  A waveguide structure consisting of a tapered nanofiber on a metal film is
proposed and analyzed to support highly localized hybrid plasmonic modes. The
hybrid plasmonic mode can be efficiently excited through the in-line tapered
fiber based on adiabatic conversion and collected by the same fiber, which is
very convenient in the experiment. Due to the ultrasmall mode area of plasmonic
mode, the local electromagnetic field is greatly enhanced in this movable
waveguide, which is potential for enhanced coherence light emitter
interactions, such as waveguide quantum electrodynamics, single emitter
spectrum and nonlinear optics.
