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1
Marzuki, Ahmad. "Ion-exchanged neodymium-doped fluoroaluminate." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396943.
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Faldon, Mary Eileen. "A high intensity, short pulse neodymium laser." Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322326.
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Hamilton, J. H. "Photoacoustic spectroscopy of neodymium-doped laser materials." Thesis, Queen's University Belfast, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374196.
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Burton, Nicholas. "X-ray magnetic scattering from neodymium metal." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396458.
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Matthewson, Kenneth. "Studies on therapeutic neodymium YAG laser endoscopy." Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241407.
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Yoon, Sung Jin. "Cryogenically-cooled neodymium-doped solid-state lasers." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/415952/.
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The central idea of this thesis is to study cryogenically-cooled neodymium (Nd3+) doped lasers operating on the 4F3/2 → 4I9/2 transition around 0.95 microns, known as a quasi-four-level (QFL) transition. The QFL transition has unavoidable reabsorption loss at room temperature that introduces additional saturable losses into the laser cavity and must be overcome to achieve efficient operation. In general, this particular transition has lower gain than the dominant four-level 4F3/2 → 4I11/2 transition, around 1 micron. While the advantages of cryogenically cooled gain media have been recognised since the birth of the laser, in more recent times there has been a trend in exploiting these advantages for power-scaling QFL lasers, such as Yb-doped gain media. The first part of the thesis explores the extensive characterization of the spectroscopic properties of Nd3+ doped crystals. The present work tracks the spectroscopic changes over the temperature range from 77K to 450K. A number of crystals (YAG, GSAG, YVO4, GdVO4, KGW, YLF) hosting Nd3+ ions have been studied. The absorption cross section spectra for 800nm and 870nm bands were determined with 0.1nm resolution. The absorbance was measured exploiting the Beer-Lambert law and a bespoke set-up using two separate broadband light sources. The fluorescence spectrum was collected and characterized for the transitions to 4I9/2, 4I11/2, and 4I13/2 energy-levels from the metastable level, 4F3/2, from which we calculated the stimulated emission cross section of the various crystals and over the temperature range by applying the Füchtbauer-Ladenburg equation, with the measured fluorescence lifetime. Furthermore, in this report we determine the energy transfer upconversion parameters, for the same set of crystals, using the Z-scan technique. The technique measures the change in transmittance of a probe beam tuned to an absorption peak of crystal sample. The measured transmitted power changes as the intensity incident on the crystal is varied via scanning the beam size and correlated to the saturation intensity through a spatially-dependent rate equation model, we found excellent fit between experiment and simulation. The second part of this thesis reports the development of cryogenic lasers. The design strategies are described by end-pumped and side-pumped systems, with two different crystal geometries reported. Conventional radially-cooled rods are first reported with an end-pumping arrangement, then with a slab (Brewster angled, and afterwards AR coated), and finally a side-pumped Zigzag slab configuration. A rod geometry is tested using a Nd:YAG and a Nd:GSAG crystal for generation of QFL laser emission. The first end-pumped Nd:YAG rod have demonstrated 3.8W at 946nm for 12.8W of pump being absorbed and slope efficiency of 47%. Similar experiment was duplicated with Nd:GSAG rod demonstrating 3.5W at 942nm for 10.5W of pump absorbed. Both suffered significant modal instability during laser oscillation, which afterwards for the Nd:GSAG crystal was found to be due to AR-coating damage. A Nd:YAG slab crystal was tested for the both pumping configurations, using a wavelength-locked 869nm diode bar as a pump source. For this in-band pump-source, the quantum defect is only 8%, in the case of the main QFL transition. A top/bottom-face cooled slab presented effective mitigation of the previously observed modal stability, assumed to be associated with reducing birefringence losses. Despite the coating damage/contamination, which was repeatedly encountered, 946nm emission for both configurations was demonstrated. An end-pumping configuration has demonstrated 5.5W for 13.6W of absorbed pump with 47% slope efficiency. While the side-pumping the zigzag slab produced 6.3W for 30W of absorbed pump with 30% slope efficiency. It is expected that with improvements in the cleanliness within the vacuum chamber used for the cryogenic setup, better results in terms of slope efficiency, output power and beam quality will be realised in the near future.
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Morkel, Paul Roos. "Active neodymium and erbium doped fibre devices." Thesis, University of Southampton, 1990. https://eprints.soton.ac.uk/399485/.
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In this thesis a number of rare-earth-doped fibre devices are described including fluorescent and superfluorescent sources as well as several laser configurations. The laser configurations are all-fibre and include a neodymium-doped ring laser and recirculating delay line, a novel tunable neodymium-doped fibre laser and a single-frequency travelling-wave erbium-doped ring laser. The latter device has been the first description of a travelling-wave fibre laser device. Theory describing general fibre amplifier and laser devices is incorporated. A novel lumped element approach to fibre laser theory has been given applicable to 3 and 4-level laser devices which, under certain conditions, allows single pass gain of a fibre device to be described simply by the absorbed pump power. Numerical modelling of the erbium-doped fibre amplifier has been described which allows for analysis of a general device showing pump excited-state absorption. Results from the analysis have shown a difference in gain characteristics between co-propagating and counter-propagating signal/pump schemes when subject to pump excited-state absorption. In addition, the effect of pump direction on the noise figure is characterised in both small and large signal operating regimes. Characterisation of neodymium-doped fibres has shown a number of effects which will affect their use in amplifier and oscillator configurations. These include observation of sensitivity of the fluorescence characteristics to pump wavelength, observation of excited state absorption and polarisation of fluorescence. Additionally, the spectral gain-saturation characteristics have been investigated.
