Dissertations / Theses on the topic 'Rare earth ions'
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1
Hansen, Peter C. "Laser spectroscopy of rare earth ions." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293472.
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Kooy, Hendrikus Johannes. "Two-body operators and rare-earth spectroscopy." Thesis, [Hong Kong : University of Hong Kong], 1994. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13787330.
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3
Todoroki, Shin-ichi. "Studies on local structure around rare earth ions in glasses." Kyoto University, 1993. http://hdl.handle.net/2433/51187.
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学位授与大学:京都大学;学位の種類:博士(工学);学位記番号:工博第1285号;学位授与日付:1993-03-23Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第5394号
工博第1285号
新制||工||903(附属図書館)
UT51-93-F151
京都大学大学院工学研究科工業化学専攻
(主査)教授 曽我 直弘, 教授 作花 濟夫, 教授 小久保 正
学位規則第4条第1項該当
4
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.
5
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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Martin, Rodica M. "Reciprocity between emission and absorption for rare earth ions in glass." Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-042806-110237/.
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Dissertation (Ph.D.)--Worcester Polytechnic Institute.Keywords: homogeneous broadening, McCumber theory, emission and absorption cross sections, rare earth ions, inhomogeneous broadening. Includes bibliographical references (p.171-178).
7
Webb, Helen Rachael 1975. "Interaction of the rare earth ions with p-sulfonatocalix[4]arene and 18-crown-6." Monash University, Dept. of Chemistry, 2001. http://arrow.monash.edu.au/hdl/1959.1/9076.
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McDougall, James. "Spectroscopic properties of rare earth ions in zirconium based fluoride glasses." Thesis, University of the West of Scotland, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261598.
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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
10
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.
11
Ahmad, Kamil Suraya. "Ultrafast laser plasma doping of rare earth ions for optical waveguiding applications." Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/19503/.
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The work presented here is to introduce and investigate a novel material and a fabrication technique for an Er3+ ion doped waveguide amplifier (EDWA) on a silicon platform. EDWA performance strongly depends on the erbium concentration and the nature of the host material. There are two materials studied for this work. For the first material, TeO2-ZnO-Na2O-Er2O3 (Er-TZN) is doped into the silica-on-silicon (SOS) substrate surface, and for the second material, Er-TZN is doped into the surface of Si3N4-on-silicon. For the first material, the mixing of Er-TZN with SiO2 produces a homogeneous layer which has the potential to be used for EDWA applications. The fabrication is carried out using a novel technique which is named ultrafast laser plasma doping (ULPD). In this technique, the Er-TZN target is bombarded using a femtosecond laser and the interfacial reaction between a high energy plasma plume and heated silica-on-silicon substrate results in a highly dense erbium doped silicate that is referred to as erbium-doped tellurite modified silica (EDTS). The success of this EDTS resulted in this work being extended to produce two types of a channel waveguide, i.e. diffused and ridge waveguide. However, for the diffused waveguide, the attempt to fabricate this type of waveguide failed to produce satisfactory results because it is believed that the metal mask moved during the fabrication process. For ridge waveguide, etching results still do not show satisfactory output. Therefore, further optimisation is needed to accomplish a practical optical waveguide. On the other hand, the doping of Er-TZN into Si3N4 which is also prepared using the ULPD technique is less successful compared to SiO2 because the doped layer exhibits inhomogeneous material distribution although various process parameters have been tried. Failure to obtain a layer like EDTS is probably due to the limitation of the current instruments and also the rigid structural network of Si3N4.
12
Fraval, Elliot. "Minimising the decoherence of rare earth ion solid state spin qubits /." View thesis entry in Australian Digital Theses Program, 2005. http://thesis.anu.edu.au/public/adt-ANU20061010.124211/index.html.
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Flanagan, Bernadine Mary. "The spectroscopy of trivalent lanthanoid ions in organic hosts /." [St. Lucia, Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16843.pdf.
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Rowlands, Aled Prys. "Thermoluminescence detection of phase transitions : their effects and applications." Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263912.
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15
Fujita, Koji. "OPTICAL AND MAGNETO-OPTICAL PROPERTIES OF RARE-EARTH IONS IN NON-CRYSTALLINE OXIDES." Kyoto University, 1999. http://hdl.handle.net/2433/59317.
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16
Ueda, Ｊunpei. "Spectral conversion materials using rare earth and transition metal ions for green photonics." Kyoto University, 2012. http://hdl.handle.net/2433/157659.
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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16948号
人博第591号
新制||人||141(附属図書館)
23||人博||591(吉田南総合図書館)
29623
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 杉山 雅人, 教授 加藤 立久
学位規則第4条第1項該当
17
Åberg, Daniel. "Transition Properties of f-electrons in Rare-earth Optical Materials." Doctoral thesis, Uppsala University, Condensed Matter Theory, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4014.
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The main purpose of this thesis is to theoretically study energy levels and intra-electronic transition intensities for various f-electron systems. The f-f electronic dipole transitions are parity-forbidden for a free ion but become non-zero when the ion is subject to a crystal-field. This is commonly described within the framework of Judd-Ofelt theory which accounts for the mixing of odd parity into the wave-functions.
Some refinements and quantitative studies have been made by applying many-body perturbation theory, or the perturbed functions approach, to obtain effective dipole operators due to correlation, spin-orbit and higher order crystal-field effects not included in Judd-Ofelt theory. A software for the computation of f-electron multiplets and Stark levels was implemented and published as well.
The single- and pair-functions used for the evaluation of intensity parameters were obtained by solving various inhomogeneous Schrödinger equations. The wave-functions and energies obtained by diagonalizing an effective Hamiltonian have been used together with the oscillator strength methods to simulate absorption spectrum. Consistent crystal-field parameters applied in some of the papers were obtained by fitting crystal polarizabilities to reflect the experimental Stark levels. The same crystal model was then used to generate odd crystal field parameters needed for the f-f transition intensities. The total effect of these refinements are spectral features that usually agree well with experimental findings. Some of these methods have also been applied and seen to be quite useful for the understanding of optical fiber amplifiers frequently used in today's optical networks.
Finally, a finite-difference approach was applied for the Helium iso-electronic sequence. The exact wave-function was expanded in a sum of partial waves, and accurate ground- and excited state energies were obtained by using the iterative Arnoldi approach.
18
Aull, Brian Francis. "The impact of ion-host interactions on the 5d-to-4f spectra of lanthanide rare earth ions." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/40343.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Includes bibliographical references.
by Brian Francis Aull.
Ph.D.
19
Jamison, Steven P. "Laser site-selective spectroscopy of rare-earth ions in crystals of the fluorite structure." Thesis, University of Canterbury. Physics, 1998. http://hdl.handle.net/10092/8172.
