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1
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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
3
Shen, Shaoxiong. "New rare earth ion-doped hosts for broadband fibre amplifier." Thesis, University of Leeds, 2000. http://etheses.whiterose.ac.uk/2379/.
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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.
4
Sakr, Hesham. "Towards mid-infrared fibre lasers : rare earth ion doped chalcogenide glasses and fibres." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33338/.
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This Project is aimed at developing rare earth ion doped chalcogenide glasses targeting mid-infrared (MIR) fibre lasers, emitting in the wavelength region 4 - 5 μm. The work reported in this thesis has two objectives: (i) a study of the Ge-As-In-Se glass system when doped with a single species of rare earth (RE) ions, i.e. praseodymium (Pr3+) or cerium (Ce3+), or when co-doped with two rare earth ion species: Pr3+ and Ce3+, and (ii) a study of the effect of replacing a gallium (Ga) additive with an indium (In) additive on the physical and optical properties of the undoped and Pr3+ doped Ge-As-(Ga/In)-Se glasses and fibres. The MIR, i.e. 3 - 25 μm wavelength, offers to advance many photonics areas including bio-medical imaging spectroscopy for human tissue sensing in vivo for early cancer diagnosis. Low loss RE-ion doped MIR fibre lasers are potential pumps for MIR supercontinuum generation (SCG) sources for a compact MIR broadband device. Also, MIR fibre narrowband lasers offer potential new wavelengths for laser medical surgery. To date, there are no MIR rare earth ion doped glass fibre lasers emitting at wavelengths ≥ 4 μm. Selenide (Se)-based glasses, a member of the chalcogenide glass family, are known for their wide transparency up to 12 μm and good rare earth ion solubility. In the Project, an additive to the Ge-As-Se glass system of indium or gallium is considered to help decluster the rare earth ions and increase their solubility in the as-prepared Pr3+ doped Ge-As-(Ga/In)-Se glasses. However, an indium additive is concluded here to achieve a lower rare earth ion solubility limit than that obtained using the equivalent gallium additive in the Ge-As-(Ga/In)-Se glass systems. On the other hand, the photoluminescent intensity is concluded here to be approximately doubled when using an indium additive in Pr3+ doped Ge-As-In- Se, compared to the analogous gallium glasses. Furthermore, the decay lifetime, at the same emission wavelength of 4.7 μm, is found to be longer in the Pr3+ doped Ge-As-In-Se glasses when compared to the Pr3+ doped Ge-As- Ga-Se glasses. Overall, for a singly-doped Ge-As-In-Se glass system, Pr3+ offer wide photoluminescence spectral emission in the range 3 - 6 μm, which promotes this type of glass fibre as an active source for MIR laser emission in the target range of 4 - 5 μm. However, the photoluminescent decay lifetime, at 4.7 μm, of Pr3+ doped Ge-As-In-Se is concluded to decrease substantially with the number of thermal processes invoked to fabricate the glass-based fibres; a lifetime of 7 - 9 ms measured on the as-prepared fibres is compared to the decay lifetime of 9 - 10.1 ms that were found in the bulk glasses. Alternatively, the addition of Ce3+ in the Ge-As-In-Se glass system is concluded to offer a larger absorption cross-section than that of the Pr3+ in the wavelength range 3.5 - 5 μm. Co-doping the Pr3+ / Ce3+ in Ge-As-In-Se in order to enhance the MIR photoluminescence emission in the range 3 - 6 μm is also investigated. It is concluded that rare earth ions, in particular Ce3+ and / or Pr3+, doped chalcogenide glass fibres based on the Ge-As-In-Se glass system, developed through this Project, are strong candidates towards achieving MIR fibre lasers.
5
Padhye, P. "Study of tunable optical properties of lanthanide-ion-doped rare earth phosphors and their applications." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2017. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/5892.
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Lovrić, Marko [Verfasser], Dieter [Akademischer Betreuer] Suter, and Philippe [Akademischer Betreuer] Goldner. "Hyperfine characterisation and enhanced optical to spin storage in rare earth ion doped crystals / Marko Lovrić. Betreuer: Dieter Suter. Gutachter: Philippe Goldner." Dortmund : Universitätsbibliothek Dortmund, 2012. http://d-nb.info/1098312368/34.
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Car, Benjamin. "Étude de la dynamique des spins autour d'un ion erbium pour le développement de mémoires quantiques." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS251/document.
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Aux basses températures, les matrices dopées aux ions terre-rare sont des systèmes prometteurs pour la réalisation de mémoires quantiques. Parmi elles, le système Er³⁺:Y₂SiO₅ a l'avantage de posséder une transition aux longueurs d'onde Télécom, adaptée aux réseaux de communication actuels. Cependant, aucun stockage quantique n'a pu être réalisé de manière efficace durant un temps suffisamment long dans ce matériau. L'objectif de cette thèse est de mieux comprendre les interactions limitant la cohérence du système aux faibles champs magnétiques. Dans ce cadre là, les interactions dominantes sont les basculements réciproques entre deux spins électroniques opposés des ions erbium et l'interaction super-hyperfine entre ces spins et les spins nucléaires des ligands yttrium. J'ai calculé la force et les caractéristiques de ces deux couplages dipolaires en incluant la grande anisotropie de la matrice Y₂SiO₅. J'ai alors pu vérifier l'effet de cette anisotropie sur les basculements réciproques des spins des ions erbium à l'aide de deux techniques optiques, le creusement de trou spectral et l'excitation transitoire. Le taux de ces basculements est maximisé lorsque le champ magnétique est orienté perpendiculairement à l'axe principal du tenseur caractérisant le spin effectif. Il augmente globalement comme le carré de la concentration en ions dopants et diminue avec le champ magnétique. Enfin, j'ai pu mesurer les caractéristiques des interactions super-hyperfines par le biais des modulations d'une décroissance d'écho de photon qu'elles provoquent. Il existe une configuration particulière où un couplage sélectif intervient entre les ions erbium et un unique yttrium de leurs environnements. Au contraire, le couplage à un nombre important d'ions ligands est responsable de la chute du temps de cohérence pour des champs magnétiques inférieurs à la dizaine de mTAt low temperatures, rare-earth doped matrices are promising supports for the development of quantum memories. Among them, Er³⁺:Y₂SiO₅ is well adapted to the current communication networks because of its transition at Telecom wavelength. However, quantum storage has a very limited efficiency and a short duration in this material. In this thesis, I study the interactions that hinder the coherence at low magnetic fields. In this regime, the dominant processes are flip-flops between opposite electronic spins of erbium ions and the super-hyperfine interaction with nuclear spins of yttrium ligands. I have included the strong anisotropy of the Y₂SiO₅ matrix in the calculation of these two dipolar interactions. In order to check the anisotropy of the flip-flops between erbium spins, I have used two different optical techniques : spectral hole-burning and transient excitation. I have showed that their rate is maximum when the magnetic field is perpendicular to the principal axis of the effective spin tensor. Moreover, the flip-flop probability globally increases as the square of the doping concentration and as the inverse of the field. Then I have also checked the calculations of super-hyperfine interactions by measuring photon echo modulations. I have found a particular situation where an erbium ion is strongly coupled to a single yttrium. On the contrary, the coupling to several ligands at very low magnetic fields drastically reduces the coherence time
8
Townsend, Janet E. "The development of optical fibres doped with rare-earth ions." Thesis, University of Southampton, 1990. https://eprints.soton.ac.uk/400704/.
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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.
9
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.
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Grigorova, A. V., V. K. Klochkov, N. S. Kavok, and O. O. Sedyh. "Colloidal Nanocrystalline Luminophors Doped by Rare-earth Ions for Biological Testing." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34997.
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nReVO4:Eu3+ (Re Gd, Y, Sm, La) luminescent nanocrystals of different shape and size from 2 to
300 nm have been synthesized. Luminescence of nReVO4:Eu3+ nanocrystals are effectively excited under
UV and visible irradiation. By means of luminescence microscopy and luminescence microspectroscopy it
has been revealed that spherical nanocrystals with an average diameter from 3 to 20 nm tend to accumulate
mainly in the isolated rat hepatocyte nuclei. Spherical nGdYVO4:Eu3+ nanocrystals are efficient inorganic
markers and can be used in systems of selective delivery of substances into the cell nucleus.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34997
11
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.
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Al-Maghrabi, Mufied Mahmoud. "Thermoluminescence spectra from sulphates, fluorides and garnets doped with rare earth ions." Thesis, University of Sussex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366054.
