Oblique propagation of light through a planar layer of a cholesteric liquid crystal (CLC) is solved by Ambartsumian's modified layer addition method. Two cases are considered, namely, the case when ...dielectric boundaries have a minimum influence on light transmission and the case when the CLC layer is in a vacuum. It is shown that in the first case a total internal reflection can happen for the fast eigen-mode at large incidence angles. New important features of light reflection (transmission) spectra, photonic density of states and accumulated energy density in the CLC layer are studied. The light localisation peculiarities in the CLC layer at oblique incidence is investigated too. It is shown that the light localisation for both the long-wavelength edge mode and the short-wavelength edge mode changes differently when the incidence angle changes. The obtained results can be used in the design of low-threshold lasers, in solar cell systems, in chiral photonics, in systems strongly absorbing light at certain wavelengths and when designing systems with absorption suppression created on the base of absorbing media, etc.
We investigated the features of the optical properties of magnetoactive cholesteric liquid crystals (CLCs) in an external static magnetic field. The boundary-value problem of light transmission ...through a finite layer of a magnetoactive CLC at normal light incidence and light reflection from a half-space is considered. We also investigated the evolution of the reflection with a change in the azimuth and ellipticity of the incident light. Some features of the reflection spectra, optical rotation, and polarization ellipticity, as well as the ellipticity spectrum of the eigen polarizations, are investigated, too. The peculiarities of the ellipticity evolution of the eigen polarizations due to a change in the magneto-optical activity parameter are considered.
We have experimentally investigated lasing peculiarities in a cholesteric liquid crystal - dye-doped polymer layer - cholesteric liquid crystal three-layer wedge-cell system with different laser dye ...concentration changing pumping energy. It was theoretically and experimentally shown that there are photonic defect modes in cholesteric photonic bandgap of the wedge-cell system. The problem was solved by Ambartsumian's layer addition modified method. It was shown that in the mentioned above system it is possible to obtain lasing generation and it should be noted that in our case the observed lasing peculiarities are not because of the isotropic defect (planar polymer layer) but the observed features are due to the cholesterics, namely by changing the thickness of the layer of cholesterics, we are able to ensure a change in the laser wavelength, due to the pitch jumps and therefore helix pitch gradient. The advantage of our experiment is the continuous change in the thickness of the cholesteric liquid crystal layer. To prevent degradation of the molecules, decrease of the fluorescence output as well as to except convective flows for higher pumping energies the dye concentration in the polymer was chosen 10
−4
mol/l. We have experimentally shown the dependences of the intensity and displacement of the lasing peaks' on the pumping power.
Spectral properties of the three-layered wedge-cell system of two identical cholesteric layers with an isotropic defect (dye-doped polymer layer) between them were investigated experimentally and ...theoretically. It was shown that multiple defect modes can be observed in this kind of system’s photonic band gap which widen the application range of system mentioned above such as low threshold lasing, multi-position trigger, multiwavelength filters, light shutters, etc. The supporting simulation was also provided showing an agreement between experimental results and theoretical calculations. The problem was solved by Ambartsumian’s layer addition modified method.
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•Functionalization of graphene oxide (GO) by amino acids (AA) was performed.•Formation of a GO liquid crystalline (LC) phase was shown.•pH-dependent behavior of AA-functionalized ...GOLCs was demonstrated.•L-cysteine dimerization occurred on the GO platform.
The colloidal 2D materials based on graphene and its modifications are of great interest when it comes to forming LC phases. These LC phases allow controlling the orientational order of colloidal particles, paving the way for the efficient processing of modified graphene with anisotropic properties. Here, we present the peculiarities of AA functionalization of GO, along with the formation of its LC phase and orientational behavior in an external magnetic field. We discuss the influence of pH on the GOLC, ultimately showing its pH-dependent behavior for GO-AA complexes. In addition, we observe different GO morphology changes due to the presence of AA functional groups, namely L-cysteine dimerization on the GO platform. The pH dependency of AA-functionalized LC phase of GO is examined for the first time. We believe that our studies will open new possibilities for applications in bionanotechnologies due to self‐assembling properties of LCs and magnificent properties of GO.
This paper experimentally demonstrated that in the cholesteric liquid-crystalline films it is possible to induce defect, which can be controlled by external electric field. Three cases of induced ...defects were examined and the main result of the experiment is that the rotation of polarization plane has maximum value when light first propagates through chiral liquid-crystalline photonic structure and then falls to the anisotropic layer. We have also supporting calculations, showing an agreement between experimental results and theoretical calculations. We present a new liquid crystal device configuration that performs as a tunable linear polarizer for both polarized and unpolarized lights.
The possibility of defect induction controlled by external electric field in nanoparticle-enriched cholesteric liquid-crystalline cells with selective reflection in visible range of light and control ...the rotation of polarization plane of light by induced defect was experimentally demonstrated. The main result of the experiment is the fact that the rotation of the polarization plane of light occurs at lower voltages when the cholesteric liquid crystal is enriched by nanoparticles. A new configuration of liquid crystal device that performs as a tunable linear polarizer for both polarized and unpolarized lights is presented.
In this paper, the peculiarities of the band structure of one-dimensional photonic crystals are studied, when the periodic (quasiperiodic) medium is inhomogeneous in relation to both the dielectric ...and magnetic properties. It is shown that the photonic band gap does not appear at small angles of incidence, in the case when the modulation depths of the dielectric permittivity and magnetic permeability coincide. The possibilities of obtaining photonic bandgaps in the terahertz radiation region are considered. The features of the band structure of photonic crystal with different spatial periods of the dielectric permittivity and magnetic permeability are investigated. It is shown that in this case, four PBGs appear in each diffraction reflection order.
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