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Site-selective laser spectroscopy, Zeeman infrared and optical absorption have been employed to investigate trivalent dysprosium centers in rare-earth doped alkaline-earth fluoride crystals. These studies have characterised the two dominant centers in SrF₂:Dy³⁺ which are determined to be the fluorine compensated C₄ᵥ and C₃ᵥ centers analogous to those observed in other SrF₂:RE³⁺ systems. The C₃ᵥ center is shown to correspond to the J-center of Sr₁:Er³⁺, rather than the B-center reported for SrF₂:Ho³⁺. In CaF₂:Dy³⁺ three single Dy³⁺ ion centers have been characterised, corresponding to the C₄ᵥ , C₃ᵥ and cubic centers. Cluster centers involving more than one Dy³⁺ ion are also present in CaF₂:0.05%Dy³⁺, and such centers undergo efficient non-radiative cross-relaxation. This cross-relaxation eliminates the possibility of a direct investigation of the laser spectroscopy of these cluster centers, leading to the consideration of double doped systems. The laser spectroscopy of CaF₂:Dy³⁺:Eu³⁺ reveals a cluster center with efficient Dy³⁺→’Eu³⁺ energy transfer. Through a correlation of the Eu³⁺ fluorescence with previous studies of CaF₂:Eu³⁺ this center has been determined to be a heterogeneous R-center dimer. The double doped CaF₂:Dy³⁺:Gd³⁺ system has enabled the Dy³⁺ R-center fluorescence to be investigated. The polarised fluorescence of the C₄ᵥ centers in CaF₂:Dy³⁺ and SrF₂:Dy³⁺ has been analysed in terms of both electric dipole and magnetic dipole transition moments, from which it is shown that magnetic dipole processes are significant for Dy³⁺ fluorescence.
The temperature dependence of fluorescence polarisation in praseodymium and europium doped CaF₂ and SrF₂ has been employed to investigate ionic motion in the C₄ᵥ centers. These experiments have enabled the barrier energies for interstitial reorientation to be determined in a site-selective manner. An anomalous temperature dependence of the polarisation anisotropy is observed in the Pr³⁺ C₄ᵥ centers, and has been shown to be a consequence of energy transfer between the C₄ᵥ centers.
20
Nishi, Masayuki. "Studies on 4f-4f transition spectra of trivalent rare-earth ions in oxide materials." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144882.
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Yeung, Yau-yuen. "Alternative parametrization schemes in lanthanide crystal field theory /." [Hong Kong : University of Hong Kong], 1986. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12324863.
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Andreev, Thomas. "Growth and optical properties of GaN and InGaN quantum dots dops with rare earth ions." Université Joseph Fourier (Grenoble), 2006. http://www.theses.fr/2006GRE10020.
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Ce travail est porté sur les propriétés structurales et optiques de structures à boîtes quantiques III-nitrures dopées avec des terres rares réalisées par épitaxie à jets moléculaires. Pendant la croissance, les terres rares ont une influence drastique sur les boîtes, expliquée par les propriétés surfactantes des atomes de terres rares. La caractérisation optique et structurale montre que les boîtes sont dopées efficacement avec les ions de Eu, Tm et Tb. D'autres localisations des terres rares ont été trouvées, par exemple, pour le Tm, à l'interface du GaN des boîtes et de l'AlN. Ce travail s'intéresse aussi à la dynamique d'excitation de boîtes quantiques dopées aux terres rares. La photoluminescence de couleurs intéressantes est stable de la température de l'hélium liquide jusque la température ambiante. Des structures à boîtes quantiques plus complexes sont aussi abordées : des boîtes InGaN:Eu QDs et des boîtes GaN co-dopées, importante pour la réalisation de composants. Une attention particulière a été mise sur les couches de GaN dopé Eu, où différents sites pour l'Eu ont été mis en évidence près de surface et à l'intérieur de matériauThis work reports on structural and optical properties of plasma assisted molecular beam epitaxy grown rare earth doped III – nitride quantum dots structures. During growth the rare earths have drastic influences on the quantum dot formation, assigned to surfactant properties of the rare earth atoms. Optical and structural characterizations have shown that GaN QDs are effectively doped with the rare earth atoms in the cases of Eu, Tm and Tb. Other rare earth locations have been also established, for example for Tm where a high amount has been found at the GaN QDs interface. The excitation dynamics of rare earth doped GaN QDs which show stable photoluminescence for the colors of interest between liquid helium and room temperature has been addressed. More complicate rare earth doped quantum dot structures are also discussed, like InGaN:Eu QDs and co-doped GaN QDs important for devices. Attention is put also onto rare earth doped GaN layers, where different Eu sites have been established, near the sample surface and inside bulk material
23
蔡慶銘 and Hing-ming Michael Chua. "Transition intensities and energy transfer of lanthanide ions in crystals." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1994. http://hub.hku.hk/bib/B31211409.
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Chua, Hing-ming Michael. "Transition intensities and energy transfer of lanthanide ions in crystals /." [Hong Kong : University of Hong Kong], 1994. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13692689.
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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)
26
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).
27
Zafarullah, Ijaz. "Thulium ions in a yttrium aluminum garnet host for quantum computing applications material analysis and single qubit operations /." Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/zafarullah/ZafarullahI0508.pdf.
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Rare-earth-doped crystals have been used for optical signal processing and storage applications. In this dissertation, their potential for quantum computing applications is explored. In one quantum computing scheme, information is stored in nuclear spin states and this information is then processed by using optical pulses through the coupling of these nuclear spin states to a common electronic level. To implement this scheme, nuclear spin states and coupling of these nuclear spin states to a common electronic level is required. Preliminary work in rare-earth materials like Pr3+ and Eu3+ has shown promising results regarding their suitability for quantum computing applications. One particular problem with these materials is that their transition wavelengths are only accessible with dye lasers. These lasers are inherently unstable, and currently few available systems exhibit the stability required for quantum computing applications. An alternative choice was to investigate other rare-earth ions like thulium. Thulium has a transition wavelength that can be accessed with diode lasers, which are commercially available, easy to stabilize, and compact. This dissertation is based on our investigations of Tm3+:YAG for quantum computing applications. Investigations involved a detailed characterization of the material. Nuclear spin states, in Tm3+:YAG, were obtained by applying an external magnetic field to the sample. First, interaction of an external magnetic field with the thulium ions at various sites in the crystal was analyzed. This analysis was used to measure the magnetic anisotropy in the material. These results show that it is possible, with the suitable choice of the magnetic orientation and the site in the crystal, to build a working 3-level quantum system. In the demonstration of single qubit operations in Tm3+:YAG, we first theoretically studied the effect of Gaussian spatial beam on the single qubit operations. Later on, we experimentally prepared a single isolated ensemble of ions in the inhomogeneously broadened absorption profile of the medium. This single isolated ensemble of ions was used as a test-bed to implement the single qubit operations. We also isolated two ensembles of ions in the inhomogeneous absorption profile of the medium. The interaction between these two isolated ensembles of ions was also studied.
28
楊友源 and Yau-yuen Yeung. "Alternative parametrization schemes in lanthanide crystal fieldtheory." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1986. http://hub.hku.hk/bib/B31231044.