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Luminescence measurements have been applied to three different structures namely, sulphate, fluorides and YAG. In all cases the RE doping suppresses the intrinsic emission and results in intense luminescence characteristic of the RE dopant. Additionally, in double doped samples, or contaminated ones, the TL data show that each dopant defines a glow peak, which is displaced in temperature relative to the others. Examples of this were discussed for CaS04:Ce,Mn; YAG:Nd,Tb,Cr,Mn; BaF2:Ho,Ce and BaF2:Tm,Ce. The data are discussed in terms of an energy transfer model between different parts of extended defect complexes which encompass the RE ion and the lattice defects. Calcium sulphate doped with Dy define a TL peak near 200°C suitable for radiation measurements, but when co-doped with Ag the TL peak move to higher temperatures with minor effects on the peak sensitivity. In Ce,Mn double doped samples, the peak temperatures differ by -7°C between the Ce and Mn sites. The TL glow curves from alkaline earth fluorides are complex and contain several overlapping peaks. Curve fitting show that the peak maxima below room temperature are insensitive to the RE dopant. Additionally the host material has a modest effect on the peak positions. Above room temperature each dopant provides a TL curve specific to the added RE ion and do not show common peaks. Concentration has many effects on the resultant glow curve, and even at the lowest concentration used here (0.01%) there is evidence of cluster formation. Samples with high RE content show low values of the frequency factor consistent with the energy transfer model in that the emission from RE-RE cluster dominates over the emission from direct charge recombination within the defect complex. The effect of concentration and the TL mechanism operating below room temperature are also discussed. Luminescence signals from the near surface of YAG:Nd (via CL) were contrasted with those from the bulk material via RL. Results indicate that the outer few micron layers differ significantly in luminescence response from the bulk crystal. The differences were ascribed to result from solvents that enter the YAG lattice during the growth stage or subsequently from cleaning treatments via the dislocations caused by cutting and polishing. Additionally, the growth stage may include gases from the residual air in the growth furnace trapped into the YAG lattice. In each case there is a discontinuity in luminescence intensity and/or emission wavelengths at temperatures which mach the phase transitions of the contaminants. At the transition temperature there will be a sudden pressure change and this will induce surface expansion or bulk compression. The differences between the two cases were detected by the alternatives of CL and RL excitation, where the Nd or Er lines have moved in opposite directions. The detection of such low concentrations of solvents/trapped gases by luminescence is extremely difficult due to experimental limitations. Hence their role in luminescence generation is normally ignored.
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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/.
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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).
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Wells, Jon-Paul Renee. "Laser spectroscopy of alkaline earth flouride crystals doped with trivalent samarium and europium ions." Thesis, University of Canterbury. Physics and Astronomy, 1996. http://hdl.handle.net/10092/5528.
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Alkaline earth fluoride crystals doped with Sm3+ and Eu3+ ions have been investigated by polarised laser selective excitation, Zeeman infrared and optical absorption. These studies identify four main centres for CaF2:Sm3+ and CaF2:Eu3+ crystals. They are a single RE3+ -F- pair having C4v symmetry, a near-cubic symmetry centre with a non-local charge compensator and two cluster centres. In CaF2:Sm3+ crystals, the cluster centres are entirely non-radiative due to efficient cross-relaxation processes between the constituent Sm3+ ions. These centres have been investigated by codoping with additional RE3+ ions. Efficient 4G 5/2 (Sm3+)→5D0(Eu3+) energy 2 transfer has been observed for the heterogeneous cluster centres in CaF2:Sm3+: Eu3+. In SrF2 crystals doped with Sm3+ and Eu3+ ions, the dominant centre consists of a single RE3+ -F- pair of C4v symmetry. In SrF2: Eu3+ a weak C3v symmetry centre has been observed which is analogous to the dominant centre in BaF2: Eu3+ crystals.
Upconversion fluorescence has been observed for the dominant spectroscopic centres in CaF2, SrF2 and BaF2 crystals doped with Eu3+. This is assigned as a sequential absorption process with 5D0 as the intermediate state. Enhancement of the upconverted fluorescence is observed for excitation of the 7F1 →5D0 transitions at room temperature.
High-resolution infrared absorption has been employed to study hyperfine structure of sharp absorption lines in CaF2 and SrF2 crystals doped with Pr3+, Tb3+ and Ho3+. An interesting hyperfine pattern is observed for CaF2:Ho3+ in which the hyperfine structure of a doublet state has been perturbed by the presence of two nearby singlet states. This pattern has been successfully analysed using the hyperfine interactions between these excited states.
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Jadwisienczak, Wojciech M. "The Luminescence prosperties of the wide bandgap nitrides doped with rare earth ions and gallium nitride doped with conventional isoelectornic impurities." Ohio University / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1179158888.
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Jadwisieńczak, Wojciech M. "The luminescence properties of the wide bandgap nitrides doped with rare earth ions and gallium nitride doped with conventional isoelectronic impurities." Ohio : Ohio University, 2001. http://www.ohiolink.edu/etd/view.cgi?ohiou1179158888.
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Cansin, Badan. "Microwave Assisted Synthesis Of Rare Earth Ions Doped Lanthanumorthoborate, Their Characterizations And Investigations Ofluminescence Properties." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614361/index.pdf.
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Lanthanum orthoborate (LaBO3) has aroused interest of scientists for many
decades because of their remarkable properties and potential applications. They
provide favorable magnetic properties for various applications. Additionally,
they possess high VUV transparency and exceptional optical damage when they
compose with rare earth elements.
This study comprises the synthesis of pure lanthanum orthoborate, europium,
dysprosium and terbium doped lanthanum orthoborate by two methods with
v
three fuels, citric acid, glycine and urea. LaBO3 has already been synthesized by
various methods, howeverin this work, two alternative roads are suggested, microwave assisted method and sol-gel microwave assisted method. The second task of the work is to find out the best luminescent product by altering the synthesis conditions, type of the doping material and the doping amount of the rare earth element. For the microwave assisted combustion method, urea was used as a fuel. After synthesis in the microwave oven, further heating up to 950°
C was performed. For the microwave assisted sol-gel method, citric acid and glycine were used. After obtaining the gel mixture, the product is synthesized in the microwave oven at 1200 W for ten minutes. For this route, again 950°
C heating for 2 hours was performed. Powder X-ray diffraction method was employed for the characterization of the material. The morphological properties of doped and un-doped materials were studied by SEM (Scanning Electron Microscope) and TEM (Transmission Electron Microscope). Besides, FT-IR (Fourier Transform Infra red) spectrometry analyses were performed to detect the differences in the bond structure and also to identify the corresponding bands. Luminescence studies were performed to detect the best emission intensities by using Fluorescence spectroscopy. The XRD patterns confirmed that lanthanum orthoborate production was successful by three precursors. The space group is Pnma, and the crystal system is orthorhombic with the unit cell dimensions
a= 5.8761(1)
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Almotari, Masaed Moti M. "Fabrication and Characterisation of Zinc Oxide Thin Films Singly doped With Trace amounts of Rare Earth Materials." Thesis, University of Canterbury. Department of Physics and Astronomy, 2013. http://hdl.handle.net/10092/8441.
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Two sets of nanostructured Zinc Oxide (ZnO) thin films doped with varying nominal concentrations of rare earth (RE) ions were prepared by pulsed laser deposition (PLD). One set was doped with europium ions (ZnO:Eu³⁺) while the other was doped with erbium ions (ZnO:Er³⁺). The nominal concentration of RE ions ranged from 0.025 to 5 atomic %. The produced films were structurally, morphologically and optically characterised using different techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), combined excitation and emission spectroscopy (CEES) and X-ray photoelectron spectroscopy (XPS).
All films were found to possess a single-crystal hexagonal structure and were strongly oriented along the c-axis. However, the crystallinity of the investigated films seemed to deteriorate as the concentration of the rare earth ions increased. This deterioration is assumed to be due to the local distortion of the ZnO structure (host material) caused by the insertion of the relatively large RE ions, hence inducing structural stresses.
Importantly, XRD measurements showed that no other crystalline phases related to europium or erbium, such as Eu₂O₃ or Er₂O₃, were observed. Surprisingly, the ZnO lattice constant (c) tended to become smaller as more RE³⁺ ions were added to the films. An explanation is offered whereby this observation can be taken as further evidence that Zn²⁺ ions were successfully substituted by RE³⁺ ions.
Interestingly, doping ZnO films with RE³⁺ ions of a nominal concentration of ≥ 0.5 at.% or higher exhibited a drastic effect on the optical properties of the host matrix (ZnO) in which the near band edge luminescence characteristic of pure ZnO completely disappeared.
According to SEM images, morphological changes also occur as dopant concentrations increase. Well-defined grains (crystallites) were clearly seen in films doped with ˂ 0.5 at.% of RE ions. However, these grains became hardly distinguishable at higher RE ion concentrations.
Typical intra-4f shell transitions of RE³⁺ ions were observed when these ions were non-resonantly excited with UV radiation, indicating that energy had been efficiently transferred from ZnO to the rare earth ions. A plausible physical mechanism for this energy transfer is proposed.
The radiative optical centres of rare earth ions were studied by CEES. In these experiments, both sets of films exhibited multiple optical sites. ZnO:Eu³⁺ thin films were found to have two distinct optical sites with differing site symmetries, whereas up to four optical sites were detected in the ZnO:Er³⁺ films.
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Al-Ahmadi, Ahmad Aziz. "Fabrication and characterization of ZnO film by spray pyrolysis and ZnO polycrystalline sintered pellets doped with rear earth ions." Ohio : Ohio University, 2003. http://www.ohiolink.edu/etd/view.cgi?ohiou1175017625.
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Al-Ahmadi, Ahmad. "Fabrication and characterization of ZnO film by spray pyrolysis and ZnO polycrystalline sintered pellets doped with rear earth ions." Ohio University / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1175017625.
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Katayama, Yumiko. "Optical and photo-electric studies on quantum cutting and persistent luminescent phosphors doped with rare-earth and transition-metal ions." Kyoto University, 2014. http://hdl.handle.net/2433/188818.
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Kyoto University (京都大学)0048
新制・課程博士
博士(人間・環境学)
甲第18380号
人博第693号
新制||人||166(附属図書館)
25||人博||693(吉田南総合図書館)
31238
京都大学大学院人間・環境学研究科相関環境学専攻
(主査)教授 田部 勢津久, 教授 加藤 立久, 教授 杉山 雅人, 教授 森本 芳則, 教授 山本 行男
学位規則第4条第1項該当
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Magne, Sylvain. "Etat de l'art des lasers à fibre : étude d'un laser à fibre dopée ytterbium et spectroscopie laser de fibres dopées." Saint-Etienne, 1993. http://www.theses.fr/1993STET4027.
