Forbidden gaps in finite periodic and quasi-periodic cantor-like dielectric multilayers at normal incidence.
Periodic and quasi-periodic Cantor-like bandgap structures that bordered upon a medium of refractive index n(0) are analyzed. An immersion model is used with the assumption that each layer is embedded between two identical regions of refractive index n(0) and thickness d(0), where d(0) is set equal to zero. Transmittance and group velocity are determined. Their dependence on n(0) is emphasized. Relations for the midgap value of the normalized group velocity are given. By use of these relations, diagrams are completed at different values of n(0), showing the pairs of quarter-wave-layer refractive indices at which there is an apparent superluminal tunneling through the finite periodic and quasi-periodic Cantor-like bandgap structures.
Cojocaru
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