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Fraval, Elliot, and elliot fraval@gmail com. "Minimising the Decoherence of Rare Earth Ion Solid State Spin Qubits." The Australian National University. Research School of Physical Sciences and Engineering, 2006. http://thesis.anu.edu.au./public/adt-ANU20061010.124211.
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[Mathematical symbols can be only approximated here. For the correct
display see the Abstract in the PDF files linked below] This work has
demonstrated that hyperfine decoherence times sufficiently long for
QIP and quantum optics applications are achievable in rare earth ion
centres. Prior to this work there were several QIP proposals using
rare earth hyperfine states for long term coherent storage of optical
interactions [1, 2, 3]. The very long T_1 (~weeks [4]) observed for
rare-earth hyperfine transitions appears promising but hyperfine T_2s
were only a few ms, comparable to rare earth optical transitions and
therefore the usefulness of such proposals was doubtful.
¶
This work demonstrated an increase in hyperfine T_2 by a factor of 7 ×
10^4 compared to the previously reported hyperfine T_2 for
Pr^[3+]:Y_2SiO_5 through the application of static and dynamic
magnetic field techniques. This increase in T_2 makes previous QIP
proposals useful and provides the first solid state optically active
Lamda system with very long hyperfine T_2 for quantum optics
applications.
¶
The first technique employed the conventional wisdom of applying a
small static magnetic field to minimise the superhyperfine interaction
[5, 6, 7], as studied in chapter 4. This resulted in hyperfine
transition T_2 an order of magnitude larger than the T_2 of optical
transitions, ranging fro 5 to 10 ms. The increase in T_2 was not
sufficient and consequently other approaches were required.
¶
Development of the critical point technique during this work was
crucial to achieving further gains in T_2. The critical point
technique is the application of a static magnetic field such that the
Zeeman shift of the hyperfine transition of interest has no first
order component, thereby nulling decohering magnetic interactions to
first order. This technique also represents a global minimum for back
action of the Y spin bath due to a change in the Pr spin state,
allowing the assumption that the Pr ion is surrounded by a thermal
bath. The critical point technique resulted in a dramatic increase of
the hyperfine transition T_2 from ~10 ms to 860 ms.
¶
Satisfied that the optimal static magnetic field configuration for
increasing T_2 had been achieved, dynamic magnetic field techniques,
driving either the system of interest or spin bath were investigated.
These techniques are broadly classed as Dynamic Decoherence Control
(DDC) in the QIP community. The first DDC technique investigated was
driving the Pr ion using a CPMG or Bang Bang decoupling pulse
sequence. This significantly extended T_2 from 0.86 s to 70 s. This
decoupling strategy has been extensively discussed for correcting
phase errors in quantum computers [8, 9, 10, 11, 12, 13, 14, 15], with
this work being the first application to solid state systems.
¶
Magic Angle Line Narrowing was used to investigate driving the spin
bath to increase T_2. This experiment resulted in T_2 increasing from
0.84 s to 1.12 s. Both dynamic techniques introduce a periodic
condition on when QIP operation can be performed without the qubits
participating in the operation accumulating phase errors relative to
the qubits not involved in the operation.
¶
Without using the critical point technique Dynamic Decoherence Control
techniques such as the Bang Bang decoupling sequence and MALN are not
useful due to the sensitivity of the Pr ion to magnetic field
fluctuations. Critical point and DDC techniques are mutually
beneficial since the critical point is most effective at removing high
frequency perturbations while DDC techniques remove the low frequency
perturbations. A further benefit of using the critical point technique
is it allows changing the coupling to the spin bath without changing
the spin bath dynamics. This was useful for discerning whether the
limits are inherent to the DDC technique or are due to experimental
limitations.
¶
Solid state systems exhibiting long T_2 are typically very specialised
systems, such as 29Si dopants in an isotopically pure 28Si and
therefore spin free host lattice [16]. These systems rely on on the
purity of their environment to achieve long T_2. Despite possessing a
long T_2, the spin system remain inherently sensitive to magnetic
field fluctuations. In contrast, this work has demonstrated that
decoherence times, sufficiently long to rival any solid state system
[16], are achievable when the spin of interest is surrounded by a
concentrated spin bath. Using the critical point technique results in
a hyperfine state that is inherently insensitive to small magnetic
field perturbations and therefore more robust for QIP applications.
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De, Oliveira Lima Karmel. "Nanocristaux dopés par des ions terres rares pour des applications en information quantique." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066611/document.
Full textAbstract:
Les cristaux dopés par des ions de terre rare (TR) apparaissent prometteurs pour des applications dans le traitement quantique de l'information. Parmi ces matériaux, les cristaux massifs d'Eu3+:Y2O3 présentent un long temps de cohérence optique (T2), un paramètre fondamental pour les technologies quantiques. Ce travail de thèse porte sur l'étude de ce système à l'échelle nanométrique, ce qui pourrait permettre de développer des systèmes hybrides dans lesquels les TR sont couplées à d'autres systèmes quantiques. Des nanocristaux de différentes tailles ont été élaborés par précipitation homogène. La largeur optique inhomogène diminue avec des recuits à haute température et peut atteindre les valeurs mesurées dans des cristaux massifs. Une corrélation quasi-linéaire avec les largeurs de raie Raman a aussi été observée. Les temps de vie de population sont plus longs que dans les échantillons massifs et peuvent être modélisés par un indice de réfraction effectif. Les T2 optiques ont ensuite été déterminés par écho de photon et creusement de trou spectral. Nous avons mesuré un temps de cohérence de 7.1 µs à 1.7 K dans un échantillon dopé à 0.5 % en Eu3+, la valeur la plus élevée observée pour un nanocristal. Une étude en température et de la diffusion spectrale indique que le déphasage est dominé par des fluctuations de la structure et des basculements de spinsRare earth (RE) doped crystals are promising materials for quantum information processing (QIP). In particular, Eu3+:Y2O3 bulk crystals present long optical coherent lifetimes (T2), a fundamental parameter for QIP. In this thesis, we investigated this system at the nanoscale, which could be used to build hybrid devices where RE are coupled to other quantum systems. This work focuses on the development of Eu3+: Y2O3 particles with sub-wavelength size and on the static and dynamical contributions to Eu3+ optical linewidth. Systems with different particle and crystallite sizes were prepared using homogeneous precipitation. Optical inhomogeneous linewidths were found to decrease with high temperature annealing and reached values close to those of bulk crystals, showing that low defect concentrations can be obtained. A quasi-linear correlation with Raman linewidths was also observed. T1 population decays were measured by fluorescence and found longer than in the bulk, in good agreement with a model based on an effective refractive index model. Optical T2 were investigated by photon echo (PE) and holeburning techniques. We observed a coherence lifetime of 7.1 µs at 1.7 K in a 0.5 % Eu3+ doped sample, the highest value reported for any nanocrystal. Temperature dependence and spectral diffusion studies indicate that structure fluctuations and spin flips dominate dephasing
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Romanenko, Anton [Verfasser], Franz [Akademischer Betreuer] Fujara, and Christina [Akademischer Betreuer] Trautmann. "Radiation damage produced by swift heavy ions in rare earth phosphates / Anton Romanenko ; Franz Fujara, Christina Trautmann." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2016. http://d-nb.info/1126644269/34.
