To see the other types of publications on this topic, follow the link: RARE EARTH DOPED.
Dissertations / Theses on the topic 'RARE EARTH DOPED'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'RARE EARTH DOPED.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Lincoln, John Roderick. "Spectroscopy of rare earth doped glasses." Thesis, University of Southampton, 1992. https://eprints.soton.ac.uk/399194/.
Full textAbstract:
An extensive investigation of the spectroscopy of rare earth doped glasses is presented. Such investigations are particularly important since they provide an insight into the physical processes affecting rare earth doped fibre devices. It is a central aim of this work to demonstrate how such devices can be improved by systematic changes to the host glass. Resonant fluorescence studies of thulium doped aluminosilicate and germanosilicate glass systems show that there are systematic variations in the Tm3+ site within the glass structure, indicating the non-random nature of the rare earth site. Fluorescence lifetime measurements in these silicate systems show a significant shortening of thulium energy level lifetimes when preforms are pulled into fibres, independent of the mechanism of decay. Furthermore, it is shown that multiphonon decay and therefore the vibrational properties of the host have a pivotal role in determining device performance. Raman spectra of a range of glass hosts are measured and analysed by new methods to enable accurate comparisons of vibrational properties to be made. Examination of the thulium 2µm laser system indicates that glasses with maximum vibrational energies of ~920cm-1 would give improved device performance. Based on these calculations the world's first lead-germanate based optical fibre was fabricated and fully characterised. Predicted improvements in thulium performance over fluoride or silicate systems are realised. Studies of the erbium-ytterbium 1.5µm amplifier system through Raman and lifetime measurements show that erbium site is determined purely by the ratio of phosphorus to aluminium in a silicate glass composition. It is shown that the type of erbium site determines the degree of vibrational coupling of the erbium to the highest energy vibrational modes of the glass. This coupling is linked to the performance of Er-Yb 1.5µm fibre amplifiers. Non-exponential decay of rare earth fluorescence frequently occurs and it is shown that such decays can easily result from purely single ion multiphonon decay processes when the rare earth is in a glassy host. Furthermore, a single stretched exponential function is shown to fit all observed and modelled non-exponential decays. Use of this function enables comparisons of the degree of non-exponentiality and time evolution of such decays to be made.
2
Ardicoglu, Burcu. "Synthesis Of Rare-earth Doped Lithium Triborate." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12606354/index.pdf.
Full textAbstract:
Research in the field of non-linear optical (NLO) devices lead to an increasing interest in new borate compounds, capable of expanding the frequency range provided by common laser sources. Lithium triborate (LBO) is a newly developed ideal non-linear optical crystal used in laser weapon, welder, radar, tracker, surgery, communication, etc. Borates containing rare-earth elements are of great interest since they are found to be superior in non-linear optical applications. In this study, synthesis and identification of rare-earth doped lithium triborate was carried out.
Lithium triborate was produced from the solid-state reaction. LBO was then doped with some rare-earth elements (Gd, La, Y) in several different concentrations. Appropriate quantities of Li2CO3 and H3BO3, weighted separately, were mixed and
finely powdered. Then, the mixture was heated at 750 ºC for 14 hrs. The expected reaction is given below. Li2CO3 + 6H3BO3 -->
2LiB3O5 + CO2 + 9H2O Prepared LiB3O5 and Gd2O3, La2O3 and Y2O3 samples were weighed separately at different concentrations and ground together. The mixture was then heated at 750 º
C for 7 hrs. Characterization of the new products was done by X-Ray Diffraction (XRD) and Infrared (IR) analysis. Differential Thermal Analysis (DTA) was used for examination of the thermal properties of the compounds, morphology of new compounds was observed by Scanning Electron Microscopy (SEM). The compounds are then subjected to thermoluminescence (TL) studies. From the XRD studies, no change in the LBO phase related to the addition of rareearth elements was observed. However, peaks of those elements were also become apparent. IR analysis showed that there is no change related to B-O link with the addition of rare earth elements. DTA studies showed that the melting point of LBO decreases with the addition of rare earth elements. In the SEM images, two phases belonging to particles of rare earth elements and lithium triborate were observed clearly. With the TL analysis, it was considered that the samples show dose response but also it was realized that they are affected by fading.
3
Shalibeik, Hotan. "Rare-earth-doped fiber lasers and amplifiers." Göttingen Cuvillier, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016360105&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Full text
4
Karali, Turgay. "Luminescence studies of rare earth doped dosimeters." Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298733.
Full text
5
Chen, Zhi-jie. "Double-clad rare-earth doped fibre devices." Thesis, University of Southampton, 1997. https://eprints.soton.ac.uk/394562/.
Full textAbstract:
This thesis reports on the exploitation of the cladding pumping technique to scale the output power of rare-earth (Er3+, Er3+/Yb3+, Yb3+, and Nd3+) doped fibre amplifiers and lasers, and on the study of alternative pumping schemes and applications. In the first three chapters, the introduction of the cladding pumping scheme, its basic fibre geometries and fundamental analyses of double-clad fibres and their devices are presented. Chapter 4 describes an investigation of various Er3+-doped and Yb3+ co-doped fibre devices. An Er3+/Yb3+-doped SM fibre amplifier pumped in the 820 nm band can not only avoid the excited state absorption (ESA) peaks of Er3+ at 800 and 840 nm, but also have a higher ratio of ground state absorption to ESA than that of Er3+ fibres. This enables a high gain amplifier with a much shorter fibre length. An experimental study of cladding pumped Er3+/Yb3+ fibres in amplifier and laser forms shows the simplicity of power scaling and brightness conversion from high-power large-area multimode laser diodes into a single diffraction-limited fibre mode, and thus scales the output powers. Efficient operation of a three-level Er3+-doped double-clad fibre in both laser and amplifier forms is described. The fibre design of a low area ratio of the inner cladding to the core reduces the threshold to an acceptable level. The study of bending effects in large area ratio double-clad fibres indicates that a fibre having a concentric geometry can have nearly as high an efficiency as an eccentric core geometry if periodic bending is employed to promote mode scrambling. In contrast, double-clad fibres with eccentric cores and rectangular inner claddings were found to be relatively insensitive to bending. In order to obtain high-peak-power pulsed sources, various kinds of novel pulsed fibre lasers have been investigated. These include a cladding pumped Nd3+ Q-switched fibre laser, an enhanced Q-switched double-clad fibre laser, a Q-switched Er3+ fibre laser double-clad fibre with a large mode-area core, and a picosecond mode-locked Yb3+fibre laser. Cladding pumped amplification of short pulses can extract high energy stored in doped fibres, thus obtain pulses with high peak power and energy.
6
Bhutta, Tajamal. "Novel rare-earth-doped planar waveguide lasers." Thesis, University of Southampton, 2002. https://eprints.soton.ac.uk/15483/.
Full textAbstract:
The planar guided-wave geometry is compatible with a wide range of materials, waveguidearchitectures and fabrication techniques. This thesis reports a series of studies of rare-earth-doped planar waveguide lasers, exploiting and extending the diverse range of possibilities that can be applied to planar technology. The areas investigated include the characterisation of guided-wave lasers produced by novel fabrication techniques, the design and implementation of new channel and planar waveguide structures and the demonstration of compact diode-bar pumped planar waveguide lasers. Laser operation of buried planar waveguides fabricated by a novel solid-state ion-exchange technique based on direct bonding is reported. The fabrication process allows buried waveguide structures to be fabricated by a single-step process, and the resulting guides are shown to have optical losses of < 0.4 dB/cm. Direct UV writing is utilised to fabricate multiple channel sources on this buried platform, and absorbed pump power thresholds as low as 3 mW are demonstrated. These structures offer a new and versatile route to the large-scale production of low-loss components for glass integrated-optics. Lanthanum fluoride thin-films fabricated by molecular beam epitaxy are investigated. The first laser action from a dielectric waveguide fabricated by molecular beam epitaxy is demonstrated using Nd-doped LaF3 thin films grown on CaF2 substrates. Channel waveguide lasers are designed and fabricated on these thin films by two techniques; ion-beam etching and a novel technique that employs a photo-definable polymer. These structures have a maximum phonon-energy of 380 cm-1, which constitutes the lowest phonon energy dielectric to show laser waveguide emission to date, offering the potential for developing compact mid-infrared sources based on this technology. The use of planar waveguides for very compact high-power sources is considered. Proximity coupling - the direct coupling of the diode-bar pump radiation is demonstrated for the first time and is used to realise a very compact and rugged laser system. Double-clad planar waveguide structures are utilised for spatial mode-control in the guided axis of the waveguide. To be compatible with planar fabrication techniques, and also due to the desire to retain a compact system, a double-clad design with large multimode core region is used. The theory of fundamental mode selection through confined doping for such structures is developed. This theory is applied to design the first double-clad planar waveguide and diffraction-limited performance in the guided axis is demonstrated from an Yb3+doped device.
7
Gajum, Naima Ramadan. "Rare-earth doped (α'/β')-Sialon ceramics." Thesis, University of Warwick, 2001. http://wrap.warwick.ac.uk/3072/.
