Ambichiral, equichiral and finely chiral layered structures

Examining the optical response characteristics of structurally chiral piles of identical dielectric plates, we introduce ambichiral and equichiral layered structures in contrast to the finely chiral layered structures that are commonly held to replicate the circular-polarization-discriminatory abilities of cholesteric liquid crystals (CLCs) and chiral sculptured thin films (CSTFs). A finely chiral layered structure, just like CLCs and CSTFs, exhibits the phenomenon of Bragg resonance for normally incident plane waves of only one circular polarization state. In contrast, an ambichiral layered structure evinces different Bragg resonances for different circular polarization states, while an equichiral layered structure evinces the same Bragg resonances for both circular polarization states. (C) 2004 Elsevier B.V. All rights reserved.