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Selective Reflection (selective + reflection)

Distribution by Scientific Domains

Polymers and Materials Science	60%

Selected Abstracts

Electrically Controllable Selective Reflection of Chiral Nematic Liquid Crystal/Chiral Ionic Liquid Composites

ADVANCED MATERIALS, Issue 4 2010
Wang Hu
A chiral nematic liquid crystal/chiral ionic liquid composite with unique electro-optical characteristics is reported. The composite can be switched electrically between three different light states: transparent, scattering, and mirror reflecting (see images). Moreover, the reflection bandwidth can be controlled accurately and reversibly by adjusting the intensity of the electric field applied. [source]

Laser frequency stabilization using selective reflection from a vapor cell with a half-wavelength thickness

LASER PHYSICS LETTERS, Issue 11 2007
E.A. Gazazyan
Abstract We have experimentally studied the selective reflection spectra of a circularly-polarized laser beam from a sub-micrometric Rb vapor cell with a thickness L around , /2 (, = 780 nm being the laser wavelength tuned to the D2 line) in the presence of a longitudinal magnetic field. Based on the results of these studies, we propose a new method for the tunable locking of the diode laser frequency, which does not require frequency modulation nor complex electronics. The experimental realization of the technique has demonstrated its effectiveness and its competitiveness with the known DAVVL-type methods. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Measurement of critical concentration for mesophase formation of chitosan derivatives in both aqueous and organic solutions

POLYMER INTERNATIONAL, Issue 12 2006
Yan-ming Dong
Abstract A novel chitosan derivative, acryloyl chitosan (AcCs), and two N -maleoyl chitosans, MaCs-1 and MaCs-2, with different degrees of substitution were synthesized using completely deacetylated chitosan as raw material under different reaction conditions. AcCs is an amphiphilic chitosan derivative, but MaCs-1 and MaCs-2 are soluble in water and organic solvents respectively. The concentrated solutions of AcCs, MaCs-1 and MaCs-2 all demonstrated mesophases and were investigated using polarizing optical microscopy (POM). Circular dichroism (CD) was also employed for determining the critical concentration for mesophase formation. A broad peak in the visible light region of CD spectra had its origin in the appearance of the mesophase, and arose from the selective reflection of cholesteric helix pitches. The results of CD measurements agreed with those of POM. The critical concentration values for aqueous solutions were much lower than those for organic solutions, which was explained by the strong interactions between the chitosan derivatives and water. Copyright © 2006 Society of Chemical Industry [source]

Short wavelength light reflecting films from side-chain liquid crystal homopolymers with chiral spacers

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2001
J. M. G. Cowie
Abstract A series of acrylate monomers with alkoxy tails of varying lengths are synthesised and polymerised. The butoxy analogue had a stable enantiotropic cholesteric liquid crystalline phase which formed a grandjean texture when prepared as a thin film between glass slides. The polymer was mixed with a low molar mass nematic liquid crystal in various proportions and the pitch of the chiral nematic phases were determined using a cano-wedge cell technique. The polymer prepared from (S)-2-(4-butoxyphenyl-4,-benzoyloxy)-1-methyl ethyl acrylate had a pitch length of 113,nm which indicates that the polymer film could be employed in optical devices requiring selective reflection of light with short wavelengths in the region of 170,nm. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Localization and imaging of local shunts in solar cells using polymer-dispersed liquid crystals

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2001
Jan Schmidt
An easy-to-use technique for the localization and imaging of local shunts in solar cells is introduced. The method is based on temperature-sensitive polymer-dispersed cholesteric liquid crystal foils, covering the reverse-biased solar cell. The unique optical properties of the cholesteric liquid crystal, known as selective reflection, render the local shunts of a solar cell visible as a color distribution in the foil, which is directly correlated with the spatial shunt distribution. The novel method is applied to several laboratory and commercial silicon solar cells and its high sensitivity is demonstrated. Copyright © 2001 John Wiley & Sons, Ltd. [source]