Search results for "laser"
showing 10 items of 3161 documents
Er3+-doped GeGaSbS glasses for mid-IR fibre laser application: Synthesis and rare earth spectroscopy
2008
International audience; With an infrared transparency extended to 10 µm, low multiphonon relaxation rates and suitable rare earth solubility, sulphide glasses in the Ge-Ga-Sb-S system allow radiative emission from rare earth ions in the mid-IR range. The Er3+ ion, widely studied in glass fibres for optical amplification at 1.5 µm, presents an interesting transition for mid-IR applications around 4.5 µm (4I9/2→ 4I11/2). Thus, the aim of this work is to evaluate the Er3+-doped Ge20Ga5Sb10S65 glass as a potential fibre laser source operating in the 3-5 µm mid-IR spectral region. For that purpose, absorption and emission spectra were recorded from visible to mid-IR and the radiative lifetimes o…
Optical, thermal, electrical, damage, and phase-matching properties of lithium selenoindate
2010
Lithium selenoindate (LiInSe2) is a new nonlinear chalcogenide biaxial crystal, related to LiInS2 and transparent from 0.54 to 10 μm at the 50% level (10 mm thickness), which has been successfully grown in large sizes and with good optical quality. We report on what we believe to be new physical properties that are relevant for laser and nonlinear optical applications and summarize all relevant characteristics, both from the literature and as measured in the present work. With respect to AgGaS(e)2 ternary chalcopyrite materials, LiInSe2 displays a nearly isotropic thermal expansion behavior with three- to five-times-larger thermal conductivities associated with high optical damage threshold…
Q-switching of an erbium-doped fibre laser modulated by a Bragg grating fixed to a piezoelectric
2003
The performance of the Q-switched erbium-doped fibre laser with two fibre Bragg gratings as cavity mirrors was theoretically analysed, employing a set of rate equations for the ion populations and the photon flux inside the cavity. The simulation considers a system where the pulsed laser emission is produced by the temporal modulation of a Bragg grating fixed to a piezoelectric and operating in the 1550 nm spectral region. The temporal evolution of different frequency components of the laser emission produced is governed by the instantaneous overlap between the two gratings. Theoretical results are in agreement with previously reported experimental values.
Pulsed laser deposition of Sr2FeMoO6 thin films
2005
Abstract The effect of various deposition conditions and after-growth protocols on the magnetic and transport properties of Sr 2 FeMoO 6 films has been explored. It is found that the saturation magnetization and the magnetoresistance (MR) are dominated by the degree of cationic order, and the strain effects are clearly evidenced in a lower T C . The after-growth annealing of the films and the deposition of a buffer layer has been found to relax the film strains. This translates into a clear increase of the measured low-field magnetoresistance ratios.
Laser-induced damage in cold-sprayed composite coatings
2011
International audience; Ag-Ni composite coatings were achieved using the cold spray process. In this work, two blends were sprayed to lead to coatings with different mechanical properties, which corresponded to either a fine or a coarse microstructure. These coatings were studied using SEM and X-ray microtomography (XMT) to determine the best coating quality through characterization of particle-to-particle bonding. The fine microstructure showed better properties than the coarse microstructure. To avoid time-consuming characterization techniques such as SEM and XMT, an innovative laser characterization test was developed. The principle of this test is based on the thermal shock-induced by a…
Polymerization and Damage of C60 Single Crystals under Low Fluency Laser Irradiation
2001
Photo-induced hardening, substructure formation and damage of C 60 single crystals under the 632.8 nm He-Ne laser irradiation in air at a power density of 1.47 mW/mm 2 was investigated by microhardness and AFM methods. Photo-induced formation of the dislocation substructure and crystallographically oriented crack patterns on the (111) face due to lattice contraction on polymerization were observed. Two phototransformed states: soft (400-450 MPa) and hard (650-1000 MPa) are found to appear under laser-irradiation. Hard fullerite is created in the subsurface layer < 1 μm at the saturation stage of phototransformation. It softens to 400-450 MPa at 340 K and reverts to non-polymerized state at …
Cationic vacancies and anomalous spectral-weight transfer in Ti1−xTaxO2thin films studied via polarization-dependent near-edge x-ray absorption fine …
2013
We report the electronic structures of Ta-doped anatase TiO 2 thin films grown by pulsed laser deposition (PLD) with varying magnetization using a combination of first-principles calculations and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. The roles of Ta doping and Ti vacancies are clarified, and the observed room-temperature ferromagnetism is attributed to the localized magnetic moments at Ti vacancy sites ferromagnetically ordered by electron charge carriers. O K -edge spectra exhibit significant polarization dependence which is discussed and supported by first-principles calculations in relation to both the crystal symmetry and the formation of defects. In particula…
Luminescence Center Excited State Absorption in Calcium and Zinc Tungsates
2002
The tungstate crystals are well known scintillators. The mechanism of luminescence center formation and the luminescence center model are under discussion today. The results of time-resolved spectroscopy of luminescence center in ZnWO4 and CaWO4 in wide temperature regions was presented. The luminescence and induced absorption under pulsed electron beam excitation (pulse duration 10 ns, 0.26 MeV) were studied. The experimental equipment used allows one to obtain the transient absorption spectra, luminescence decay kinetics and transient absorption relaxation times.
Picosecond energy relaxation in
2005
Abstract Investigating the reflectance response dynamics of La 0.67 Ca 0.33 MnO 3 thin films after excitation by femtosecond laser pulses, we identify for the first time a picosecond relaxation step which only exists below the Curie temperature T C . The relaxation time increases from zero at T C to several picoseconds at low temperatures. The data can be explained with the existence of a magnetization-related effective energy gap, and assuming relaxation between these states to be mediated by a Frohlich-type electron–lattice interaction.
Local structure and magnetization of ferromagnetic Cu-doped ZnO films: No magnetism at the dopant?
2016
Abstract Relationship between magnetism and structure of Cu-doped ZnO was investigated at macroscopic and microscopic levels. Thin Zn1−xCuxO films (x = 0.02, 0.04, 0.07 and 0.10) were prepared by a pulsed laser deposition and characterized via superconducting quantum interference device (SQUID) magnetometry, high-resolution x-ray diffraction, and Cu K-edge and Zn K-edge x-ray absorption, x-ray linear dichroism and x-ray circular magnetic dichroism spectroscopy. Even though the samples exhibit room-temperature ferromagnetism with magnetization that increases with Cu concentration, we did not detect signatures of local magnetic moments associated with Cu atoms, as evidenced by the lack of any…