  In this work we report two designs of subwavelength fibers packaged for
practical terahertz wave guiding. We describe fabrication, modeling and
characterization of microstructured polymer fibers featuring a
subwavelength-size core suspended in the middle of a large porous outer
cladding. This design allows convenient handling of the subwavelength fibers
without distorting their modal profile. Additionally, the air-tight porous
cladding serves as a natural enclosure for the fiber core, thus avoiding the
need for a bulky external enclosure for humidity-purged atmosphere. Fibers of 5
mm and 3 mm in outer diameters with a 150 \mu m suspended solid core and a 900
\mu m suspended porous core respectively, were obtained by utilizing a
combination of drilling and stacking techniques. Characterization of the fiber
optical properties and the near-field imaging of the guided modes were
performed using a terahertz near-field microscopy setup. Near-field imaging of
the modal profiles at the fiber output confirmed the effectively single-mode
behavior of such waveguides. The suspended core fibers exhibit broadband
transmission from 0.10 THz to 0.27 THz (larger core), and from 0.25 THz to 0.51
THz (smaller core). Due to the large fraction of power that is guided in the
holey cladding, fiber propagation losses as low as 0.02 cm-1 are demonstrated.
Low-loss guidance combined with the core isolated from environmental
perturbations make these all-dielectric fibers suitable for practical terahertz
imaging and sensing applications.
