Birefringence dispersion in Šolc-type anisotropic periodic bandgap structures

Abstract

Forbidden gaps in Solc folded-type anisotropic periodic structures are analyzed. The azimuth angle in the first quadrant and unequal thicknesses of alternating uniaxial layers are considered. Unit-cell translation matrices are explicitly given at oblique and normal incidences. Implicit dispersion relations are obtained. Birefringence and normal group velocities are determined. Numerical examples make the distinction between the gaps determined by one root and those determined by two roots of the eigenvalue equation. When layers have unequal thicknesses, the gap determined by one root is much wider, but inside the gap the reflectivity is lower than unity, breaks appear, and an increased birefringence results.