Characterization of terahertz field confinement at the end of a tapered metal wire waveguide

We present experimental verification of the possibility of strong subwavelength confinement of the terahertz electric field at the end of a tapered metal wire waveguide. The axial field component at the end of the tapered waveguide shows a lateral confinement that is an order of magnitude greater than an untapered waveguide, and over 100 times greater than the free-space wavelength. The axial component is also strongly confined in the propagation direction, in contrast to the radial field component. Comparison to numerical simulation yields excellent agreement when the effect of the detecting probe is included in the analysis.