The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Sensors and Actuators A: Physical

The dispersion of ferroelectric nanomaterials in liquid crystals has recently emerged as a promising way for the design of advanced and tunable electro-optical materials. The goal of this paper is a broad overview of the current technology, basic physical properties, and applications of ferroelectric nanoparticle/liquid crystal colloids. By compiling a great variety of experimental data and discussing it in the framework of existing theoretical models, both scientific and technological challenges of this rapidly developing field of liquid crystal nanoscience are identified. They can be broadly categorized into the following groups: (i) the control of the size, shape, and the ferroelectricity of nanoparticles; (ii) the production of a stable and aggregate-free dispersion of relatively small (~10 nm) ferroelectric nanoparticles in liquid crystals; (iii) the selection of liquid crystal materials the most suitable for the dispersion of nanoparticles; (iv) the choice of appropriate experimental procedures and control measurements to characterize liquid crystals doped with ferroelectric nanoparticles; and (v) the development and/or modification of theoretical and computational models to account for the complexity of the system under study. Possible ways to overcome the identified challenges along with future research directions are also discussed.

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Ferroelectric Nanoparticles in Liquid Crystals: Recent Progress and Current Challenges.

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Liquid Crystals Physical Properties And Nonlinear Optical Phenomena

This study aims to numerically investigate the Marangoni convective flow of nanoliquid initiated by surface tension and heading towards a radiative Riga surface. The surface tension appears in the problem due to the gradients of temperature and concentration at the interface. The influence of first order chemical reaction is involved in the system with sufficient boundary conditions. Set of governing nonlinear PDEs is transformed into highly nonlinear ODEs using suitable transformations. HAM is applied for convergent series solutions. Impact of various pertinent fluid parameters on momentum, thermal and solutal boundary layers is analyzed graphically. The chemical reaction plays vital role in saturation of nanoparticles in the base fluid near the surface as well as away from it. The Lorentz forces originated by the Riga surface become powerful when the radiation parameter comes into effect. The significance of Riga plate is thus more prominent through thermal radiation. However, the magnetic effect dampens down for higher radiation parameter. Fluid parameters, Nusslt and Sherwood numbers are analyzed with detailed discussion and concluding remarks. DOI: 10.14302/issn.2689-2855.jan-19-2598 Corresponding author: Ghulam Rasool, School of Mathematical Sciences, Zhejiang University, Hangzhou 310027, PR-China, Email: grasool@zju.edu.cn

Influence of Chemical Reaction On Marangoni Convective Flow of Nanoliquid in the Presence of Lorentz Forces and Thermal Radiation: A Numerical Investigation

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...

Light energy accumulation by cholesteric liquid crystal layer at oblique incidence

Onset of regular convection in nanoparticle doped isotropic and anisotropic fluids with one free surface under absorption of light with Gaussian distribution of intensity due to temperature dependence of surface tension coefficient is experimentally studied. It is shown that nanoparticles essentially increase the thermal conductivity of the mixture, which leads to decrease of the velocity of convective motion. Dependence of velocity of hydrodynamic motions on intensity of laser beam and concentration of nanoparticles is also studied.

Experimental investigation of Marangoni convection in nanofluids

The possibility of inducing a planar defect in a plane structure of a cholesteric liquid crystal by an external electric field is demonstrated experimentally for the first time. The results of experimental and theoretical study of the behavior of the coefficient of reflection (transmission) of light from a layer of a cholesteric liquid crystal with a planar defect induced in it are considered. Possible applications of such a system are considered.

Chiral photonic crystals with an electrically tunable anisotropic defect. Experiment and theory

The influence of hydrodynamic flow on the lasing wavelength and stability of the laser emission average power of a dye-doped chiral liquid crystalline (DDCLC) structure is studied. Multiple lasing peaks at equidistant wavelengths are observed, which are originating from multiple domains that are induced by the hydrodynamic flow of the DDCLC. A simultaneous blue shift over 4 nm for all lasing peaks is observed after increasing the flow velocity to 0.3 mm/s for cells with a thickness of 10 μm. It is observed that the CLC flow dramatically increases the stability of the laser emission compared to conventional cells because dye bleaching and LC molecular reorientation due to pumping beam is reduced.

Tuning the lasing wavelength of dye-doped chiral nematic liquid crystal by fluid flow

The possibility of excitation of convective motions of the Rayleigh — Benard and Marangoni type in isotropic liquids and nematic liquid crystals upon absorption of light with a spatially periodic intensity distribution is demonstrated theoretically and experimentally. It is shown that gravitational and thermocapillary surface hydrodynamic waves are observed in the case of a running interference pattern. The possibility of control and the stability of convective motions are investigated. Benard cells become unstable when the light intensity is high. These instabilities are of thermal origin because the Prandtl number for the medium under investigation is considerably larger than unity. The competition between the gravitational and thermocapillary mechanisms of photohydrodynamic reorientation of the nematic liquid crystal director is also studied. The effect of convective motions on the thermodynamic phase transition is observed and explained.

https://iopscience.iop.org/article/10.1070/QE2003v033n01ABEH002368/pdf

R. B. Alaverdyan

Papers

Light energy accumulation by cholesteric liquid crystal layer at oblique incidence

Experimental investigation of Marangoni convection in nanofluids

Chiral photonic crystals with an electrically tunable anisotropic defect. Experiment and theory

Tuning the lasing wavelength of dye-doped chiral nematic liquid crystal by fluid flow

Excitation of convective motions in isotropic and anisotropic liquids by light