Search results for "Toe"
showing 10 items of 3824 documents
SIMULATION OF THERMAL EFFECTS IN OPTOELECTRONIC DEVICES USING COUPLED ENERGY-TRANSPORT AND CIRCUIT MODELS
2008
A coupled model with optoelectronic semiconductor devices in electric circuits is proposed. The circuit is modeled by differential-algebraic equations derived from modified nodal analysis. The transport of charge carriers in the semiconductor devices (laser diode and photo diode) is described by the energy-transport equations for the electron density and temperature, the drift-diffusion equations for the hole density, and the Poisson equation for the electric potential. The generation of photons in the laser diode is modeled by spontaneous and stimulated recombination terms appearing in the transport equations. The devices are coupled to the circuit by the semiconductor current entering the…
1.65-μm Er:Yb:YAG diode-pumped laser delivering 80-mJ pulse energy
2005
We demonstrate efficient lasing of bulk diode-pumped Er 31 :Yb 31 :YAG at 1.645 mm. The material is transversely pumped using three quasi-cw 960-nm laser diode arrays in a simple arrangement. In the free-running mode of operation, an output pulse energy of 79 mJ is obtained at 4.7 J of incident optical pump energy. The lasing threshold lies in the range 1.0 to 1.9 J in long-pulse operation, depending on pumping conditions, and optical slope efficiencies of 2.2% to 3.4% were measured with respect to the incident pump energy. Furthermore, initial Q-switching experiments with a Co:MALO saturable absorber yielded pulses of 1.7-mJ energy and 340-ns FWHM duration. As the reported laser setup also…
Experimental Observation of Strong Exciton Effects in Graphene Nanoribbons
2019
Graphene nanoribbons (GNRs) with atomically precise width and edge structures are a promising class of nanomaterials for optoelectronics, thanks to their semiconducting nature and high mobility of charge carriers. Understanding the fundamental static optical properties and ultrafast dynamics of charge carrier generation in GNRs is essential for optoelectronic applications. Combining THz spectroscopy and theoretical calculations, we report a strong exciton effect with binding energy up to 700 meV in liquid-phase-dispersed GNRs with a width of 1.7 nm and an optical bandgap of 1.6 eV, illustrating the intrinsically strong Coulomb interactions between photogenerated electrons and holes. By trac…
Enhancing the photocatalytic properties of PbS QD solids: the ligand exchange approach.
2019
Surface engineering of nanomaterials is a promising tool towards the design of new materials for conversion of solar energy into chemical energy. In this work, we examine the influence of ligand exchange on the photocatalytic performance of solution-processed PbS films. We test different ligands such as oleylamine (OAm), 1,2-ethanedithiol (EDT), 3-mercaptopropionic acid (MPA) and tetrabutylammonium iodide (TBAI). The study demonstrates that PbS films capped with MPA and EDT exhibit 3.5-fold enhanced photocatalytic performance for the photodecomposition of methyl orange upon sunlight exposure. Both band energy alignment and charge carrier transport have a strong impact on the generation of r…
Flexible light-emitting electrochemical cells with single-walled carbon nanotube anodes
2016
Abstract In this work, we demonstrate flexible solution processed light emitting electrochemical cells (LECs) which use single-walled carbon nanotubes (SWCNTs) films as the substrate. The SWCNTs were synthesized by an integrated aerosol method and dry-transferred on the plastic substrates at room temperature. The addition of a screen printed poly (3,4-ethylene dioxythiophene) doped with poly (styrene sulfonate) (PEDOT:PSS) film onto the nanostructured electrode further homogenizes the surface and enlarges the work function, enhancing the hole injection into the active layer. By using an efficient phosphorescent ionic transition metal complex (iTMC) as the active material, efficacies up to 9…
Quadratic nonlinear optical parameters of 7% MgO-doped LiNbO3 crystal
2016
International audience; Pure and 7% MgO-doped lithium niobate (LiNbO3) single crystals were grown by the Czochralski technique. The shift of optical absorption edge in 7% MgO-doped crystal in direction of shorter wavelength compared to undoped crystal was observed. The second harmonic generation measurements of 7% MgO-doped LiNbO3 crystal were performed at room temperature by means of the rotational Maker fringe technique using Nd:YAG laser generating at 1064 nm in picoseconds regime. Experimentally obtained value of nonlinear optical coefficient d33 for 7% MgO-doped LiNbO3 was found to be less than for undoped crystal but higher than for 5% MgO-doped. I-type phase-matched second harmonic g…
Hybrid organic-inorganic light-emitting diodes.
2011
The demonstration of colour tunability and high efficiency has brought organic light-emitting diodes (OLEDs) into the displays and lighting market. However, high production costs due to expensive deposition techniques and the use of reactive materials still limit their market entry, highlighting the need for novel concepts. This has driven the research towards the integration of both organic and inorganic materials into devices that benefit from their respective peculiar properties. The most representative example of this tendency is the application of metal oxides in organic optoelectronics. Metal oxides combine properties such as high transparency, good electrical conductivities, tuneable…
Geometrical dependence of domain wall propagation and nucleation fields in magnetic domain wall sensor devices
2017
We study the key domain wall properties in segmented nanowires loop-based structures used in domain wall based sensors. The two reasons for device failure, namely the distribution of domain wall propagation field (depinning) and the nucleation field are determined with Magneto-Optical Kerr Effect (MOKE) and Giant Magnetoresistance (GMR) measurements for thousands of elements to obtain significant statistics. Single layers of Ni$_{81}$Fe$_{19}$, a complete GMR stack with Co$_{90}$Fe$_{10}$/Ni$_{81}$Fe$_{19}$ as a free layer and a single layer of Co$_{90}$Fe$_{10}$ are deposited and industrially patterned to determine the influence of the shape anisotropy, the magnetocrystalline anisotropy an…
Overview on Induced Chirality in Magnetic Field Controlled Electro-Deposition and Induced Magnetic Moment Originating from Chiral Electrodes
2018
Magneto-electrochemistry (MEC) is a unique paradigm in science, where electrochemical experiments are carried out as a function of an applied magnetic field, creating a new horizon of potential scientific and technological applications. Over the time, detailed understanding of this research domain was developed to identify and rationalize the possible effects exerted by a magnetic field on the various microscopic processes occurring in an electrochemical system, such as: electrolyte properties governed by charge-transfer process (electric conductivity, viscosity, and diffusivity), mass transfer, electrochemical kinetics and on the structure/quality of products formed either at the working e…
Effect of antisite defects on the magnetic properties of ZnFe2 O4
2013
Magnetic zinc ferrite (ZnFe2O4) nanopowders were synthesized using the sol–gel autocombustion method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements demonstrated that thermal decomposition of the 1-mm-thick xerogel layers in air formed monophasic spinel ferrite nanopowders with a particle size less than 30 nm. X-ray photoelectron spectroscopy (XPS) showed that the obtained reaction product contained antisite defects, with zinc ions occurring at the octahedral sites of the spinel structure. The concentration of antisite defects or inversion degree decreased when the relatively low annealing temperature was increased from 150 to 500 °C. Overall, the obtained ZnFe2…