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Cette thèse montre l'intérêt de l'amplification optique et des lasers à fibres dopées par des ions de terres-rares pour l'instrumentation et les capteurs à fibres optiques. Nous détaillons les avantages et les inconvénients d'une telle technologie placée dans son contexte d'optique intégrée, ainsi que ses perspectives d'utilisation. Apres rappel de la théorie de la propagation guidée dans les fibres optiques, les technologies permettant de réaliser des fibres optiques dopées sont décrites. Une étude comparative des méthodes d'analyses de préformes et de fibres dopées permettant de déterminer leurs profils de guidage et de dopage est également présentée. Le comportement amplificateur des fibres optiques dopées est ensuite décrit théoriquement en insistant sur les limites fixées par l'élargissement inhomogène de la transition laser. L'évolution du gain intégré de la fibre est mise en évidence en fonction des paramètres influants (longueur, rayon de dopage. . . ) en soulignant l'intérêt d'un rayon de dopage optimisé. Le seuil d'accrochage du laser est modélisé par des équations et des abaques sans dimension déterminant la longueur de fibre optimale en fonction des pertes de la cavité laser. La conception générale du laser à fibre est ensuite synthétisée et les technologies des composants d'optique intégrée adaptés à la fibre amplificatrice le constituant sont comparées. Les techniques expérimentales concernent principalement l'étude de l'accordabilité par excitation sélective de sites et de la limitation du gain par émission stimulée sur la transition de pompage induisant une absorption résiduelle non saturable ; l'étude des effets de transferts dans les fibres dopées par luminescence coopérative : l'étude d'un procédé de changement de valence par irradiation y conduisant à une réduction des ions uranium placés en matrice verre fluoré (zblan) ; la démonstration d'un effet laser à trois niveaux, fonctionnant en régime continu et en contre-réaction externe par réseau
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SENE, FRANK F. "Sintese e caracterizacao de vidros niobofosfato de bario e potassio para aplicacoes como matriz hospedeira de ions de terras raras." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10990.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Cao, Kanyu. "Crystal-field splitting of Er 3+in ZnO and experimental observations." Ohio : Ohio University, 1997. http://www.ohiolink.edu/etd/view.cgi?ohiou1177608455.
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Jouanno, Jean-Marc. "Amplification optique dans des guides d'ondes réalises par échange d'ions dans des verres phosphates dopes par des terres rares." Grenoble INPG, 1995. http://www.theses.fr/1995INPG0013.
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Les amplificateurs optiques realises a partir de fibres dopees par des ions erbiums ont fait, grace a leurs bonnes performances, fortement evoluer les systemes de transmission a fibre optique. Nous en avons transpose les principes pour realiser des composants actifs d'optique integree sur des verres dopes par des terres rares. Cette technologie permet en effet une meilleure compacite et l'insertion simultanee de fonctions variees. Nous presentons les resultats obtenus dans des guides fabriques par echange ionique dans des verres phosphates. Les ions de terres rares, inclus des la synthese du materiau, y presentent des sections efficaces elevees et peuvent etre portes a une concentration de quelques pourcents en poids sans induire de reduction importante de la duree de vie de leur niveau metastable. Leurs caracteristiques spectroscopiques sont preservees apres l'echange d'ions. Les guides obtenus sont monomodes aux longueurs d'onde de pompe et de signal. Enterres, ils presentent de faibles pertes de propagation. En utilisant un dopage au neodyme, nous avons realise des amplificateurs a une longueur d'onde voisine de 1,05 micron ainsi qu'une source laser de faible seuil et de bonne efficacite de conversion de puissance. A l'aide d'un modele, nous avons pu estimer l'influence de l'addition de photons par transfert d'energie due a la concentration elevee de dopants. Nous avons egalement releve les gains autour de 1,3 micron. Ils sont limites par l'absorption a partir du niveau metastable et la faible probabilite d'emission. Nous avons modelise et realise des amplificateurs optiques a 1,5 micron en effectuant un co-dopage par des ions erbium et ytterbium. Nous avons mesure un gain net de 6 db sur des guides de 44 mm de long et nous avons pu mettre en evidence l'importance du confinement du mode guide. Ces resultats peuvent etre largement ameliores en optimisant les caracteristiques geometriques des guides et la concentration de dopants. Ils montrent que la technologie de l'echange d'ions constitue aujourd'hui une excellente marche d'acces a une utilisation plus large des dispositifs d'optique integree
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Hamaïdia, Abderrahmane. "Etude par dichroisme circulaire magnetique et par resonance paramagnetique electronique des centres colores dans caf : :(2) et srf::(2) dopes par des ions alcalins." Caen, 1987. http://www.theses.fr/1987CAEN2027.
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Etude des centres colores de quatre cristaux de fluorures alcalinoterreux dopes par li, na et k, colores additivement ou par rayonnement gamma. Mise en evidence de deux types de centre f::(a) par dichroisme circulaire magnetique. On a etudie ensuite le centre f::(2a) dont il a ete montre que l'analogie avec le centre f::(2) est trompeuse. D'autres centres ont ete etudies. On a pu comprimer l'identification de l'un d'entre eux comme f::(3a) ionise
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Venet, Caroline. "Développement d’un filtre spectral ultra résolu pour l’imagerie acousto-optique." Thesis, Paris Sciences et Lettres (ComUE), 2019. https://pastel.archives-ouvertes.fr/tel-02929318.
Full textAbstract:
L'imagerie médicale optique est limitée par la perte de résolution spatiale due à la diffusion des tissus biologiques. L'imagerie acousto-optique permet de palier à ce problème car elle utilise à la fois de lumière et des ondes ultrasonores. Par conséquent elle donne accès au contraste optique local en profondeur dans les tissus biologiques avec la résolution submillimétrique des ultrasons. Diverses méthodes interférométriques ont été développées pour détecter le signal acousto-optique, mais elles ne sont pas adaptées à l'imagerie in vivo. Au cours de cette thèse nous avons développé un filtre spectral intrinsèquement robuste à une mise en œuvre in vivo et capable de filtrer le signal de photons marqués. Ce filtre est basé sur le phénomène de creusement spectral, il est réalisé dans un cristal de grenat d'yttrium aluminium dopé au thulium (Tm:YAG) sous champ magnétique. Le manuscrit décrit d'abord la caractérisation du filtre spectral en condition d'imagerie. Ensuite nous présentons le montage expérimental qui a permis d' imager un gel diffusant simulant un tissu biologique. Dans la suite nous avons changé le laser principal et nous l'avons asservi en fréquence dans le but d'augmenter le niveau de maturation de la technologie. Enfin, la dernière partie du manuscrit détaille comment l'expérience a été compactée pour être apportée à un laboratoire pharmaceutique afin de lancer une campagne d'imagerie in vivoOptical imaging for Medicine is limited by the spatial resolution loss due to light scattering in turbid media. A hybrid imaging method called ultrasound optical tomography can overcome this botteneck. Indeed the simultaneous use of light and ultrasound gives access to optical contrast in depth within scattering medium with the ultrasounds resolution. Several interferometric methods have been developed in order to detect an acousto-optic signal. However, none of them is adapted to in vivo imaging. For this reason a filter created with spectral hole burning is of special interest. This thesis presents the development of an ultra-narrow filter based on spectral hole burning in a thulium doped yttrium aluminum garnet crystal (Tm:YAG) under magnetic field. The first part of the manuscript describes the characterization of the filter in the imaging setup. Next, the actual imaging of a scattering gel is described. The following part presents the change of the main laser and its frequency stabilization for technological maturation. The last part of the manuscript details how the experiment have been compacted to be bring in a pharmacetical laboratory in order to launch in vivo imaging trials
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Yan, Kunlun. "Rare-earth ion doped chalcogenide waveguide amplifiers." Phd thesis, 2018. http://hdl.handle.net/1885/162514.
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Chalcogenide glass waveguide devices have received a great deal
of attention worldwide in the last few years on account of their
excellent properties and potential applications in mid-infrared
(MIR) sensing and all-optical signal processing. Waveguide
propagation losses, however, currently limit the potential for
low power nonlinear optical processing, and the lack of suitable
on chip integrated MIR sources is one of the major barriers to
integrated optics based MIR sensing. One approach to overcome the
losses is to employ rare-earth ion doped waveguides in which the
optical gain can compensate the loss, in such a way that the
conversion efficiency of nonlinear effects is increased
significantly. For infrared applications, the long wavelengths
potentially attainable from rare-earth ion transitions in
chalcogenide hosts are unique amongst glass hosts. New rare-earth
ion doped chalcogenide sources in the MIR range could benefit
molecular sensing, medical laser surgery, defence etc. Despite
these promising applications, until now, no one has succeeded in
fabricating rare-earth ion doped chalcogenide amplifiers or
lasers in planar devices.
This work develops high quality erbium ion doped chalcogenide
waveguides for amplifier and laser applications. Erbium ion doped
As2S3 films were fabricated using co-thermal evaporation. Planar
waveguides with 0.35 dB/cm propagation loss were patterned using
photolithography and plasma etching on an erbium ion doped As2S3
film with an optimised erbium ion concentration of 0.45x1020
ions/cm3. The first demonstration of internal gain in an erbium
ion doped As2S3 planar waveguide was performed using these
waveguides. With different film deposition approaches, promising
results on intrinsic lifetime of the Er3+ 4I13/2 state were
achieved in both ErCl3 doped As2S3 films (2.6 ms) and radio
frenquency sputtered Er3+:As2S3 films (2.1 ms), however, no
waveguide was fabricated on these films due to film quality
issues and photopumped water absorption issues.
