Nonlinear optics and saturation behavior of quantum dot samples under continuous wave driving

The nonlinear optical response of self-assembled quantum dots is relevant to the application of quantum dot based devices in nonlinear optics, all-optical switching, slow light and self-organization. Theoretical investigations are based on numerical simulations of a spatially and spectrally resolved rate equation model, which takes into account the strong coupling of the quantum dots to the carrier reservoir created by the wetting layer states. The complex dielectric susceptibility of the ground state is obtained. The saturation is shown to follow a behavior in between the one for a dominantly homogeneously and inhomogeneously broadened medium. Approaches to extract the nonlinear refractive index change by fringe shifts in a cavity or self-lensing are discussed. Experimental work on saturation characteristic of InGa/GaAs quantum dots close to the telecommunication O-band (1.24-1.28 mm) and of InAlAs/GaAlAs quantum dots at 780 nm is described and the first demonstration of the cw saturation of absorption in room temperature quantum dot samples is discussed in detail

Correlation between optical properties and interfaces morphology of GaAs/AlGaAs quantum wells

We investigate the embedded interfaces of GaAs/AlGaAs quantum wells grown by metal organic vapor phase epitaxy on slightly (< 1 degrees)-misoriented (001) substrates using selective etching and atomic force microscopy. Depending on the substrate misorientation, we observe different growth modes at the embedded interfaces, which are directly correlated to the photoluminescence linewidth. We show that the narrowest linewidth is obtained on 0.2 degrees-off (001) substrates for which the heterointerfaces consist of atomically smooth narrow terraces. We investigate the embedded interfaces of GaAs/AlGaAs quantum wells grown by metal organic vapor phase epitaxy on slightly (< 1 degrees)- misoriented (001) substrates using selective etching and atomic force microscopy. Depending on the substrate misorientation, we observe different growth modes at the embedded interfaces, which are directly correlated to the photoluminescence linewidth. We show that the narrowest linewidth is obtained on 0.2 degrees-off (001) substrates for which the heterointerfaces consist of atomically smooth narrow terraces. (c) 2006 American Institute of Physics

Control of the degree of surface graphitization on 3C-SiC(100)/Si(100)

International audienceThe current method of growing graphene by thermal decomposition of 3C-SiC(100) on silicon substrates is technologically attractive. Here, we investigate the evolution of the surface graphitization as a function of the synthesis temperature. We establish that the carbon enrichment of the surface is characterized by a clear modulation of the surface potential and structuration. The structural properties analysis of the graphene layers by low energy electron diffraction and micro-Raman spectroscopy demonstrate a graphitization of the surfac

From nanographene to monolayer graphene on 6H-SiC(0001) substrate

International audienceGraphene quantum dots, nanoribbons, and nanographene are great promising in various applications owing to the quantum confinement and edge effects. Here we evidence the presence of epitaxial nanographene on SiC. Morphology and electronic structure of the graphene layers have been analyzed by SPELEEM. Using Scanning Tunneling Microscopy, we show that the increase of relative number of clusters carbon enabled the observation of nanographene, the diameter of which was around 20 nm. This nanographene shows a honeycomb structure at atomic level. The local chemical and electronic properties of the sample have been determined by photoelectron spectroscopy using synchrotron radiation

High Frequency Elastic Properties of Nitride Nanowires-Based Structures

International audienceThe present research aims at studying the elastic properties of III-Nitride nanowires (NWs) embedded in HSQ matrix, capable to efficiently convert the mechanical energy into electricity. We report on elastic properties of such novel nano-engineered functional materials studied by using "transient grating" acoustic experiment

Density of InAs∕InP(001) quantum dots grown by metal-organic vapor phase epitaxy: Independent effects of InAs and cap-layer growth rates

International audienc

Density of InAs∕InP(001) quantum dots grown by metal-organic vapor phase epitaxy: Independent effects of InAs and cap-layer growth rates

International audienc