NANOPARTICULES DE SILICIUM ET IONS ERBIUM POUR L'AMPLIFICATION OPTIQUE.

Trivalent erbium ions (Er3+) have played an important role in the development of optical communication technology in the last years. The transition from the first excited state to the ground state in Er3+ at 1.53?m corresponds to an important telecommunication wavelength since standard silica based optical fibers have their maximum transparency at this wavelength. Unfortunately, the absorption cross section of Er3+ ions is rather small, typically on the order of 10-21cm2. For this reason there is a considerable interest in sensitizing the Er3+ ions by adding a strong absorbing species, Si-Np for example, that can transfer energy efficiently to Er3+ ions. Several studies were performed on silica thin films codoped with Si-Np and Er3+ ions, but many questions remain without answers, as for example, the excitation and desexcitation mechanisms of the Er3+ ions, the low percentage of excitable Er3+ and the local environment of Er3+ ions.We have used a fluorescence line narrowing technique to study the erbium local environment. We were able to quantify the inhomogeneous structure of the 4I13/2--> 4I15/2 of Er3+ ions in the case of silica thin films doped with Si-Np. We have also put in evidence the presence of one kind of site distribution within the limit of our technique. A study of the 4I13/2 temporal behaviour allowed us to propose the presence of energy migration between Er3+ ions. Furthermore we didn?t observe any efficient energy back transfer between Er3+ ions and Si- Np in our sample. Finally, we have observed a fast emission (nanosecond) in the near infrared. This emission was attributed to some defects related to Si-Np.Les ions erbium trivalents (Er3+) ont joué un rôle important dans le développement de la technologie des télécommunications optiques dans les dernières années. L'émission des ions Er3+ à 1.53?m est cruciale pour lestélécommunications optiques car cette émission correspond au minimum d'atténuation des fibres de silice utilisée pour transporter l'information. Malheureusement, la section efficace d'absorption des ions Er3+ est faible, de l'ordre de 10-21cm2. Pour cette raison, la sensibilisation des ions Er3+ par des espèces dont la section efficace d'absorption est élevée, comme les nano particules de silicium (Np-Si) par exemple, présente un intérêt majeur.Plusieurs études ont été effectuées sur des couches minces de silice codopée par des Np-Si et des ions Er3+, mais plusieurs questions restent sans réponses. Par exemple, les mécanismes d'excitation et de désexcitation des ions Er3+, le faible pourcentage des ions Er3+ excités et l'environnement local des ions Er3+.Nous avons utilisé une technique d'affinement de raie de fluorescence pour étudier l'environnement local des ions Er3+. Nous avons quantifié la largeur inhomogène de la transition 4I13/2--> 4I15/2 des ions Er3+ dans des couches minces de silice dopées par des Np-Si. Nous avons mis en évidence la présence d'un seul type de site. Une étude de la dynamique du niveau 4I13/2 nous a permis de proposer l'existence du phénomène de migration d'énergie entre les ions Er3+. Nous n'avons pas observé l'existence d'un transfert retour entre les ions Er3+ et les Np-Si. De plus, nous avons remarqué la présence d'une émission rapide (nanoseconde) dans le domaine de l'infrarouge. Nous avons attribué cette émission aux défauts liés aux Np-Si

