On the total mean curvature of non-rigid surfaces

Using Green's theorem we reduce the variation of the total mean curvature of a smooth surface in the Euclidean 3-space to a line integral of a special vector field and obtain the following well-known theorem as an immediate consequence: the total mean curvature of a closed smooth surface in the Euclidean 3-space is stationary under an infinitesimal flex.Comment: 4 page

Harvesting Single Ferroelectric Domain Stressed Nanoparticles for Optical and Ferroic Applications

We describe techniques to selectively harvest single ferroelectric domain nanoparticles of BaTiO3 as small as 9 nm from a plethora of nanoparticles produced by mechanical grinding. High resolution transmission electron microscopy imaging shows the unidomain atomic structure of the nanoparticles and reveals compressive and tensile surface strains which are attributed to the preservation of ferroelectric behavior in these particles. We demonstrate the positive benefits of using harvested nanoparticles in disparate liquid crystal systems

Theory of dielectric and optical properties of PDLC films

We present results of the light scattering properties of PDLC films in the Rayleigh-Gans long wavelength régime. The calculations take into account dependent scattering effects using an effective medium theory. The Percus-Yevick hard-sphere approximation is used to introduce droplet correlation effects. We discuss the light scattering properties of radial and bipolar partially ordered droplets, making detailed comparisons with the literature where appropriate

Tunable-Focus Liquid Crystal Lens With Non-Planar Electrodes

We study a tunable-focus lens with convex and flat electrodes in a homogeneous liquid crystal (LC) cell. In a voltage-on state, a centro-symmetric gradient refractive index is generated within the LC layer, which causes the focusing behavior for the extraordinary wave. There have been experimental studies of the systems with spherical or parabolic shape of the top electrodes and there is a need in the theoretical modeling. We present a theoretical model of the lens with spherical top electrode and analyze its properties. We solve the Maxwell equations that are coupled to the Euler-Lagrange equations from the variational principle applied to the total free energy minimization. LC director spatial profile is found subject to the applied voltage. After that the phase retardation profile of the test light beam is calculated and thus a focal length dependence on the applied field. The simulation results agree well with experimental data. This LC lens has advantages in relatively large focal length range and low operating voltage. Copyright © Taylor & Francis Group, LLC

Modelling the Surface Plasmon Spectra of an ITO Nanoribbon Grating Adjacent to a Liquid Crystal Layer

The reflection and transmission coefficients of an indium tin oxide (ITO) nanoribbon grating placed between a nematic liquid crystal (LC) layer and an isotropic dielectric medium are calculated in the infrared region. Reflection and transmission spectra in the range of 1–5 μm related to the surface plasmon excitation in the ITO nanoribbons are obtained. Dependence of the peak spectral position on the grating spacing, the ribbon aspect ratio, and the 2D electron concentration in the nanoribbons is studied. It is shown that director reorientation in the LC layer influences the plasmon spectra of the grating, enabling a control of both the reflection and transmission of the system. The data obtained with our model are compared to the results obtained using COMSOL software, giving the similar results

Hybrid Organic–Inorganic Materials for Novel Photonic Applications

This novel joint feature issue on “Hybrid organic–inorganic materials for photonic applications” in Applied Optics and Optics Materials Express comprises 14 papers on liquid crystals, polymers, photoconductive materials, and gratings and filters. It is hoped that this feature issue encourages and stimulates further research into hybrid materials with enhanced linear and nonlinear optical properties, their mechanisms of operation, and their applications

Theoretical modeling of heterogeneous liquid crystal systems: nano-suspensions and polymer-stabilized LC lens

Heterogeneous liquid crystal (LC) systems are a new class of anisotropic materials which have been intensively studied over the last decade. This article is concerned with two such systems: ferroelectric LC nano-suspensions and LCs with polymer network. The significant implication of ferroelectric LC-colloids is the possibility of a significant reduction in the threshold electric Fredericksz voltage. Here we present a theory of this phenomenon, which agrees qualitatively with experiment. A second example of heterogeneous LC systems is a gradient-polymer-stabilized LC (G-PSLC) structure, which has been proposed for a tunable-focus lens application. We report on theoretical model that describes the dependence of the G-PSLC lens focal length on applied voltage. A previous model is improved by considering light absorption during the polymerization. Again we find qualitative agreement with the experimental data