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Alcock, Ian Peter. "Laser action in neodymium doped silica fibre." Thesis, University of Southampton, 1988. https://eprints.soton.ac.uk/404730/.
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This thesis describes an investigation into the suitability of neodymium doped monomode optical fibre as a gain medium for miniature laser systems. Characterisation of the material and parameters required for quantitative analysis of such laser systems are presented in a spectroscopic analysis carried out in the first part of the thesis. Measurements performed in this section also indicate that at room temperature the wide fluorescence bands of the neodymium doped silica fibre are spectrally broadened by a homogeneous process. The behaviour of a longitudinally pumped continuous-wave fibre laser is modelled in the next section followed by the design and realisation of a practical system. Efficiencies of approximately 6% and threshold pump powers of 8-12 mW have been obtained, even under narrow linewidth operation. Tunability over ranges of 45-60nm has also been demonstrated. The thesis is concluded by experiments on pulsed fibre lasers. Q-switching the laser has achieved peak powers of several watts in pulses 180ns wide with good agreement between the results obtained and predicted values. Shorter pulses 450ps wide have been realised by mode-locking a fibre laser. Suggestions for reducing the pulse width further and the effects of material dispersion are also given. Finally modulated pump sources have been investigated and it is shown that synchronous pumping with short pulses has limitations due to dispersion, while resonantly pumping relaxation oscillations is a simple means of obtaining a pulsed output.
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Canchal, Arias D. "Optical tunnelling studies of gold and neodymium nickelate." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403190.
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Selvas-Aguilar, Romeo de Jesus. "Cladding-pumped neodymium and ytterbium doped fibre lasers." Thesis, University of Southampton, 2004. https://eprints.soton.ac.uk/41526/.
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This thesis details my work on both high-power neodymium-doped fibre lasers (at around 1.1 μm and around 0.9 μm) and ytterbium-doped fibre lasers (at 980 nm). The main subjects were the study of efficient three-level compact continuous-wave fibre lasers and their power scaling.Ytterbium-doped fibre lasers (YDFLs) with emission at 980 nm were also investigated. I, in collaboration, obtained the highest reported output power from any compact single-mode 980 nm laser to this point. For this, speciality fibres, with special core and inner-cladding designs, were developed, notably the jacketed-air-clad (JAC) fibre, with properties that are not attainable in conventional double-clad fibres. The JAC structure allows for a small pump waveguide (inner cladding) with a high NA. This is an essential advantage for lasers operating on a transition to the ground state, such as YbThere are many considerations involved with making practical, reliable, and usable 980 nm fibre devices. The integration of all required functions into a single fibre device with a small, high-NA, inner cladding is a challenge that required a large research effort to solve. A thorough and careful design and characterisation effort led to the milestone achievement of an all-fibre pigtailed fibre laser at 980 nm, which later on was used in practice as a pump source for an 8-channel DFB fibre laser transmitter array. In addition, a 980 nm Q-switched fibre laser is realised in a cladding-pumped configuration for the first time.Furthermore, a fibre laser cladding-pumped by a high brightness intra-cavity beam-combined diode was demonstrated. Here, a multi-stripe, multi-mode diode was set-up for intra-cavity beam combination and used for cladding-pumping of fibre lasers with a small inner cladding. This high-brightness pumping scheme with a multi-emitter diode appears very attractive for power scaling of three-level fibre lasers.
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Lambelet, Myriam Liliane. "Cadmium and neodymium geochemical cycles in the marine environment." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/34397.
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The roles of trace elements and their isotopes in the marine environment are essential and diverse (e.g., nutrients, tracers of oceanic processes, anthropogenic pollutants), but are not well understood yet. In this thesis, two elements and their isotopes were investigated in two distinct marine environments: cadmium (Cd) in the Siberian shelf seas and neodymium (Nd) in the western North Atlantic Ocean. Whereas the role of Cd as nutrient in the open ocean is reflected by Cd isotope data, its behaviour in estuaries is poorly constrained. Chapter 2 of this thesis presents new Cd isotopes and concentrations of 19 water samples from the mixing zone of Siberian rivers with the Arctic Ocean. The results provide the first constraints on the isotope composition of natural riverine Cd fluxes to the ocean and the cycling of Cd in a shelf environment. Chapter 3 describes the method developed to isolate and analyse seawater Nd isotopes and concentrations in the MAGIC laboratories. The Nd isotopic composition of seawater is a promising tracer for ocean circulation and exchange between the continental margins and the oceans. By analysing 12 seawater depth profiles from the Dutch GEOTRACES transect GA02 (Chapters 4 and 5), we demonstrate that Nd features different behaviour in regions close to the formation area of deep water masses compared to export areas, where it behaves conservatively away from continental margins. Besides, we show that upper- North Atlantic Deep Water (NADW) and lower-NADW have distinct Nd isotopic compositions, and that the signature of lower-NADW is significantly more radiogenic than the commonly accepted value, which should be taken into account for future applications. Overall, the present thesis underlines the important role that isotope analyses can play in deciphering marine biogeochemical cycles of trace elements.
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Sterling, Elizabeth. "Precipitation and recrystallization in a binary magnesium-neodymium alloy." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54396.
