon-polariton modes with tight field confinement guided by asymmetrical waveguides

A finite width dielectric-metal-dielectric (DMD) waveguide placed on a substrate is numerically investigated near the telecom wavelength lambda = 1550 nm by the finite element method. With proper waveguide sizes, the asymmetrical DMD waveguide can support hybrid long-range surface plasmon-polariton modes which have tight field confinement (approximately 700 nm) and long propagation lengths (L> 300 microm) simultaneously. Compact plasmonic waveguide-ring resonators (WRRs) based on such asymmetrical DMD waveguide show high quality factors compared with dielectric-loaded surface plasmon-polariton, channel plasmon polariton, plasmonic whispering-gallery microcavity, and pure dielectric waveguide cases.