Full textAbstract:
The objectives of this research were to investigate the possibility of controlling the '/' phase ratio and morphology in Sialon ceramics. These objectives have been sought by the control of the starting composition, and by post sintering heat treatment. The main emphasis has been on the production of a series of ' and (+') Sialon ceramics with a minimum amount of the glass phase by the pressureless sintering technique and using ytterbium (Yb) as an ' stabilising element. The Yb additions were made via the oxide or the alumino-silicate presynthesised glass; the latter was found to improve the density. The XRD analysis of the as sintered materials revealed ' to be the dominant phase with minor contributions from ' sialon and/or or 12H AIN polytype. Additions of SiO2 or -Si3N4 were made to various materials to assess potential mechanisms for obtaining control over the microstructural development of '/' sialon materials. The addition of silica (SiO2) to sialon with high ' content in Yb system significantly improves the densification and increased the amount of ' phase. The incorporation of -Si3N4 as a seeding agent had a very small effect on the '/' phase ratio and the phase morphology. Further experiments were aimed at optimizing sinterability and sialon microstructure through the introduction of two ' stabilizing cations. Compositions were prepared that contained a combination of light and heavy rare-earth (Yb-Nd and Gd-Nd), and then pressureless sintered and compared with the single cation materials. Materials in the as sintered state were composed of a high ' sialon content with a minor amount of ' sialon and 12H AIN polytype indicating that the heavy rare-earth (which is the principal ' stabilizer) has a dominant effect although EDAX analysis confirmed the presence of both cations (light and heavy) within the ' structure. The research also compared, and developed an understanding of, the thermal stability of '-sialon using single Yb or mixed cations. The Yb single cation '/' materials exhibited excellent stability over a range of temperature (1200 - 1600°C) and for different periods of time up to 168 hrs. The heat treatments result in the crystallisation of the residual phase as a Yb garnet phase which formed at ˜1300°C. The mixed cation '/' materials showed some '-' transformation. The transformation was accompanied by dissolution of RA1O3 (normally crystallized with R=Nd,Gd) and crystallization of melilite.
8
Binder, Michael. "Magnetization dynamics of rare earth doped magnetic films." Berlin Logos-Verl, 2006. http://deposit.d-nb.de/cgi-bin/dokserv?id=2917185&prov=M&dok_var=1&dok_ext=htm.
Full text
9
Binder, Michael. "Magnetization dynamics of rare-earth doped magnetic films /." Berlin : Logos-Verl, 2007. http://deposit.d-nb.de/cgi-bin/dokserv?id=2917185&prov=M&dok_var=1&dok_ext=htm.
Full text
10
Harrison, Michael Thomas. "Laser spectroscopy of rare earth doped inorganic glasses." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308599.
Full text
11
Bonar, James R. "Waveguide lasers in rare earth doped planar silica." Thesis, University of Glasgow, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297036.
Full text
12
Zhen, Y. S. "Oxygen ion conduction in doped rare earth oxides." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383333.
Full text
13
Karimi, Sarah. "Structure-property relations in rare earth doped BiFeO3." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/12876/.
Full textAbstract:
RE-doped BiFe03 (RE = La, Nd, Srn, Gd) compositions have been produced and investigated with a view to establishing a broad overview of their crystal chemistry and domain structure. For less than 10% RE dopant, the perovskite phase in all compositions could be indexed according to the rhombohedral, R3c cell of BiFe03. For La, Nd and Srn doped compositions with more than 15% dopant, a new antipolar phase was stabilised similar in structure to PbZr03 Pbam symmetry with a -V2ao2-V2ac,4ac unit cell where a, is the psuedocubic unit cell. The orthoferrite, Pnma structure was present in all RE-doped BiFe03 compounds with higher dopant concentration. The compositional window over which the PbZrO3-like phase was stable increased with increasing end-member tolerance factor, t (effectively controlled by the RE ionic radius). On heating, the PbZrO3-like phase transformed to the orthoferrite, Pnma structure. Tc for all compositions decreased with decreasing A-site, average ionic polarizabilty and end member tolerance factor. For compositions with R3c symmetry, superstructure and orientational and translational (anti-phase) domains were observed in a manner typical of an anti-phase tilted, ferroelectric perovskite. For the new PbZrO3-like phase orientational domains were observed along with antiphase boundaries associated with quadrupling of the unit cell due to the antipolar displacements of the Bi/RE-ions Neutron powder diffraction was used to determine changes in the nuclear and magnetic structures across the phase transitions that relate the high-temperature non- polar (Pnma) to the low temperature polar (R3c) and anti-polar (Pbam) structures, respectively. The high-temperature Pnma phase has a -√2ac, --√2ac,2ac cell with an aa c + octahedral tilting. The low-temperature polar R3c structure is similar to the B-phase of pure BiFe03 and is rhombohedral with aaa octahedral rotations and cation displacements along the peudocubic [111] direction. Although electron diffraction revealed weak additional doubling along c (denoted by the appearance of ¼ {001} in addition to ~{11O} reflections) of the PbZr03 cell, Neutron and X-ray diffraction could not reliably refine a larger cell. This is attributed to the weak intensity of the 1/4 {OO I} reflections and the short coherence length of the 4ac modulation in the c- direction. The transitions from the high temperature Pnma phase to both low temperature phases are accompanied by a large discontinuous expansion of the lattice volume in the low- temperature structure. The Pnma to R3c transition occurs in the paramagnetic state and generates no detectable changes in the magnetic structure. In contrast, the Pnma to Pbam transition, which occurs in the magnetic state, is accompanied by abrupt 90 ° reorientation of the magnetic dipoles. Coupling between the nuclear and magnetic structures is manifested in a significant magnetization anomaly. The dielectric properties were studied as a function of temperature but no anomalies were recorded that were coincident with the structural phase transitions observed by differential scanning calorimetry. The absence of peaks in permittivity at T c was attributed to high conductivity with space charge polarisation dominating the dielectric response.
14
Helbers, Andrew J. "Magneto-Optical Properties of Rare-Earth Doped Semiconductors." Thesis, Lehigh University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10623187.
Full textAbstract:
15
Furusawa, Kentaro. "Development of rare-earth doped microstructured optical fibres." Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/15481/.
Full textAbstract:
This thesis describes the development of novel optical fibres, microstructured optical fibres (MOFs), and demonstrates device applications based on these structures. A particular emphasis is made on incorporating rare-earth ions within these fibres in order to realise novel active devices. Together with the development of the fabrication technique, characterisation and applications of these radically different fibre types are presented. First, the fabrication techniques of MOFs, which heavily rely upon fibre drawing, are studied. A mathematical model developed for the capillary drawing process is experimentally examined. Good agreement is obtained whilst it is also found that the model provides useful physical insights for determining the fibre draw parameters even for MOFs with complex geometries. Details of the fabrication techniques developed to optimise fibre structures are also presented. Transmission properties of highly nonlinear MOFs are then studied experimentally. It is found that the transmission losses are strongly influenced by the core dimensions due to the high Rayleigh scattering coefficient that originates from the holey cladding. A simple model is used to explain the observations. In addition, a continuous effort towards reducing OH-induced losses of this fibres type is outlined. Rare-earth doped highly nonlinear MOFs are fabricated and characterised. Then, three device demonstrations are carried out for the first time. These include a mode-locked ytterbium doped MOF laser, a nonlinear amplifier based on an ytterbium doped MOF, and a continuous wave erbium doped MOF laser with a very low threshold and high efficiency. Using the ytterbium doped MOF, wide tunability of ultrashort pulses from 1µm to 1.58µm is demonstrated using the soliton self frequency shift effect. For the erbium doped MOF, a pump power threshold of 0.5mW and a slope efficiency of 57% are demonstrated. Novel cladding pumped fibres, air clad MOFs, which use a conventional inner cladding and a holey outer cladding, are developed aiming at improved performance of cladding pumped fibre lasers. Wide tunability over 110nm and pure three level operation at 980nm of ytterbium doped cladding pumped fibre lasers are demonstrated. Finally, the fabrication and characterisation of large mode area microstructured fibres (LMA-MOFs) are described, and a comparison with conventional counterparts is made in terms of bend losses and corresponding effective mode areas. The results show that a slight refractive index difference introduced in the core region of this fibre type strongly modifies its waveguide characteristics. By applying this knowledge, a novel ytterbium doped cladding pumped fibre, which uses different sizes of air holes to define the inner and outer cladding, is developed. A continuous wave output power in excess of 1W is obtained. Results concerning various forms of pulsed laser operation using this fibre are presented and future possibilities are discussed.
16
Amin, Jaymin. "Integrated optical devices in rare-earth-doped LiNbO3." Thesis, University of Southampton, 1996. https://eprints.soton.ac.uk/397282/.
Full textAbstract:
This thesis describes the fabrication and characterisation of rare-earth-doped Ti:LiNbO3 channel waveguide devices. Rare-earth-doped integrated optical sources in LiNbO3 are expected to play key roles in optical communication and sensor systems, due to their potential of mass production at reduced cost and their ability to perform several signal processing functions on a single chip. The fabrication of neodymium-diffused Ti:LiNbO3 waveguide devices is described in detail, and their spectroscopic and laser characteristics are given. Laser results for emission at 1084nm and ~900nm are presented, the latter for the first time. Room temperature lasing has been demonstrated for the first time in these devices. Y-branch resonator cavities have been analysed using a transfer matrix approach, and their tuning and wavelength selective properties have been studied. The latitude offered by the planar configuration was then demonstrated through the fabrication of Y-branch laser devices in Nd-diffused LiNbO3, with on-chip electro-optic modulators. The potential of multiple-cavity structures for added functionality has been demonstrated by tuning and Q-switching these devices. Diode pumped operation of these devices has been demonstrated. A detailed spectroscopic analysis, using the Judd-Ofelt theory, has been carried out in the Er:LiNbO3 system for the first time. Results are presented on the lifetimes and quantum efficiencies of various energy levels. ESA transition strengths have been calculated and qualitative comparisons have been made with Er-doped glass to evaluate the efficiency of the 980nm pumping scheme in Er:LiNbO3. Er-diffused Ti:LiNbO3 waveguides have been fabricated and characterised. The versatility of the diffusion technique for the incorporation of rare-earth ions in LiNbO3 has been demonstrated by the fabrication of locally-diffused Er:Ti:LiNbO3 devices. Net gain has been measured in these waveguides, pumped at 1480nm, and the measurement techniques employed and the results obtained are presented. Comparisons have been made of the pump power requirements for gain threshold in planar and locally diffused waveguides, and it is shown that gain localisation may potentially allow the realisation of low threshold waveguide lasers in this system.
