In this work, we theoretically predict the possibility to obtain a giant hypersonic elastic mirror in porous silicon superlattices by using a phononic heterostructure. The heterostructure is composed of a tandem of multiple phononic crystal lattices with periods in the range 37–167 nm, which recently have been experimentally reported [L. C. Parsons and G. T. Andrews, Appl. Phys. Lett. 95, 241909 (2009)]. Considering the scalability of the eigenvalues of the elastic wave equation, the lattices are chosen such that each stop band can be superposed to obtain a larger overall stop band. Theoretical evidence of a giant hypersonic phononic mirror for longitudinal and transverse vibrations is found in the gigahertz range.
Abstract-In this work we report the modeling of an one-dimensional photonic heterostructure which presents a giant omnidirectional photonic band gap. This omnidirectional reflector is made by the union of lattices with the same filling fraction and index contrast, but with different lattice periods. Using the scalability of the electromagnetic wave equation we present a simple manner to enlarge -as large as desired-the omnidirectional mirror. We apply our method to design an omnidirectional reflector for all the visible range.
Using the configuration of an imprinted cholesteric elastomer immersed in a racemic solvent, the authors find the solution of the boundary-value problem for the reflection and transmission of incident optical waves due to the elastomer. They show a significant width reduction of the reflection band for certain values of nematic penetration depth, which depends on the volume fraction of molecules from the solvent, whose handedness is preferably absorbed. The appearance of nested band gaps of both handednesses during the sorting mixed chiral process is also obtained. This suggests the design of chemically controlled optical filters and optically monitored chiral pumps.
We have found that a chiral twist defect inserted in a cholesteric elastomer gives rise to circularly polarized localized modes of both handedness. This defect enhances the resonant mode amplitude whose handedness is opposite to that of the cholesteric helix for high cross-linked density, whereas for low cross-linked density, the same mode is decoupled with the defect and thus the resonant mode disappears. Finally, the resonant mode of the same handedness as the elastomer helix is maintained for both high and low cross-linked density.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.