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Carleschi, Emanuela. "Electronic structure of transition metal and rare earth ions in complex materials by resonant core-level spectroscopies." Doctoral thesis, Università degli studi di Trieste, 2009. http://hdl.handle.net/10077/3061.
Full textAbstract:
2007/2008In the course of this thesis I present an experimental investigation into various strongly correlated transition metal and rare earth compounds using core-level spectroscopic techniques, which have augmented the understanding of the electronic properties of these different systems. I will discuss the orbital occupation and the symmetry of the states near the Fermi level, responsible for the variety of ground states shown by a variety of strongly correlated systems such as misfit cobaltates, strontium ruthenates, metallic manganese and rare earth compounds.
XXI Ciclo
1978
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Lo, Tak-shing. "Two-body operators and correlation crystal field models /." [Hong Kong : University of Hong Kong], 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13437549.
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Ribeiro, Cristina Tereza Monteiro. "Espectroscopia optica dos ions terras raras Er+3 e Gd+3 em vidros fluoroindatos." Universidade de São Paulo, 1996. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-06022014-110700/.
Full textAbstract:
Este trabalho consiste na caracterização óptica dos íons terras raras Er+3, Yb+3 e Gd+3 quando em vidros fluoroindatos. As técnicas utilizadas foram: absorção óptica, luminescência e tempo de vida. Foram realizadas medidas de upconversion em vidros dopados com os íons Er+3 e Yb+3 nas concentrações de 2% mol de ErF3 e concentrações de 0, 2 e 8% mol de Yb+3 com excitação em 0.8 e 0.98μm observando as transições 2H11/2 → 4I15/2 4S3/2 → 4I15/2 (verde) e 4F9/2 → 4I15/2 (vermelho). Como resultado verificou-se que o Yb+3 aumenta a eficiência da emissão por upconversion no vermelho. Através de medidas espectroscópicas nos vidros fluoroindatos com Gd+3 não foi verificado tendência a cristalização destes vidros, mesmo para altas concentrações de Gd+3 Para o íon Gd+3em vidros fluoroindatos foram determinados os parâmetros de Judd-Ofelt, através dos quais determinamos as propriedades ópticas do íon e comparamos com os dados obtidos experimentalmente. Estes resultados se encontram em boa concordânciaThis work consists of the optical characterization of rare earth Er+3, Yb+3 and Gd+3 fluoroindate glasses by means of luminescence, optical absorption and lifetime techniques. Upconversion process were studied in Er+3, Yb+3 doped glasses (with the same ErF3 concentration and different Yb+3 concentrations) excited at 0.8 and 0.98μm. Transitions 2H11/2 → 4I15/2 4S3/2 → 4I15/2 (green) e 4F9/2 → 4I15/2 (red) were detected. As a result, we conclude that the Yb+3 incorporation increases the emission efficiency of the red upconversion process. Spectroscopic measurements performed on Gd+3 fluoroindate glasses didn\'t point out crystallization tendency of the glasses, even for high Gd+3 concentrations. The Judd-Ofelt parameters of Gd+3 fluoroindate glasses were obtained, so that the optical properties of Gd+3 were determined. The results are in good agreement with the experiment
35
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.
Full textAbstract:
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.
36
De, Oliveira Lima Karmel. "Nanocristaux dopés par des ions terres rares pour des applications en information quantique." Electronic Thesis or Diss., Paris 6, 2015. http://www.theses.fr/2015PA066611.
Full textAbstract:
Les cristaux dopés par des ions de terre rare (TR) apparaissent prometteurs pour des applications dans le traitement quantique de l'information. Parmi ces matériaux, les cristaux massifs d'Eu3+:Y2O3 présentent un long temps de cohérence optique (T2), un paramètre fondamental pour les technologies quantiques. Ce travail de thèse porte sur l'étude de ce système à l'échelle nanométrique, ce qui pourrait permettre de développer des systèmes hybrides dans lesquels les TR sont couplées à d'autres systèmes quantiques. Des nanocristaux de différentes tailles ont été élaborés par précipitation homogène. La largeur optique inhomogène diminue avec des recuits à haute température et peut atteindre les valeurs mesurées dans des cristaux massifs. Une corrélation quasi-linéaire avec les largeurs de raie Raman a aussi été observée. Les temps de vie de population sont plus longs que dans les échantillons massifs et peuvent être modélisés par un indice de réfraction effectif. Les T2 optiques ont ensuite été déterminés par écho de photon et creusement de trou spectral. Nous avons mesuré un temps de cohérence de 7.1 µs à 1.7 K dans un échantillon dopé à 0.5 % en Eu3+, la valeur la plus élevée observée pour un nanocristal. Une étude en température et de la diffusion spectrale indique que le déphasage est dominé par des fluctuations de la structure et des basculements de spinsRare earth (RE) doped crystals are promising materials for quantum information processing (QIP). In particular, Eu3+:Y2O3 bulk crystals present long optical coherent lifetimes (T2), a fundamental parameter for QIP. In this thesis, we investigated this system at the nanoscale, which could be used to build hybrid devices where RE are coupled to other quantum systems. This work focuses on the development of Eu3+: Y2O3 particles with sub-wavelength size and on the static and dynamical contributions to Eu3+ optical linewidth. Systems with different particle and crystallite sizes were prepared using homogeneous precipitation. Optical inhomogeneous linewidths were found to decrease with high temperature annealing and reached values close to those of bulk crystals, showing that low defect concentrations can be obtained. A quasi-linear correlation with Raman linewidths was also observed. T1 population decays were measured by fluorescence and found longer than in the bulk, in good agreement with a model based on an effective refractive index model. Optical T2 were investigated by photon echo (PE) and holeburning techniques. We observed a coherence lifetime of 7.1 µs at 1.7 K in a 0.5 % Eu3+ doped sample, the highest value reported for any nanocrystal. Temperature dependence and spectral diffusion studies indicate that structure fluctuations and spin flips dominate dephasing
37
盧德成 and Tak-shing Lo. "Two-body operators and correlation crystal field models." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1993. http://hub.hku.hk/bib/B31210922.
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Ganesan, Parameshwari. "Investigation of Luminescent Properties in Rare-Earth free Metallophosphonate Hybrid Materials : structural Insights in photophysical studies." Electronic Thesis or Diss., Normandie, 2023. http://www.theses.fr/2023NORMC266.