17
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.
Full textAbstract:
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.
18
Vivona, Marilena. "Radiation hardening of rare-earth doped fiber amplifiers." Thesis, Saint-Etienne, 2013. http://www.theses.fr/2013STET4008.
Full textAbstract:
Cette thèse est consacrée à l'étude de la réponse aux radiations d'amplificateurs à fibre optiques dopées Er 3+ et Yb3+. Ces dispositifs fonctionnant à 1,5 µm ont été conçus pour des applications spatiales et l'évaluation de leurs performances revêt d’une importance capitale dans un tel environnement hostile. Deux traitements, le chargement en H2 et le co-dopage au Ce du cœur de la fibre, ont été étudiés comme solutions de durcissement aux radiations. Une étude spectroscopique a permis d’approfondir la connaissance des mécanismes physiques de base responsables de la dégradation de ces composants et par conséquent de proposer des solutions de durcissement. La thèse est organisée en trois parties. La Partie I présente une description générale des fibres dopées aux ions de Terres Rares (TR), avec l'introduction des concepts de base de la physique de tels éléments et leur interaction avec la matrice hôte (verre phosphosilicate). L'état de l'art concernant les effets des rayonnements sur les fibres dopées aux TR est également présenté. La Partie II décrit les échantillons et les techniques expérimentales utilisées. La Partie III décrit les principaux résultats dont les tests, en configuration active, démontrent que le co-dopage au Ce ainsi que le chargement en H2 ont un rôle-clé dans la limitation des pertes induites par rayonnement. L'analyse spectroscopique de la matrice vitreuse (Raman) et des ions TR (par mesures de luminescence stationnaire et résolue en temps) mettent en exergue un fort effet de durcissement, conduisant à une préservation de l'efficacité du système physique en opérationThis thesis is devoted to the study of the radiation response of optical amplifiers based on Er/Yb doped fibers. These devices operating at 1.5 µm are conceived for space applications and contextually the evaluation of their performance in such harsh environment becomes of crucial importance. Two treatments, the H2-loading and the Ce-doping of the fiber core, are investigated as radiation hardening solutions. A spectroscopic study has been associated, in order to improve the knowledge of the physical mechanisms responsible for the signal degradation and the action of the hardening solutions. The thesis is organized in three parts. Part I deals with a general description of the Rare-Earth (RE)-doped fibers, with the introduction of some basic concepts of the RE-ion physics and their interaction with the host matrix material (phosphosilicate glass). The state-of-art of the radiation effects on the optical fibers, particularly the RE- doped fibers, is also overviewed. Part II describes the samples (fiber fabrication, geometry and chemical compositions), and the used experimental techniques, including a short discussion on the related theoretical background. Part III describes the main results; firstly, the active tests, performed on the RE-doped fiber as part of an optical amplifier, demonstrate that the Ce-codoping and H2-load have a key-role in the limitation of the radiation induced losses. Then, the spectroscopic analysis of the phosphosilicate glass (Raman study) and of the RE-ions (stationary and time-resolved luminescence) show a stabilization effect due to the two treatments, leading to a preservation of the high efficiency of the physical system under study
19
Alshoaibi, Adil. "Electrical properties of rare earth-doped barium titanate." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/17289/.
Full textAbstract:
Samples of undoped BaTiO3, BT were prepared by three mixed oxide routes; hand mixing, HM using a pestle and mortar, ball milling, BM using Y2O3-stabilised zirconia balls and planetary ball milling, PBM using tungsten carbide balls. The electrical properties of slow cooled (SC) and quenched (Q) BT material for HM, BM and PBM samples were studied by impedance spectroscopy, IS after heat treatments in air at different temperatures. IS measurements with application of applied voltage and in atmospheres of different oxygen partial pressure were used to determine the conduction mechanism. The application of bias voltage was used during IS measurements to separate Schottky barrier interfacial impedances from sample impedances. In general, two types of Schottky barrier can be detected: (i) barriers at electrode-sample interfaces due to Fermi level mismatch and (ii) barriers between grains associated with partial oxidation of sample surfaces. In-Ga electrodes were considered to yield ohmic contacts and associated with partial oxidation that also produced the positive temperature coefficient of resistance, PTCR effect. A methodology has been developed to understand the effect of an applied voltage and changing oxygen partial pressure on electrical properties and possible explanations. Rare earth dopants can occupy either Ba or Ti sites or a mixture of Ba and Ti sites depending on their size. This requires charge compensation mechanisms which can be ionic or electronic. The ionic mechanism can involve either cation or oxygen vacancies. A survey has been carried out of the charge compensation mechanism for different rare earth ions (Gd, Dy, Ho, Y, Er and Yb). It was found that Y3+ preferentially occupied the Ti4+ site with charge compensation by oxygen vacancies and therefore, Y behaved as an acceptor with solid solubility limit of ~ 15%. Y3+ can also simultaneously occupy both Ba and Ti sites with a solubility limit of ~ 7.5%, but exclusive occupancy of Ba sites is limited to ~ 1.5%. A partial phase diagram BaO-TiO2-Y2O3 can been presented showing the different solid solutions and the polymorphism of doped BaTiO3. Several parameters affected the electrical properties of pure and doped BT ceramics: the charge compensation mechanism, whether ionic or electronic; the sample preparation methods; the cooling rate at the end of sample heat treatment because many samples lost a small amount of oxygen at high temperature and showed n-type semiconductivity. A common observation was that many slow cooled samples showed weak p-type behaviour attributed to uptake of oxygen on cooling. The holes may be associated with either underbonded oxide (O - ) ions or unavoidable impurities such as Fe3+. Leaky dielectric properties were observed for extrinsic n-type region whereas, normal dielectric properties were observed for extrinsic p-type region. The electrical properties of BaTi1-xYxO3-x/2 samples fired and cooled in air were ferroelectric insulators at x . 0.05 and relaxor ferroelectrics at higher x with no evidence of semiconductivity in any of the samples, whether they were cooled slowly or quenched from high temperatures (1200-1600 .C). The possible occurrence of a resistivity minimum in rare earth doped BT was investigated. Three possible mechanisms for semiconductivity were considered for generating Ti3+ ions: direct donor doping, oxygen loss at high temperatures and a more complex double doping mechanism involving Y3+ and Ti3+ ions to chargebalance the oxygen vacancies. No semiconductivity and resistivity minimum were observed for Yb-BT for all three joins and Er-BT. Semiconductivity was observed for other RE dopants and the total resistivity passed through a minimum at 0.1% RE substitution then increased generally for > 1% Y, Ho, Dy and Gd substitution on all three joins.
20
Kuzminykh, Yury. "Crystalline, rare-earth-doped sesquioxide and YAG PLD-films." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981073182.
Full text
21
Longdell, Jevon Joseph, and jevon longdell@anu edu au. "Quantum Information Processing in Rare Earth Ion Doped Insulators." The Australian National University. Research School of Physical Sciences and Engineering, 2004. http://thesis.anu.edu.au./public/adt-ANU20061010.105020.
Full textAbstract:
A great deal of theoretical activity has resulted from blending the fields of computer science and quantum mechanics. Out of this work has come the concept of a quantum computer, which promises to solve problems currently intractable for classical computers. This promise has, in turn, generated a large amount of effort directed toward investigating quantum computing experimentally.
¶
Quantum computing is difficult because fragile quantum superposition states of the computers register must be protected from the environment. This is made more difficult by the need to manipulate and measure these states.
¶
This thesis describes work that was carried out both to investigate and to demonstrate the utility of rare earth ion dopants for quantum computation. Dopants in solids are seen by many as a potential means of achieving scalable quantum computing. Rare earth ion dopants are an obvious choice for investigating such quantum computation. Long coherence times for both optical and nuclear spin transitions have been observed as well as optical manipulation of the spin states. The advantage that the scheme developed here has over nearly all of its competitors is that no complex nanofabrication is required. The advantages of avoiding nano-fabrication are two fold. Firstly, coherence times are likely to be adversely effected by the damage to the crystal structure that this manufacture represents. Secondly, the nano-fabrication presents a very serious difficulty in itself.
¶
Because of these advantages it was possible to perform two-qubit operations between independent qubits. This is the first time that such operations have been performed and presents a milestone in quantum computation using dopants in solids. It is only the second time two-qubit operations have been demonstrated in a solid.
¶
The experiments performed in this thesis were in two main areas: The first was the characterisation of hyperfine interactions in rare earth ion dopants; the second, simple demonstrations directly related to quantum computation.
¶
The first experiments that were carried out were to characterise the hyperfine interactions in Pr[superscript 3]+:Y[subscript 2]SiO[subscript 5]. The characterisation was the first carried out for the dopants in a site of such low symmetry. The resulting information about oscillator strengths and transition frequencies should prove indispensable when using such a system for quantum computation. It has already enabled an increase in the coherence times of nuclear spin transitions by two orders of magnitudes.
¶
The experiments directly related to the demonstration of quantum computation were all carried out using ensembles. The presence of a significant distribution of resonant frequencies, or inhomogeneous broadening, meant that many different sub-ensembles could be addressed, based on their resonant frequencies. Furthermore, the properties of the sub-ensembles could be engineered by optically pumping unwanted members to different hyperfine states away from resonance with the laser.
