Search results for "electromagnetic"
showing 10 items of 1595 documents
Single molecules probe local density of modes (LDOS) around photonic nanostructures
2008
International audience; According to Fermi's golden rule, the fluorescence decay rate is directly proportional to the projected local density of photonic modes (LDOS) at the molecule location. The relevant LDOS depends on the molecule orientation. In this paper, the direct measurement of the fluorescence lifetime near gold dot photonic structures is investigated and compared to calculated LDOS. Detailed analysis of the decay channels is presented on the basis of numerical simulations.
Optical absorption and Raman spectroscopy of CuWO4
2010
Th e electronic absorption and Raman spectra of CuWO4 are studied as a function of pressure in the 0 - 20 GPa range. The below-gap absorption bands at 1.15, 1.38 and 1.56 eV correspond to Cu 2+ d-transitions split by the Jahn-Teller distortion of CuO6 (Req = 1.98 A; Rax = 2.39 A; Qθ = 0.47 A). Pressure induces a strong reduction of the JT distortion up to 10 GPa. Above this pressure we observe, by optical absorption and Raman spectroscopy, a first-order phase transition at 11 GPa with phase coexistence in the 10-12 GPa range, as it is confirmed by Raman spectroscopy. The absorption spectra suggest that two different Cu 2+ sites are formed in the high pressure phase, each having rather diffe…
Millimeter wave absorption by confined acoustic modes in CdSe/CdTe core-shell quantum dots
2007
International audience; Taking advantage of the specific core-shell charge separation structure in the CdSe/CdTe core-shell Type-II quantum dots (QDs), we experimentally observed the resonant-enhanced dipolar interaction between millimeter-wave (MMW) photons and their corresponding (l = 1) confined acoustic phonons. With proper choice of size, the absorption band can be tuned to desired frequency of MMW imaging. Exploiting this characteristic absorption, in a fiber-scanned MMW imaging system, we demonstrated the feasibility of CdSe/CdTe QDs as the contrast agents of MMW imaging.
Local dynamics and phase transition in quantum paraelectric SrTiO3 studied by Ti K-edge x-ray absorption spectroscopy
2016
Strontium titanate is a model quantum paraelectric in which, in the region of dominating quantum statistics, the ferroelectric instability is inhibited due to nearly complete compensation of the harmonic contribution into ferroelectric soft mode frequency by the zero- point motion contribution. The enhancement of atomic masses by the substitution of 16 O with 18O decreases the zero-point atomic motion, and low-T ferroelectricity in SrTi18O3 is realized. In this study we report on the local structure of Ti in SrTi16O3 and SrTi18O3 investigated by Extended X-ray Absorption Fine Structure measurements in the temperature range 6 - 300 K.
Nanoscale x-ray absorption spectroscopy using XEOL-SNOM detection mode
2007
The first results obtained with the prototype system at the synchrotron beamline ID03 at ESRF are presented and illustrate the possibility to detect an element-specific contrast and to perform nanoscale x-ray absorption spectroscopy experiments at the Zn K and W L 3 absorption edges in mixed zinc oxide-zinc tungstate thin films.
An accurate optical technique for measuring the nuclear polarisation of 3He gas
2010
12 pages; International audience; In the metastability exchange optical pumping cells of our on-site production unit and of our other experimental set-ups, we use a light absorption technique to measure the 3He nuclear polarisation. It involves weak probe beams at 1083 nm, that are either perpendicular or parallel to the magnetic field and cell axis, with suitable light polarisations. When metastability exchange collisions control the populations of the sublevels in the 23S state, absolute values of the 3He ground state nuclear polarisation are directly inferred from the ratio of the absorption rates measured for these probe beams. Our report focuses on the transverse detection scheme for w…
Laminated carbonate deposits in Roman aqueducts: Origin, processes and implications
2013
Carbonate deposits in Roman aqueducts of Patara and Aspendos (southern Turkey) were studied to analyse the nature of their regular layering. Optical microscopy and electron-backscattered diffraction results show an alternation of dense, coarsely crystalline, translucent laminae composed of bundles and fans of elongate calcite crystals with their c-axes parallel to the long axis, and porous, fine-grained laminae with crystals at near-random orientation. The ?18O and ?13C data show a strong cyclicity and anti-correlation, whereby high and low ?18O values correspond to dense columnar and porous fine-grained laminae, respectively. Geochemical analyses show similar cyclic changes in carbonate co…
Effects induced by 4.7 eV UV laser irradiation on pure silica core multimode optical fibers investigated by in situ optical absorption measurements
2011
We investigated by in situ optical absorption measurements the effects induced by 4.7 eV UV laser irradiation on pure silica core optical fibers. Laser irradiation with 100 MWcm−2 laser intensity generates in the fiber E′ centers which partially decay after irradiation due to their reaction with diffusing H2. An absorption band peaked at 5.3 eV is observed to grow in the post-irradiation stage with a kinetics anti-correlated to the decay of the 5.8 eV band of the E′ centers. The defect absorbing at 5.3 eV is proposed to be formed by trapping on pre-existing precursors of hydrogen atoms made available by breaking of H2 on E′.We also show by repeated irradiation experiments that the 5.3 eV-ab…
Technical Feasibility of Electromagnetic US/CT Fusion Imaging and Virtual Navigation in the Guidance of Spine Biopsies.
2020
To test the technical feasibility of electromagnetic computed tomography (CT) + ultrasound fusion (US)-guided bone biopsy of spinal lesions. This retrospective study included 14 patients referred for biopsy of spinal bone lesions without cortical disruption or intervertebral disc infection. Lesions were located in the sacrum (n = 4), lumbar vertebral body (n = 7) or intervertebral disc (n = 3). Fusion technology matched a pre-procedure CT scan with real-time ultrasound. The first six procedures were performed under both standard CT and CT + US fusion guidance (group 1). In the last eight procedures, the needle was positioned under fusion imaging guidance alone, and CT was only used at the …
High-Frequency Experimental Characterization and Modeling of Six Pack IGBTs Power Modules
2016
In this paper, a method to characterize the high-frequency (HF) behavior of six pack insulated gate bipolar transistors (IGBTs) power module (PM) is presented. The method is based on experimental measurements at the external pins of the device and it allows one to extract internal inductive and capacitive parasitic coupling without the knowledge of structural and physical parameters of the PM. The HF model of a six pack IGBTs PM has been developed, in the frequency range of 150 kHz-30 MHz, and it has been implemented in MATLAB environment. The method has been experimentally validated by comparing the frequency behavior of the PM with the simulated response. Moreover, the HF conducted distur…