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Full-Text Articles in Physics

Pretransitional Fluctuations In The Isotropic Phase Of A Lyotropic Chromonic Liquid Crystal, Yuriy A. Nastishin, Sergij V. Shiyanovskii, Oleg Lavrentovich, A. F. Kostko, M. A. Anisimov Nov 2004

Pretransitional Fluctuations In The Isotropic Phase Of A Lyotropic Chromonic Liquid Crystal, Yuriy A. Nastishin, Sergij V. Shiyanovskii, Oleg Lavrentovich, A. F. Kostko, M. A. Anisimov

Chemical Physics Publications

We have studied isotropic-to-nematic pretransitional fluctuations in an aqueous solution of disodium cromoglycate (cromolyn) by static and dynamic light scattering. Cromolyn is a representative of lyotropic chromonic liquid crystals with building units being elongated rods formed by aggregates of disk-like molecules. By combining light-scattering and viscosity measurements we have determined the correlation length and relaxation time of the orientational order-parameter fluctuations and estimated the size of the cromolyn aggregates. The pretransitional behavior of light scattering does not completely follow the classic Landau-de Gennes model. This feature is most probably associated with the variable length of cromolyn aggregates. We have observed ...


Performance Evaluation Of A Liquid-Crystal-On-Silicon Spatial Light Modulator, Xinghua Wang, Bin Wang, John Pouch, Felix A. Miranda, James E. Anderson, Philip J. Bos Nov 2004

Performance Evaluation Of A Liquid-Crystal-On-Silicon Spatial Light Modulator, Xinghua Wang, Bin Wang, John Pouch, Felix A. Miranda, James E. Anderson, Philip J. Bos

Chemical Physics Publications

2-D optical phased array antennas formed by a liquid crystal on silicon (LCOS) spatial light modulator are described for free-space laser communication and high-resolution wavefront control. The device consists of an 2-D array of 1024×768 phase modulator elements, each with controlled voltage, and can induce a phase shift from 0 to 2π for wavelengths up to the near IR. When the device is used as a wavefront corrector, 18.7 waves peak-valley (at 632.8 nm) of aberration in the optical system is corrected to a residual of 1/9 wave peak-valley, or 1/30 wave rms. The Strehl ...


Cholesteric Liquid-Crystal Laser As An Optic Fiber-Based Temperature Sensor, M. F. Moreira, I.C.S. Carvalho, W. Cao, C. Bailey, Bahman Taheri, Peter Palffy-Muhoray Oct 2004

Cholesteric Liquid-Crystal Laser As An Optic Fiber-Based Temperature Sensor, M. F. Moreira, I.C.S. Carvalho, W. Cao, C. Bailey, Bahman Taheri, Peter Palffy-Muhoray

Chemical Physics Publications

In this work, we have studied the temperature dependence of a cholesteric liquid-crystal laser coupled to an optical fiber, with a view towards optical fiber sensor applications. To stabilize the laser emission, we developed a procedure to align the liquid crystal placed in the fiber. Unexpected oscillations in the laser emission were observed as the temperature was varied, which can be understood in terms of the competition between bulk and surface anchoring torques. (C) 2004 American Institute of Physics.


Ordered Droplet Structures At The Liquid Crystal Surface And Elastic-Capillary Colloidal Interactions, Ivan I. Smalyukh, S. Chernyshuk, B. I. Lev, A. B. Nych, U. Ognysta, V. G. Nazarenko, Oleg Lavrentovich Sep 2004

Ordered Droplet Structures At The Liquid Crystal Surface And Elastic-Capillary Colloidal Interactions, Ivan I. Smalyukh, S. Chernyshuk, B. I. Lev, A. B. Nych, U. Ognysta, V. G. Nazarenko, Oleg Lavrentovich

Chemical Physics Publications

We demonstrate a variety of ordered patterns, including hexagonal structures and chains, formed by colloidal particles (droplets) at the free surface of a nematic liquid crystal (LC). The surface placement introduces a new type of particle interaction as compared to particles entirely in the LC bulk. Namely, director deformations caused by the particles lead to distortions of the interface and thus to capillary attraction. The elastic-capillary coupling is strong enough to remain relevant even at the micron-scale when its buoyancy-capillary counterpart becomes irrelevant.


Comment On "Self-Organized Periodic Photonic Structure In A Nonchiral Liquid Crystal", Oleg P. Pishnyak, Yuriy A. Nastishin, Oleg Lavrentovich Sep 2004

Comment On "Self-Organized Periodic Photonic Structure In A Nonchiral Liquid Crystal", Oleg P. Pishnyak, Yuriy A. Nastishin, Oleg Lavrentovich

Chemical Physics Publications

No abstract provided.