¶
A previously demonstrated technique for realising ensembles that could be used as single qubits was investigated and improved. Also, experiments were carried out to demonstrate the resulting ensembles utility as qubits. Further to this, ions from one of the ensembles were selected out, based on their interaction with the ions of another. Elementary two qubit operations were then demonstrated using these ensembles.
22
Bjurshagen, Stefan. "Diode-pumped rare-earth-doped quasi-three-level lasers." Doctoral thesis, Stockholm : Fysik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-544.
Full text
23
Marzahl, Daniel-Timo [Verfasser]. "Rare-Earth-Doped Strontium Hexaaluminate Lasers / Daniel-Timo Marzahl." München : Verlag Dr. Hut, 2016. http://d-nb.info/1113336226/34.
Full text
24
Perkins, James M. "Microstructure and properties of (rare earth) doped oxide ceramics." Thesis, University of Warwick, 2006. http://wrap.warwick.ac.uk/3705/.
Full textAbstract:
A study of alumina (AI203 ) and magnesium aluminate spinel (MgAb04) was undertaken with the aim of investigating the changes in properties and microstructural characteristics upon doping with specific rare earth elements. Microscopic imaging and analysis of RE doped polycrystalline oxide ceramics has shown convincing evidence for monolayer segregation of RE cations to grain boundaries. State of the art aberration corrected scanning transmission electron microscopy (SuperSTEM I Daresbury Laboratories) has shown monolayer segregation to grain boundaries, and atomic resolution parallel electron energy loss spectroscopy has confirmed the presence of the RE cation at the grain boundary position. The region affected by segregation has been shown to extend no further than one monolayer from the centre of the grain boundary with RE cations occupying matrix cation boundary sites. The effect of RE dopants on the powder processing and sintering of high purity commercial grade precursor powders was investigated. Differences were found between doped alumina and spinel in the sintering whereby the alumina grain growth was restricted by grain boundary mobility such that the grain size was reduced for a given sintering temperature. The grain size of spinel was unaffected by sintering temperature. Differences in the fracture behaviour between doped alumina and spinel was found. The alumina samples manifested a change from trans-granular fracture to inter-granular fracture due to the addition of RE dopants. Spinel did not show such an effect. Alumina was shown to posess an approximate Hall-Petch relationship between hardness and grain size for both doped and undoped samples, such that sub-micron grain size samples posessed high hardness. Optical characterisation has shown the potential for the use of fine grained RE doped alumina and spinel samples for hard window applications. A reduction in the grain size of alumina to below 1 μm leads to a change in the scattering mechanism, thus reducing low angle scatter and birefringence due to the refractive index mismatch. The benefits to optical properties are in addition to the benefits in mechanical properties of a submicron grain structure.
25
Kukkonen, Liv Linnea. "Transparent, rare earth doped, oxyfluoride glass-ceramics for photonics." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340220.
Full text
26
Beggiora, Marco. "Characterisation of rare earth doped oxy-fluoride glass ceramics." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401189.
Full text
27
Magden, Emir Salih. "Rare-earth doped aluminum oxide lasers for silicon photonics." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/89860.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
88
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 61-66).
A reliable and CMOS-compatible deposition process for amorphous Al2O3 based active photonic components has been developed. Al2O3 films were reactively sputtered, where process optimization was achieved at a temperature of 250°C, with a deposition rate of 8.5 nm/min. With a surface roughness of 0.3 nm over a 1 [mu]m2 area, background optical losses as low as 0.1 dB/cm were obtained for undoped films. The development of active photonics components has been realized by use of rare-earth metals as dopants. By co-sputtering aluminum and erbium targets, Er3+ dopants at concentrations on the order of 1.0x1020 cm-3 have been added to the Al2O3 host medium. Resulting Er3+:Al2O3 films have been characterized, and over 3 dB/cm absorption has been measured over a 20 nm bandwidth. Following the material development, distributed Bragg reflector lasers were designed and fabricated in a CMOS foundry. The laser cavity was created by introducing gratings on either side of a Si3N4 waveguide. Er3+:Al2O3 was deposited in SiO2 trenches on top of the Si3N4 layer, eliminating the need for any subsequent etching steps. On-chip laser output of 3.9 [mu]W has been recorded at a wavelength of 1533.4 nm, with a side mode suppression ratio over 38.9 dB.
by Emir Salih Magden.
S.M.
28
Pearson, Adrian. "High-resolution spectroscopy of rare-earth doped novel glasses." Thesis, University of Southampton, 1994. https://eprints.soton.ac.uk/399137/.
Full textAbstract:
Spectroscopic investigations using high-resolution techniques of two novel rare-earth doped glasses are presented. By using high-resolution techniques, the effect of inhomogeneous broadening due to the incorporation of the ion into the glass host is reduced. The aim of this thesis is two-fold. Firstly, to show how the increased resolution these techniques provide can be used to study the ion-host interaction. Secondly, to use this knowledge to explain and predict the performance of the systems under study as components for the optical communications industry. Optical devices have already been demonstrated in the thulium doped fluoride glass ZBLAN. We present site-selective studies that show that the rare-earth ion can occupy two different site subsets within the glass. These subsets are shown to have radiative lifetimes that differ by greater than 10% at 4.2K. This difference, combined with the observation at room temperature of pump wavelength dependent fluorescence, is suggested as an explanation for the disagreement of modelled optical amplifier performance with measured results. Time resolved site selective studies of a highly doped sample allow for the investigation of the thulium-thulium energy transfer process. This allows it to be shown that the transfer process in the absence of resonant energy diffusion is phonon-assisted dipole-dipole transfer. In the search for an optical amplifier to work at 1.3µm, the rare-earth ion praseodymium is a popular candidate. However, to reduce the problems associated with non-radiative decay, glass hosts with low maximum vibrational energies are required. Two such hosts are ZBLAN and the chalcogenide glass Gallium-Lanthanum-Sulphide (GLS). Site-selective studies show that both glasses have spectroscopic features that may affect devices. In ZBLAN, two ion site subsets are again observed. In GLS, there is seen to be a large degree of correlation between the inhomogeneous broadening mechanisms affecting different energy levels. Combined with the room temperature site-selection observed, this will lead to an inhomogeneous amplifier system. In both praseodymium systems, it was demonstrated that persistent spectral holes could be burnt, allowing the homogeneous linewidth of the observed transition to be measured. By monitoring the wavelength dependence of the burning efficiency, it is seen that the interaction of the rare-earth ion with the host in ZBLAN differs greatly in the two site subsets.
29
HEIKENFELD, JASON CHARLES. "RARE EARTH-DOPED GALLIUM NITRIDE FLAT PANEL DISPLAY DEVICES." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1003428694.
Full text
30
Ohtsuki, Tomoko 1960. "Rare-earth-doped glass waveguides for amplifiers and lasers." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282169.
Full textAbstract:
Several different glass materials were investigated for waveguide amplifier and laser applications, and the potential to realize practical devices with these materials were examined using waveguides fabricated by ion exchange processes. Channel waveguides in an erbium doped phosphate laser glass were fabricated by a dry silver-film ion exchange technique, and the effects of high Er³⁺ concentration were investigated in terms of Er³⁺ ion interactions and energy transfer from Yb³⁺ to Er³⁺. Cooperative upconversion coefficients of the ⁴I₁₃/₂ level,7.7±0.7x 10⁻¹⁹ cm³/sec and 9.3±0.7x10⁻¹⁹ cm³/sec, were obtained experimentally for Er³⁺ concentration of 1x10²⁰ cm³ in the bulk and waveguide samples, respectively. These values are one order of magnitude smaller than the ones reported for silica glass. The increase in the cooperative upconversion coefficient with the increase in Er³⁺ concentration was found to be small. The effects of cooperative upconversion on the gain performance were analyzed for different Er³⁺ concentrations using a theoretical model which adopted experimentally obtained parameters. Given the small cooperative upconversion coefficients in this glass, Er³⁺ concentrations potentially as high as 3.7x10²⁰ cm⁻³ were shown to be feasible by the modeling. This would result in a 12 dB gain with a 4 cm long waveguide for 150 mW pump power at 1.48 μm. The transfer efficiency from Yb3+ to Er³⁺ was found to be 95% or higher for samples with Er³⁺ concentrations of 1.9x10²⁰ cm⁻³, and 24x10²⁰ cm⁻³, even when the ratio of the concentrations, Yb/Er, is only about 1.2 and 2. Planar channel waveguides of rare-earth doped fluoride glass were demonstrated with single mode excitation and propagation loss below 3 dB/cm. The waveguide core was fabricated by Ag⁺-Na⁺ molten salt ion exchange process in a borosilicate glass (BGG31), and a Nd³⁺-doped ZBLAN glass was used as a cladding. A 0.45 dB signal amplification at 1.064 μm was observed in the fabricated 1cm long waveguide, and a 0.9 dB amplification is expected at the emission peak (1.049 μm). Modeling results suggest that 2.5 dB/cm is possible by improving surface flatness of the ZBLAN glass.
31
Siddiqui, Saiful Anam. "Erbium doped silicon light emitting diodes." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/843408/.