Full textAbstract:
Durant ce travail de thèse, les propriétés structurelles et photoniques des metallophosphonates luminescents hybrides ont été étudiées en abordant le rôle de leur structure dans les propriétés luminescentes. Les métallophosphonates possèdent différentes coordinations chimiques montrant leurs capacités à former plusieurs centres métalliques ainsi qu’une forte liaison chimique de type P-O-M. L’objective de ce travail est l’étude des matériaux hybrides organiques-inorganiques luminescents dont le composant organique offre une plateforme solide facilement amovible avec divers groupes fonctionnels. Cette étude s’articule sur différents metallophosphonates hybrides synthétisés par voie hydrothermale à l’aide de ligands organiques tels que le fluorène, le thianthrène et l’acide phosphonique avec des éléments alcalino-terreux (Mg, Ca, Sr, Ba) et des métaux de transitions (Mn, Co, Cu, Zn). Ces derniers ont été obtenus en manipulant la nature de la molécule, le nombre de groupes fonctionnels et les propriétés cationiques au sein de la structure. Grace à leurs caractéristiques liés à leurs différents arrangements structurels, les matériaux synthétisés montrent diverses propriétés, notamment la rigidité et la stabilité thermique. De plus, ces matériaux montrent des propriétés de luminescences intéressantes tel que la fluorescence, phosphorescence à température ambiante (PTA), les déplacements bathochrome et hypsochrome, l’émission de type excimère ainsi que l’apparition de nouvelles bandes de luminescence rouge et verte pour certains cations spécifiques. Enfin, la variation des propriétés de composés hybrides en fonction de la structure est discutée, en tenant compte le phénomène d’émission induite par Agrégation (AIE) et d’émission améliorée par agrégation (AEE)This thesis work systematically investigates the structural and photophysical properties of rare-earth-free metallophosphonate hybrid luminescent materials, emphasizing the role of structure in luminescent properties. Metallophosphonates demonstrate exceptional versatility with their coordination chemistry, highlighted by their ability to interact with multiple metal centers and form robust P-O-M metal bonds. We aim to study crystalline organic-inorganic hybrid luminescent materials in which the organic part provides a rigid platform which is easily modifiable with various functional groups. we present various metallophosphonate hybrids synthesized through the hydrothermal route using functionalized organic ligands such as Fluorene, Thianthrene, and Tetraphenylethylene (TPE) phosphonic acid with different alkaline-earth elements (Mg, Ca, Sr, Ba) and transition elements (Mn, Co, Cu, Zn). Different metallophosphonate materials are obtained by manipulating the nature of molecules, the number of functional groups, and the characteristics of cations in the structure. Due to that, the synthesized metallophosphonate hybrid materials exhibit diverse structural properties, including rigidity, thermal stability, and different arrangements like face-to-face or edge-to-face and herringbone stacking patterns. Furthermore, these materials display intriguing luminescent properties, such as Fluorescence, Room Temperature Phosphorescence (RTP), Bathochromic and Hypsochromic shift (red and blue shift), Excimer emission, and other novel green and red luminescence bands, particularly in the presence of specific cations. Lastly, we discuss and explore the interconnection between structural and physical properties including the phenomena of Aggregation Induced Emission (AIE) and Aggregation Enhanced Emission (AEE) for hybrid compounds
39
Kumar, Deepu [Verfasser], Plessen Gero [Akademischer Betreuer] von, and Thomas [Akademischer Betreuer] Taubner. "Influence of metal nanoparticles on the light emission properties of rare-earth ions / Deepu Kumar ; Gero von Plessen, Thomas Taubner." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/122169748X/34.
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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.
Full textAbstract:
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
41
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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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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Guille, Antoine. "Étude de matériaux convertisseurs de fréquence appliqués au photovoltaïque." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10294.
Full textAbstract:
Dans le but d'augmenter le rendement des cellules solaires tout en conservant des coûts modérés, de manière à les rendre compétitives face aux énergies fossiles, plusieurs solutions sont envisageables. L'une d'elles, que nous allons étudier dans ce travail, consiste à déposer une couche mince d'un matériau convertisseur de fréquence à l'avant d'une cellule photovoltaïque. Cette couche doit pouvoir convertir chaque photon de la gamme UV-bleu en deux photons infrarouges, capables chacun de générer une paire électron-trou. Cette étude porte sur la synthèse et la caractérisation d'un tel matériau applicable aux cellules en silicium. Nous étudions la possibilité de mettre à profit un mécanisme de quantum-cutting avec le couple d'ions Pr3+-Yb3+. Ce phénomène est mis en évidence dans les matrices CaYAlO4 et NaLaF4. De plus, dans le but de rendre ce concept utilisable en couche mince, nous évaluons aussi la possibilité d'utiliser les ions Ce3+ et Eu2+ comme sensibilisateurs des niveaux 3Pj de l'ion Pr3+In order to increase the efficiency of solar cells with limited costs, several solutions worth considering. One of them consists in the deposition a down conversion thin film in front of a silicon solar cell. This layer should convert each incident photon from the UV-blue range of the solar spectrum into two infrared photons, both able to generate an electron hole pair. This work is about the synthesis and the characterization of a down converting materials for silicon solar cells. We study the possibility to use a quantum-cutting mechanism within the Pr3+- Yb3+ couple. We give evidence of this phenomenon in CaYAlO4 and NaLaF4 matrices. Moreover, in order to make it suitable for thin film application, we also study sensitization of 3Pj levels of Pr3+ ion with Ce3+ and Eu2+ ions
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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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Gao, Guojun [Verfasser], Doris [Akademischer Betreuer] Ehrt, and Lothar [Akademischer Betreuer] Wondraczek. "Tunable photoluminescence from rare earth and transition metal ions activated silicate glasses and glass ceramics / Guojun Gao. Gutachter: Doris Ehrt ; Lothar Wondraczek." Jena : Thüringer Universitäts- und Landesbibliothek Jena, 2014. http://d-nb.info/1048047180/34.
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Vermillac, Manuel. "Nanoparticules dans les fibres optiques en silice dopées aux ions luminescents et leur évolution au cours de l’étirage." Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4098/document.