The low rare-earth ion solubility of As2S3 is considered the main
factor limiting its performance as a host. Gallium-containing
chalcogenide glasses are known to have good rare-earth ion
solubility. Therefore, a new glass host material, the Ge-Ga-Se
system, was investigated. Emission properties of the bulk glasses
were studied as a function of erbium ion doping. A region between
approximately 0.5 and 0.8 at% of Er3+ ion was shown to provide
sufficient doping, good photoluminescence and adequate lifetime
to envisage practical planar waveguide amplifier devices. Ridge
waveguides based on high quality erbium ion doped Ge-Ga-Se films
were patterned. Significant signal enhancement at 1540 nm was
observed and 50 % erbium ion population inversion was obtained,
in waveguides with Er3+ concentration of 1.5x1020 ion/cm3. To the
Author's knowledge, this is the highest level of inversion ever
demonstrated for erbium ions in a chalcogenide glass host and is
an important step towards future devices operating at 1550 nm and
on the MIR transitions of erbium ions in chalcogenide glass
hosts. Photoinduced absorption loss caused by upconversion
products in the waveguides is the remaining hurdle to achieving
net gain. Further research is needed to find suitable
compositions that possess high rare-earth ion solubility whilst
avoiding the detrimental photoinduced losses.
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Longdell, J. "Quantum Information Processing in Rare Earth Ion Doped Insulators." Phd thesis, 2003. http://hdl.handle.net/1885/47689.
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 computer’s 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. ¶ ...
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Marzban, Sara. "Rare-earth ion doped planar waveguides for integrated quantum photonics." Phd thesis, 2017. http://hdl.handle.net/1885/144606.
Full textAbstract:
This thesis presents a spectroscopic study of Pr3+ ions in a
novel passive waveguide architecture. To make this structure, the
high refractive glass TeO2 was selected as the thin film and it
was deposited on a Pr3+:Y2SiO5 crystal. In this waveguide, the
3H4 to 1D2 transition of Pr3+ ions were probed by the optical
evanescent field extending into the substrate. The main concern
in assessing the suitability of this material for quantum
information applications was ensuring that the coherence
properties of rare-earth ions, making them suitable for quantum
information purposes, are preserved in this architecture. After
which, to make low loss devices with these waveguides, efficient
coupling techniques had to be developed.
To prove that the coherence properties of the rare-earth ion
doped crystal were preserved, the critical parameters of
inhomogeneous linewidth, the absorption of the ions, the
coherence time and spin lifetimes of the Pr3+ ions were studied.
The inhomogeneous linewidth of evanescent coupled ions was about
10.0 GHz, which was consistent with the linewidth of bulk samples
with the same Pr3+ doping concentration (Hedges, 2011). The
absorption due to the evanescent coupling was 9.38 dB,
approximately 90% of what was expected with respect to the bulk
crystal with the same doping concentration. Therefore, despite
using the evanescent field, the absorption is high enough for
quantum memory applications.
An optical coherence time of about 121 microseconds was measured,
which corresponded to a homogeneous linewidth of about 2.6 kHz.
This is very close to bulk sample measurements of 111
microseconds, with the same temperature and doping concentration
(R. W. Equall, 1995). The spin state lifetime observed was about
9.8 s, which is also very close to the bulk sample measurement of
8.67 s (Mieth, 2016).
Initial Stark shifting experiments were performed to determine
whether the active ions in the substrate of the passive
waveguides could be electrically controlled by applying a small
voltage to electrodes on the thin film. In these experiments with
a voltage change of 100 mV, the measured holewidth broadening was
increasing about 0.55 MHz, which was similar to the calculated
values of 0.45 MHz. The Stark coefficient for site 1 was 51.6
kHzcm/V along the D2 axis of the crystal (site 1 will be
explained in Section 4.3). (F.R. Graf, 1997).
Prism coupling and grating coupling were used to couple light to
the ions in the substrate. Prism coupling is an easy and quick
method to couple light into a waveguide and observe the
properties of the system. However, grating coupling is much more
practical when moving towards building a device using this
method.
The measurements described above indicated that the properties of
ions interacting with the evanescent tail of the waveguide mode
were consistent with those of bulk ions. This investigation also
showed that depositing a glass thin film on a rare-earth ion
doped crystal was not affecting the good coherence properties of
the substrate. These results establish the foundation for large,
integrated, controllable and high performance rare earth ion
quantum waveguide systems.
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Naskar, Milan Kanti. "Preparation and Characterization of Rare Earth ion Doped Zirconia Fibres." Thesis, 1998. http://cgcri.csircentral.net/3310/.
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SRIVASTAVA, ASTHA. "MORPHOLOGICAL STUDIES ON RARE EARTH ION DOPED KCeF4 UPCONVERSION NANOPARTICLES." Thesis, 2018. http://dspace.dtu.ac.in:8080/jspui/handle/repository/16399.
Full textAbstract:
Upconversion nanoparticles (UCNPs) are the fluorophores of new era. They comprise the unique property of converting near IR radiation (low energy) into visible radiation(high energy) through nonlinear optical process. Currently the Upconversion nanoparticles have gain importance as alternatives to traditional fluorophores, as they provide for a large scope in the field of imaging and bio detection assays in both – applications of in-vivo and in-vitro techniques. Upconversion nanoparticles demonstrate extraordinary luminescent properties, including sharp emission band, low background signals, larger penetration depth in tissues, large stoke shifts and high protection from photo bleaching, hence making Upconversion nanoparticles elective hotspot for coming over current related constraints in conventional fluorescent probes. By and large for synthesizing Upconversion nanoparticles Rare Earth doped materials are utilized, due to their excellent properties like high chemical stability and low phonon energy. Upconversion nanoparticles provide a great opportunity for enhancing solar cell efficiency. Photovoltaic cells convert sunlight into electricity, using photovoltaic effect. They help us in generating one of the cleanest and abundant energy to fulfill the energy requirements. But, the photovoltaics current’s efficiency is hindered by the loss of photons of sub band gap during transmission. Photon upconversion provides us with the way to overcome the issue as the loss can be minimised by converting the transmitted photons of sub band gap into above band gap. Hence, by this technique the efficiency of solar cells could be increased. In the project wet chemical route is used to synthesize undoped KCeF4 and Rare earth doped KCeF4 samples. The β-phase (hexagonal phase) of UCNPs is obtained. The morphology, composition and structural properties of synthesized samples were observed and studied using X-Ray Diffraction, Fourier Transform infrared spectroscopy and Transmission electron microscopy. The obtained results confirm the formation of Upconversion nanoparticles.
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Tissue, Brian Max. "Energy transfer in rare earth ion clusters and fluorescence from rare earth doped La₁ ̣₈₅Sr₀ ̣₁₅CuO₄ superconductors." 1988. http://catalog.hathitrust.org/api/volumes/oclc/20189246.html.
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Han-LinHsu and 徐漢霖. "Synthesis and luminescent properties of rare-earth ion doped Li3Ba2La3(MoO4)8 phosphors." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/42024449184955709194.
Full textAbstract:
碩士國立成功大學
材料科學及工程學系碩博士班
98
Rare-earth (RE) ion doped phosphors, Li3Ba2La3-xREx(MoO4)8 (RE = Eu3+, Dy3+), were synthesized by a solid-state reaction process at 800C. The structural and photoluminescent properties of the prepared phosphors were investigated by X-ray diffraction, scanning electron microscopy, Raman scatter spectroscopy, UV-visible absorption, and photoluminescence (PL) spectroscopy. The aim of the research was to develop novel phosphors for the UV-LED to white light conversions. The experimental results showed that the dominant emissions of the Li3Ba2La3-xEux(MoO4)8 phosphors under the UV excitation (394 nm) were at 593 nm and 618 nm, originating from the electronic transitions between the trivalent RE states. Due to the high phonon frequency of the host lattice, the transitions from the emitting levels higher than 5D0 were not observed in the PL spectra. The above two observed emissions were due to the 5D0-＞7F1 (593 nm) and 5D0-＞7F2 (618 nm) transitions. In particular, the 5D0-＞7F2 emission was very strong and for the x=2.1 samples, its peak intensity was about 3.3 times more than the commercial phosphors ZnS:(Mn2+,Te2+). The CIE chromaticity coordinate of the Li3Ba2La0.9Eu2.1(MoO4)8 red emissions was calculated to be at (0.67, 0.33), which is almost the same as the standard red chromaticity of the NTSC system. In the Li3Ba2La3-xDyx(MoO4)8 (x=0.01-0.24) series, the dominant emissions under the UV excitation (388 nm) were from the 4F9/2-＞6H15/2 (blue) and 4F9/2-＞6H13/2 (yellow) transitions, and the intensity of the later was stronger. The mixture of all the emissions had the CIE chromaticity coordinates at (0.35, 0.40), which is at the yellowish-white color region.
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Chang, Yee-Cheng, and 張翌誠. "Synthesis and photo-luminescence properties of rare earth ion doped Li3Ba2Gd3(MoO4)8 phosphors." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/03947122628165768871.
