Figure 1

Dual-periodical multilayer structure. Schematic view of the 1D dual-periodic structure showing the layer parameters, where n and m represent the period numbers of a and b in A and B substructures, respectively; n₁ and n₂ are high and low refractive indexes of alternating dielectric layers in a and b; the layer thickness is d₁ and d₂ for a, and d₃ and d₄ for b, respectively.