Search results for "HIF"
showing 10 items of 1515 documents
Cover Feature: Crystallographic Visualization of a Double Water Molecule Addition on a Pt 1 ‐MOF during the Low‐temperature Water‐Gas Shift Reaction …
2021
Si nanocrystals embedded in $SiO_2$: Optical studies in the vacuum ultraviolet range
2011
Photoluminescence excitation and transmission spectra of Si nanocrystals of different diameters embeddedin a SiO2 matrix have been investigated in the broad visible-vacuum ultraviolet spectral range usingsynchrotron radiation. The dependence of the photoluminescence excitation spectra on the nanocrystals sizewas experimentally established. It is shown that the photoluminescence excitation and absorption spectra aresignificantly blueshifted with decreasing Si nanocrystal size. A detailed comparison of photoluminescenceexcitation and absorption spectra with data from theoretical modeling has been done. It is demonstrated thatthe experimentally determined blueshift of the photoluminescence exc…
Optical properties of ZnMgO films grown by spray pyrolysis and their application to UV photodetection
2015
This work presents a comprehensive optical characterization of Zn1−xMgxO thin films grown by spray pyrolysis (SP). Absorption measurements show the high potential of this technique to tune the bandgap from 3.30 to 4.11 eV by changing the Mg acetate content in the precursor solution, leading to a change of the Mg-content ranging from 0 up to 35%, as measured by transmission electron microscopy-energy dispersive x-ray spectroscopy. The optical emission of the films obtained by cathodoluminescence and photoluminescence spectroscopy shows a blue shift of the peak position from 3.26 to 3.89 eV with increasing Mg incorporation, with a clear excitonic contribution even at high Mg contents. The lin…
Depth profiling of optical and vibrational properties in GaN/AlN quantum dot superlattices
2009
Spatially resolved confocal μ-Raman and μ-photoluminescence experiments were performed to analyze the vibrational and optical properties of GaN/AlN quantum dots as a function of depth. Two approaches have been followed. First, spectra were taken by defocusing the microscope objective at various depths on the sample surface. In a second set of experiments a bevel at an angle of 20° with respect to the surface normal was prepared by mechanical polishing of the surface, and spectra were taken across the bevel. The E2h vibrational modes ascribed to the GaN QDs and the AlN spacer redshift towards the surface, indicating the progressive relaxation of the QDs and a considerable increase of the ten…
Luminescence properties of wurtzite AlN nanotips
2006
The optical properties of aluminum nitride nanotips (AlNNTs) synthesized via vapor transport and condensation process have been studied by cathodoluminescence, photoluminescence (PL), thermoluminescence (TL), and UV absorption measurements. Two defect related transitions around 2.1 and 3.4eV and an excitonic feature at 6.2eV were identified. Compared to the AlN macropowders, the AlNNTs showed a blueshift (+0.2eV) of the ∼3.2eV peak. Analysis of both PL and TL excitation measurements indicated the existence of subband gap multiple energy levels in AlNNTs. A significant TL intensity even at 145°C suggests possible ultraviolet detector and dosimetric applications of these AlNNTs.
Temperature Sensor Based on Colloidal Quantum Dots PMMA Nanocomposite Waveguides
2012
In this paper, integrated temperature sensors based on active nanocomposite planar waveguides are presented. The nanocomposites consist of cadmium selenide (CdSe) and cadmium telluride (CdTe) quantum dots (QDs) embedded in a polymethylmethacrylate (PMMA) matrix. When the samples are heated in a temperature range from 25$^{circ}{rm C}$ to 50 $^{circ}{rm C}$, the waveguided photoluminescence of QDs suffers from a strong intensity decrease, which is approximately quadratic dependent on temperature. Moreover, the wavelength peak of the waveguided emission spectrum of CdTe-PMMA shows a blue shift of 0.25 ${rm nm}/^{circ}{rm C}$, whereas it remains constant in the case of CdSe-PMMA. A temperature…
SiPMs coated with TPB: coating protocol and characterization for NEXT
2012
[EN] Silicon photomultipliers (SiPM) are the photon detectors chosen for the tracking readout in NEXT, a neutrinoless \bb decay experiment which uses a high pressure gaseous xenon time projection chamber (TPC). The reconstruction of event track and topology in this gaseous detector is a key handle for background rejection. Among the commercially available sensors that can be used for tracking, SiPMs offer important advantages, mainly high gain, ruggedness, cost-effectiveness and radio-purity. Their main drawback, however, is their non sensitivity in the emission spectrum of the xenon scintillation (peak at 175 nm). This is overcome by coating these sensors with the organic wavelength shifte…
Theory of parabolic pulse propagation in nonlinear dispersion decreasing optical fiber amplifiers
2008
Optical fibers ; Nonlinear optics ; Optical fiber amplifiers ; Optical amplifier ; Optical solitons ; Electromagnetic wave propagation ; Pulse propagation ;; International audience; We show that pulse spectral broadening in normally dispersive nonlinear fiber amplifiers may be enhanced by introducing a suitable dispersion tapering. We obtain an analytical dispersion profile that permits one to reduce pulse propagation in a varying dispersion fiber to the case of an equivalent fiber with constant parameters.
High frequency microwave signal generation using dual-wavelength emission of cascaded DFB fiber lasers with wavelength spacing tunability
2010
[EN] A dual wavelength fiber laser source based on two cascaded phase-shifted fiber Bragg gratings is presented The gratings are written in an erbium-doped fiber each configuring the cavity of a distributed feedback fiber laser The spacing between lasing modes is controlled dynamically by the use of piezoelectric actuators A continuous tuning range of 5-724 pm of the wavelength difference which is equivalent to a photodetected 072-92 GHz range is obtained Efficient generation from the L to the W microwave and millimeter bands has been achieved by heterodyne photodetection of the dual-wavelength optical signal (C) 2010 Elsevier BV All rights reserved
Polarization insensitive wavelength conversion of 40 Gb/s DPSK signals in a silicon germanium waveguide
2015
We demonstrate polarization insensitive FWM-based wavelength conversion of 40Gb/s DPSK signals in a SiGe waveguide, with 0.42-dB polarization-dependent loss. A 1.5-dB Dower nenaltv was measured at a BER of 10−9.