Search results for "OPTICS"
showing 10 items of 10033 documents
Design and Optimization of Chromophores for Liquid Crystal and Photorefractive Applications
1999
ABSTRACTOrganic chromophores have been exploited for a wide range of discrete optical and electronic functions as well as a growing number of combined opto-electronic functions. We are pursuing development of organic and polymer materials for a range of applications that require properties including liquid crystallinity, second order optical nonlinearity, photorefractivity and, more recently, special nonlinear optical behavior involving molecular chirality.
Indanedione based binary chromophore supramolecular systems as a NLO active polymer composites
2010
Novel route to obtain EO material is proposed by supramolecular assembly of neutral-ground-state (NGS) and zwitterionic (ZWI) NLO chromophores in binary chromophore organic glass (BCOG) host–guest system. On a basis of our Langeven Dynamics (LD) molecular modeling combined with quantum chemical calculations, we have shown that anticipated enhancement NLO efficiency of BCOG material is possible via electrostatic supramolecular assembly of NGS with ZWI chromophore in antiparallel manner. Binding energy of such complex could be more dependent on molecular compatibility of components and local (atomic) charge distribution, then overall molecular dipole moments. According to our LD simulations t…
Photoluminescence waveguiding in CdSe and CdTe QDs–PMMA nanocomposite films
2011
In this paper, active planar waveguides based on the incorporation of CdSe and CdTe nanocrystal quantum dots in a polymer matrix are demonstrated. In the case of doping the polymer with both types of quantum dots, the nanocomposite film guides both emitted colors, green (550 nm, CdTe) and orange (600 nm, CdSe). The optical pumping laser can be coupled not only with a standard end-fire coupling system, but also directing the beam to the surface of the sample, indicating a good absorption cross-section and waveguide properties. To achieve these results, a study of the nanocomposite optical properties as a function of the nanocrystal concentration is presented and the optimum conditions are fo…
Formation, phase composition, and transformations of Langmuir-Blodgett multi- and monolayers containing Fe
1992
Mono- and multilayers of ferric stearate were formed by the Langmuir-Blodgett technique. Thermodesorption of the hydrocarbon chains results in well defined thin oxidic films. Their reduction to Fe2+ and α-Fe was followed by conversion electron Mossbauer spectroscopy. Resonance lines can be observed even if the Fe coverage is less than one monolayer.
Phase transitions in polymeric systems: A challenge for Monte Carlo simulation
1995
Polymers are more difficult to simulate than small molecule systems, due to the large size of random polymer coils (and their slow relaxation, that is observed when dynamic simulation algorithms are used). However, variation of the chain length N of a flexible polymer chain provides a very useful additional control parameter, allowing stringent tests of theories, and new physical phenomena may emerge. As an example of these concepts, critical phenomena in polymer mixtures are described. It is shown that unmixing of symmetrical mixtures ( N A = N B = N ) is described by an equation for the critical temperature T c ( N ) = aN + b rather than T c ∝ N as claimed by some theories. While for fini…
The Mössbauer effect and collective motions in glass-forming liquids and polymeric networks
1994
Glass-forming liquids, synthetic polymers and biopolymers share essential properties. Dynamic processes in these complex systems are characterized by cooperative motions with wide distributions of time scales, which manifest themselves in broad quasielastic lines in the Mossbauer spectrum. In this article, the application of the Mossbauer effect to the study of structural dynamics in complex systems is discussed.
Atmospheric aging and surface degradation in As2S3 fibers in relation with suspended-core profile
2015
Abstract Microstructured optical fibers (MOF) can be seen as next generation fiber of significance in advancing the compact optics because of its excellent compatibility in integrated optics. However, the degradation of their physicochemical properties limits their efficiency and lifetime. Atmospheric moisture is responsible for the degradation of amorphous systems especially chalcogenide glasses. In the light of previously reported studies, in order to clarify the aging process continuously evolving in sulfide microstructured optical fiber over time, a detailed investigation of this phenomenon has been conducted. The time-dependent transmission and glass chemical deterioration have been st…
Synthesis and magnetic properties of an iron 1,2-bisthienyl perfluorocyclopentene photochromic coordination compound
2011
Abstract The coordination compound Fe(BM-4-PTP) 2 (NCS) 2 ⋅2MeOH ( 1 ) including the photoisomerizable ligand BM-4-PTP (1,2-bis(2′-methyl-5′-(pyrid-4″-yl)thien-3′-yl)perfluorocyclopentene) was obtained as an orange powder. The powder turns blue upon photocyclization of the 1,2-bisthienyl photochromic ligand induced by UV light irradiation at room temperature. Photocycloreversion is obtained by visible light irradiation of the material in the solid state. The orange and blue powders were investigated over the temperature range (5–293 K) and pressure range (1 bar–12 kbar) by magnetic susceptibility measurements and variable temperature 57 Fe Mossbauer spectroscopy. The photo-induced colour ch…
Chalcogenide Fibers for Mid-IR Light Generation: Potentialities and Drawbacks of the Microstructured Design in Sulfide Waveguides
2014
We study optical and structural aging in As2S3 microstructured optical fibers, submitted to room atmosphere that may have, among others, an impact on mid-infrared supercontinuum generation.
On the phase transition in CsCN
1983
X-ray diffraction and dielectric measurements have been performed on the molecular crystal CsCN as a function of temperature. The order parameter of the cubic to rhombohedral phase transition (Tc=186 K) was determined and interpreted by a coupling of the (CN)− orientations to the shear strain. At lower temperatures the dielectric response is dominated by thermally activated relaxations processes rather than by electrical ordering of the CN dipoles.