Full textAbstract:
Erbium, a rare earth element, has been shown to exhibit characteristic luminescence at 1.54mum due to its internal 4f transition from the first excited state (4pi3/2) to the ground state (4pi5/2). As this emission wavelength falls inside the maximum transmission window of silicon based optical fibers, erbium doped silicon might lead to the opportunity of silicon based optoelectronics. The introduction of erbium in silicon allows excitation through electron-hole recombination and subsequent radiative emission from the rare earth centers. The works reported here describe the structural, electrical and optical properties of crystalline silicon codoped with erbium and boron by ion implantation technique. Four sets of samples, co-implanted with erbium and boron at different Er dose, implantation energy and at different conditions, were prepared. Post-implantation annealing has been performed to recover the implantation damage to an acceptable value and to activate the dopant atoms optically and electrically. PL and EL measurements have been performed in the temperature range between 80K to room temperature. The sample with the lowest erbium concentration and energy gives the best PL and EL results. The observed emission peaks in both PL and EL measurements were at around 1.129mum, ~1.303mum, 1.50mum and 1.597mum at 80K. At higher temperatures, a broader peak at around 1.50mum with long tail towards the both end of wavelength has been observed. The peak at 1.129mum corresponding to the Si band edge emission, the reason for the peaks at around l.303mum has not been identified while the remaining two peaks correspond the Er3+ emission. Virtually no temperature quenching of Er luminescence is observed in some samples rather room temperature intensity is higher than that at 80K. The improvement of the temperature quenching effect on Er luminescence at room temperature has been attained in our results, which is significant improvement in comparison to the result found in the literature. The structural properties were studied by TEM in both cross-sectional and plan view configurations. TEM analyses showed dislocation loops and other defects of random size and distribution from the surface to 600nm below the surface. Er precipitates defects were also seen in the sample doped with Er comparatively at higher dose (1x1015Er/cm2) and energy (1.0 MeV). No detectable room temperature PL and EL signals were observed from the sample implanted at higher doses and energies.
32
Akhtar, Nadim. "Synthetic routes to rare earth cuprates and yttria doped ceria." Thesis, Manchester Metropolitan University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391979.
Full text
33
Ladaci, Ayoub. "Rare earth doped optical fibers and amplifiers for space applications." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSES027/document.
Full textAbstract:
Les fibres dopées aux terres rares (REDFs) représentent un composant clef dans la fabrication de sources laser et d’amplificateurs optiques (REDFAs). Leurs hautes performances rendent cette technologie particulièrement attractive pour les applications spatiales en tant que partie active des gyroscopes à fibres optiques, pour le transfert de données et les applications LIDARS. Cependant, la grande sensibilité de ces fibres actives limite l’intégration des REDFAs au sein des missions spatiales. De nombreuses études ont été menées pour dépasser ces limitations et différentes techniques de mitigation ont été identifiées telles que le co-dopage au Cérium ou le chargement en hydrogène de ces fibres optiques. Toutes ces solutions interviennent au niveau du composant sensible et sont classées parmi les stratégies de durcissement par composant permettant la fabrication de fibres dopées aux terres rares résistantes aux radiations adaptées aux besoins des missions spatiales actuelles associées à de faibles doses d’irradiation. Cependant, l’avènement de nouveaux programmes, de nouvelles missions invitent à considérer des doses d’irradiation plus importantes, nécessitant des REDFs et des RDFAs encore plus tolérants aux radiations. A cette fin, une optimisation de l’amplificateur optique au niveau système est étudiée dans le cadre de ce doctorat en exploitant une approche couplant simulation et expériences dont les avancées pourront venir en appui des techniques de durcissement plus conventionnelles. Après la présentation du contexte, des objectifs de ce travail (Chapitre I), les mécanismes fondamentaux de l’amplification et des effets des radiations sont brièvement décrits dans le Chapitre II. Les outils de simulation basés sur l’enrichissement d’un code à l’état de l’art et ses nouvelles fonctionnalités, décrites au Chapitre III, permettent non seulement l’évaluation des performances optiques du REDFA mais aussi de prédire leurs évolutions sous irradiation. De nombreuses études expérimentales ont été réalisées sur différents REDFAs développés durant la thèse et présentés dans le chapitre IV, leurs résultats comparés à ceux issus de la simulation afin de valider nos outils de simulation. Une fois validé, le code a été utilisé pour montrer comment l’optimisation de l’architecture du REDFA permet de mitiger les effets des radiations sur ses performances (Chapitre V). Finalement, le Chapitre VI présente l’étude de l’implémentation dans le code de nouveaux effets, tels que les effets thermiques, le multiplexage du signal d’entrée à travers un couplage théorie/expérienceRare earth doped fibers (REDFs) are a key component in optical laser sources and amplifiers (REDFAs). Their high performances render them very attractive for space applications as the active part of gyroscopes, high data transfer links and LIDARs. However, the high sensitivity of these active fibers to space radiations limits the REDFA integration in actual and future missions. To overcome these issues various studies were carried out and some mitigation techniques were identified such as the Cerium co-doping or the hydrogen loading of the REDFs. All these solutions occur at the component level and are classified as a hardening by component strategy allowing the manufacturing of radiation hardened REDFAs with adapted performances for low doses space mission. However, with the new space research programs, more challenging space missions are targeted with higher radiations doses requiring even more tolerant REDFs and REDFAs. To this aim, an optimization of the REDFA at the system level is investigated in this PhD thesis exploiting an approach coupling simulations and experiments offering the opportunity to benefit from the outputs of this hardening by system strategy in addition to other state-of-the-art approaches. After presenting the context, objectives of this work, the basic mechanisms about amplification and radiation effects as well as the architectures of REDFAs are described in chapters I and II. After that, we update a state of art REDFAs simulation code described in Chapter III, to consider not only the REDFA optical performances but also their evolutions when exposed to radiations. Several experiments on dedicated home-made REDFA have been performed using accelerated irradiation tests (Chapter IV) and the comparison between these data and those obtained through the new code validated the simulation tools. Thereafter, we exploit the validated code to highlight how the optimization of the REDFA architecture can participate to the mitigation of the radiation effects on the amplifier performances (Chapter V). Finally, in chapter VI the implementation in the code of several other effects, such as thermal effects, input signal multiplexing was investigated both from experimental and calculation point of views
34
Townsend, Janet E. "The development of optical fibres doped with rare-earth ions." Thesis, University of Southampton, 1990. https://eprints.soton.ac.uk/400704/.
Full textAbstract:
Research into rare-earth ion doping of silica based optical fibres is described and a detailed study of the fabrication process reported. Dilute solutions of rare-earth ions are employed to incorporate dopants into preforms prepared by conventional methods. Alternative core glass compositions are also studied. Parameters affecting dopant incorporation, host composition and refractive index, as well as impurity concentration are investigated. Spectroscopic fluorescence and absorption measurements are presented and provide important information for device applications. In addition, fluorescence lifetime data allow the effect of dopant concentration and host composition to be analysed. Thus, a model describing the limits of doping levels is developed. The use of rare-earth ion doped fibre in several devices, both active and passive, is assessed, with special reference to the fabrication process. In particular, the effect of host glass on the laser characteristics of Tm3+ doped fibres and of the ratio of doping levels on the behaviour of Er3+/Yb3+ codoped fibre lasers is discussed. A practical temperature sensor based on fibre doped with low levels of rare-earth ions and a fibre filter requiring heavily doped fibre are demonstrated, with suggested design for improved performance. Finally, a novel radiation dosimeter, based on Nd3+ doped fibre, is described. Unusually, the response is found to be both rereadable and linear, even at elevated temperatures, and a model is proposed to describe the behaviour of this material. In summary, the fabrication, characterisation and applications of a wide range of rare-earth ion doped optical fibres have been investigated in detail.
35
Carter, Jeremy Nigel. "Investigations of rare earth doped fluorozirconate fibre lasers and amplifiers." Thesis, University of Southampton, 1992. https://eprints.soton.ac.uk/399360/.
Full textAbstract:
This thesis presents the results of a three year study into the use of thulium and praseodymium doped fluorozirconate fibres as low threshold, potentially miniature laser sources at a variety of wavelengths from the visible to the infrared. Thulium doped fluorozirconate fibre is also investigated as a high gain optical amplifier at 810nm. Pumped at the semiconductor diode compatible wavelength of 790nm, laser emission has been demonstrated at 1.9µm, 2.3µm, 1.47µm and 810nm in thulium doped fluorozirconate fibres, with diode pumped operation achieved at 1.91µm. The transition at 810nm has been operated as an optical amplifier where single pass gains in excess of 22dB have been demonstrated for less than 60mW of pump power. The gain characteristics of this transition have been modelled and show good agreement with the experimentally observed performance. Operated as a laser emitting around 810nm, this transition has demonstrated both high efficiencies (> 70%), low thresholds (< 13mW of pump power) and tunability over 30nm. A Judd-Ofelt analysis has been carried out for thulium-doped fluorozirconate fibre to extract spectroscopic data for explanation of the system performance. In praseodymium doped fluorozirconate fibre, visible laser emission has been observed at 635nm, 605nm, 520nm and 491nm both when pumped by an argon ion laser at 472.7nm and by upconversion pumping when using two Ti:sapphire pump lasers tuned to 1.01µm and 835nm. An analytical model of the performance of these upconversion pumped visible fibre laser transitions is presented and shows good agreement with experiment. Pump power requirements for laser action on the high gain 635nm transition have been shown to be as low as 20mW from each pump laser and there exists, therefore, the possibility of semiconductor laser diode pumping.
36
Xu, Amei. "Luminescence properties of Zinc oxide doped with rare earth ions." Ohio University / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1174408190.
Full text
37
Hayashi, Hideaki. "Material design of rare earth doped glasses for WDM amplifiers." Kyoto University, 2008. http://hdl.handle.net/2433/136469.
Full textAbstract:
Kyoto University (京都大学)0048
新制・課程博士
博士(人間・環境学)
甲第13933号
人博第406号
新制||人||100(附属図書館)
19||人博||406(吉田南総合図書館)
UT51-2008-C849
京都大学大学院人間・環境学・環境学研究科相関環境学専攻
(主査)准教授 田部 勢津久, 教授 村中 重利, 准教授 木下 俊哉, 教授 平尾 一之
学位規則第4条第1項該当
38
Shen, Shaoxiong. "New rare earth ion-doped hosts for broadband fibre amplifier." Thesis, University of Leeds, 2000. http://etheses.whiterose.ac.uk/2379/.