Full textAbstract:
碩士國立成功大學
材料科學及工程學系碩博士班
97
The objet of this study is to synthesize Li3Ba2Gd3(MoO4)8 doped with various activators(Eu3+,Tb3+,Dy3+,Er3+,Sm3+), and the raw material had been mechanically activated by grinding in high energy vibromill followed by calcined at temperature of 900℃ for 12 h. By using XRD, SEM, PL spectra, and UV-visable spectra, the characterization of structure, morphology of powders and photo-luminescent properties of phosphors were analized. The dominant emission peaks of Li3Ba2Gd3(MoO4)8:Eu3+ phosphor are 5D0→7F1(591nm)、5D0 →7F2(614nm) which are originate from intra-4f transitions of excited state. The intensity of the emission from 5D0 to 7F2 is stronger than 5D0 to 7F1 and three times more than commercial phosphors, ZnS:Mn2+,Te2+ when Eu3+ concentration in x=2.4. The CIE chromaticity coordinates of red emission of the Li3Ba2Gd0.6Eu2.4(MoO4)8 phosphor is (0.67, 0.33) which is just at NTSC system standard red chromaticity. There are two regions in the excitation spectra of Li3Ba2Gd2 Tb1(MoO4)8 phosphor；one is assigned from 4f��5d transition in 200 to 300 nm, and the others are from intra-4f transitions in 350 to 500 nm. The dominant emission peak of Li3Ba2Gd2Tb1(MoO4)8 phosphor is 5D4��7F5 under excitation of 307nm. The CIE chromaticity coordinates of green emission of the Li3Ba2Gd2 Tb1(MoO4)8 phosphor is (0.25, 0.58). The the other series of green phosphor is Li3Ba2Gd2.95Er0.05(MoO4)8.Because its emission peaks locates in the light of green region, it has better color rendering index than Li3Ba2Gd2 Tb1(MoO4)8. However, the valence electrons are shielded by the 5s and 5p outer electrons, the valance electrons of trivalent rare earth ions are weakly affected by ligand ions in crystals, so the features of optical spectra of the most phosphors doped with trivalent rare earth, such as Li3Ba2Gd3(MoO4)8:Dy3+ and Li3Ba2Gd3(MoO4)8:Sm3+ is similar to those expected for free ions.
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Chen, Hou-Ren, and 陳厚仁. "Passive Mode Locking of Rare-Earth Ion Doped and Semiconductor Optical Amplifier Based Lasers." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/93059022344171104008.
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博士國立交通大學
光電工程研究所
101
In the thesis, we investigate two topics. First, we use a new fabrication method for single-walled carbon nanotube (SWCNT) and graphene oxide (GO) saturable absorbers (SAs) to sustain high-power illumination. Using a series of SAs incorporating different amounts of SWCNTs and GOs, we demonstrate mode-locking for Nd:GdVO4 and Nd:LuVO4 lasers in the 1 μm spectral range. Using SWCNT-SAs for Nd:GdVO4 laser, continuous-wave mode-locking (CWML) with a maximum output power of 3.6W at 1063 nm and high noise extinction of 61 dB has been achieved to give the highest pulse peak power of 3.6 kW and pulse energy of 30 nJ under 15-W pumping. For Nd:LuVO4 laser, GOSAs are used and CWML pulses with maximal output power of 3.89 W at 1065.7 nm are obtained under 15-W pumping to give the highest pulse peak power of 5.44 kW and pulse energy of 32 nJ, for which the high noise extinction of 66 dB has been achieved. To our knowledge, those are the highest reported output power for CWML lasers with SWCNT-SAs and GO-SAs, respectively. The measured nonlinear absorption of the SWCNT-SAs shows a modulation depth of ~3% with subpicosecond recovery time of ~630 fs. For GOSAs, the nonlinear absorption shows the modulation depth of about 2.54%, 4.14%, and 5.36% for GO amounts of 0.6, 0.9, and 1.25 mg. On the other hand, in order to insert the GOSAs between two fiber connectors, we fabricate the polymer-based GOSAs to be use in the all fiber laser system. Broadband graphene oxide/PVA films, which are used as saturable absorbers in the mode locking of erbium-doped and ytterbium-doped fiber lasers, have been demonstrated. They provide modulation depths of 2.95% and 6% at 1.06 μm and 1.55 μm, respectively. Stable self-starting mode-locked pulses are obtained for both lasers, confirming that graphene oxide does not have wavelength selectivity and is cost effective for 1.06-μm and 1.55-μm pulse generations. Second, we report the generation of passively harmonic mode-locked pulses using a 1.06 μm semiconductor optical amplifier (SOA) in a figure-eight laser configuration operated in the all-normal-dispersion regime. Different orders of harmonic mode locking can be obtained from 30 MHz to 12.02 GHz by tuning the injection current of the SOA from 80 to 660 mA together with the adjustment of polarization controllers. The highest pulse repetition rate increases almost linearly with the SOA current. As SOA current is set to 660 mA, we obtain the intracavity power of 46 mW at the highest repetition rate of 12.02 GHz, corresponding to the 1202th harmonic of the fundamental mode locking frequency. To our best knowledge, this is the lowest intracavity power to generate the highest repetition rate with a passively mode-locked laser in the all-normal-dispersion regime.
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Honnavar, Gajanan V. "Mixed Alkali Effect in Oxyfluoro Vanadate Glasses And The Effect of Rare Earth Ions on Oxyfluoro Tellurite Glasses - A Spectroscopic Study." Thesis, 2016. http://etd.iisc.ac.in/handle/2005/2667.
Full textAbstract:
The main motivation of this thesis is to study the long standing problem of mixed alkali effect (MAE) in oxyfluro vanadate glass systems from the point of view of structural arrangement and to investigate the effect of two rare earth ions, namely, erbium and europium on the structure of tellurium dioxide based glass. In glass science, it is well known that when one alkali in a glass matrix is gradually replaced by another alkali, leads to a non-linear variation in some of the physical properties. There are many a theories trying to explain this effect. Recently the renewed interest lies in explaining MAE in-terms of structural consideration. Rare earth (RE) ion doped glasses are of interest in a variety of applications in photonics because of the special optical properties exhibited by these materials. Atomic like f-f transitions of RE ions depend on the local environment of the these ions. A particular glass matrix may be able to bring out the optical properties of a RE ion better than the other matrix. In this regard structural characterization of a glass matrix with different RE ions for optical properties is of importance. Spectroscopic tech-niques are best suited to investigate structural arrangement in glasses and in this thesis we have used techniques like Raman, electron paramagnetic resonance (EPR), impedance, photoluminescence and UV- visible absorption spectroscopies.
The thesis comprises of five chapters and an appendix. Chapter 1 consists of brief introduction of general properties of glasses and their behavior under different spectroscopic techniques. Chapter 2 deals with the sample preparation and the experimental techniques used in this work. Chapter 3 elaborates on the Raman and EPR spectroscopic studies on the structural arrangement of the mixed alkali oxyfluro vanadate glass systems. Chapter 4 focuses on the ac and electrical modulus analysis to study the MAE in the above samples. Chapter 5 deals with the optical spectroscopic techniques used to study the compatibility of RE ions (erbium and europium) with the tellurium dioxide based glass matrix.
Chapter 1: Disordered materials pose a challenge to understand their structure mainly because of their random arrangement of the constituent units. In this chapter the glassy systems and the different experimental techniques used to study them are discussed in general. The behavior of glassy systems to the external stimuli in various frequency ranges is highlighted. A short review of mixed alkali effect in glasses mainly covering the advances in the last two decades is given. Brief outline of the theory of Raman, EPR and ac impedance spectroscopy are given.
Chapter 2: This chapter discusses the major experimental techniques used in the thesis to study the glass systems at block diagram level. The Raman and EPR spectrometers are discussed. Experimental technique used in ac impedance measurement is outlined. Different methods of preparing glass are listed and melt quenching technique is discussed in detail.
Chapter 3: This chapter discusses the results and analysis of Raman and EPR study in oxyfluoro vanadate glasses emphasizing MAE. The glass having batch formula 40V2O5
- 30BaF2 - (30 - x) LiF - xRbF (x = 0 – 30) is prepared by melt quenching technique. Raman spectroscopic study in back scattering geometry is performed to see the effect of alkali ions on the V – O bond length of VO6 polyhedra in the glass. The de-convoluted Raman peaks corresponding to V = O and VO2 are considered and the effect of alkali mixture on these bonds are studied.
• The peak shift of V = O and VO2 bonds shows that V = O is affected only a little by the replacement of lithium (Li) by rubidium (Rb), while VO2 bond gets affected to a larger extent.
• From the peak shift the most probable value of the bond length and the spread in it are estimated. The bond length corresponding to V = O is found to increase and that of VO2 decrease as a consequence of alkali replacement.
• From the FWHM of the corresponding Raman peaks, it is concluded that O - Rb coordination sphere around VO6 polyhedra is more homogeneous than either O – Li or O - Li /Rb coordination.
These results are published in J. Non-Cryst. Solids 370 (2013) 6.
EPR studies on the samples are carried out in X band frequency and spin – Hamilto-nian parameters were extracted by simulating and fitting the EPR spectra to experimental data using EasySpin which is a Matlab toolbox.
• it is observed that the ratio 4gjj=4g?, which is a measure of tetragonality of octa-hedral crystal symmetry of V2O5, varies non-monotonically with Rb content.
• A model based on this observation is proposed. The essential idea of this model is that Rb atoms that are substituted for Li atoms initially prefer terminal positions over planar positions. Continued substitution then replaces planar Li atoms. It is seen that this model of “preferential substitution” explains the observation very well.