Nanoparticules de silicium et ions erbium pour l'amplification optique

Les ions erbium trivalents (Er3+) ont joué un rôle important dans le développement de la technologie des télécommunications optiques dans les dernières années. L émission des ions Er3+ à 1.53 m est cruciale pour les télécommunications optiques car cette émission correspond au minimum d atténuation des fibres de silice utilisée pour transporter l information. Malheureusement, la section efficace d absorption des ions Er3+ est faible, de l ordre de 10-21cm2. Pour cette raison, la sensibilisation des ions Er3+ par des espèces dont la section efficace d absorption est élevée, comme les nano particules de silicium (Np-Si) par exemple, présente un intérêt majeur. Plusieurs études ont été effectuées sur des couches minces de silice codopée par des Np-Si et des ions Er3+, mais plusieurs questions restent sans réponses. Par exemple, les mécanismes d excitation et de désexcitation des ions Er3+, le faible pourcentage des ions Er3+ excités et l environnement local des ions Er3+.Nous avons utilisé une technique d affinement de raie de fluorescence pour étudier l environnement local des ions Er3+. Nous avons quantifié la largeur inhomogène de la transition 4I13/2->4I15/2 des ions Er3+ dans des couches minces de silice dopées par des Np-Si. Nous avons mis en évidence la présence d un seul type de site. Une étude de la dynamique du niveau 4I13/2 nous a permis de proposer l existence du phénomène de migration d énergie entre les ions Er3+. Nous n avons pas observé l existence d un transfert retour entre les ions Er3+ et les Np-Si. De plus, nous avons remarqué la présence d une émission rapide (nanoseconde) dans le domaine de l infrarouge. Nous avons attribué cette émission aux défauts liés aux Np-Si.Trivalent erbium ions (Er3+) have played an important role in the development of optical communication technology in the last years. The transition from the first excited state to the ground state in Er3+ at 1.53 m corresponds to an important telecommunication wavelength since standard silica based optical fibers have their maximum transparency at this wavelength. Unfortunately, the absorption cross section of Er3+ ions is rather small, typically on the order of 10-21cm2. For this reason there is a considerable interest in sensitizing the Er3+ ions by adding a strong absorbing species, Si-Np for example, that can transfer energy efficiently to Er3+ ions. Several studies were performed on silica thin films codoped with Si-Np and Er3+ ions, but many questions remain without answers, as for example, the excitation and desexcitation mechanisms of the Er3+ ions, the low percentage of excitable Er3+ and the local environment of Er3+ ions.We have used a fluorescence line narrowing technique to study the erbium local environment. We were able to quantify the inhomogeneous structure of the 4I13/2->4I15/2 of Er3+ ions in the case of silica thin films doped with Si-Np. We have also put in evidence the presence of one kind of site distribution within the limit of our technique. A study of the 4I13/2 temporal behaviour allowed us to propose the presence of energy migration between Er3+ ions. Furthermore we didn t observe any efficient energy back transfer between Er3+ ions and Si-Np in our sample. Finally, we have observed a fast emission (nanosecond) in the near infrared. This emission was attributed to some defects related to Si-NpLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Aerosol Mineralogical Study Using Laboratory and IASI Measurements: Application to East Asian Deserts

East Asia is the second-largest mineral dust source in the world, after the Sahara. When dispersed in the atmosphere, mineral dust can alter the Earth’s radiation budget by changing the atmosphere’s absorption and scattering properties. Therefore, the mineralogical composition of dust is key to understanding the impact of mineral dust on the atmosphere. This paper presents new information on mineralogical dust during East Asian dust events that were obtained from laboratory dust measurements combined with satellite remote sensing dust detections from the Infrared Atmospheric Sounding Interferometer (IASI). However, the mineral dust in this region is lifted above the continent in the lower troposphere, posing constraints due to the large variability in the Land Surface Emissivity (LSE). First, a new methodology was developed to correct the LSE from a mean monthly emissivity dataset. The results show an adjustment in the IASI spectra by acquiring aerosol information. Then, the experimental extinction coefficients of pure minerals were linearly combined to reproduce a Gobi dust spectrum, which allowed for the determination of the mineralogical mass weights. In addition, from the IASI radiances, a spectral dust optical thickness was calculated, displaying features identical to the optical thickness of the Gobi dust measured in the laboratory. The linear combination of pure minerals spectra was also applied to the IASI optical thickness, providing mineralogical mass weights. Finally, the method was applied after LSE optimization, and mineralogical evolution maps were obtained for two dust events in two different seasons and years, May 2017 and March 2021. The mean dust weights originating from the Gobi Desert, Taklamakan Desert, and Horqin Sandy Land are close to the mass weights in the literature. In addition, the spatial variability was linked to possible dust sources, and it was examined with a backward trajectory model. Moreover, a comparison between two IASI instruments on METOP-A and -B proved the method’s applicability to different METOP platforms. Due to all of the above, the applied method is a powerful tool for exploiting dust mineralogy and dust sources using both laboratory optical properties and IASI detections

Fluorescence line narrowing and decay dynamics of Er3+ ions in silicon-rich silicon oxide multilayers

International audienceErbium doped silicon-rich silica layer, known for their potential application for active devices, have been investigated by means of site selective laser spectroscopy and fluorescence dynamics at low temperature. It is pointed out that only one erbium local surrounding is identified within the relaxation limit introduced by the non-resonant fluorescence line narrowing technique. Furthermore, radiative relaxation of erbium ions exhibits a non-exponential behavior tentatively explained by diffusion-limited energy transfer between erbium ions and towards unknown traps