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The influence of precipitate state and annealing temperature on the recrystallization of a Mg-2.8wt.%Nd alloy has been investigated. Precipitation kinetics at 190°C, 350°C and 400°C were studied in order to understand precipitate evolution during recrystallization. Precipitation was studied primarily through electrical resistivity measurements, and modelled using a mean radius model. It was found that predicting the kinetics required the spatial distribution of solute to be considered. Pre-aging conditions were selected in order to study the influence of either pre-existing or concurrently formed precipitates during recrystallization. After aging, the samples were cold rolled to a strain of 20%. The microstructures were characterized primarily through EBSD, and also through hardness measurements. Pre-aging the samples at 400°C for three hours resulted in a dispersion of stable β precipitates during annealing. This led to a recrystallized microstructure with recrystallization nucleation sites similar to those previously reported in the literature. Pre-aging the sample at 190°C for 24 hours lead to the formation of metastable β'' precipitates which strengthened the sample, but dissolved rapidly upon annealing at higher recrystallization temperatures. When samples previously solutionized at 545°C or aged at 190°C were subsequently annealed at 350°C, recrystallization stagnated. This was attributed to concurrent precipitation pinning grain boundaries. In all samples, irrespective of aging condition, recrystallization was observed primarily in twins and shear bands. The twins which recrystallized were found to be {10-11} contraction twins and {10-11}{10-12} contraction-extension twins. As the nuclei forming within these regions were not randomly oriented, recrystallization in these alloys did not randomize the texture. The work presented in this thesis increases understanding of recrystallization in Mg-Nd alloys. In particular, the means by which Nd interacts with and affects the recrystallizing microstructure have never been studied in detail. Furthermore, this work points to possible ways in which new magnesium alloys and thermomechanical processes could be designed to improve final material properties.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Zhang, Yiying. "Peak Neodymium : Material Constraints for Future Wind Power Development." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-211692.
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Developing renewable alternatives for energy production is one of the main methods for climate change mitigation and sustainable development. As the key component in permanent magnets, neodymium is considered as one of the most critical elements in the rare earth family in the development of modern society. It plays a significant role in increasing efficiency and reducing weight in many applications like hard disc drives, audio equipment, direct- driven gearless and conventional wind turbine design, as well as electric vehicles designs with NiMH batteries. The emerging problem of neodymium production is the peak neodymium issue, which implies a potential risk of supply in the future due to the unsustainable production pathway. Now, China is producing more than 90% of the rare earth elements with an around 40% reserves and is facing severe problems of environmental pollution, smuggling, and increasing domestic demand. This paper makes efforts to see if the risk of supply would constrain future wind power development with a special focus on the China’s dominance in production and policies. By fitting historic production data with three curve models (logistic, Gompertz, and Richards) and designing future demand based on IEA’s scenarios, the projections of future supply and demand trends of neodymium was obtained. This paper shows that though neodymium-based wind turbine construction might not be the cause for neodymium shortage, it would be confronted with material constraints in the future. Thus, more consideration should be taken in the investment of wind turbines with permanent magnet. Also, a mineral strategy, which integrates technological innovation, joint effort from different stakeholders, and better resource management, is required for a sustainable production of neodymium in the long run.
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Han, T. P. J. "Solid state spectroscopy: laser selective excitation studies of neodymium." Thesis, University of Canterbury. Physics, 1988. http://hdl.handle.net/10092/7972.
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When trivalent rare earth (RE³⁺) ions are introduced into the alkaline earth fluoride, they substitute for the divalent cation and some form of charge compensation is required for the crystal to maintain charge neutrality. A wide variety of symmetry configurations can be produced depending on the charge compensator(s) and the rare earth ion(s) in the lattice. The selective laser excitation technique was used to determine the symmetry of the various dopant centres in CaF₂ and Sr F₂ doped with Nd³⁺ ions; both before and after hydrogenation treatment.
Previously unassigned energy levels of F¯ charge compensating centres of tetragonal and orthorhombic symmetry in CaF₂ : Nd³⁺ and SrF₂ : Nd³⁺ have been identified by the energy upconversion processes. The upconversion mechanisms for the tetragonal centre are attributed to be dominated by the sequential two photon excitation process (STEP), whereas the two orthorhombic centres are attributed to be dominated by the phonon-assisted energy transfer upconversion process (ETU).
The hydrogenic analogues of the well established tetragonal centre in CaF₂ : Nd³⁺ and SrF₂ : N d³⁺, and other hydrogenic charge compensating centres were studied. The fluorescence of some of the multiple charge compensating hydrogenic centres were found to exhibit 'bleaching' behaviours. These effects are attributed to the migration of the hydrogenic ions adjacent to the rare earth ion.
For the tetragonal centres, the C₄v irreducible representation designations of the crystal field levels were identified by their intensity variations in the polarisation studies.
Energy transfer between the rare earth ions within a cluster centre was established by studying the M' centres in the CaF₂ : Nd³⁺ co-doped with Ce³⁺, Gd³⁺ or Yb³⁺ rare earth ions. These multiple rare earth ion centres also exhibit energy upconversion processes similar to those observed for the orthorhombic centres in CaF₂ : Nd³⁺.
Crystal field analyses have been carried out for the tetragonal centres observed in CaF₂ : Nd³⁺ and SrF₂ : Nd³⁺ and a simplified superposition model was used to analyse the distortions in these centres. The crystal field results are in satisfactory agreement with the experimental data and predicted the experimentally unobserved Z₄ energy level for the various C₄v centres.
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Jubb, Gary Anthony. "Production and properties of neodymium-iron-boron permanent magnets." Thesis, University of Bradford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236470.