• Another observation is that the EPR signal intensity, which is due to concentration of V4+ ions, also shows non-monotonous behavior with Rb content. This is also explained using preferential substitution, taking into consideration the oxidation states of the vanadium ions.
• The value of 4gjj=4g?, is a minimum for all rubidium environments around V2O5, which infers that Rb coordination is more symmetric than all Li or Li−Rb.
• A good correlation is found between Raman and EPR study of the above system. These results are published in J. Phys. Chem. A 118 (2014) 573.
Chapter 4: The chapter brings out the results of ac conductivity and electrical mod-ulus study of MAE in the glass system mentioned above. The Agilent 4294A precision impedance analyzer operating in frequency range 40 Hz to 110 MHz, is used for per-forming impedance and capacitance experiments carried out in this thesis. Impedance measurements in our studies are performed in sandwich geometry.
• Room temperature dc conductivity shows a decrease as Li is replaced by Rb and reaches its minimum - five orders less than its all Li value at 0.33 molar fraction of Rb, which is attributed to MAE. This observation is explained using the structural aspect.
• Using the linear response theory the number of mobile ions participating in the conduction is estimated.
• Imaginary part of the electrical modulus is fitted to Kohlrausch – Williams – Watts (KWW) relation by using a complex nonlinear least squares fitting procedure given by Bergmann.
• The stretching parameter b estimated from the above procedure is found to exhibit MAE. The observed variation in b with Rb mole fraction is explained by taking into considerations the contributions from fast and slow processes, and coupling between different relaxing sites.
The manuscript is under preparation.
Chapter 5: This chapter illustrates the optical study of RE doped TeO2 based glasses to determine the suitability of a particular RE ion with a given glass matrix. TeO2 based glasses having a general formula (in mol %) 65TeO2 – 5BaF2 – 30ZnF2 (TBZ) were prepared by usual melt quenching technique. RE doping was done at the expense of TeO2. 3 mol % of Eu or Er are added to prepare RE doped glass. Raman, PL, UV-visible absorption studies are carried out on the glass samples.
• From the peak shift, intensity variation and FWHM of the Raman spectra of the
glass samples it is observed that Eu doped TBZ glass has a greater tendency towards depolymerizing the glass matrix by influencing the conversion of TeO4 units into the formation of TeO3 units.
• PL spectra of the glass samples shows emission due to different possible transitions. Position of the peak of the de-convoluted spectra shows the position of the particular Stark component and the FWHM is a measure of the inhomogeneous broadening.
• The UV-visible absorption spectra are used to calculate the optical density and fitted to the Mott equation to determine the band edge of the glass samples. It is seen that Eu doped TBZ glass has a lesser band gap than that of Er doped glass. The manuscript is submitted to Bul. Mat. Sci.
Appendix : This consists of a collection of details of EDS study carried on the VBL series glasses and some MATLAB codes used to simulate the EPR spectrum for VBL series glasses.
38
Honnavar, Gajanan V. "Mixed Alkali Effect in Oxyfluoro Vanadate Glasses And The Effect of Rare Earth Ions on Oxyfluoro Tellurite Glasses - A Spectroscopic Study." Thesis, 2016. http://etd.iisc.ernet.in/handle/2005/2667.
Full textAbstract:
The main motivation of this thesis is to study the long standing problem of mixed alkali effect (MAE) in oxyfluro vanadate glass systems from the point of view of structural arrangement and to investigate the effect of two rare earth ions, namely, erbium and europium on the structure of tellurium dioxide based glass. In glass science, it is well known that when one alkali in a glass matrix is gradually replaced by another alkali, leads to a non-linear variation in some of the physical properties. There are many a theories trying to explain this effect. Recently the renewed interest lies in explaining MAE in-terms of structural consideration. Rare earth (RE) ion doped glasses are of interest in a variety of applications in photonics because of the special optical properties exhibited by these materials. Atomic like f-f transitions of RE ions depend on the local environment of the these ions. A particular glass matrix may be able to bring out the optical properties of a RE ion better than the other matrix. In this regard structural characterization of a glass matrix with different RE ions for optical properties is of importance. Spectroscopic tech-niques are best suited to investigate structural arrangement in glasses and in this thesis we have used techniques like Raman, electron paramagnetic resonance (EPR), impedance, photoluminescence and UV- visible absorption spectroscopies.
The thesis comprises of five chapters and an appendix. Chapter 1 consists of brief introduction of general properties of glasses and their behavior under different spectroscopic techniques. Chapter 2 deals with the sample preparation and the experimental techniques used in this work. Chapter 3 elaborates on the Raman and EPR spectroscopic studies on the structural arrangement of the mixed alkali oxyfluro vanadate glass systems. Chapter 4 focuses on the ac and electrical modulus analysis to study the MAE in the above samples. Chapter 5 deals with the optical spectroscopic techniques used to study the compatibility of RE ions (erbium and europium) with the tellurium dioxide based glass matrix.
Chapter 1: Disordered materials pose a challenge to understand their structure mainly because of their random arrangement of the constituent units. In this chapter the glassy systems and the different experimental techniques used to study them are discussed in general. The behavior of glassy systems to the external stimuli in various frequency ranges is highlighted. A short review of mixed alkali effect in glasses mainly covering the advances in the last two decades is given. Brief outline of the theory of Raman, EPR and ac impedance spectroscopy are given.
Chapter 2: This chapter discusses the major experimental techniques used in the thesis to study the glass systems at block diagram level. The Raman and EPR spectrometers are discussed. Experimental technique used in ac impedance measurement is outlined. Different methods of preparing glass are listed and melt quenching technique is discussed in detail.
Chapter 3: This chapter discusses the results and analysis of Raman and EPR study in oxyfluoro vanadate glasses emphasizing MAE. The glass having batch formula 40V2O5
- 30BaF2 - (30 - x) LiF - xRbF (x = 0 – 30) is prepared by melt quenching technique. Raman spectroscopic study in back scattering geometry is performed to see the effect of alkali ions on the V – O bond length of VO6 polyhedra in the glass. The de-convoluted Raman peaks corresponding to V = O and VO2 are considered and the effect of alkali mixture on these bonds are studied.
• The peak shift of V = O and VO2 bonds shows that V = O is affected only a little by the replacement of lithium (Li) by rubidium (Rb), while VO2 bond gets affected to a larger extent.
• From the peak shift the most probable value of the bond length and the spread in it are estimated. The bond length corresponding to V = O is found to increase and that of VO2 decrease as a consequence of alkali replacement.
• From the FWHM of the corresponding Raman peaks, it is concluded that O - Rb coordination sphere around VO6 polyhedra is more homogeneous than either O – Li or O - Li /Rb coordination.
These results are published in J. Non-Cryst. Solids 370 (2013) 6.
EPR studies on the samples are carried out in X band frequency and spin – Hamilto-nian parameters were extracted by simulating and fitting the EPR spectra to experimental data using EasySpin which is a Matlab toolbox.
• it is observed that the ratio 4gjj=4g?, which is a measure of tetragonality of octa-hedral crystal symmetry of V2O5, varies non-monotonically with Rb content.
• A model based on this observation is proposed. The essential idea of this model is that Rb atoms that are substituted for Li atoms initially prefer terminal positions over planar positions. Continued substitution then replaces planar Li atoms. It is seen that this model of “preferential substitution” explains the observation very well.
• Another observation is that the EPR signal intensity, which is due to concentration of V4+ ions, also shows non-monotonous behavior with Rb content. This is also explained using preferential substitution, taking into consideration the oxidation states of the vanadium ions.
• The value of 4gjj=4g?, is a minimum for all rubidium environments around V2O5, which infers that Rb coordination is more symmetric than all Li or Li−Rb.
• A good correlation is found between Raman and EPR study of the above system. These results are published in J. Phys. Chem. A 118 (2014) 573.
Chapter 4: The chapter brings out the results of ac conductivity and electrical mod-ulus study of MAE in the glass system mentioned above. The Agilent 4294A precision impedance analyzer operating in frequency range 40 Hz to 110 MHz, is used for per-forming impedance and capacitance experiments carried out in this thesis. Impedance measurements in our studies are performed in sandwich geometry.
• Room temperature dc conductivity shows a decrease as Li is replaced by Rb and reaches its minimum - five orders less than its all Li value at 0.33 molar fraction of Rb, which is attributed to MAE. This observation is explained using the structural aspect.
• Using the linear response theory the number of mobile ions participating in the conduction is estimated.
• Imaginary part of the electrical modulus is fitted to Kohlrausch – Williams – Watts (KWW) relation by using a complex nonlinear least squares fitting procedure given by Bergmann.
• The stretching parameter b estimated from the above procedure is found to exhibit MAE. The observed variation in b with Rb mole fraction is explained by taking into considerations the contributions from fast and slow processes, and coupling between different relaxing sites.
The manuscript is under preparation.
Chapter 5: This chapter illustrates the optical study of RE doped TeO2 based glasses to determine the suitability of a particular RE ion with a given glass matrix. TeO2 based glasses having a general formula (in mol %) 65TeO2 – 5BaF2 – 30ZnF2 (TBZ) were prepared by usual melt quenching technique. RE doping was done at the expense of TeO2. 3 mol % of Eu or Er are added to prepare RE doped glass. Raman, PL, UV-visible absorption studies are carried out on the glass samples.
• From the peak shift, intensity variation and FWHM of the Raman spectra of the
glass samples it is observed that Eu doped TBZ glass has a greater tendency towards depolymerizing the glass matrix by influencing the conversion of TeO4 units into the formation of TeO3 units.
