Plasmonic waveguides based on symmetric and asymmetric T-shaped structures.

We describe the fabrication and characterization of plasmonic waveguides based on a periodic one-dimensional array of symmetric and asymmetric T-shaped structures. The devices are fabricated in a polymer resin using conventional 3D printing and subsequently overcoated with ~500 nm of Au. Using terahertz (THz) time-domain spectroscopy, we systematically measure the guided-wave transmission properties of the devices as a function of the different geometrical parameters. Through these measurements, we find that the resonance frequency associated with the lowest order mode depends primarily on the structure height and the cap width and appears to be independent of its lateral width. We also perform numerical simulations using the same geometrical parameters and find excellent agreement between experiment and simulation. We fabricate a waveguide in which the lateral width of the T-shaped structures is tapered in a linear fashion. While the spectrum of this device is similar to one without tapering, we observe relatively little reduction in the mode size, even as the structure width is reduced by a factor of eight.