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Rickli, Jörg Dominik. "The hafnium and neodymium isotopic composition of seawater and rivers /." Zürich : ETH, 2009. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18089.
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Bertram, Caroline Jane. "Rare earth elements and neodymium isotopes in the Indian Ocean." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277641.
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Reynolds, Ben Christopher. "Neodymium and lead isotope time series from Atlantic ferromanganese crusts." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342540.
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Wang, Zhiran. "The demagnetising factors for bonded neodymium iron boron (NdFeB) magnets." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340145.
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Ranta, Päivi. "Retinal detachment after neodymium : yttrium-aluminum-garnet laser posterior capsulotomy." Helsinki : University of Helsinki, 2002. http://ethesis.helsinki.fi/julkaisut/laa/kliin/vk/ranta2/.
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Ward, Barry. "Generation of acoustic waves by focused infrared neodymium-laser radiation." Thesis, Loughborough University, 1991. https://dspace.lboro.ac.uk/2134/10626.
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When the radiat Ion from a sufficient Iy powerful pulsed laser Is focused into transparent gaseous, liquid or solid media, dielectric breakdown may occur around the beam waist giving rise to a shortI ived high-temperature plasma which quickly heats the surrounding material. As a consequence of various energy-coupling mechanisms, this phenomenon causes the emission of one or more high-frequency ultrasonic acoustic waves whose speeds of propagation are dependent upon the physical propert les of the host medium. In the high-speed photographic studies described In this doctoral thesis, the 1.06-l'm near-Infrared radlat Ion from an 8-ns, lO-mJ Q-swl tched Nd:YAG laser Is focused In or onto a variety of fluid and solid materials. The rapid variations In density around the resulting plasma events are visualised using a Mach-Zehnder Interferometer with a sub-nanosecond dye-laser light source and a vldeo-Imaglng system. Calculat Ions of the corresponding transient pressure distributions are then enacted from the digitally-recorded Interferograms using a semi-automat Ic procedure under the control of a personal computer. Measurements of position. displacement and velocity are also carried out using the same opt ical apparatus In schlleren and focused shadowgraph highspeed photographic arrangements. The experimental work outlined In the following chapters is divided Into three broad fields of Interest. In the first of these, a study of the laser-generation of spherical shock waves· in atmospheric air is carried out. In the second, the neOdymium-laser beam Is focused onto different solid-fluid Interfaces resulting In the formation of bulk longitudinal and shear waves and surface acoustic waves. The Interactions of these waves with various obstacles and defects are Investigated with reference to their application to non-destructive test Ing. In the third and most important field, a detailed study of the dynamics of laser-Induced cavitation bubbles In water Is carried out. With regard to the associated phenomenon of cavitation erosion, particular attention Is paid to the formation of spherical acoustic waves by radlally-oscillatlng vapour cavities at various distances from transparent rigid boundaries.
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Yelland, Carl. "Diode-pumped IμM neodymium lasers and their internal frequency doubling." Thesis, University of St Andrews, 1997. http://hdl.handle.net/10023/14788.
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In this thesis the design, construction and performance of several diode-laser pumped continuous-wave neodymium lasers are described. These lasers were operated both around 1 mum and, by internal frequency-doubling, at 0.5 mum. The main emphasis has been on the assessment of the various laser designs with regard to their potential for efficient, high-power visible operation. A variety of pumping geometries, resonator configurations, gain media and internal frequency-doubling schemes were investigated, and their relative merits explored. Both side-pumping and end-pumping arrangements were employed, with Nd:YAG, Nd:YLF and Nd:YVO4 being used as gain media. Travelling-wave and standing-wave resonator designs were used. The polarisation-rotation effect in non- planar ring resonators was investigated and used to obtain single-frequency output. Single-frequency 0.5 mum powers up to 1.2 W were generated, and the highest 0.5 mum output power achieved was 4 W on two-longitudinal modes spaced by 450 MHz. The highest 1 mum output power achieved was 10 W, with a slope efficiency of 43%. Maximum pump powers for the lasers were in the region 15 - 35 W. A review of diode-laser pumped devices is included, with particular emphasis on the role of the spatial distributions of the pump and signal fields, because this is an important limiting factor in the performance of diode-pumped bulk laser systems. The criteria governing the harmonic output power when internally frequency-doubling are discussed. Issues relating to noise in the harmonic output, and techniques for its avoidance, are also discussed.
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Howe, Jacob Nathan William. "Investigating Atlantic meridional overturning circulation in the Quarternary using neodymium isotopes." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709394.
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Harwood, Duncan William John. "Towards a 1.39 µm planar neodymium doped fluoride glass waveguide amplifier." Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/15495/.
