  A novel plasmonic THz fiber is described that features two metallic wires
that are held in place by the porous dielectric cladding functioning as a
mechanical support. This design is more convenient for practical applications
than a classic two metal wire THz waveguide as it allows direct manipulations
of the fiber without the risk of perturbing its core-guided mode. Not
surprisingly, optical properties of such fibers are inferior to those of a
classic two-wire waveguide due to the presence of lossy dielectric near an
inter-wire gap. At the same time, composite fibers outperform porous fibers of
the same geometry both in bandwidth of operation and in lower dispersion.
Finally, by increasing cladding porosity one can consistently improve optical
properties of the composite fibers.
