We report on the first experimental demonstration of terahertz (THz) whispering-gallery modes (WGMs) with an ultra-high quality factor of 1.5 × 104 at 0.62 THz. The WGMs are observed in a high resistivity float zone silicon spherical resonator coupled to a sub-wavelength silica waveguide. A detailed analysis of the coherent continuous wave THz spectroscopy measurements combined with a numerical model based on Mie-Debye-Aden-Kerker theory allows us to unambiguously identify the observed higher order radial THz WGMs.
Vogt, D. W., & Leonhardt, R. (2018). Ultra-high Q terahertz whispering-gallery modes in a silicon resonator. APL Photonics, 3(5). https://doi.org/10.1063/1.5010364