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This thesis describes the steps towards the fabrication of a planar neodymium doped fluoride glass waveguide amplifier operating in the 1.3µm band. Approximations of the amplifier performance, combined with more detailed models of an integrated neodymium doped fluoroaluminate glass amplifier based on spectroscopic measurements from the bulk glass (Nd:ALF70), show that channel waveguides with propagation losses below 0.5dB/cm at the pump wavelength are needed to produce a device with a pump requirement of 200mW or less. In the absence of any fabrication technique available for fluoride glasses with this level of performance, the novel process of hot dip spin coating was developed for the fabrication of single mode Nd:ALF70 planar waveguides. The process is based on the inverted spin coating of molten glass onto a solid glass substrate and currently holds the record for the minimum propagation losses of less than 0.1dB/cm @ 1048nm in a fluoride glass waveguide measured in a 5 micron thick film. In order to capitalise on such exceptional waveguide performance, a new method for fabricating channel waveguides in fluoride glass thin films was developed based on direct UV writing of a negative index change using photothermal expansion. The process is based on generating a negative index change, via exposure to laser radiation at a wavelength of 244nm. The negative index change forms the lower refractive index 'cladding' on either side of the desired guiding region and is induced by a thermal mechanism generated by the large absorption of UV radiation by cerium ions doped into the slab guiding region. A maximum index range of close to 0.01 was produced for a 40µm thick unclad waveguide doped with 0.5mol% Ce3+ and an index change of approximately 2x10-3 was estimated for a 2.5mol% Ce3+ doped, 6 micron thick buried waveguide. Propagation losses of 0.1±0.1dB/cm @ 1048nm were determined by the Findlay-Clay technique for a 90µm wide multimode channel waveguide laser whilst an average value of 0.3±0.1dB/cm @ 1048nm was obtained for less multimode guides with an average width of 20µm. The best device performance has been characterised in a 1mol% Nd3+ doped 90µm wide and 6µm thick waveguide. Laser action at 1048nm has been observed with a slope efficiency of 27% for a 56% output coupler and a threshold pump Power of just 4mW. The threshold for laser action at 1317nm was 32mW for a 0.3% output coupler giving a slope efficiency of 2%. A peak internal gain of 1dB at 1317nm was achieved in this waveguide for a pump power of 100mW and suggests that the performance of optimised single mode guides should be close to that predicted by theory.
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THACHERY, JUGUL RAVINDRAN. "SYNTHESIS AND CHARACTERIZATION OF NEODYMIUM SULFIDE BULK SAMPLES AND THIN FILMS." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1012424793.
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White, Andrew Lee. "Wavelength selection and wide-temperature-range operation of neodymium-doped lasers." Thesis, Heriot-Watt University, 2014. http://hdl.handle.net/10399/2743.
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This thesis presents research results in two general areas of the solid-state laser technology commonly used in defence applications. The first area uses volume Bragg gratings (VBGs) as cavity mirrors, giving wavelength selection, linewidth reduction and improved frequency doubling efficiency. The second area is in extending the operating temperature range of diode-pumped Nd-doped pulsed lasers through the use of VBGs, external-cavity absorber-locked diode lasers and enhancements of pump chamber efficiency. For a laser-diode end-pumped Nd:YVO4 solid-state laser, a VBG laser cavity, with output powers of up to 6.2W is demonstrated at 1064 nm. With a conversion efficiency of 0.4 and M2 of 1.2, the laser linewidth is reduced by a factor of 16, to 72 pm, compared to a conventional dielectric mirror cavity. Intra-cavity losses due to the VBG are shown to be 2%. The 1064nm VBG cavity is then Q-switched using an AO modulator to generate peak powers of 2.3 kW. The second harmonic generation in a MgO:PPSLT crystal produced a 20% increase in second harmonic power, compared to a cavity with a conventional dielectric mirror. The improvement is attributable to the reduced linewidth. A similar configuration, but using a VBG with 98% reflectivity at 1342 nm, generates up to 3.8W of output power. The use of two VBG mirrors in a single cavity, further narrows the linewidth, allowing for output powers up to 2.3 W, in a single longitudinal mode. In-cavity heating of the VBG is found to give a reduction in reflectivity, a shift in the centre wavelength and increased linewidth. This is both modelled and experimentally demonstrated. For enhanced pumping of high-energy Q-switched Nd:YAG zigzag-slab lasers, two techniques of externally locking the wavelength of the QCW laser diodes are demonstrated. A chirped 808nm VBG locks the wavelength of a newly developed chirped quantum-well laser-diode array, without the need for fast-axis collimation. Locking over a temperature range of 50 C is demonstrated, with a predicted locking range of 70 C. As an alternative to VBG locking, a laser diode bar locked at 885nm is also demonstrated by using a thin Nd:YVO4 absorber. Filtered feedback locks the spectrum into peaks, which are in the Nd:YAG absorption bands over a 45 C range. In a parallel effort, a pump laser array configuration that increases the overall absorption path length from 1 to 3 cm in a side-pumped zigzag slab is demonstrated. By optimising the bounce lengths of the pump light and the inclusion of multi-wavelength laser bars, operation up to 80 C is demonstrated with an absorption efficiency of 80%. By adjusting the diode drive pulse duration, a Q-switched laser using this pump head operates from -40 to +60 C with a constant energy of 60 mJ. The operational temperature range of this configuration is shown to be over 120 C.
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Frei, Bruno. "Diode laser-pumped neodymium lasers in pulsed and continuous wave operation /." [S.l : s.n.], 1993. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Verlinden, Nicholas H. P. "The excited state absorption cross section of neodymium-doped silica glass fiber in the 1200-1500 nm wavelength range." Worcester, Mass. : Worcester Polytechnic Institute, 2008. http://www.wpi.edu/Pubs/ETD/Available/etd-072508-145557/.
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Armstrong, Christopher Robert. "Synthesis, spectroscopic, and thermodynamic study of uranyl and neodymium phosphate solid phases." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Fall2009/c_armstrong_102809.pdf.
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Klešč, Tania. "Neodimio magnetų eksperimentinis tyrimas." Bachelor's thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130821_115730-10514.
