Whispering-gallery-mode terahertz pulse propagation on a curved metallic plate

We demonstrate terahertz (THz) pulse propagation on a cylindrical aluminum plate, with low loss and negligible dispersion via transverse-electric type whispering gallery (WG) modes. We observe an apparent superluminal effect where the group velocity is greater than c, and explain this phenomenon by means of a plane-wave description of the WG modes. The propagation loss is dominated by the diffraction loss due to unbounded lateral spreading, with a negligible ohmic-loss contribution. Both experimental and theoretical results indicate a total loss as low as 2.6 dB/m at a frequency of 0.47 THz. (C) 2010 American Institute of Physics. [doi:10.1063/1.3466909]