Search results for "Physics::Optics"
showing 10 items of 1958 documents
Profiling of traps in SiO2/Al2O3 gate stack by the charge pumping technique
2006
In this paper, we present our results on the distribution and generation of traps in a SiO 2 /A1 2 O 3 transistor. The investigation has been carried out by using charge pumping measurements, both variable voltage and frequency techniques, and constant voltage stress. By increasing the amplitude of the gate pulse we observe an increase of the charge recombined per cycle closely related to the contribution of shallow traps near the SiO 2 /Al 2 O 3 interface. By reducing the pulse frequency we measure an increase in the charge pumping current due to traps located deeper in the Al 2 O 3 . By combining charge pumping and constant voltage stress measurements, we found that the traps are mostly g…
Study of short-lived tin isotopes with a laser ion source
1995
A chemically selective laser ion source based on resonance ionization of atoms in a hot cavity has been applied for the study of short-lived silver isotopes at CERN/ ISOLDE. Silver atoms were ionized by two resonant excitations and final laser ionization into the continuum. Decay properties of the neutron-rich isotopes121–127Ag were studied with a neutron long-counter and aβ-detector.
Plano-concave microlenses with epsilon-near-zero surface-relief coatings for efficient shaping of nonparaxial optical beams
2017
Abstract Epsilon-near-zero (ENZ) materials, including artificial metamaterials, have been advanced to mold laser beams and antenna-mediated radiated waves. Here we propose an efficient method to control Ohmic losses inherent to natural ENZ materials by the assembly of subwavelength structures in a nonperiodic matrix constituting an ENZ metacoating. Implemented over plano-concave transparent substrates whose radius can be of only a few wavelengths, ENZ surface-relief elements demonstrate to adequately shape a plane wave into highly localized fields. Furthermore, our proposal provides an energy efficiency even higher than an ideally-lossless all-ENZ plano-concave lens. Our procedure is satisf…
Characteristics of laser operation at 1064 nm in Nd:YVO_4 under diode pumping at 808 and 914 nm
2011
International audience; A comparative study between 808 and 914nm pumping of Nd:YVO4 crystals for laser operation at 1064nm has been carried out. Using similar setups, performances of both configurations were first studied in the continuous wave, small-signal gain, and Q-switched regimes. Thanks to a numerical model, it is shown that fluorescence quenching and upconversion processes limit the possible uses for the 914nm pumping scheme to regimes with low population inversions
Proton exchange channel waveguides compatible with surface domain engineering in Lithium Niobate crystals
2006
First experiments of proton exchange channel waveguides compatible with electric field surface periodic poling of congruent lithium niobate crystals are addressed. Picosecond nonlinear copropagating QPM-SHG measurements have been carried out on such structures.
Proton implanted waveguides in LiNbO3, KNbO3and BaTiO3
1992
Abstract By using a Van De Graaf accelerator, planar waveguides in LiNbO3, KNbO3, and BaTiO3 are fabricated (at 300 K) by thermally controlled proton implantation. The waveguide properties are investigated by dark line mode spectroscopy. The reconstructed profiles closely follow the ion concentration profiles as determined by simulation (TRIM).
Time resolved luminescence spectroscopy of CsPbBr3 single crystal
2020
Abstract The work reports the results of spectroscopic and luminescence-kinetic studies of CsPbBr3 single crystal over 14–300 K temperature range. It is shown that at low temperatures the luminescence spectrum contains three narrow bands at 534, 537, and 541.5 nm exhibiting a fast decay and a broad emission band at ca. 560 nm with long decay. The evolution of the luminescence bands and their temporal characteristics with temperature are discussed from the viewpoint of possible emission mechanisms. The origin of the luminescence bands is discussed in relation with the observed features of their temporal characteristics. The mechanism of luminescence quenching for different emission band is s…
Structure characterization of hard materials by precession electron diffraction and automatic diffraction tomography: 6H-SiC semiconductor and Ni1+xT…
2012
Using a combination of automated diffraction tomography and precession electron diffraction techniques, quasi-kinematical electron diffraction data sets were collected from intermetallic Ni1+xTe1 embedded nanodomains and ion-thinned specimens of 6H–SiC semiconductor. Cell parameters and space groups were found automatically from the reconstructed 3D diffraction volume. The extracted intensities were used for fast ab initio structure determination by direct methods.
Energy scales and dynamics of electronic excitations in functionalized gold nanoparticles measured at the single particle level.
2019
The knowledge of the electronic structure and dynamics of nanoparticles is a prerequisite to develop miniaturized single-electron devices based on nanoparticles. Low-temperature transport measurements of individual stable metallic nanoparticles enable unravelling the system specific electronic structure while ultrafast optical spectroscopy gives access to the electron dynamics. In this work, we investigate bare and thiol-functionalized gold nanoparticles. For the latter, we employ a fast and low-cost fabrication technique which yields nanoparticles with narrow size distribution. Using relatively long thiol-ended alkane chains for the functionalization modifies the electronic density of stat…
Rheological Percolation Threshold in High-Viscosity Polymer/CNTs Nanocomposites
2017
AbstractPolystyrene (PS)/multi-walled carbon nanotubes (CNT) nanocomposites have been prepared through melt mixing processing aiming at obtaining a uniform and homogeneous dispersion of the used nanoparticles within the polymeric matrix. Optical and scanning electron microscopy has been employed to determine the dispersion and distribution of CNTs at different length scales. Furthermore, the linear viscoelastic behavior of formulated nanocomposites has been deeply investigated. As a result of CNTs added, the nanocomposites experience a transition from liquid-like to solid-like rheological behavior, and a disappearance of relaxation processes at low frequency can be noticed. By plotting G’ v…