Search results for "Photon"
showing 10 items of 3171 documents
<title>Effect of light exposure on dislocation mobility in fullerite C60 crystals</title>
2001
The illumination-time evolution and the wavelength dependence of the photoinduced changes in dislocation mobility on the (111) face of C60 single crystals in air for the wavelength range 150 - 900 nm and power densities 0.2 - 2 mW/cm2 has been investigated. The results show that the light exposure in air leads to the decrease of the dislocation mobility. The magnitude of the effect as a function of the illumination time was investigated and a two-stage relationship was obtained. The ultraviolet light was found to be more effective than the visible light in the photoinduced reduction of dislocation mobility and solubility. In the wavelength range of 150 - 700 nm, the reduction of dislocation…
Photon correlation spectroscopy to study the dynamics of α- and β-relaxation in amorphous poly(Alkylmethacrylates) above Tg
2008
A short survey of the underlying principles of isotropic light scattering from amorphous bulk polymers is given. The interrelation between the time dependent longitudinal compliance and the autocorrelation function of density fluctuations is briefly reviewed and a comparison with poly(vinylacetate) PVAc is presented. For four poly-(alkylmethacrylates) - poly(methylmethacrylate) PMMA, poly(ethylmethacrylate) PEMA, poly(n-butylmethacrylate) PBMA and poly(n-hexylmethacrylate) PHMA - the results of photon spectroscopic studies are given and discussed in terms of the occurrence of primary and secondary relaxation processes within the accessible time range of the experiment.
3D defect engineering in polymer opals
2006
The possibility to create defined structures inside a synthetic opal is a key step towards applications in optics, where control of the propagation of light inside a photonic crystal is necessary. Here we report different methods for realizing defined embedded defects in opaline structures. Monodisperse colloids are synthesized by surfactant free emulsion polymerization of the acid labile monomer t-butyl-methacrylate (tBMA). The PtBMA colloids can be filled with sensitizer and photo acid generator and it is possible to crystallize them into photosensitive polymer opals. One method for the introduction of defects is a multilayer build-up of photo-labile (filled with photo acid generator) and…
Functional 3D Photonic Films from Polymer Beads
2007
This paper describes synthesis and properties of polymer opals with a special emphasis on functional opals. Polymer opals are formed from monodisperse polymer colloids by self-assembly. Their potential applications range from coloring pigments, 3D bicontinuous supports for catalysis to photonic materials. This latter application requires especially the controlled creation of defects and the incorporation of fluorescent materials. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Solvatochromy and electro-optical study of new fluorine-containing chromophores
1998
technology requires tailored functional materials which fulfill the demands for optimal operation parameters, reliability andprocessability. Organic chromophores and polymers which contain covalently bound chromophores are promising materialclasses which can satisfy a broad spectrum of demands on functional materials for photonics, and they are, therefore,favorites for the development of new photonic devices. However, it is almost impossible to satisfy all physico-chemical andtechnological requirements simultaneously with a polymer consisting of only one type of functional unit. The developmentof a series of different building blocks which allow to cover the whole range of physico-chemical …
Chemical Approach to Functional Artificial Opals
2007
Artificial opals are self-assembled colloidal crystals, which consist of a cubic dense packing (fcc) of hard (not film-forming) colloids with diameters ranging from 200 to 900 nm. Because of their periodic nanostructure the assemblies are able to reflect light that matches their periodicity, i.e., UV- to IR-radiation depending on the size of the colloids. Thus, they present a subgroup of 'photonic crystals'. While, originally, the chemistry inside the colloids and the resulting opals was of minor significance, nowadays the chemical variation of opals is becoming more and more important for the preparation of functional and patterned opals. The search for functional opals is, therefore, espe…
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.
Surface plasmon near-field imaging of very thin microstructured polymer layers.
2004
We report on the near-field imaging of microstructured polymer layers deposited on an homogeneous metal thin film on which a surface plasmon mode is excited. The microstructures in the polymer layers are designed by electron beam lithography, and the near-field imaging is performed with a photon scanning tunneling microscope (PSTM). We show that, despite their very small height, the microstructures can be conveniently imaged with a PSTM thanks to the field enhancement at the surface of the metal thin film supporting the surface plasmon. The influence of the illumination conditions on the contrast of the PSTM images is discussed. In particular, we show that both the field enhancement and the…
Photosensitive functionalized surface-modified quantum dots for polymeric structures via two-photon-initiated polymerization technique.
2015
In this paper, the surface modification of CdSe- and CdZnS-based quantum dots (QDs) with a functional silica shell is reported. Functionalized silica shells are prepared by two routes: either by ligand exchange and a modified Stober process or by a miniemulsion process with amphiphilic poly(oxyethylene) nonylphenylether also know as Igepal CO-520 (IG) as oligomeric amphiphile and modified silica precursors. The polymerizable groups on the functionalized silica shell allow covalent bonding to a polymer matrix and prevent demixing during polymerization and crosslinking. This allows the homogeneous incorporation of QDs in a crosslinked polymer matrix. This paper furthermore demonstrates that t…
Polymers films with indandione derivatives as alternatives to azobenzene polymers for optical patterning
2008
Surface relief gratings (SRGs) on organic thin films are studied extensively for both scientific interest and in relevance to the applications. Among the chromophores being used the azobenzenes showed the best performance, but the use of alternative photo-sensitive groups provides better general understanding of the phenomena. A thermodynamic theory and molecular dynamics simulations of photoinduced effects are discussed. In this study we use indandione derivatives, known as promising materials for photonics applications, as an alternative to the azobenzenes. We consider their photoreactions when incorporated into a polymer film. One of interesting features is the spectral dependence of the…