Full textAbstract:
Three kinds of oxide glasses doped with Er3+ ions were chosen for investigation. Both the properties of glass and fluorescence from rare earth dopant ions are measured and discussed. In Er3+ ion doped silicate glass, the changes in the structure of glass as a result of fluorine addition are studied by measuring the glass properties: density, molar volume, refractive index, IR and UV edges. The absorption and emission cross- sections of Er3+ ion increase with increasing value of F/O ratio as do the full width of half maximum (FWHM) and figure-of-merit (FOM) for gain and bandwidth. In Er3+ ion doped heavy metal germanate glass, the structural units of forming network in germanate glass change with the addition of PbO, Bi2C>3, Ga2C>3 and TeC>2. The molar volume, glass transition temperature Tg, IR and UV edges have been measured and discussed with the relation of glass structure. More Er3+ ion sites result in the increase of absorption and emission cross-sections, emission FWHM and FOM for gain. In Er3+ doped Te02 - ZnO - R2O (R2O = Li20, Na20 and K2O) tellurite glass system, glass properties such as density, molar volume, transition temperature Tg, IR and UV edges are measured and discussed. The glass structure has been characterised using Raman spectra. The role of F' and Cl' has also been studied in tellurite glass. Crystallisation kinetics has been analysed in tellurite glass using isothermal and non- isothermal methods. The properties of Er3+ absorption and emission have been measured and discussed with the change of glass structure and concentrations. FOM for gain and bandwidth have also been compared and discussed in Er3+ doped modifies silicate, HMO germanate, tellurite and ZBLAN fluoride glasses. The tellurite glass fibre has been made and the emission spectra of Er3+ ion in fibre have been measured. Absorption and emission spectra have been studied in Tm -doped tellurite glass, it shows to be a highly promising host for a 1.47 (im amplifier capable of providing extended short-wavelength gain and a continuous band with the tellurite EDFA. Nd3+- doped tellurite and silicate glasses have also been studied, amplifier operating around 1.34 (j.m is clearly desirable in tellurite glass. A continuous gain band extending from 1310 to 1600 nm may become possible by using Nd3+, Tm3+ and Er3+ amplifiers.
39
Bowron, Daniel Timothy. "A study of rare earth doped silicate and phosphate glasses." Thesis, University of Kent, 1994. https://kar.kent.ac.uk/38697/.
Full textAbstract:
The complementary techniques of X-ray diffraction and EXAFS have been applied to silicate and phosphate glass systems containing varying quantities of rare earth elements. The silicate systems that have been studied are rare earth doped fibre optic preforms of interest to the optoelectronics and telecommunications industry. Techniques were developed to allow spatially resolved diffraction and EXAFS data to be taken from the small ~1mm diameter core region of the preforms. Absorption maps were made displaying the distribution of the rare earth ions as a function of radial position, and similarly for the germanium codopant incorporated in these systems. The diffraction results show as expected, that silica dominates the structure evident in the preforms whilst EXAFS measurements taken at the germanium K-edge, suggest that this codopant occupies an eightfold coordinated site surrounded by oxygen atoms at 1.7A. The phosphate glasses studied are rare earth metaphosphates of the composition R(PO3)3. X-ray diffraction measurements were taken showing that the network structure of these systems is essentially constructed from PO4 tetrahedra. The EXAFS experiments, performed on a range of glasses over the rare earth LIII edges, show a trend in the first shell distance rare earth-oxygen, consistent with the Lanthanide contraction, the rare earth ions occupy-ing sites with between six and eight-fold coordination of oxygen atoms about the rare earth ions.
40
COVA, FRANCESCA. "Rare-Earth doped Scintillating Silica Fibers for ionizing radiation detection." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2020. http://hdl.handle.net/10281/263105.
Full textAbstract:
I materiali con proprietà di scintillazione trovano ampio impiego in applicazioni che riguardano la rivelazione di radiazioni ionizzanti, quali il monitoraggio e la diagnostica per immagini, la dosimetria in campo medico, la sicurezza nazionale ed industriale, e la fisica delle alte energie.
Recentemente, la scoperta di nuovi scintillatori veloci ed efficienti ha rappresentato un campo di ricerca in attivo e continuo sviluppo. Fra i numerosi sistemi indagati, le fibre ottiche scintillanti hanno suscitato grande interesse grazie alla loro estrema versatilità che permette la progettazione di rivelatori con un design innovativo.
In questa tesi si propone lo studio di fibre scintillanti di silice che mostrano efficienti proprietà luminescenti quando drogate con ioni di terre rare, come Cerio e Praseodimio.
L’argomento è trattato sia da un punto di vista fondamentale che applicativo, al fine di migliorare ed ottimizzare la resa del materiale perché possa essere impiegato in rivelatori di nuova generazione.
A questo scopo, si è deciso di studiare gli effetti dell’esposizione ad elevate dosi di radiazioni ionizzanti sulla trasparenza del materiale.
L’ottimizzazione della concentrazione del drogante luminescente nella matrice di silice, nonché dei processi di sintesi sol-gel e di filatura della fibra ha permesso di ottenere un’efficiente propagazione della luce all’interno della fibra stessa. É stata altresì dimostrata la fattibilità di una rivelazione simultanea di luce Cherenkov e di scintillazione, esponendo a fasci di elettroni altamente energetici un piccolo prototipo di calorimetro realizzato con fibre scintillanti drogate con Cerio. Le fibre di silice possono quindi essere considerate promettenti candidate in quell’ambito della calorimetria che prevede l’utilizzo della doppia lettura del segnale Cherenkov e di scintillazione per compensare le fluttuazioni energetiche caratteristiche dell’interazione con adroni pesanti.
Inoltre, una completa conoscenza dei fattori che limitano l’efficienza di scintillazione è di primaria importanza per una futura ingegnerizzazione del materiale: l’esistenza di difetti di punto, che competono con i centri luminescenti nella cattura dei portatori di carica generati a seguito dell’interazione con la radiazione ionizzante, risulta essere la principale causa della presenza di una componente temporale lenta nella cinetica di ricombinazione. É stato quindi condotto uno studio approfondito del ruolo dei difetti nelle fibre di silice, al fine di comprenderne la natura e gli effetti sulle proprietà di scintillazione.
I risultati ottenuti in questa tesi hanno confermato il potenziale di questa tecnologia per applicazioni in rivelatori per fisica delle alte energie e gettato le basi per un ulteriore futuro sviluppo del materiale.
Questo lavoro è stato svolto presso i laboratori del Dipartimento di Scienze dei Materiali dell’Università di Milano-Bicocca, in collaborazione con il Centro Europeo per la Ricerca Nucleare (CERN, Ginevra, Svizzera) e con il Lawrence Berkeley National Laboratory (Berkeley, USA). Parte dei dati è stata ottenuta in collaborazione con Saint Gobain Research (Aubervilliers, Parigi, Francia) e con l’Istituto di Fisica dell’Accademia delle Scienze della Repubblica Ceca (Praga, Repubblica Ceca).Scintillating materials find a wide variety of applications in ionizing radiation detection systems, monitoring and imaging, real time dosimetry in the medical field, homeland and industrial security, and high energy physics. In the recent years, the development of new, fast, and performing scintillators has been an active field of research. Scintillating fiber technology freshly raised a lot of interest because its extreme flexibility can provide a powerful tool for innovative detector designs. This thesis focuses on the study of scintillating fibers made of silica glass which show efficient luminescent properties when activated with rare-earth ions, like Cerium and Praseodymium. Both fundamental and practical aspects are discussed, in view of the improvement and optimization of the material performances for application perspectives in the future generation of high energy physics detectors. With this objective, the effects of high dose levels of ionizing radiation on the transparency of the material are studied. The fine-tuning of the activator content incorporated in the silica matrix and of the sol-gel synthesis and fiber drawing processes allow to obtain a good light guiding and a well-controlled optical quality. The feasibility of a simultaneous readout of Cherenkov and scintillation light is demonstrated in high energy calorimetry conditions, probing Ce-doped silica fibers embedded in a small detector prototype exposed to beams of electrons. Silica fibers can be considered as promising candidates in the framework of the dual readout calorimetry approach, which aims at compensating the energy fluctuations, inherent to the detection of hadronic particles. A deep understanding of the factors limiting the scintillation performances is of primary importance for future material engineering: they are found to be mainly related to the presence of point defects, which compete with the luminescent centers in capturing the free carriers created upon irradiation and introduce a delay in the recombination kinetics. A fundamental study of the role of defects in silica fibers, detrimental for the scintillation efficiency, is proposed and discussed. The potential of silica fibers for applications in high energy physics detectors is outlined and further optimization of the material technology is foreseen. This work was performed at the Department of Materials Science at the University of Milano - Bicocca, in collaboration with the European Organization for Nuclear Research (CERN, Switzerland) and with the Lawrence Berkeley National Laboratory (US). Some measurements were carried out in collaboration with Saint Gobain Research (France) and the Institute of Physics of the Czech Academy of Sciences (Czech Republic).
41
Grafe, Hans-Joachim. "Nuclear Magnetic Resonance Studies of Rare Earth co-doped Lanthanum Cuprates." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1136896294995-95684.
