Tunable reflectance spectra of multilayered cholesteric photonic structures with anisotropic defect layers

Abstract

In this paper, we investigate the spectral characteristics of normal incident light reflected by a multilayered structure composed of an alternated sequence of single-pitch cholesteric liquid-crystal (ChLC) and anisotropic layers. Using the Berreman 4x4 matrix formalism, we numerically obtain the reflection spectrum and the chromaticity diagram as a function of the anisotropic layers thickness d. For d-->0 , the structure behaves like a single ChLC layer, showing a single reflection band. As the anisotropic layer thickness increases, the reflection band shifts toward high-wavelength spectral regions, while new reflection bands appear. As a consequence, the reflection chromaticity continuously changes with d . It is observed that a suitable choice of the anisotropic layer thickness can produce a threefold reflection band with a red-green-blue associated color for both polarized and unpolarized incident lights.

Coupling of Defect Modes in Cholesteric Liquid Crystals Separated by Isotropic Polymeric Layers

“…Subsequently, they realized a quasi-periodic system using single-pitch CLCs and isotropic films of polyvinyl alcohol and fabricated a red-green-blue reflector [15]. There were further theoretical studies that considered reflectors [16,17,18], studied optical properties of composites of CLCs and isotropic layers [19,20,21,22] or calculated the DOS of a stack structure of CLCs and isotropic medium [23,24]. However, up until now, very little attention has been paid to the coupling of defect modes in such composite assemblies.…”

Photonic density of states of a stack of cholesteric liquid crystals and isotropic medium layers

“…The formation of multiple PBSs in one-dimensional multilayer structures containing CLC and isotropic layers has been reported in theoretical and experimental studies [4][5][6][7][8][9] . Analogous studies of one-dimensional multilayer structures including CLC and anisotropic layers were reported in 10 . Quasiperiodic structures described by the Fibonacci series and containing CLC layers were investigated in 11 .…”

Cholesteric Liquid Crystals with a Broad Light Reflection Band

“…Topics that are out of the scope of the review include: multiple bandgaps49–65 for which the reflection consists of the sum of well‐defined (separate) narrow peaks; cells with different colors in the x ‐ y plane of the layer;66–73 broadening of the bandgap such as occurs for light scattering, but not reflection, from a polydomain focal‐conic texture;74 nonequilibrium conditions such as field‐induced,75–80 light‐driven,81–84 stress‐induced,85 or thermally controlled60, 86, 87 broadening of the bandgap. The basic property disappears at the same time as the stimulus, or is not displayed if the temperature program is not followed; increased reflection and coexistence of double‐handed CP reflection bands as an expected consequence of oblique incidence 88–99.…”

“…multiple bandgaps49–65 for which the reflection consists of the sum of well‐defined (separate) narrow peaks;…”