Computing The Liquid Crystal Director Field In Optical Phased Arrays, George F. Barrick, Philip J. Bos, Charles E. Titus, Bruce K. Winker Apr 2004

Computing The Liquid Crystal Director Field In Optical Phased Arrays, George F. Barrick, Philip J. Bos, Charles E. Titus, Bruce K. Winker

Chemical Physics Publications

Optical phased arrays using birefringent liquid crystals can efficiently steer a laser communication beam to a small angle. The algorithm presented derives a thickness for the liquid crystal cell and computes a sequence of voltages for the device electrodes that best deflects the beam. (C) 2004 Society of Photo-Optical Instrumentation Engineers.


Antiferroelectric Ordering Of Amphiphilic Glycolipids In Bent-Core Liquid Crystals, Sugat Abeygunaratne, Antal Jakli, Gotz Milkereit, Hans Sawade, Volkmar Vill Feb 2004

Antiferroelectric Ordering Of Amphiphilic Glycolipids In Bent-Core Liquid Crystals, Sugat Abeygunaratne, Antal Jakli, Gotz Milkereit, Hans Sawade, Volkmar Vill

Chemical Physics Publications

Lipids are the main constituents of biological cell membranes, and their liquid crystalline properties play a crucial role in cell functions. We have discovered that dodecyl-beta-D-glucopyranoside glycolipid layers can be electrically polarized in supramolecular structures of glycolipid and bent-core ("banana-shape") molecules. Interestingly the glycolipid molecules, known to be excellent chiral dopants, are not able to transfer their chirality to the bent-core layers. Our observations indicate that glycolipid molecules self-assemble into pairs of tilted and antiferroelectric double layers, sandwiched between layers of bent-core molecules. These systems may provide a basis for understanding "bioferroelectricity," which is important in biological cell membrane functions.


Glass Forming Banana-Shaped Compounds: Vitrified Liquid Crystal States, S. Rauch, C. Selbmann, P. Bault, Hans Sawade, G. Heppke, O. Morales-Saavedra, M. Y. M. Huang, Antal Jákli Feb 2004

Glass Forming Banana-Shaped Compounds: Vitrified Liquid Crystal States, S. Rauch, C. Selbmann, P. Bault, Hans Sawade, G. Heppke, O. Morales-Saavedra, M. Y. M. Huang, Antal Jákli

Chemical Physics Publications

The synthesis and physical properties, in particular electro-optic switching behavior, of 3-chloro-biphenyl-3('),4-bis{4-[4-(3,7-dimethyloctyloxy)-phenyliminomethyl]} benzoate are reported. The compound exhibits an antiferroelectric tilted smectic liquid crystalline phase (Sm-CP) in a broad temperature range. Below 20 degreesC the sample goes over to a glassy state and no crystallization appeares down to -50 degreesC. It is observed that below the glass transition temperature both achiral and chiral structures of the Sm-CP phase can be frozen. Each of them can have three polarization states (two ferroelectric and one antiferroelectric), thus giving six different vitrified textures. This enables atomic force ...


Three-Dimensional Orientational Order In The Bulk And On The Surface Of Polymer Films And Its Effect On Liquid-Crystal Alignment, O. V. Yaroshchuk, Yu. Zakrevskyy, Satyendra Kumar, J. Kelly, Liang-Chy Chien, J. Lindau Jan 2004

Three-Dimensional Orientational Order In The Bulk And On The Surface Of Polymer Films And Its Effect On Liquid-Crystal Alignment, O. V. Yaroshchuk, Yu. Zakrevskyy, Satyendra Kumar, J. Kelly, Liang-Chy Chien, J. Lindau

Chemical Physics Publications

The correlation between orientation ordering of polymer chains in the bulk of polymer film and at the polymer-liquid-crystal (LC) interface has been studied to determine it's role in LC alignment. The bulk and surface ordering of polymer were investigated by null ellipsometry and x-ray reflectivity, respectively. Two kinds of liquid-crystalline polymers were used; side-chain azopolymers with azochromophores containing hydrophobic OC(4)H(9) alkyl chain (P1) and strongly polar NO(2) group (P2) as the end substituents. The uniaxial tilt orientation of azochromophores in the films of both polymers was induced by the oblique irradiation with unpolarized UV light ...


Optimizing The Nematic Liquid Crystal Relaxation Speed By Magnetic Field, Bin Wang, Xinghua Wang, Philip J. Bos Jan 2004

Optimizing The Nematic Liquid Crystal Relaxation Speed By Magnetic Field, Bin Wang, Xinghua Wang, Philip J. Bos

Chemical Physics Publications

Nematic liquid crystalline materials have been widely used in electro-optical control of visible light. However, when IR light is considered, the thickness of the liquid crystal layer must be increased which causes the relaxation time of the material to be slower than required for many applications. In this paper we use a magnetic field to increase the speed of thick nematic devices. We show that above a particular magnetic field strength, thicker cells relax more quickly than thinner ones. Also, we find that there exists an optimal voltage range for devices of a particular thickness and with a particular applied ...