Full textAbstract:
The work described in this thesis uses oxygen NMR to probe the electronic system of rare earth co-doped La_{2-x}Sr_xCuO_4, the prototypical high temperature superconducting cuprate (HTSC). Oxygen NMR turns out to be a powerful tool for this purpose. The nucleus is located directly inside the CuO_2 planes. It has a spin of 5/2 and a quadrupole moment and therefore can probe both, interactions with the magnetic hyperfine field as well as interactions through the electric field gradient of the crystal. Furthermore, the spin lattice relaxation time T_1 and the spin spin relaxation time T_2 contain information about the dynamics of these interactions. Such a link between the spin and charge structures in high temperature superconductors has been elusive until today. Instead, there are magnetic probes such as neutron scattering and muSR that provide evidence for a modulation of the spin structure and static magnetic moments, respectively, and charge probes like STM that reveal inhomogeneous doping distributions in the CuO_2 planes. In either case, inhomogeneities in the spin and charge system seem to be typical for HTSCs. Whereas the spin and charge modulations are believed to be dynamic in the superconducting compounds, they become static at low temperatures in Eu doped La_{2-x}Sr_xCuO_4, where superconductivity is suppressed. As could be demonstrated here, evidence for such a spin and charge separation, that often revealed stunning similarities to the spin ladder compounds, is apparent in almost all measured NMR parametersIn dieser Arbeit werden Sauerstoff NMR Untersuchungen der elektronischen Struktur von Selten-Erd dotiertem La_{2-x}Sr_xCuO_4, dem prototypischen Hochtemperatursupraleiter (HTSL), vorgestellt. Sauerstoff NMR ist zu diesem Zweck besonders gut geeignet. Der Kern befindet sich innerhalb der Kupferoxid-Ebenen. Er hat einen Spin von 5/2 und ein Quadrupolmoment. Damit lassen sich Wechselwirkungen mit dem magnetischen Hyperfeinfeld der Cu-Atome sowie Wechselwirkungen mit dem elektrischen Feldgradienten des Kristalls untersuchen. Des Weiteren geben die Spin-Gitter-Relaxationszeit T_1 sowie die Spin-Spin-Relaxationszeit T_2 Aufschluss über die Dynamik dieser beiden Wechselwirkungen. Eine Verbindung zwischen der Spin- und Ladungsordnung gibt es in den HTSL bisher nicht. Statt dessen haben magnetische Messmethoden wie Neutronenstreuung oder muSR Aussagen über die magnetische Ordnung geliefert. Unabhängig davon liefern Messmethoden wie STM nur Informationen über eine Ladungsordnung oder inhomogene Ladungsverteilungen. Inhomogenitäten der Spins und Ladungen scheinen aber typisch für die HTSL zu sein. Man vermutet, dass diese Inhomogenitäten dynamisch in den supraleitenden Verbindungen sind, während sie in Eu dotiertem La_{2-x}Sr_xCuO_4 bei tiefen Temperaturen statisch werden und die Supraleitung unterdrücken. In dieser Arbeit wird gezeigt, dass sich diese Ladungs- und Spininhomogenitäten in vielen Parametern der NMR Spektren bemerkbar machen
42
Metz, Philip Werner [Verfasser]. "Visible lasers in rare earth-doped fluoride crystals / Philip Werner Metz." München : Verlag Dr. Hut, 2015. http://d-nb.info/1070124516/34.
Full text
43
Barnard, Chris. "Properties and applications of rare-earth doped fiber amplifiers and lasers." Thesis, University of Ottawa (Canada), 1994. http://hdl.handle.net/10393/6507.
Full textAbstract:
An analytical model for two-, three-, and four-level system rare-earth-doped fiber amplifiers and lasers is presented. Fiber amplifier gain is expressed in terms of easily measured attenuation coefficients, intrinsic saturation powers, and cross saturation powers at the pump and signal wavelengths. System-independent formulas are given for the slopes and thresholds of ring and linear fiber lasers. Good agreement between theory and experiment is shown for erbium-doped fiber amplifiers and lasers and thulium-doped fiber lasers. Approximate system-independent solutions are also given for fiber amplifiers with excited state absorption at either the pump or signal wavelengths. A novel technique, requiring only one tunable light source, is proposed for finding the best pump wavelength when pump ESA is present. Analysis of erbium doped fiber amplifier (EDFA) gain and noise yields a new expression for the amplifier signal-to-noise ratio (SNR) as a function of the fiber length. This leads to a new expression for the fiber length that optimizes the output SNR. Optical gain switching of EDFAs with short pulses at wavelengths within the amplifier bandwidth is modelled to determine how the pump and signal powers, pulse energy, fiber length, and dopant concentration affect the switching time and gain compression. Greater than 20 dB gain compression with nanosecond switching times is demonstrated with good agreement between theory and experiment. Remote EDFA switching from as far as 50 km away is demonstrated. The distance is limited by spontaneous Raman scattering of the switching pulses. These limitations are experimentally and theoretically investigated. Novel configurations are proposed for bidirectional amplification in both single-mode fiber and polarization maintaining fiber. New frequency dependent optical isolators are demonstrated for OTDR testing of amplified fiber links. The new bidirectional amplifier design is much better at attenuating backreflections than a standard EDFA. Polarization separated bidirectional fiber local area networks are proposed. Point-to-point and reflective N-star coupler networks where N = $M\sp2$ or 2$M\sp2$ are considered for an integer M. Reflective star coupler networks use a novel proposed fiber device: an orthogonal polarization variable reflector which can act as an orthogonal polarization full or half reflector. A bidirectional fiber amplifier configuration for polarization separated signals is also proposed.
44
Yahel, Eldad. "Spectrally-resolved approach to rare-earth-doped fibre lasers and amplifiers." Thesis, University of Surrey, 2007. http://epubs.surrey.ac.uk/843263/.
Full textAbstract:
This work presents a new theoretical framework that extends the standard theory of quasi continuous-wave (CW) rare-earth-doped fibres to the ultrashort pulsed regime. We derive a time dependent, spectrally-resolved, nonlinear propagation equation for the coupled spectral components of the amplified pulse, within the rate-equation approximation. Our approach combines in a unified manner the effects of gain saturation, gain dispersion, fibre dispersion, fibre nonlinearity, stimulated Raman scattering, spontaneous Raman emission (with its temperature dependence) and amplified spontaneous emission (ASE). We also present theoretical models for rare-earth-codoped fibre lasers and amplifiers, in which the donor ions absorb a significant fraction of the pump power, delivering it to the acceptor ions through- an efficient energy transfer mechanism. In particular, we consider the rate-equation model for the Er3+-Yb3+ codoped system with and without Er3+ clustering, which takes into account energy transfer between the (donor) Yb3+ and the (acceptor) Er3+ ions. We also derive rate-equations for the Nd3+-Yb3+ codoped system that includes energy transfer between Nd3+ and Yb3+ ions, interactions among Nd3+ ions, single-ion transitions, and ASE due to Nd3+ and Yb3+ ions. An approximate, quasi-analytical solution to the model equations is derived for CW lasers. Previous theoretical works on short pulse amplification in doped fibres were derived mainly from the generalized nonlinear Schroedinger equation in the time domain. Furthermore, works on high-power rare-earth-codoped fibres have been limited mainly to CW Er3+-Yb3+ codoped fibre lasers and amplifiers. Using our new formulation, we extend previous works on short pulse amplification in doped fibres to the mixed spectrotemporal domain, allowing the full spectral resolution of both the incident pulse and the fibre parameters. We also apply our theoretical models to extend previous works on short length Er3+-Yb3+ codoped fibre amplifiers (EYDFA) to the quasi-CW regime and to study CW Nd3+-Yb3+ codoped fibre lasers (NYDFL). To this end, we solve numerically the rate-propagation equations and investigate various system design parameters of practical interest. The effects of the most important pulse and fibre parameters (e.g., incident pulse wavelength, pulse peak power, pulse chirp, fibre length and pump power) on the spectral and temporal characteristics of short amplified pulses are studied, both in the anomalous and in the normal fibre dispersion regimes. We analyze transient dynamic effects (e.g., amplifier stability) in short length, high-concentration, all-optical gain-clamped EYDFAs, in response to input signal modulations. We also study the effects of key parameters (e.g., fibre length, pump and laser wavelengths, output mirror reflectivity and dopant concentrations) on the output power, efficiency and optimal design (e.g., optimal fibre length and optimum dopant concentrations) of high-power CW NYDFLs. Key words: Optical fibre theory, optical fibre amplifiers, optical fibre dispersion, optical pulse amplifiers, Raman scattering, gain clamping, wavelength-division-multiplexing (WDM), optical fibre lasers, Erbium (Er), Ytterbium (Yb), Neodymium (Nd).
45
Krishnaswamy, Madhu. "Modeling and fabrication of rare-earth-doped integrated optical waveguide amplifiers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0001/NQ29057.pdf.
Full text
46
Ireland, Terry G. "Precipitation techniques and characterisation of rare earth element doped phosphor materials." Thesis, University of Greenwich, 2008. http://gala.gre.ac.uk/6195/.
Full textAbstract:
The work in this thesis had two main aims. The first aim was to study the use of a number of precipitation methods to control the size and morphology of precursor phosphor materials for potential applications in a new generation of high definition and field emission displays. The morphological and luminescent characteristics of these precursor phosphor materials were studied after they were annealed to form their respective luminescent oxides using electron microscopy and light measuring techniques. The first set of experiments presented describes the development of a range of spherical submicron europium-doped yttrium oxide phosphor particles and their optimisation for use in the aforementioned applications. A homogeneous precipitation technique exploiting a hydrothermal decomposition of urea that provides hydroxycarbonate phosphor precursor ligands is at the centre of this work. In the presence of rare earth element nitrates the hydroxycarbonate ligands form spherical phosphor precursor particles that after annealing yield the luminescent oxides. This is followed by the presentation of a novel synthetic method using a micellar phase of rare earth element chlorides, after annealing, yielding europium-doped yttrium oxide. This method produces a variety of morphologies with crystallites as small as a few nanometres and up to hundreds of nanometres. Next is described a new precipitation method using ammonia and carbon dioxide gases that are introduced in a controlled manner into a solution of rare earth element chlorides at room temperature. Rare earth element hydroxycarbonates rapidly precipitate upon supersaturation, yielding a range of morphologies and particles sizes. The second aim of the thesis was to prepare a novel range of three-dimensional photonic band gap materials composed of conventional phosphor materials.