Full textAbstract:
Le développement de nouvelles fibres optiques en silice repose sur l’insertion des ions luminescents (ions de terres rares) dans des nanoparticules diélectriques. Dans ce contexte, la taille des particules est un paramètre clef qu’il convient de contrôler afin de bénéficier des nouvelles propriétés. Pour répondre à cet impératif, l’objectif de cette thèse était double. Premièrement, dans un objectif de structuration, il a été important d’étudier l’évolution des caractéristiques du matériau au cours de la fabrication, et deuxièmement, l’évolution des propriétés de luminescence avec les caractéristiques du matériau. La première partie de ce manuscrit décrit les différents types d’évolution des nanoparticules qui ont été observées au cours de ce travail de thèse. La réaction chimique de nanoparticules avec la matrice en silice est abordée dans l’étude du dopage par des nanoparticules de LaF3. Une observation originale de l’allongement et de la fragmentation de particules durant l’étirage en fibre optique est présentée. L’évolution thermodynamique des particules au cours de l’étirage, ainsi que l’influence des paramètres de l’étirage sont abordées. Enfin, la seconde partie de ce manuscrit se focalise sur le lien entre le matériau et ses propriétés spectroscopiques (Tm3+, Er3+). Les résultats montrent notamment que l’ajout de lanthane dans les fibres optiques dopées aux ions thulium augmente les pertes optiques, mais permet aussi d’augmenter la durée de vie du niveau 3H4 du Tm3+ jusqu’à un record de 58 μs pour une fibre transparente (pertes inférieures à 0,1 dB.m−1). Ces résultats confirment ainsi la nécessité d’un compromis sur la taille des particules et l’importance de ces travaux sur leurs possibilités de structurationThe development of new silica-based optical fibers is relies on the insertion of luminescent ions (rare-earth ions) in dielectric nanoparticles. In this context, particle size is a key parameter that should be controlled in order to benefit from the new properties. To reach this goal, the objective of this thesis was twofold. Firstly, it was important to understand, to engineer its structuration, the evolution of the characteristics of the material during its fabrication process, and secondly, the evolution of the spectroscopic properties with the characteristics of the material. The first part of this manuscript describes the different types of evolution of the nanoparticles that were observed during this thesis work. The chemical reaction of nanoparticles with the silica matrix is discussed in the study of LaF3-nanoparticles doping. Also, an original observation of the elongation and the break-up of particles during the fiber drawing are presented. The thermodynamic evolution of the particles during the fabrication process as well as the influence of its parameters are discussed. Finally, the second part of this manuscript focuses on the link between the material and its spectroscopic properties (Tm3+, Er3+). In particular, the addition of lanthanum in the Tm3+-doped fibers increased the optical losses, but also enabled the increase of the lifetime of the 3H4 level up to a record in silica of 58 μs (optical losses below 0,1 dB.m−1). These results highlight the need for a compromise on particle size and the importance of this work on structuring possibilities
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Jambunathan, Venkatesan. "Infrared lasers based on ho3+:kre(wo4)2 crystals with tm3+or yb3+ as sensitizers." Doctoral thesis, Universitat Rovira i Virgili, 2011. http://hdl.handle.net/10803/34762.
Full textAbstract:
Laseres de estado sólido que operan en la región espectral de seguridad ocular alrededor de los 2 micrómetros (2µm) son de elevado interés en la actualidad debido a su potencial aplicación en los campos de la medicina, teledetección remota y como fuentes de bombeo en osciladores ópticos paramétricos (OPOs) para conversión en el infrarrojo medio. La transición láser en las 2 µm es posible en los iones de tulio (Tm) ligeramente por debajo de las 2 µm y en iones de holmio (Ho) ligeramente por encima de las 2 µm.
La generación láser en iones de Tm es relativamente simple con la utilización de láseres de diodo como fuentes de bombeo, sin embargo, los láseres basados en Ho se han conseguido tradicionalmente en el pasado mediante el codopaje con Tm o mediante bombeo directo del nivel emisor del Ho. Recientemente, diodos láser que operan a 1.9 µm han aparecido en el mercado con buena eficiencia y con alto potencial para el escalado en potencia de los láseres de Ho.
Los láseres de Ho son más apropiados que los láseres de Tm especialmente para aplicaciones médicas por dos razones: La longitud de onda láser ligeramente por encima de las 2 µm, donde el agua (mayor componente del cuerpo humano) presenta una ligera menor absorción que la típica longitud de onda láser del Tm, hace que el láser penetre más en el tejido humano. La segunda razón es que los láseres de Ho pueden operar en régimen pulsado generando mayores energías por pulso que los láseres de Tm debido al mayor tiempo de vida del nivel emisor 5I7 y las aplicaciones médicas requieren por lo general régimen pulsado para evitar daño térmico del tejido.
Numerosos óxidos y fluoruros cristalinos han demostrado ser adecuadas matrices para Ho, sin embargo, poca atención se ha puesto en los dobles tungstatos cristalinos de fase monoclínica, de fórmula química KRE(WO4)2, brevemente KREW, donde RE = Y, Gd y Lu conocidos por ser matrices láser muy eficientes para la generación láser a potencias intermedias. Estos cristales anisotrópicos presentan una elevada sección eficaz de absorción y emisión cuando son dopados con iones lantánidos y especialmente para ciertas polarizaciones.
Considerando el potencial del Ho y las buenas propiedades de KREW, nuestro trabajo se centra en la investigación de las prestaciones láser en cristales de KREW dopados con Ho utilitzando tanto Tm o Yb como iones sensibilizadores y utilizando fuentes de bombeo emitiendo a 1.9 µm que permiten la excitación directa del nivel emisor.
En esta tesis, presentamos los resultados basados en el crecimiento cristalino de monocristales de Ho:KREW, codopajes (Ho,Tm) y (Ho,Yb):KLuW a diferentes concentraciones de Ho, su caracterización en términos de estructura, composición y espectroscopia y finalmente la generación láser alrededor de 2.1 µm.Eye-safe solid-state lasers that operate in the 2µm spectral range are the subject of interest in the present years because of their potential applications in the field of remote sensing, medicine and as a pump source for Optical Parametric Oscillators (OPOs). Laser transitions around 2 µm are possible in the trivalent lanthanide ions Tm3+ (Tm) (slightly below 2 µm) and Ho3+ (Ho) (slightly above 2 µm). Laser generation in Tm ions is easily achieved with comfortable diode pump sources, however, Ho lasers have usually been achieved in the past either by co-doping the active medium with Tm or by direct pumping of the Ho ions with Tm lasers. Recently, relatively cheap diodes emitting around 1.9 µm are in the market to realize Ho lasers with great potential for power scaling. Ho lasers are more suitable than Tm lasers especially for medical applications because of two reasons: The laser wavelength is slightly above 2µm, where water (main component of human tissue) shows slightly less absorption than the typical wavelength of Tm leading to a deeper penetration in human tissue. The second reason is that Ho lasers can operate in pulsed regime delivering higher energies than Tm lasers due to the longer lifetime of the emitting level 5I7 and medical applications are required to be generally in pulsed regime to avoid thermal damage of human tissue. Many oxide and fluoride crystals were shown to be suitable host for Ho, however little attention was paid to the monoclinic potassium rare earth double tungstate crystal, shortly KRE(WO4)2 or KREW, where RE= Y, Gd, Lu known to be very efficient rare earth solid state hosts for generating intermediate power levels. These anisotropic crystals exhibit very high absorption and emission cross sections when doped with lanthanide ions and especially for selected polarizations. Considering the potentialities of Ho and good properties of KREW, our work focuses in the investigation of the laser performances of a Ho doped KREW either by using Tm or Yb as sensitizers and by using in-band pump sources emitting around 1.9 µm, where the development of compact solid state infrared laser emitting at 2.1 µm for intermediate power levels is followed. Here, in this thesis, we present the results based on growth of single doped Ho:KREW, co-doped (Ho,Tm) and (Ho,Yb):KLuW crystals of several doping concentrations, their characterisation in terms of structure, composition and spectroscopy and finally dedicated for the laser generation around 2.1 µm from these materials, which was highly successful.