• PL spectra of the glass samples shows emission due to different possible transitions. Position of the peak of the de-convoluted spectra shows the position of the particular Stark component and the FWHM is a measure of the inhomogeneous broadening.
• The UV-visible absorption spectra are used to calculate the optical density and fitted to the Mott equation to determine the band edge of the glass samples. It is seen that Eu doped TBZ glass has a lesser band gap than that of Er doped glass. The manuscript is submitted to Bul. Mat. Sci.
Appendix : This consists of a collection of details of EDS study carried on the VBL series glasses and some MATLAB codes used to simulate the EPR spectrum for VBL series glasses.
39
Wade, Scott A. "Temperature measurement using rare earth doped fibre fluorescence." Thesis, 1999. https://vuir.vu.edu.au/15723/.
Full textAbstract:
Optical fibre sensors have been developed to measure a wide range of parameters and in many circumstances show significant advantages over conventional measurement techniques. This thesis investigates a relatively new method of measuring temperature using optical fibres, known as the fluorescence intensity ratio technique. The fluorescence intensity ratio technique uses the thermal coupling of two closely spaced energy levels in an ion. When populated the relative number of ions, and hence the intensity of fluorescence from each of the two closely spaced levels, follow a Boltzmann distribution. Measurements of the fluorescence intensity originating from the two levels can therefore be used to determine temperature. The fluorescence intensity ratio was studied using six different rare earth ions, doped into a variety of glasses and crystals to investigate the feasibility of developing an accurate, low cost temperature sensor.
40
Kabongo, Guy Leba. "Luminescence investigation of zinc oxide nanoparticles doped with rare earth ions." Diss., 2013. http://hdl.handle.net/10500/14191.
Full textAbstract:
Un-doped, Tb3+ as well as Yb3+ doped ZnO nanocrystals with different concentrations of RE3+ (Tb3+, Yb3+) ions were successfully synthesized via sol-gel method to produce rare earth activated zinc oxide nanophosphors. The phosphor powders were produced by drying the precursor gels at 200˚C in ambient air.
Based on the X-ray diffraction results, it was found that the pure and RE3+ doped ZnO nanophosphors were highly polycrystalline in nature regardless of the incorporation of Tb3+ or Yb3+ ions. Moreover, the diffraction patterns were all indexed to the ZnO Hexagonal wurtzite structure and belong to P63mc symmetry group. The Raman spectroscopy confirmed the wurtzitic structure of the prepared samples.
Elemental mapping conducted on the as prepared samples using Scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer (EDX) revealed homogeneous distribution of Zn, O, and RE3+ ions. The high resolution transmission electron microscope (HR-TEM) analyses indicated that the un-doped and RE3+ doped samples were composed of hexagonal homogeneously dispersed particles of high crystallinity with an average size ranging from 4 to 7 nm in diameter, which was in agreement with X-ray diffraction (XRD) analyses.
ZnO:Tb3+ PL study showed that among different Tb3+ concentrations, 0.5 mol% Tb3+ doped ZnO nanoparticles showed clear emission from the dopant originating from the 4f-4f intra-ionic transitions of Tb3+ while the broad defects emission was dominating in the 0.15 and 1 mol% Tb3+doped ZnO. Optical band-gap was extrapolated from the Ultraviolet Visible spectroscopy (UV-Vis) absorption spectra using TAUC‟s method and the widening of the optical band-gap for the doped samples as compared to the un-doped sample was observed. The PL study of ZnO:Yb3+ samples was studied using a 325 nm He-Cd laser line. It was observed that the ZnO exciton peak was enhanced as Yb3+ions were incorporated in ZnO matrix. Furthermore, UV-VIS absorption spectroscopic study revealed the widening of the band-gap in Tb3+ doped ZnO and a narrowing in the case of Yb3+ doped ZnO system.
X-ray photoelectron spectroscopy demonstrated that the dopant was present in the doped samples and the result was found to be consistent with PL data from which an energy transfer was evidenced. Energy transfer mechanism was evidenced between RE3+ and ZnO nanocrystals and was discussed in detail.Physics
M.Sc. (Physics)
41
Diamente, Peter Robert. "Development of water-soluble Ln³⁺-doped LaF₃ nanoparticles as potential biolabels." 2005. http://hdl.handle.net/1828/607.
Full text
42
Alexander, Annabel Lucy. "Investigation of quantum information storage in rare earth doped materials." Phd thesis, 2007. http://hdl.handle.net/1885/109376.
Full textAbstract:
Following the explosion of interest in quantum information processing the
field has now reached the point where a quantum memory is becoming a
real necessity for further improvements. A quantum memory is fundamentally
different from a classical memory due to the "Superposition" principle.
Unlike classical information no measurement can be made on the quantum
information when it is to be stored. Quantum information is also difficult to
store due to its fragile nature and the need to isolate it from the surrounding
environment.
This thesis describes work that was carried out both to investigate and
demonstrate the utility of rare earth ion dopants for quantum memories.
Rare earth ion dopants are obvious choices for a quantum memory. Long
coherence times in both the optical and hyperfine levels have been observed
as well as optical manipulation of the nuclear spin states. The rare earth ions
of interest also possess a linear Stark shift which is essential for the quantum
memory under investigation here.
The scheme investigated here for a quantum memory involves reversible
inhomogeneous broadening achieved via macroscopic electric field gradients.
The advantage that this scheme has over its competitors is its simplicity.
The scheme presented here requires no optical coupling beams and t he only
light interacting with the sample is the light to be stored. For that reason
the scheme inherently suffers less from noise than other quantum memory
proposals.
These advantages meant that it was possible to demonstrate the first
optical memory using reversible inhomogeneous broadening via macroscopic
electric field gradients.
The experiments performed in this thesis were in two main areas. The first
was characterisation of the hyperfine structure of rare earth ion materials.
The second area was demonstrations of reversible inhomogeneous broadening
as an optical memory.
43
Sellars, Matthew John. "Ultra-high resolution laser spectroscopy of rare earth doped solids." Phd thesis, 1995. http://hdl.handle.net/1885/138406.
Full text
44
Zheng, Hairong. "Dynamical process of rare earth ions doped in nanocrystals embedded in amorphous matrices." 2003. http://purl.galileo.usg.edu/uga%5Fetd/zheng%5Fhairong%5F200305%5Fphd.
Full text
45
Bhebhe, Nkosiphile Andile. "Blue-laser excitation studies of ZnO thin films and rare-earth doped ZnO powders." Thesis, 2016. http://hdl.handle.net/10539/21750.
Full textAbstract:
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the academic requirements for the degree of Master of Science. Johannesburg, March 2016.Zinc oxide (ZnO) continues to receive widespread attention due to its excellent optical and electronic properties; it demonstrates the combined characteristics of high transmittance and electrical conductivity. Despite the tremendous drive for its application in optoelectronic devices, the full nature of the point defects and defect complexes have not been characterised comprehensively. In this work, luminescence characteristics of the intrinsic defects in ZnO thin films and the rare-earth ions Eu3+ and Tb3+ in ZnO powders are investigated under blue-laser excitation. The thin films used in this study were deposited using the radio-frequency magnetron sputtering method over a 2 hour duration under varied power and substrate bias conditions. The powders were synthesized by the chemical bath deposition method with dopant concentrations of 1.0 mol%. Grazing incidence X-ray diffraction (XRD) was used to determine the lattice properties of the samples. Photoluminescence studies were primarily conducted at room temperature (300 K) with the 457.9 nm, 476.5 nm and 488.0 nm laser lines as excitation sources. For the ZnO thin films, XRD patterns of a hexagonal wurtzite structure with a c/a ratio of about 1.60 and a u-parameter of 0.38 were obtained. Photoluminescence measurements show a broad emission band in the 500.0-900.0 nm range, centred at 656.0 nm. Annealed films yielded relatively more intense photoluminescence spectra than the as-prepared films. The intrinsic point defects and defect level transitions responsible for the broad emission are discussed. For the ZnO powders, the XRD patterns of the annealed samples of pristine ZnO, ZnO:Eu3+ and ZnO:Tb3+ are similarly consistent with a hexagonal wurtzite ZnO phase. Energy dispersive spectroscopy (EDS) confirmed the presence of the Eu3+ and Tb3+ dopants in the respective ZnO host while scanning electron microscopy (SEM) measurements showed the morphology of the sample powders. Photoluminescence spectra of pelletized samples, obtained in the 460.0-900.0 nm range, exhibit relatively intense Eu3+ and Tb3+ emission bands superimposed on a broad emission background. The RE3+ emission bands are attributed to the 5D0 → 7FJ (J = 0, 1, 2, 3, 4) and the 5D4 → 7FJ (J = 0, 1, 2, 3, 4, 5, 6) electronic transitions of Eu3+ and Tb3+, respectively, while the background emission is attributed to intrinsic defects. Crystal-field energy levels for the Eu3+ ion and the Tb3+ ion occupying a C3v symmetry site were deduced from fitting Gaussian curves to the RE3+ emission bands. Possible channels for transfer of energy from the intrinsic defects to Eu3+ and Tb3+ are discussed.
LG2017
46
Lu, Tsung-Po, and 盧宗伯. "Effect of Rare earth Magnetic ions on Superconductivity in hole-doped La0.87-XLnXSr0.13FeAsO systems." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/49597913821349642106.
