On the mechanism of high selectivity of two-dimensional coaxial Bragg resonators

The analysis of electrodynamic properties of two-dimensional (2D) Bragg resonators of coaxial-geometry realizing 2D distributed feedback was carried out with diffraction effects taken into account. Such resonators represent coaxial waveguide sections with a shallow double-periodic corrugation, which provides mutual coupling of four partial waves. It is shown that the high selectivity of 2D Bragg resonators over the azimuthal mode index can be explained by different behavior of the normal symmetrical and non-symmetrical waves near the Bragg resonance in an unbound double-periodic corrugated waveguide.