  The hybrid plasmonic waveguide consists of a high-permittivity dielectric
nanofiber embedded in a low-permittivity dielectric near a metal surface. This
architecture is considered as one of the most perspective candidates for
long-range subwavelength guiding. We present qualitative analysis and numerical
results which reveal advantages of the special waveguide design when dielectric
constant of the cylinder is greater than the absolute value of the dielectric
constant of the metal. In this case the arbitrary subwavelength mode size can
be achieved by controlling the gap width. Our qualitative analysis is based on
consideration of sandwich-like conductor-gap-dielectric system. The numerical
solution is obtained by expansion of the hybrid plasmonic mode over single
cylinder modes and the surface plasmon-polariton modes of the metal screen and
matching the boundary conditions.
