Search results for "doping"
showing 10 items of 801 documents
Design of Er3+-doped chalcogenide glass laser for MID-IR application
2009
Abstract The feasibility of a photonic crystal fiber laser (PCF laser), made of a novel Er 3+ -doped chalcogenide glass and operating at the wavelength λ s = 4.5 μm is investigated. The design is performed on the basis of spectroscopic and optical parameters measured on a fabricated Er 3+ -doped Ga 5 Ge 20 Sb 10 S 65 chalcogenide bulk sample. The simulations have been performed by employing a home made numerical code that solves the multilevel rate equations and the power propagation equations via a Runge-Kutta iterative method. The numerical results indicate that a laser exhibiting slope efficiency close to the maximum theoretical one and a wide tunability in the wavelengths range where t…
Ultraviolet-induced paramagnetic centers and absorption changes in singlemode Ge-doped optical fibers
2009
We investigated the laser-energy-density dependence of absorption changes and paramagnetic centers induced by a cw Ar+ laser operating at 5.1 eV, in both unloaded and H-2-loaded single mode Ge-doped optical fibers. The induced absorption is measured in the blue and near ultraviolet spectral range by using the 3.1 eV photoluminescence, ascribed to Ge lone pair center (GLPC), as an in situ probe source. We find that the Ge (1) center (GeO4-) is induced upon UV exposure by electron trapping on GeO4 precursors, where the free electrons are most likely produced by ionization of GLPC. Ge (1) is responsible of optical transmission loss of the fiber in the investigated range. Hydrogen loading stron…
X-ray irradiation effects on a multistep Ge-doped silica fiber produced using different drawing conditions
2011
International audience; We report an experimental study based on confocal microscopy luminescence (CML) and electron paramagnetic resonance (EPR) measurements to investigate the effects of the X-ray (from 50 krad to 200 Mrad) on three specific multistep Ge doped fibers obtained from the same preform by changing some of the drawing conditions (tension and speed). CML data show that, both before and after the irradiation, Germanium Lone Pair Center (GLPC) concentrations are similarly distributed along the diameters of the three fibers and they are partially reduced by irradiation. The irradiation induces also the Non Bridging Oxygen Hole Center (NBOHC) investigated by CML and other paramagnet…
Evolution of Photo-induced defects in Ge-doped fiber/preform: influence of the drawing
2011
International audience; We have studied the generation mechanisms of two different radiation-induced point defects, the Ge(1) and Ge(2) centers, in a germanosilicate fiber and in its original preform. The samples have been investigated before and after X-ray irradiation using the confocal microscopy luminescence and the electron paramagnetic resonance techniques. Our experimental results show the higher radiation sensitivity of the fiber as compared to the perform and suggest a relation between Ge(1) and Ge(2) generation. To explain our data we have used different models, finding that the destruction probability of the Ge(1) and Ge(2) defects is larger in fiber than in preform, whereas the …
Excited-state absorption in erbium-doped silica fiber with simultaneous excitation at 977 and 1531 nm
2009
We report a study of the excited-state absorption (ESA) in erbium-doped silica fiber (EDF) pumped at 977 nm, when the fiber is simultaneously excited by signal radiation at 1531 nm. We show, both experimentally and theoretically, that ESA efficiency at 977 nm gets strongly enhanced only in the presence of signal power. Experimentally, this conclusion is supported through the detection of upconversion emission, a “fingerprint” of the ESA process, and through the measurements of the EDF nonlinear transmission coefficient for the pump wavelength, which is sensitive to the ESA value. It is shown that the experimental data are precisely modeled with an advanced five-level Er3+ model developed fo…
Efficient photo-thermal activation of gold nanoparticle-doped polymer plasmonic switches
2012
International audience; We report on the photo-thermal activation of dielectric loaded plasmonic switches comprised of gold nanoparticle-doped polymer deposited onto a gold film. The plasmonic switches rely on a multi-mode interferometer design and are fabricated by electron beam lithography applied to a positive resin doped with gold nanoparticles at a volume ratio of 0.52%. A cross-bar switching is obtained at telecom wavelengths by pumping the devices with a visible beam having a frequency within the localized surface plasmon resonance band of the embedded nanoparticles. By comparing the switching performances of doped and undoped devices, we show that for the modest doping level we cons…
Humidity Insensitive Conductometric Sensors for Ammonia Sensing
2014
Interest in molecular materials has been driven in large part by their various and prosperous applications, especially in the domain of organic electronics, where they offer many advantages as well as alternative approaches compared to their inorganic counterparts. Most of conductometric transducers are resistors[[ and transistors[[[, but rarely diodes[6]. In our laboratory, we designed and characterized new molecular material based devices. Molecular Semiconductor Doped Insulator (MSDI) heterojunctions were built around a heterojunction between a Molecular Semiconductor (MS) and a Doped Insulator (DI)[7][8]. This new device exhibits interesting electronic properties that allow ammonia sens…
Photoelectrochemical properties of doped lanthanum orthoferrites
2013
Abstract LaFeO 3 powders doped with Sr (20 mol%) and Cu (0-10-20 mol%) were prepared by citrate auto-combustion synthesis and investigated in terms of crystal structure, morphology, surface area and optical properties. All powders showed photocurrent response in the form of a pasted and annealed electrode and as slurry electrode; the highest value was obtained for undoped orthoferrite calcined at 600 °C. Their physical–chemical properties were related to photoelectrochemical behaviour. The position of the quasi-Fermi level of electrons for all the photocatalysts calcined in the range 600–980 °C is about the same within experimental error (between −0.62 and −0.67 V with respect to Ag/AgCl re…
OH/OD-IR absorption bands in SrxBa1−xNb2O6
1995
Single crystals of Sr x Ba 1−x Nb 2 O 6 (SBN) with congruent composition (x = 0.61) and Sr 0.61 Ba 0.39 Nb 2 O 6 crystals doped with various concentrations of cerium are grown with the Czochralski method. A subsequent doping of the crystals with protons and deuterons is performed either by hydrothermal high temperature treatment or by field supported hydrogen diffusion at elevated temperatures in humid atmosphere. The presence of the protons is revealed by the infrared absorption of the OH stretching vibration. This broad OH absorption band is essentially the same for Sr 0.61 Ba 0.39 Nb 2 O 6 and Sr 0.61 Ba 0.39 Nb 2 O 6 :Ce (0.025 wt% CeO 2 ). It shows a polarization dependence with respec…
Sputtered cuprous oxide thin films and nitrogen doping by ion implantation
2016
Abstract The structural, optical and electrical properties of sputtered cuprous oxide thin films have been optimized through post-deposition thermal treatments. Moreover we have studied the effects of nitrogen doping introduced by ion implantation followed by the optimized oxidant thermal annealing. Three concentrations have been used, 0.6 N%, 1.2 N%, and 2.5 N%. Along with the preservation of the Cu 2 O phase, a slight optical band gap narrowing and a significant conductivity enhancement has been observed with respect to the undoped samples. These results can be justified by the absence of further oxygen vacancies promoted by dopant introduction and by the substitution of O atoms by N ones…