Search results for " optical characterization"

showing 5 items of 5 documents

MBE growth and properties of low-density InAs/GaAs quantum dot structures.

2011

We present the results of a comprehensive study carried out on morphological, structural and optical properties of InAs/GaAs quantum dot structures grown by Molecular Beam Epitaxy. InAs quantum dots were deposited at low growth rate and high growth temperature and were capped with InGaAs upper confining layers. Owing to these particular design and growth parameters, quantum dot densities are in the order of 4-5x109 cm-2 with emission wavelengths ranging from 1.20 to 1.33 µm at 10 K, features that make these structures interesting for single-photon operation at telecom wavelength. High resolution structural techniques show that In content and composition profiles in the structures depend on …

Arrhenius equationeducation.field_of_studystructural and optical characterizationPhotoluminescenceMaterials scienceCondensed matter physicslow-dimensional semiconductor systemsCondensed Matter::OtherPopulationmolecular-beam epitaxyGeneral ChemistryCondensed Matter PhysicsEpitaxyCondensed Matter::Mesoscopic Systems and Quantum Hall Effectlow-dimensional semiconductor systems molecular-beam epitaxy structural and optical characterizationsymbols.namesakeCondensed Matter::Materials ScienceQuantum dotQuantum dot lasersymbolsGeneral Materials ScienceeducationMolecular beam epitaxyWetting layer
researchProduct

Stability improvement of PMMA and Lumogen® coatings for hybrid white LEDs

2014

Hybrid white LEDs employing perylene-based dyes for the frequency down-conversion of blue light, generated by a standard inorganic source, suffer from colour rendering variations due to the degradation of the organic molecule under prolonged irradiation. To avoid such inconvenient, proper encapsulation of the dyes in resins or other polymer matrices can prevent their accelerated ageing; nevertheless, embedding polymers can also exhibit significant bleaching caused by chemico-physical agents. Among all, polymethyl methacrilate (PMMA) is one of the most used materials for the fabrication of hybrid LEDs' colour conversion coatings, therefore its stability needs to be investigated.

PMMA white LEDs hybrid LEDs perylene-based dyes Lumogen® polymer degradation LED optical characterization spin coating.Settore ING-INF/01 - Elettronica
researchProduct

Optical characterization of polystyrene direct opals and of inverse-opal hydrogels

2012

Settore CHIM/07 - Fondamenti Chimici Delle TecnologieOpals polystyrene hydrogel optical characterizationSettore ING-INF/01 - Elettronica
researchProduct

Optical characterization of TiO2 suspensions: influence of some operational parameter on mean particle size

2007

TiO2 Photocatalysis Optical Characterization
researchProduct

Warm white LED light by frequency down-conversion of mixed yellow and red Lumogen®

2013

This work reports on the benefits and promising opportunities offered by white LED hybrid technology, based on a mixing perylene-based dyes in order to obtain a warm white light for frequency-down conversion. In a standard Ce:YAG-based white LED, the white light appears cold due to the weakness of red wavelength components in the emission spectrum. In order to obtain a warmer white, one possible solution is to add a red phosphor to the yellow one to move the chromatic coordinates properly, though the luminous efficiency drastically decreases due to the increased light absorption of the coating layer. It is generally believed that the low efficiency of warm white LEDs is the main issue today…

Warm white LEDs hybrid LEDs perylene-based dyes Lumogen® LED optical characterization dip coatingMaterials sciencebusiness.industryPhosphorColor temperatureSettore ING-INF/01 - Elettronicalaw.inventionLuminous fluxColor rendering indexLED lampchemistry.chemical_compoundchemistrylawOptoelectronicsbusinessLuminous efficacyPeryleneLight-emitting diode
researchProduct