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Bakalauro darbą „ Neodimio magnetų eksperimentinis tyrimas“ sudaro įvadas, keturi skyriai, išvados, priedai ir literatūros sąrašas. Šio darbo apimtis 30 puslapių. Darbe yra 26 paveikslėliai ir 1 lentelė.Įvade iškeliama darbo problema, tikslai ir uždaviniai. Pirmajame skyriuje pateikta literatūros analizė. Antrajame skyriuje aprašoma eksperimento metodika. Trečiajame skyriuje pateikti sistemų su neodimio magnetais tyrimo rezultatai. Ketvirtajame skyriuje pateikta eksperimento rezultatų analizė. Darbo pabaigoje pateiktos išvados apibendrinančios atliktą darbą ir pateikti pasiūlymai, kur būtų galima panaudoti neodimio magnetus.The final bachelor‘s work “Experimental analysis of neodymium magnets” consist of introduction, four chapters, conclusions and references. The work consists of 30 pages. There are 26 images and 1 table.Problem of the research along with objectives and goals are provided in the introduction of this work. The first chapter provides analysis of literature. The second chapter is about methodology of experiment. The third chapter provides the results of systems of neodymium magnets. The fourth chapter provides analysis of the experiment results. At the end of the work there are conclusions and suggestions about neodymium magnets usage.
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VIEIRA, RENATO J. R. "Laser a base de pó de neodímio com granulação nanometrica." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10014.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Wisdom, Jeffrey Alan. "Design, characterization and fabrication of neodymium doping profiles in transparent YAG ceramics /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Bronski, Mark T. "Development of a process for characterization of Nd:YAG crystals." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0409103-104942.
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Tarverdi, Karnik. "Preparation and testing of lanthanum and neodymium with 8-hydroxyquinoline as potential biocide." Thesis, Brunel University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332067.
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Attanasio, Steven A. 1967. "Corrosion and environmentally-assisted cracking of rapidly solidified neodymium-iron-boron permanent magnets." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/39748.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996.Vita.
Includes bibliographical references (p. 383-388).
by Steven A. Attanasio.
Ph.D.
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Copp, Rebecca. "Recovery of Yttrium and Neodymium from Copper Pregnant Leach Solutions by Solvent Extraction." Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/595982.
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The solvent extraction of yttrium and neodymium from copper pregnant leach solutions (PLS) using Primene JM-T, a primary aliphatic amine, has been studied. Effect of contact time, pH, sulfate concentration, and extractant concentration were investigated using synthetic and actual PLS systems. Standard experimental conditions were 5 minute contact time, pH ~2.5, 10% v/v Primene JM-T concentration, and 1:1 O:A phase ratio. Distribution isotherms were constructed for the pure systems and for actual copper leach solutions. Synthetic solutions contained 100 ppm Y and ~75 ppm Nd. Copper PLS contained 2.1 ppm Nd and 14.9 ppm Y. Results showed that complete extraction of both yttrium and neodymium occurred within five minutes and at pH values greater than 1. It was also found that sulfate concentration does not inhibit extraction at any concentration. Additionally, the distribution isotherms created show that extraction for these metals can operationally take place in one stage from both synthetic solutions and copper leach solutions.
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Wright, Jennifer B. Hirsch David M. "Development of a new method for measuring metamorphic kinetics /." Online version, 2010. http://content.wwu.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=368&CISOBOX=1&REC=17.
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Dopieralska, Jolanta. "Neodymium isotopic composition of conodonts as a palaeoceanographic proxy in the Variscan oceanic system." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968646263.
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Thériault, Réginald J. "Evolution of the ca. 1.9 gallium Taltson magmatic zone, Northwest Territories: A neodymium isotope perspective." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5788.
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The Taltson magmatic zone is a north-trending belt of Early Proterozoic granitoids exposed over an area exceeding 18,000 km$\sp2$ in the Northwest Territories. Three petrologically and chronologically distinct intrusive suites comprise the Taltson zone. These are the 1986 Ma Deskenatlata suite, the 1955 to 1925 Ma Slave suite and the 1935 Ma Konth suite. The Deskenatlata suite is composed of a biotite-hornblende diorite to granite suite whose major and trace element chemistry supports derivation by arc magmatism. The Slave and Konth suites are leucocratic granitoids which contain numerous xenoliths of dominantly pelitic high grade paragneiss and display S-type granite mineralogy which commonly duplicates that of the pelitic gneisses. Bulk rock chemistry for the Konth suite is consistent with a homogeneous crustal magma source whereas the Slave suite is compositionally more heterogeneous. The Deskenatlata suite is considered as continental arc-derived granitoids resulting from eastward subduction of oceanic lithosphere beneath the Churchill Province. The Slave suite is regarded as the result of melting of various segments of heterogeneous Archean crust whereas the Konth may have evolved exclusively from melting of pelitic metasediments. (Abstract shortened by UMI.)
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Swift, C. I. "A study of the effects of bends on the operation of neodymium doped fibre lasers." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360325.
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Stewart, Joseph A. "Variation in silicate weathering across the Oligocene-Miocene boundary : evidence from lithium and neodymium isotopes." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/351811/.
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DAMENTO, MICHAEL ANTHONY. "DETECTION OF MAGNETIZATION REVERSAL IN A NEODYMIUM-IRON-BORON MAGNET USING A HALL-EFFECT MICROPROBE." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183945.