Full textAbstract:
博士國立中興大學
物理學系所
98
In this dissertation, we have investigated the superconducting and magnetic properties of the hole-doped FeAs-based superconducting compounds La0.87-xLnxSr0.13FeAsO (Ln = Sm, Gd, Dy; 0 ≤ x ≤ 0.06). The existence of the RE+3 paramagnetic ions causes the depression of superconductivity. The properties of the hole-doped FeAs-based superconducting compound have been measured over wide temperature and magnetic field ranges. The hysteresis loop of the La0.87-XLnXSr0.13FeAsO sample shows a superconducting hysteresis in addition to a magnetic moment background. The experiment demonstrates that the coexistence of magnetism and superconductivity in the hole doped FeAs-based superconducting compounds is possible. We found that by substituting in the FeAs-based superconductors of the hole-doped system with the magnetic rare-earth element, the value of Tc in the resultant material starts to decrease, even the samples have not superconductivity with doping more magnetic rare-earth element. On the other hand, it is clear that the influence of superconductivity of doping Dy3+ is more evident than Gd3+,while the influence of Sm3+ is the weakest among these three magnetic rare-earth element.
47
Mofokeng, Sefako John. "Investigation of up and down-converting rare earth ions doped ZnTiO3 for photovoltaic applications." Thesis, 2019. http://hdl.handle.net/10500/26702.
Full textAbstract:
We are living in an age where the demand for energy is growing rapidly. This means that
supplies to easily accessible oil and natural gas is unlikely to keep up with the demand as times
goes on. The world will have to use energy more efficiently and increase its use of other
sources of energy. This study is aiming at developing materials that will improve the power
conversion efficiency of photovoltaic cells by using up and down-converting phosphor
materials. ZnTiO3-Zn2TiO4 composite and ZnTiO3 phosphors doped with Er3+,Yb3+, Eu3+ and
Al3+, which display up and down-converted luminescence were synthesized by a simple high
temperature conventional solid state reaction method. The structure, particle morphology,
absorption, photoluminescent properties and elemental distribution were analyzed using X-ray
diffraction (XRD), scanning electron microscopy (SEM), UV-Vis-NIR absorption
spectrometer, photoluminescence (PL) spectroscopy and time of flight secondary ion mass
spectroscopy (TOF-SIMS), respectively.
ZnTiO3-Zn2TiO4 composite doped with different concentration of Er3+ ions was synthesized
via solid state chemical reaction method at 1100 ℃. The X-ray diffraction (XRD) confirmed
the crystallization of both the hexagonal ZnTiO3 and cubic spinel Zn2TiO4 phases of the
composite. The SEM images of ZnTiO3-Zn2TiO4:Er3+ composite showed that the particle
morphology was made up of faceted hexagons. Furthermore, the ZnTiO3-Zn2TiO4:Er3+
phosphors were excited in the near-infrared (NIR) region using a laser diode with a wavelength
of 980 nm and displayed both green and red up-conversion emission bands in the visible range
at 543, 553, 650 – 670 nm. These emission bands correspond to 2H11/2,
4S1/2→ 4
I15/2 and 4F9/2→
4
I15/2 transitions of Er3+ ions. However, the interaction mechanisms involved in the upconversion process of ZnTiO3-Zn2TiO4:Er3+ phosphor is discussed with the help of an energylevel schematic diagram and the number of the photons involved in the up-conversion
luminescence process were of a double photon mechanism. The decay lifetimes were studied
by fitting the luminescence decay curve with a single-component exponential decay.
Er3+ and Yb3+ incorporated zinc titanate (ZnTiO3) phosphor powders were synthesized using
conventional solid-state reaction method at 800 ℃. A ZnTiO3:Er3+,Yb3+ phosphor that
resembled an ecandrewsite single phase with space group R-3 (148) was obtained, as proven by X-ray diffraction (XRD). The SEM image showed a surface morphology composed of
agglomerated irregular shaped particles. The energy band gap of ZnTiO3 was engineered by
incorporating different concentration of the dopant ions. After irradiating ZnTiO3:Er3+with a
980 nm laser beam, the phosphor up-converted the photon energy to display green and red
emissions in the visible range that were positioned at 527, 545 and 665 nm. Enhancement of
the luminescence intensity of ZnTiO3:Er3+ phosphor was achieved by variation of Er3+
concentration. Co-doping with Yb3+ ions proved to be effective in enhancing the luminescence
intensity of the optimized Er3+ ion emission and new emission bands at 410 and 480 nm,
through an energy transfer mechanism were observed. The enhancement of the lifetime of the
up-conversion luminescence was also achieved by co-doping ZnTiO3:Er3+ phosphor with Yb3+
ion. The energy transfer mechanisms involved in Er3+
- Yb3+ co-doped ZnTiO3 phosphor was
illustrated and discussed in detail.
The ZnTiO3:Er3+, Yb3+ thin films were successfully deposited by pulsed laser deposition (PLD)
by varying the silicon (100) substrate temperature. The distribution of the ions in the films was
investigated and the TOF-SIMS showed that the ions were homogeneously distributed
throughout the ZnTiO3 host lattice which indicated a successful incorporation of the Er3+ and
Yb3+ ions. The optical response of the phosphors revealed that the reflectance percentages of
the ZnTiO3:Er3+, Yb3+ vary with the silicon substrate temperature due to the differences in the
thickness and morphological roughness of the thin films. The ZnTiO3:Er3+, Yb3+ thin films also
exhibited up-conversion emission from Er3+ electronic transitions, with violet, blue, green and
red emission lines at 410, 480, 525, 545 and 660 nm from 2H9/2 → 4
I15/2,
4F7/2 → 4
I15/2,
2H11/2
→ 4
I15/2,
4S3/2 → 4
I15/2 and 4F9/2 → 4
I15/2 transitions, respectively. These up-conversion
emissions were enhanced by increasing the silicon substrate temperature during the deposition.
ZnTiO3 host co-doped with Eu3+ and Al3+ was synthesized by solid state reaction to convert
the UV photons to visible photons. Charge compensation effects of Al3+ incorporated
ZnTiO3:Eu3+ as a co-dopant ion was reported in detail. The structural and morphological
characterization show that the addition of Eu3+ and Al3+ does not affect the phase formation
and the surface morphology of the host. The visible emission intensity of Eu3+ ions for an
optimal concentration of 2 mol% under 395 nm excitation, was enhanced by incorporating
Al3+. The energy level diagram showing the charge compensation mechanism was proposed
for the co-doped system.College of Engineering, Science and Technology
48
Han-YuLin and 林含諭. "The Syntheses and Optical Analyses of Down-Shifting and Up-Conversion Phosphors: Calcium Vanadate-Based Hosts Doped with Trivalent Rare Earth Ions." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/b9mjyj.
Full textAbstract:
博士國立成功大學
電機工程學系碩博士班
101
Our previous work [J. Am. Ceram. Soc., 93, 138 (2010)] reported a red phosphor Ca2.82(VO4)2:0.12Eu3+ which was well-excited by 465-nm blue light and was therefore a candidate for application to the phosphor-converted WLED (pc-WLED) with a blue chip (450-470 nm). On the basis of Ca2.82(VO4)2:0.12Eu3+, we sought to develop down-shifting (DS) inorganic phosphors for use in pc-WLEDs by the commonly-used solid-state reaction method, which was the main purpose of the present research. We found that substitution of not only a larger ion like Ba2+ [J. Am. Ceram. Soc., 93, 138 (2010)] but also a smaller one like Mg2+ (this research) replacing no ＞ 14.9% Ca2+ ions could enhance the integrated DS emission intensity of red phosphor Ca3(VO4)2:0.12Eu3+, indicating that both lattice expansion and contraction could decrease the site symmetry of Eu3+ in Ca3(VO4)2:0.12Eu3+ phosphor. This finding is anticipated to improve the Eu3+ emission intensity of other Eu3+-doped phosphors. To further investigate Eu3+ up-conversion (UC) behaviors, Yb3+ ion was used as a sensitizer. Interestingly, the enhanced Eu3+ emission from 5D1,2,3 states under UC excitation was observed as compared to that under DC excitation. This phenomenon led to the variation in the emission color of the optimized (Ca0.742Mg0.067)2.82(VO4)2:0.36Yb3+,0.12Eu3+ phosphor from red to near warm white as the excitation mechanism changed from DS to UC. Additionally, it was found that substitution of 3% Sr2+ replacing Ca2+ enhanced the red emission intensity of Ca2.82(VO4)2:0.12Eu3+ by 14% under 465-nm excitation. The conventional methods to determine multipolar mechanisms responsible for the energy transfer between different ions (I0/I － C plot) and alike ions (log(C/I) － logC plot) supposed hypotheses of I0/I ≫ 1 and βCθ/3 ≫ 1, respectively, where I0 and I are the emission intensity of the energy donor in the absence and presence of the acceptor; C is the sum of both energy donor and acceptor contents; θ represents the type of multipolar interactions, and β is a constant for each interaction. Compared with the conventional methods, the modified methods for investigation of the multipolar energy transfer proposed in this research demonstrated more precise and valid results. Excluding the prerequisite of I0/I ≫ 1, the concentration-dependent dipole-dipole multipolar interactions for the Sm3+ → Eu3+ energy transfer were observed for the first time based on the fitting results of (I0/I － 1) － C plots. Additionally, the Harris model was found to be an alternative way to release us from the prerequisite of βCθ/3 ≫ 1 when fitting the I/C － C plot. And a dipole-dipole multipolar interaction of 3-body type was found to be responsible for the concentration quenching of Sm3+ emission around 951 nm in the (Ca0.97Sr0.03)3(VO4)2 host.