Guided propagation of terahertz pulses on metal wires

We demonstrate a new waveguiding structure for terahertz (THz) radiation in which broadband THz pulses are confined and guided along a bare metal wire. The propagation of THz pulses on such a waveguide is characterized with a fiber-coupled terahertz time-domain spectroscopy system. Free-space THz radiation is coupled onto the waveguide at different positions along the wire, and spatially resolved detection of the electric field of the guided wave is performed at the end of the wire. This waveguide exhibits the lowest attenuation of any waveguide for broadband THz pulses reported so far because of the minimal exposed metallic surface area. It also supports propagation of broadband radiation with negligible group-velocity dispersion, making it especially suitable for use in THz sensing and diagnostic systems. In addition, the structural simplicity lends itself naturally to the facile manipulation of the guided pulses, including coupling, directing, and beam splitting. These results can be described in terms of a model developed by Sommerfeld for waves propagating along the surface of a cylindrical conductor.