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Magnetization processes in a sintered Nd-Fe-B permanent magnet (NEOMAX-35) were examined on a small scale using a Hall-effect microprobe with an active area 75 μm on a side. Probes were made by evaporating bismuth through a stencil mask onto glass slides. Experiments were performed by placing a probe onto the polished pole face of a Nd-Fe-B magnet and inserting the probe-magnet assembly into an electromagnet. Barkhausen steps, indicating rapid domain wall motion, were observed (superimposed upon the blank probe signal) in the demagnetization of a fully magnetized magnet. Magnetization traces for a thermally demagnetized Nd-Fe-B magnet did not exhibit measurable Barkhausen steps until a field of approximately 1.2 T was applied. The following observations were made for two thermally demagnetized samples which were cycled through minor hysteresis loops (maximum applied field of approximately 2 T): (1) virgin magnetization traces did not contain measurable Barkhausen steps, however all other forward and reverse magnetization traces did; (2) the initial reverse magnetization trace exhibited more and larger Barkhausen steps than subsequent traces; and (3) some Barkhausen steps were repeatable, that is, occurring at approximately the same field on each subsequent forward or reverse trace. Hall voltage signals were on the order of millivolts for probe currents of 10 mA.
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CAVALCANTI, FABIO. "Desenvolvimento de um laser pulsado com emissão em 1053 nm para utilização na técnica de "Cavity Ring-Down Spectroscopy." reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11790.
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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Brodie, Lyn. "Welding of skin using Nd:YAG laser with bipolar contact applicators." University of Southern Queensland, Faculty of Engineering and Surveying, 2003. http://eprints.usq.edu.au/archive/00001412/.
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[Abstract]: This thesis investigates the feasibility of closing wounds in skin tissue by laser welding as a substitute for suturing. Such a process would provide advantages in some surgical procedures. The investigation revised available theory on the action of lasers on skin tissue as a basis for the experimental program. The results of experiments using rat skin are then reported. In addition a thorough investigation of the normal (uninjured) tensile strength of rat skin was undertaken to provide a base line comparison. Laser systems permit very high-energy radiation of a single wavelength to be focused on a tiny spot, and have found application in many areas of engineering. They are also currently used in many branches of medicine including ophthalmology, gynaecology, dermatology, otolaryngology, and gastroenterology. These medical applications employ argon, YAG, and carbon dioxide type lasers. In many cases, lasers have been found to be more effective than conventional treatment methods with advantages including reduced blood loss, more accurate removal of unwanted tissue, shorter operating times and less postoperative pain and care (Gibson and Kernohan, 1993). Tissue welding using laser energy represents a small but growing area of medical research and is largely focused on anastomosis. This thesis investigates, using a specific experimental program, the feasibility of the bipolar contact Nd:YAG laser to weld cutaneous tissue. No similar published research has been identified in this area. The available literature focuses on non-contact lasers of various types and settings and mainly in the area of anastomosis. The experimental methodology and the specific technique for the bipolar contact laser is developed, tested and evaluated as part of this project. The welding techniques developed in this project overcome the previous difficulties of tissue alignment. The use of the bipolar laser probes substantially improves the ability to align the tissue edges to be joined. The probes give tactile feedback to the user and the pressure effect of the probes may assist with the welding process. The developed technique was no faster or easier than suturing. Viable welds and a useable technique for welding skin on rats were developed and tested. The resultant healing was comparable with published literature and both sutured and welded wounds returned to full strength as compared with the baseline data collected. All wounds had returned to full strength within 91 days. At 75 days there was not significant difference between laser welded and sutured wounds and they had achieved approximately 90 percent of full strength. Time to half strength was approximately 42 days and there was a larger standard deviation for both laser welded and sutured wounds. The most significant increase in strength and therefore healing occurred in the first 42 days. Simhon et al, 2001 states that a tensile strength of 0.6 N plus/minus 0.4 N was sufficient to hold tissue together. By day 7 the strength of the wound (laser welded) was more than twice the strength needed to maintain closure. There may have been sufficient healing for this to occur earlier but there were insufficient animals to allow for testing of this theory. In conclusion this experimental program and investigation has reviewed the available literature on the current use of lasers in medicine and their specific laser-tissue interaction which leads to tissue welding. It has provided a large database of tensile strength measurements collected with a reproducible methodology and reported in a standardised format. The developed technique for laser tissue welding using a bipolar contact Nd:YAG laser has been established and verified. It produces viable welds comparable in strength and healing rates to sutures.
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Wang, Huabin 1969. "The magnetic properties, crystal and magnetic structures of Nd5SixGe4-x /." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101661.
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The magnetic properties, crystal and magnetic structures of Nd5 SixGe4-x were investigated by ac susceptibility and high resolution neutron powder diffraction. The magnetic and crystalline phase diagrams were derived. Four distinct structures exist in the Nd 5SixGe4-x system: Gd5Ge 4-type [O(II)], Gd5Si2Ge2-type (M), Gd5Si4-type [O(I)], and Zr5Si4-type (T). The refinements of the neutron powder diffraction patterns revealed that the Nd5SixGe4-x compounds exhibit mixed ferro-antiferromagnetic structures. The ac susceptibility measurements showed that the magnetic ordering temperature of Nd5SixGe 4-x increases slightly with increasing silicon content, except that it increases by a factor of 2 in the orthorhombic Gd5Si 4-type [O(I)] phase region. The abrupt change of the magnetic ordering temperature between x = 2.25 and x = 2.5, where the monoclinic Gd5Si 2Ge2-type (M) structure changes to the orthorhombic Gd 5Si4-type [O(I)] structure, suggested that a first order magnetostructural transition likely takes place in this narrow composition range (2.25 < x < 2.5). The investigation of Nd5Si2.335 Ge1.665 revealed that Nd5Si2.335Ge 1.665 adopts the Gd5Si2Ge2-type (M) structure and undergoes a first order magnetostructural transition from the paramagnetic-monoclinic Gd5Si2Ge2-type (M) structure to the orthorhombic Gd5Si4-type [O(I)] structure upon cooling. The T1-T1 bonds increases by ∼1 A when the the Gd 5Si4-type [O(I)] structure (10 K) transforms to the Gd 5Si2Ge2-type (M) structure (140 K). The giant magnetocaloric effect is not observed in Nd5Si2.335Ge 1.665 probably due to the co-existence of the M phase and the O(I) phase. The maximum magnetic entropy change in Nd5Si2.335Ge 1.665 is 7.3 J/kg K for magnetic field change from 0 to 7 Tesla, which is similar to that obtained in Nd5Si1.5Ge2.5, the neighboring phase O(I).
