Demonstration of THz waves propagation within a hollow-core THz waveguide based on an out-of-plane photonic bandgap crystal cladding

The development of terahertz (THz) waveguides is limited by the high-conductivity losses of metals, the surface roughness, and the high-absorption of the dielectric materials. Consequently, dry air is certainly the most favorable medium to propagate THz radiations. A novel hollow-core THz waveguide enabling efficient THz wave propagation over 72 cm long length, is presented in this study. THz waves guiding in a hollow-core is achieved by an out-of-plane Photonic Band Gap (PBG) crystal cladding with a design inspired from the technology of hollow core PBG-crystal fibers. These fibers developed in the optical domains have demonstrated exceptional performances such as single mode propagation of light with low attenuation on kilometer length scales. The properties of the PBG guiding mechanism to forbid THz waves extension in the crystal cladding is exploited for enabling low-loss propagation in a waveguide fabricated with a highly absorptive material (ex. silica). PBG guidance into this new class of hollow-core THz waveguide were demonstrated theoretically and experimentally.