A cylindrical dielectric whispering-gallery mode terahertz cavity coupled with a dielectric slab waveguide

Scope and method of study. The purpose of this study was to demonstrate a whispering-gallery mode (WGM) cavity for terahertz (THz) radiation, and to develop a theoretical description of the coupling properties of the cavity and the propagation properties of the WGM THz pulses. A dielectric slab waveguide and a dielectric cylinder were used as the coupler and the WGM cavity, respectively. In order to reduce the pulse broadening, the slab waveguide was sandwiched in between two metal plates, with an open window in the middle to bring the cylinder into contact with the slab waveguide.; Findings and conclusions. The THz pulse was successfully coupled into and out of the cylindrical cavity via the dielectric slab waveguide. We observed two cavity pulses coupled out of this structure, separated by a fixed delay. The cavity pulses cover a continuous frequency range from 0.4 to 1.8 THz, compared with discrete frequency points in the case where the cw laser is used as the coupling source. The WGM THz pulse was composed of several WGM modes. The group velocity dispersion of the WGM modes caused the pulse broadening and spectral oscillations of the cavity pulses. Coupled mode theory was derived for the slab-cylinder coupling structure and gave reasonably good agreement with the experimental results. This study demonstrated the propagation properties of the WGM THz pulses, and showed that this is a promising structure for future THz circuits.