Wide-range coupling between surface plasmon polariton and cylindrical dielectric waveguide mode.

A modified hybrid waveguide with a wide-range coupling and long propagation has been proposed and the coupled mode theory has been applied to study the hybrid waveguide systematically. Two structures are comparatively discussed, namely, a dielectric wire and a circular capillary tube, which are buried in a polymer matrix and separated from the silver substrate by a gap. The simulated results indicate that the circular capillary tube demonstrates a stronger coupling between the surface plasmon polariton and the waveguide mode compared to the solid dielectric wire. Furthermore, the electric field is highly confined in the gap area and can propagate several hundred micrometers.