Increase of charge-carrier redistribution efficiency in a laterally organized superlattice of coupled quantum dots

We report the observation of enhanced charge-carrier redistribution in laterally organized and coupled InAs/InP quantum dots (QDs). We show that a periodic organization appears in the QD plane for a high in-plane QD density (QDD). This organization enhances the lateral coupling between the dots, which is evidenced by photoluminescence and magnetophotoluminescence experiments. Electronic inter-QD lateral coupling results in an improved charge-carrier distribution at low temperature, as shown by electroluminescence on high QDD QD lasers. We conclude that the inter-QD tunneling occurs via the tunneling of excited states through the wetting layer, and discuss the prospects of using coupled QDs for improving the quantum efficiency and dynamical properties of QD lasers

Volume-Diffusion of 59Fe in Al62Cu25.5Fe 12.5 Icosahedral Quasicrystals

The volume diffusion of 59Fe in Al62Cu25.5Fe12.5 Icosahedral quasicrystals is analyzed using classical diffusion techniques. Over the temperature range from 550°C to 800°C, the volume diffusion coefficients show a classical diffusion behavior and the temperature dependence can be expressed by the following relation : [MATH]. In the absence of data on a crystalline phase with similar composition, diffusion coefficients are compared to those obtained for Fe in aluminium and in aluminides (FeAl and Al13Fe4) : no strong peculiarity linked to the quasicrystalline structure appears

Volume-diffusion of 59Fe in Al62Cu25.5Fe12.5 icosahedral quasicrystals

Communication to : 38th Conference on metallurgy, INSTN 95 : 'des Quasicristaux aux Superalliages', Saclay (France), june 20-22, 1995SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1996 n.9 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Optical characterisation of InAs/InP self-assembled quantum dots for optimisation of lasing properties

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Nonlinear optical properties of silicon carbide (SiC) nanoparticles by carbothermal reduction

International audienceSiC nanoparticles by carbothermal reduction show promising properties in terms of second harmonic and multiphoton excited luminescence. In particular, we estimate a nonlinear efficiency = 17 pm/V, as obtained by Hyper Rayleigh Scattering. We also present results of cell labelling to demonstrate the potential use of SiC nanoparticles for nonlinear bioimaging by simultaneous detection of second harmonic and luminescence

Harmonic Nanocrystals for Biolabeling: A Survey of Optical Properties and Biocompatibility

Nonlinear optical nanocrystals have been recently introduced as a promising alternative to fluorescent probes for multiphoton microscopy. We present for the first time a complete survey of the properties of five nanomaterials (KNbO3, LiNbO3, BaTiO3, KTP, and ZnO), describing their preparation and stabilization and providing quantitative estimations of their nonlinear optical response. In the light of their prospective use as biological and clinical markers, we assess their biocompatibility on human healthy and cancerous cell lines. Finally, we demonstrate the great potential for cell imaging of these inherently nonlinear probes in terms of optical contrast, wavelength flexibility, and signal photostability