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Koksel, Bahar. "The Use Of N-polyethereal Polypyrroles In Preconcentration And Surface Enhanced Raman Scattering Studies." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610495/index.pdf.
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Polypyrroles containing polyether pseudocages (PI, PII, PIII) have been synthesized via chemical oxidation of 1,5-bis(1,1-pyrrole)-3-oxabutane (MI), 1,8- bis(1,1-pyrrole)-3,6-dioxahexane (MII), and 1,11-bis(1,1-pyrrole)- 3,6,9-trioxaundecane (MIII) using anhydrous FeCl3 in CHCl3. Because as obtained polymer resins did not give any response toward any cations, they were reduced (undoped) using chemical reducing agents. Tetrabutylammonium hydroxide (TBAOH) was found to be more effective in undoping to obtain more reproducible and reusable polymer resins. It was investigated whether the undoped polymer resins were used for the extraction of rare earth metal ions from the aqueous medium. Among them, only PIII resin can extract La(III), Eu(III) and Yb(III) from their aqueous solutions and can be employed for the preconcentration of these metal ions. For batch extraction of La(III), Eu(III) and Yb(III) at neutral pH values, percent recoveries of 98.0, 90.7 and 87.3, respectively, has been obtained by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) technique. The sorption capacity is found as 1.3 mg of La(III) per gram of PIII resin. The PIII resin could be reused at least five times without significant change in its sorption capacity. PIII has also been synthesized via electrochemical method to be used in the preparation of Surface Enhanced Raman Scattering (SERS) active substrate. PIII has been polymerized on Indium Tin Oxide (ITO) glass by using constant potential electrolysis. In an electrolyte solution containing 0.05M tetrabutylammonium perchlorate (TBAP), 1.2 V vs. Ag wire (oxidation potential of MIII) was applied for coating and then silver particles were deposited on the surface of PIII coated ITO electrode by reducing Ag(I) in monomer free electrolyte solution electrochemically. As an alternative, another SERS substrate was prepared electrochemically by depositing silver particles directly on ITO glass. The performances of prepared ITO-PIII-Ag and ITO-Ag SERS substrates were evaluated with dilute solutions of brilliant cresyl blue (BCB), crystal violet (CV), para amino benzoic acid (PABA), nicotine and nicotinic acid.
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Sampaio, Jurací Aparecido. "Preparação e caracterização de vidros aluminato de cálcio com baixa concentração de sílica dopados com Nd2O3 e Er2O3." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-24062008-162022/.
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O desenvolvimento de laseres de estado sólido compacto operando na região do infravermelho médio, entre 2 - 5 ?m, tem recebido considerável atenção nos últimos anos. Esses dispositivos oferecem grande potencial como fonte de luz para uma infinidade de aplicações, como por exemplo laseres para medicina e sensores químicos remotos. Laseres operando na região de 2.8 ?m tem interesse particular na medicina devido a forte banda de absorção da água nessa região espectral. Para se conseguir forte emissão laser próximo a 2.8 ?m têm sido investigadas famílias de vidros não-óxidos, como por exemplo vidros fluoretos de metais pesados e vidros chalcogenetos, dopados com Er3+. Entretanto esses vidros são caros, difíceis de serem feitos, além de serem tóxicos. Por essa razão o desenvolvimento de um vidro óxido seria ideal, já que são mais baratos, relativamente fáceis de serem produzidos, além de não serem tóxicos. A desvantagem dos vidros óxidos é a sua alta energia de fônons, quando comparada aos vidros haletos e chalcogenetos, que aumenta a taxa de transição não radiativa. Seria interessante investigar um sistema vítreo que tivesse propriedades otimizadas, ou seja, boas propriedades ópticas, térmicas e mecânicas, e baixa energia de fônons. O sistema vítreo aluminato de cálcio seria um candidato para essas aplicações, já que preenche essas exigências. Porém não há na literatura informações a respeito da influência de pequenas quantidades de elementos terras raras nas propriedades desses vidros, e qual é a concentração ideal desses íons. O objetivo dessa tese foi investigar composições de vidros aluminato de cálcio (48,1 CaO : 40.8 Al2O3 : 4.1 MgO : 7.0 SiO2) dopados com Nd2O3, Er2O3 ou Yb2O3, e verificar qual a influência desses íons nas propriedades ópticas, térmicas, mecânicas e termo-ópticas. Investigou-se também qual a influência da atmosfera de fusão. Com esse objetivo as amostras foram fundidas em cadinhos de grafite sob vácuo, e em cadinhos de platina, ao ar, ambas as fusões ocorreram a 1400 °C. As amostras foram investigadas através de difração de raios-X e microscopia óptica, cujos resultados confirmaram o estado amorfo das amostras preparadas. As amostras não apresentaram estrias e tiveram boa transparência óptica. Os espectros de transmitância mostraram que o processo de fusão a vácuo eliminou completamente a forte banda de absorção próxima a 3 ?m devida a água. O corte da transmitância na região do infravermelho ocorreu em 5.5 ?m, sendo independente do tipo do íon terra rara presente na composição do vidro. O índice de refração em 546.1 nm aumentou de 1.6702 (amostra base) para 1.6876 (amostra dopada com 8% de Er2O3). Este acréscimo no índice de refração é atribuído a um aumento da polarizabilidade eletrônica do vidro devido ao aumento de oxigênios nonbridging. A densidade aumenta de 2.92 g/cm3 (amostra base) para 3.12 g/cm3 (amostra dopada com 8% de Er2O3), esse aumento é explicado levando em consideração a massa dos átomos terras raras, que são maiores em relação ao Al2O3. A dureza dos vidros aluminato de cálcio diminuiu de 865 kg/mm2 (amostra base) para 781 kg/mm2 (amostra dopada com 8% de Er2O3), ou seja aproximadamente 11% de decréscimo. No caso da temperatura de transição vítrea, Tg, esse decréscimo é de aproximadamente 8%, sendo 841 °C para a amostra base e 782 °C para a amostra dopada com 8% de Er2O3. Para o vidro base, a difusividade térmica foi de 5.75 x 10-3 cm2/s e a condutividade térmica foi de 15.5 x 10-3 cm-1 K-1. Tanto a difusividade quanto a condutividade térmica decresceram na mesma proporção da dureza e Tg, conforme substitui-se a alumina pelo óxido terra rara. Esta é uma indicação de que os átomos terras raras atuam como modificadores de rede, abrindo a estrutura do vidro, diminuindo a resistência mecânica e atuando como barreiras térmicas no material. A resistência ao choque térmico dos vidros aluminato de cálcio é de 339 W/m, semelhante aos vidros silicatos que é de 358 W/m, e aproximadamente quatro vezes maior que a dos vidros fluoretos, 86 W/m. Este resultado confirma a hipótese de que os vidros aluminato de cálcio podem suportar variações abruptas de temperatura. Através da espectroscopia de lente térmica foram obtidas a eficiência quântica dos vidros aluminato de cálcio dopados com Nd2O3 e Er2O3. No caso das amostras dopadas com concentrações menores de 3% de Nd2O3 a eficiência quântica foi de aproximadamente 80%. Esses resultados indicam que os vidros aluminato de cálcio são excelentes candidatos para laseres de estado sólido e demais aplicações ópticas na região do infravermelho médio.The development of compact solid-state