Fluorescence dynamics and energy migration in Er3+-doped SRSO structure

Decay time properties of erbium ions in silicon rich silicon oxide multilayers are reported. A non-exponential time behaviour for the 4I13/2 decay profile is observed and is interpreted in a diffusion-limited model. Furthermore, an appreciable increase of the lifetime of the 4I13/2 is observed when the sample temperature is lower than 50 K. The lifetime dependence of the 4I13/2 as a function of temperature was successfully fitted with a model taking into account the temperature dependence of the energy migration between Er3+ ions in the presence of quenching impurities

Submicrosecond fluorescence dynamics in erbium-doped silicon-rich silicon oxide multilayers

International audienceThe energy transfer process between amorphous silicon nanoparticles and erbium ions in Er-doped silicon-rich silicon oxide is investigated by fluorescence dynamics measurements. A fast decay is observed in the wavelength range of the radiative relaxation of erbium excited ions at 1.53 μm. Alternatively to a previous interpretation, we assign this fast decay to emission of deep traps induced by Si-based sensitizers of Er3+ ions, which emit in the visible and the infrared region

Stark effect and Franz-Keldysh effect of a quantum wire realized by conjugated polymer chains of a diacetylene 3NPh2

International audienceConjugated polymer chains diluted in monomer single crystals of a diacetylene, 1,10-bis(diphenylamino)-4,6-decadiyne, represent quantum wires of long-range coherence. They differ from most polydiacetylenes by their repeat unit that consists of two C4 units with twisted molecular planes. The resulting modification of exciton and band states is studied by electroabsorption which resolves an increase in the exciton transition energy to 2.399 eV and of the free-electron gap to 3.158 eV. The Stark shift of the exciton reveals a significant reduction in the exciton radius by about 40% to 61 Å which is consistent with a similar increase in the exciton binding energy to 759 meV. The line shape of electroabsorption spectra at the free-electron gap is for fields larger than 30 kV/cm in accordance with the one-dimensional Franz-Keldysh effect and yields a reduced mass of 0.07m0 larger than in other polydiacetylene (PDA). Spectra at smaller fields are distorted by contributions of a weak dipole allowed and a forbidden exciton 38 and 12 meV, respectively, below the band gap. Coherent coupling of free electrons and vibrational modes leads to replicas of the Franz-Keldysh effect. Since light polarized parallel to the conjugated chain excites two propagating modes in the monomer crystals the quantitative analysis was restricted to electroabsorption spectra taken with perpendicular polarization in samples which transmit only the weakly absorbed polariton mode

Preparations and Characterizations of Luminescent Two Dimensional Organic-inorganic Perovskite Semiconductors

This article reviews the synthesis, structural and optical characterizations of some novel luminescent two dimensional organic-inorganic perovskite (2DOIP) semiconductors. These 2DOIP semiconductors show a self-assembled nano-layered structure, having the electronic structure of multi-quantum wells. 2DOIP thin layers and nanoparticles have been prepared through different methods. The structures of the 2DOIP semiconductors are characterized by atomic force microscopy and X-ray diffraction. The optical properties of theb DOIP semiconductors are characterized from absorption and photoluminescence spectra measured at room and low temperatures. Influences of different components, in particular the organic parts, on the structural and optical properties of the 2DOIP semiconductors are discussed

Excitons in a perfect quasi-1D organic quantum wire, an isolated polydiacetylene chain

Symposium on Modern Developmnets in Multiphysics Materials Simulations, Berlin, GERMANY, 2008International audienceThe exciton in single luminescent polydiacetylene (PDA) chains dispersed in their single crystal monomer matrix is studied. As reported these quantum wires have the properties of a perfect quasi-1D semiconducting system. The macroscopic spatial coherence of a single exciton state on a chain as a function of temperature is investigated using an interference experiment. The interference pattern contrast decreasing with increasing temperature is non zero up to 30 K. Experiments developed in order to observe the regime of formation of the stationary coherent exciton state are described. Within the time resolution of the experiment, it is concluded that the formation of this state is faster than similar to 5 picoseconds which confirms the assumption of a transient regime. Finally the first steps of the manipulation of phase locked excitonic wave-packets on a PDA wire are discussed. The experimental results measured in a weak exciton-photon coupling regime are compared to simulations obtained through the Bloch optical equations in the framework of a three-levels model. A direct estimate of the coherence time of the vibronic state photocreated in the present non resonant scheme is derived. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA. Weinhei