47
Ben, Liubin. "Synthesis and Characterisation of Rare-earth and Calcium Doped BaTiO3 Ceramics." Thesis, University of Sheffield, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522567.
Full text
48
Probst, Sebastian [Verfasser]. "Hybrid quantum system based on rare earth doped crystals / Sebastian Probst." Karlsruhe : KIT Scientific Publishing, 2016. http://www.ksp.kit.edu.
Full text
49
Gonçalves, Tássia de Souza. "Rare earth doped fluorophosphate glass and glass-ceramics: structure-property relations." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-30102018-100600/.
Full textAbstract:
Rare earth RE3+ doped fluorophosphates glasses and glass ceramics are among the most promising candidates for high efficiency laser generation in the near-infrared spectral region. Glass ceramics are polycrystalline materials of fine microstructure that are produced by the controlled crystallization (devitrification) of a glass. By developing fluorophosphate base glasses with appropriate compositions and by controlling crystal nucleation and growth in them, glass ceramics with special properties can be fabricated combining the advantages of fluorides (low phonon energy, low refractive indexes, extensive optical window, lower hygroscopicity) and oxides (high chemical and mechanical stability and high dopant solubility), resulting in enhancement of the RE3+ emissive properties. In this study, we present the synthesis by melting/quenting and structural/spectroscopic investigation of new glasses and glass ceramics with composition 25BaF225SrF2(30-x)Al(PO3)3xAlF3(20-z)YF3: zREF3, where x = 15, 20 or 25, RE = Er3+ an/or Yb3+ and Nd3+. A detailed structural investigation of a series of this glasses has been conducted, using Raman, solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopies.Vidros e vitrocerâmicas fluorofosfatos dopados com íons terras raras (TR3+) estão entre os candidatos mais promissores para a geração de laser de alta eficiência na região espectral do infravermelho próximo. As vitrocerâmicas são materiais policristalinos com microestrutura bem definida obtida a partir da cristalização controlada do vidro base. Desenvolvendo vidros base de fluorofosfato com composições apropriadas e controlando a nucleação e crescimento de cristais, vitrocerâmicas com propriedades especiais podem ser fabricadas combinando as vantagens dos fluoretos (baixa energia de fônons, baixos índices de refração, janela ótica extensa, baixa higroscopicidade) e óxidos (alta estabilidade química e mecânica e alta solubilidade dopante), resultando no aumento das propriedades emissoras dos íons TR3+. Neste estudo, apresentamos a síntese por fusão/resfriamento e investigação estrutural/espectroscópica de novos vidros e vitrocerâmicas com composição 25BaF225SrF2(30-x)Al(PO3)3xAlF3(20-z)YF3: zREF3, onde x = 15, 20 ou 25, RE = Er3+ an / ou Yb3+ e Nd3+. Uma investigação estrutural detalhada de uma série destes vidros foi conduzida utilizando espectroscopias Raman, de ressonância magnética nuclear de estado sólido (RMN) e de ressonância paramagnética eletrônica (EPR).
50
Wang, Jing. "Investigation of rare earth-doped ceramics as thermal barrier coating materials." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/37230/.
Full textAbstract:
Increasing operating temperatures of gas engines is an effective approach to further improve thermal efficiency. But the ceramic top-coat (conventional 7-8 wt% yttria-stabilised zirconia, 7-8YSZ) in thermal barrier coatings (TBCs) cannot afford application temperatures above 1250 oC, the main reason of which is the accelerated phase transformation, due to quick cation diffusion. In addition, 7-8YSZ has relatively large thermal conductivity, small coefficient of thermal expansion (CTE) and large oxygen ion diffusivity. The relatively small CTE could create the mismatch between ceramic top-coat and metallic bond coat in thermal barrier coatings (TBCs), which can generate strain or stress at the interface to cause the spallation of TBCs. The oxygen atoms for the formation of thermally grown oxides (TGO) in TBCs come from ceramic top-coat, but the thickness of TGO cannot exceed 10 μm in order to avoid the spallation of TBCs. Therefore, it is extremely important to find new ceramic candidates to replace 7-8YSZ and to be used at elevated temperatures. According to these critical criteria of ceramic top-coat, three ceramic candidates were chosen and studied, which are stannate with pyrochlore crystal structure, erbia-based oxides stabilised zirconia and yttrium aluminium garnet. All candidates were synthesised using a sol-gel method. Crystalline phases of all as-synthesised powders were characterised by X-ray diffraction (XRD). Thermal conductivity, coefficient of thermal expansion (CTE), phase stability, chemical compatibility were also studied. Furthermore, molecular dynamics (MD) simulations were used to calculate thermal conductivity and CTE, and to analyse and explain experimental results. Pyrochlore has excellent phase stability and relatively low thermal conductivity, but relatively small CTE. From the consideration of crystal structure and ion radius, La3+ doped Yb2Sn2O7 ceramics with pyrochlore crystal structures are investigated as one TBCs candidate material. As La3+ and Yb3+ ions have the largest radius difference in lanthanide group, La3+ ions are expected to produce significant disorders by replacing Yb3+ ions in cation layers of Yb2Sn2O7. Both experimental and computational XRD data and phase analysis are carried out and good agreement has been obtained. The lattice constants of solid solution (LaxYb1-x)2Sn2O7 (x=0.3, 0.5, 0.7) increase linearly when the content of La3+ is increased. The thermal properties (thermal conductivity and coefficients of thermal expansion) have been compared with the traditional 8 wt% yttria-stabilised zirconia (8YSZ) and La2Zr2O7 (LZ). La3+ doped Yb2Sn2O7 exhibits lower thermal conductivities than un-doped stannates and thermal conductivity deceases with the increase of doping concentration, but it reaches a minimum value when x=0.5 then increases again. Thus among (LaxYb1-x) 2Sn2O7 compositions, (La0.5Yb0.5)2Sn2O7 exhibits the lowest thermal conductivity (0.851 W•m-1•K-1 at room temperature), which is much lower than that of 8YSZ (1.353 W•m-1•K-1). Moreover, it possesses a high coefficient of thermal expansion (13.530×10-6 K-1 at 950 oC). In addition, the simulation results obtained from the MD simulations, indicate that the variation of thermal conductivity with increasing doping concentration in solid solution (LaxYb1-x) 2Sn2O7 (x=0.3, 0.5, 0.7) is independent of external effects, like porosity, grain size and grain boundary. Stabilised zirconia is still one of the most popular TBCs top-coat systems, but new stabilisers are still under-seeking. For stabilised zirconia, to improve thermal phase stability and further reduce thermal conductivity are the most urgent challenges. Erbia-based rare earth oxides stabilised zirconia is studied at 1400 oC. XRD patterns confirmed that erbia-stabilised zirconia have the non-transformable phase. Thermal conductivity decreases and thermal phase stability is improved with the increase of the erbia content. Mono- or bi-rare earth oxides doped erbia-stabilised zirconia is studied to further reduce thermal conductivity due to creating cluster defects. The influences on thermal phase stability produced by different dopants are also analysed. The chemical formulas of Mono- or bi-rare earth oxides doped erbia stabilised zirconia are Er0.05R0.05Zr0.9O1.95 (R=Yb, Gd and Dy) and Er0.04R0.04 R*0.04Zr0.88O1.94 (R+R*=Yb+Dy, Yb+Gd and Dy+Gd), respectively. Thermal conductivities of Er0.05R0.05Zr0.9O1.95 (R=Yb, Gd and Dy) and Er0.04R0.04 R*0.04Zr0.88O1.94 (R+R*=Yb+Dy, Yb+Gd and Dy+Gd) are lower than that of conventional 8YSZ and also they exhibit comparable CTEs to 8YSZ. Importantly, it is found that the thermal phase stability is dependent on the tetragonality, c/a√2 ratio. When the c/a√2 ratio decreases from 1.010 to 1.006 for mono- or bi-rare earth oxides doped erbia, the thermal phase stability is better. Yttrium aluminium garnet (YAG) is also an attractive candidate as thermal barrier material, due to its relatively low thermal conductivity, low oxygen diffusivity and good phase stability at elevated temperatures. YAG has a complex crystal structure, in which Y3+ ions locate in dodecahedra and Al3+ ions in octahedra and tetrahedra. Replacing the host cations with rare earth elements can cause the distortion of polyhedrons which influences the thermal properties of YAG. Because the space inside the octahedra are relatively small, Yb3+ ions which have the smallest ionic radial sizes in the lanthanide series, have been selected and doped on dodecahedral and octahedral sites to investigate the effects on thermal conductivity and thermal expansion. The variation of lattice constant indicates that Yb3+ ions are located on the dodecahedra or octahedra. In addition, when Yb3+ ions replace Al3+ ions on octahedral sites, thermal conductivity at room temperature is dramatically reduced and the coefficient of thermal expansion is over 10×10-6 K-1 at high temperatures, which results from the expansion of octahedra due to Yb3+ ions with much larger radii compared with the host cations (Al3+ ions). On the contrary, replacing Y3+ ions with Yb3+ ions in dodecahedra, thermal conductivity gradually reduces but the coefficient of thermal expansion is smaller, due to the relatively small ionic radii of Yb3+ ions causing the contraction of the dodecahedra. Additionally, it is found that the largest decrease in thermal conductivity results from phonon scattering caused by the large atomic mass difference rather than the relatively small difference in ionic radius.