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Jumali, Mohammad Hafizuddin Haji. "Nd and Gd (α/β)-SiAlON ceramics." Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343129.
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Xia, Chun, and Chun Xia. "Concentration Quenching Effect in Rare-earth Doped Glasses." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/624145.
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Concentration quenching effect in ytterbium (Yb) and neodymium (Nd) doped phosphate glasses, thulium (Tm) doped germanate glass, and praseodymium (Pr) doped tellurite glass were studied. The fluorescence and lifetime of these rare-earth doped glasses with different concentrations were measured. Ion pair and clustering are included in the model to explain the quenching effect occurring in highly doped glasses. This study will help us in designing and fabricating high unit gain optical fibers.
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Scher, Howard D. "Paleogene deep water circulation in the Atlantic sector of the Southern Ocean revealed from neodymium isotopes." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0009461.
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Barovich, Karin Marie. "Behavior of lutetium-hafnium, samarium-neodymium and rubidium-strontium isotopic systems during processes affecting continental crust." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185602.
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Combined Lu-Hf, Sm-Nd and Rb-Sr isotopic studies of continental crustal rocks were undertaken to assess the relative effects of secondary crustal processes on isotopic systematics of whole-rock systems. The processes studied include ductile deformation, and three cases of hydrothermal alteration, involving fluids of varying composition. The Rb-Sr system proved to be easily disturbed during all secondary processes, while Sm-Nd and Lu-Hf systems were, for the most part, resilient. These results show that Nd or Hf isotopic information obtained from old rocks that have undergone typical crustal deformational and alteration events can be counted on to be equally reliable. Nd and Hf isotopic analyses were performed on four suites of Early Archean felsic gneiss complexes from Greenland, Labrador, Swaziland, and Michigan to explore questions associated with Early Archean crustal growth. The Sm-Nd isotopic data yield initial ∊(Nd) values that are mostly consistent with published age data for the suites. Calculations show limited scatter may be attributed to subtle changes in the Sm/Nd ratio or Nd isotopic composition. The Hf isotopic results are more variable and complex than the Nd results. The relevance of the studies on isotopic mobility in the first part of this work is that they have demonstrated that Nd and Hf isotopes are equally resilient during a range of secondary crustal processes. Given the robustness of the Nd isotopic data from the Archean samples, however, it seems unreasonable to attribute the much wider variation in Hf isotopic data to post-Archean isotopic disturbances. Differences in initial Hf isotopic ratios from differing magma sources seem called for. Nd and Hf whole-rock analyses of a Late Archean pristine garnet-bearing granitoid complex from northern Canada point out the importance of garnet in fractionating Lu/Hf ratios, and in developing anomalous ∊(Hf) signatures in potential source regions. Calculations show that even short-lived upper mantle/lower crustal heterogeneities, products of previous partial melting events involving garnet fractionation, can develop the range of positive and negative ∊(Hf) values seen in the Early Archean samples.
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PAES, JOAO P. F. "Estudo de lasers Raman para dobramento de frequência no azul." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/27975.
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Os lasers Raman permitem a exploração de novos comprimentos de onda, não comumente acessíveis, graças ao Espalhamento Raman Estimulado. Unidos a processos de conversão não linear, abrem-se campos para emissão de comprimentos de onda na região do visível no espectro eletromagnético. Com uma mesma configuração, diversas combinações de cristais possibilitam a geração de múltiplas frequências, transformando esse tipo de laser em um dispositivo compacto e barato quando comparado com outras tecnologias existentes. Este trabalho apresenta a busca da conversão intracavidade em frequências de lasers Raman, em uma configuração linear. Com dois comprimentos de onda de bombeamento de energia (797 nm e 872 nm), diodos semicondutores foram utilizados para acessar dois picos de absorção do cristal Nd:YLF. O bombeamento em 797 nm levou a emissão fundamental em 908 nm. E através do cristal KGW, com linhas de emissão Stokes, um novo comprimento de onda foi alcançado, em 990 nm. Com o cristal dobrador, BiBO, soma de frequência e segundo harmônico foram gerados, permitindo as emissões em uma região espectral azul bastante larga (450 500 nm). Com o bombeamento em 872 nm, uma emissão de três níveis no cristal Nd:YLF não foi possível, conseguindo apenas a emissão em 1064 nm, linha comum para cristais de neodímio. Uma outra cavidade foi estudada, porém com bombeamento em 880 nm e cristal de Nd:YVO4, conhecido por ser self-Raman. Com uma configuração linear semelhante à anteriormente citada, somente sua linha de emissão fundamental em 914 nm foi obtida, não sendo possível com as condições trabalhadas a emissão Stokes, que permitisse dar continuidade ao estudo.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP