Characterization of Materials and Mode Structure for High-Q Resonators using Bragg Confined Modes

This paper describes the design and mode structure of resonators using Bragg confined modes. We investigate a range of low-loss dielectric materials with aim to maximize the Q-factor. The structure is composed of a hollow dielectric cylinder with the mode confined in the central low-loss region. We illustrate the importance of material permittivity and show it is possible to obtain a better Q-factor using higher permittivity materials with larger intrinsic dielectric losses than single crystal sapphire. Also we illustrate the discovery of a new type of Bragg confined mode in a dielectric loaded cavity. The dielectric is placed in a silver platted copper cavity. A resonance was observed at 13.4 GHz with an unloaded Q-factor of order 2×10, which is more than a factor of six above the dielectric loss limit. Usually a Bragg structure requires a pure Transverse Electric mode with no azimuthal variations and only an electric field component, Eθ, while this mode possesses a number of azimuthal variations greater than zero.