224 research outputs found
Temperature dependence of the asphericity of magnetic moment distribution in transition metal alloys
No full textThe temperature dependence of the asphericity of the 3d magnetic moment distribution has been calculated by the two-band CPA technique. It is shown that this asphericity in the case of Co-Ni and Co-Fe alloys is almost constant, and this behaviour agrees with recent measurements
Special Issue on Materials for Nonlinear Optics
No full textNumero Speciale del giornale Pure and Applied Optics contenente gli Atti del Congresso della Società Europea di Ottica Materials for Nonlinear Optic
11th Topical Meeting of the European Optical Society MATERIALS FOR NONLINEAR OPTICS
No full textThe 11th Topical Meeting of the European Optical Society, on Materials for Nonlinear Optics, was held in Capri, Italy, 8-12 July 1997. The meeting was devoted to producing a general overview of different problems connected with the preparation, characterization and use of materials for nonlinear optical applications. It consisted of invited and contributed papers outlining the latest developments and two poster sessions.
The main aim of the symposium organized in Capri was to give a forum on the advancement of the research in the field of optical nonlinear materials in Europe. Participation from both company and university research centres was sought after, and achieved, in order to boost the transfer of ideas and initiate research contacts. The importance of the field under debate was indicated by the level of attendance: about 120 participants, mostly from Europe but with representatives from the Americas, Japan and Australia, took part in the symposium. In total 123 papers were presented during invited talks, oral contributions and poster presentations
Controlling energy transfer routes in dye-sensitized lanthanide-based nanoparticles for enhanced emission
No full textNear-infrared luminescent lanthanide (Ln)-doped nanomaterials are currently attracting high interest in view of their sharp f-f emission peaks and long luminescence lifetimes, which establish a unique value for the development of optical amplifiers, lasers and biosensors. To improve the optical pumping of the weakly absorbing lanthanide ions (Ln3+), the doped nanoparticles are coupled with an organic dye sensitizer able to efficiently harvest light and subsequently transfer the absorbed energy to the emitter. However, this through-space "remote" sensitization is severely subjected to energy losses due to competitive energy migration or deactivation routes limiting the overall luminescence quantum yields. The implementation of the Förster's model of resonance energy transfer on the basis of advanced ultra-fast transient absorption and photoluminescence spectroscopy with the support of density functional theory calculations demonstrate that the sensitization efficiency from the dye to the doped nanoparticle is strictly regulated by the geometry and localization of the transition dipole moment of the dye molecule. Within the nanoparticle, the energy transfer pathways can be harnessed through the spatial confinement of â€energy bridges', accepting energy from the surface dyes and donating to core emitters. We show that the FITC (fluorescein-isothiocyanate) dye allows reaching exceptional sensitization efficiency close to unity for the NIR-emitting triad Nd3+, Er3+ and Yb3+
NOVEL HIGH GLASS TRANSITION TEMPERATURE POLYURETHANES FUNCTIONALIZED WITH EFFICIENT CT CHROMOPHORES FOR SECOND ORDER NLO APPLICATION
No full textNonlinear optical proprieties of polymers containing pyrido-imidazole and pyrido-oxazole groups
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Surface enhanced SHG from macrocycle, catenane and rotaxane thin films: experiments and theory.
No full textSurface enhanced second harmonic generation experiments on supramolecules: macrocycles, catenanes and rotaxanes, monolayers and multilayers deposited by vacuum evaporation on silver layers are reported and described. The measurements show that the molecules are ordered in thin films. The highest order is observed in the case of macrocycles and the lowest in thin films of fumaramide [2] rotaxanes. Also a better ordering is observed in the case of monolayers. The observed second harmonic generation activity is interpreted in terms of electric field induced second harmonic generation. The electric field contributing to SHG signal is created by silver atoms on the surface of silver layers. The measured second order NLO susceptibilities for a fumaramide [2] rotaxane is compared with that obtained by considering only EFISH contribution to SHG intensities. The electric filed on the surface of silver layer is calculated using TINKER molecular mechanics/dynamics software and the Embedded Atom model. An excellent agreement is observed between the calculated and the measured SHG susceptibilities
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