lasers operating in the midinfrared wavelength region (2 -5 ?m) has been an area of considerable activity in the last few years. These devices offer great potential as light sources for applications as medical lasers as well as in remote chemical sensing devices. Light sources in the 2.8?m region are of particular interest for medical applications due to the strong water absorption in this spectral region. Apart from allowing extremely precise cutting and ablation of water-containing tissues, the other advantages of using light sources operating at 2.8 ?m are related to the possibilities of reducing skin burning in surgeries, decrease in the use of anesthesia and shortening of recovery time, especially in skin surgeries and in the cutting and remova1 of hard tissues, such as tooth enamel and bone. In order to achieve strong laser emission around 2.8 ?m the effort so far has been concentrated on the family of Er3+ doped non -oxide glasses such as heavy metal fluorides and chalcogenides. However the production of these glasses is expensive, and it is difficult to make them, besides they are toxic. On the other hand, the oxide glasses are cheaper, atoxic and easy to produce them. The disadvantaged, however, is its the relative high phonon energy that promote high nonradiative transition rates. Since calcium aluminate glasses are formed with non-network forms, CaO and Al2O3, they have high tendence towards devitrification. The addition of small amounts of alkali and alkaline earth elements enlarges the glass forming region. Several calcium aluminate glasses compostions containing SiO2, BaO and MgO are now reported in the literature. In this thesis, low silica calcium aluminosilicate glasses doped with Nd2O3 and Er2O3 were prepared. Since the sample compositions were close to the phase diagram glass formation, the rare earth doping was performed up to 8wt.%. The samples was melted under vacuum condition in a graphite crucible at 1500 °C, and in air in a platinum crucible. The influence of the rare earth doping on the thermal diffusivity, thermal conductivity and Vickers hardness was such that all these physical parameters decreased by roughly the same amount, namely 8%, between the undoped and 5 wt% of Nd2O3. The dependence of these parameters, as a function of the Nd2O3 doping, strongly supports the idea that the Nd3+ or Er3+ act as network modifiers. Elastic module (E, G, K, v) of calcium aluminosilicate glasses with < 10 mole% of SiO2 doped with Er2O3 and Yb2O3, melted in air and under vacuum conditions, have been measured using the pulse echo ultrasonic technique. There was a decrease of the elastic properties, about 5%, as rare earth doping increases from 0.2 to 1.5-mol% (about 8 wt%). The Young\'s modulus did not vary within errors of measurements. The Debye temperature varied between (369±9)K and 352±9 K, which is explained assuming that the rare earth ions acts as network modifiers disrupting the glasses structure. The undoped calcium aluminate glasses fracture toughness is (1.4±0.3) MPa m1/2 and the thermal shock resistance is (339±102) W/m. The fluorescence quantum efficiency determined by thermal lens spectroscopy, was found be about 80% for the 2wt% Nd2O3 doped calcium aluminosilicate glass. The fluorescence quenching was observed to doping higher than 2wt% Nd2O3. The variation of the refractive index as a function of the temperature, dn/dT, was found be 8.0 x 10-6/0c. Among the various glass system investigated, CA glasses presented greater mechanical properties and larger thermal shock resistance, indicating that these materials are candidates for solid state laser applications and other infrared applications.
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Silva, Davinson Mariano da. "Produção e caraterização de materiais vítreos de germanato com nanopartículas metálicas e íons de érbio para aplicações em fotônica." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-08012008-092018/.
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Neste trabalho são apresentadas a preparação e investigação das propriedades luminescentes dos sistemas vítreos PbO-GeO2 e PbO-GeO2-Ga2O3 dopados com íons de érbio e contendo nanopartículas (NPs) metálicas de prata, ouro e cobre, para aplicações em dispositivos fotônicos. Estes vidros apresentam larga janela de transmissão (400-4500nm), alto índice de refração (~1,9) e baixa energia de fônon (700cm-1). Com a finalidade de verificar a nucleação das nanopartículas metálicas, foram realizadas análises por Microscopia Eletrônica de Transmissão que indicaram a presença de nanopartículas metálicas, cristalinas, aproximadamente esféricas e com tamanho médio entre 2 e 10nm. As medidas de absorção óptica evidenciaram a incorporação dos íons de Er3+ na forma trivalente e a presença de bandas de absorção relacionadas à ressonância dos plasmons superficiais, localizadas em aproximadamente 470nm (no caso das NPs de prata) e em torno de 800nm (no caso das NPS de cobre). As medidas de emissão foram realizadas através da excitação das amostras com laser cw de 980nm e potência de 80mW. Foram medidas bandas de emissão associadas à conversão ascendente de freqüências do Er3+ em 530, 550 e 670nm devidas às transições 2H11/2->4I15/2, 4S3/2->4I15/2 e 4F9/2->4I15/2 respectivamente. Nas amostras contendo NPs de prata, para concentrações de 1,0 e 2,0% de AgNO3, foi observado aumento significativo da emissão da luz verde (530 e 550nm) com o crescimento do tempo de tratamento térmico, quando comparadas com a emissão em 670nm. Para as amostras com NPs de ouro, com concentrações de 0,5 e 1,0% de Au2O3 verificamos um aumento maior da emissão em 670nm quando comparada com as emissões em 530 e 550nm. Para amostras com NPs de cobre, as emissões associadas à conversão ascendente de freqüências do Er3+ foram igualmente afetadas pela presença das NPs e possuem intensidade significativamente inferior as dos casos anteriores. O estudo da variação da intensidade de fluorescência com a potência do laser de excitação nos permitiu concluir que dois fótons participam do processo de conversão ascendente de freqüências na presença e na ausência de NPs metálicas. Os aumentos ocorridos na luminescência são provavelmente causados pelo aumento do campo local nas proximidades dos íons de terras-raras devido ao tamanho observado para as NPs (2-10nm). Portanto, a presença das NPs metálicas desempenha papel fundamental no aumento e/ou diminuição da luminescência da conversão ascendente de freqüências dos íons de Er3+, conferindo aos vidros propriedades novas que são bastante interessantes para aplicações em dispositivos fotônicos.This work presents the preparation and investigation of the luminescent properties of PbO-GeO2 and PbO-GeO2-Ga2O3 vitreous systems, doped with Erbium ions and containing silver, gold and copper metallic nanoparticles (NPs), for applications in photonic devices. These glasses have a large transmission window (400-4500nm), high refractive index (~1,9) and low phonon energy (700cm-1). Transmission Electronic Microscopy analysis were performed, to verify the metallic NPs nucleation. This analysis indicated that the NPs are metallic and crystalline, approximately spherical, with average size between 2 and 10nm. Optical Absorption measurements showed the Er3+ ions incorporation are in trivalent form and the presence of the absorption bands related to the surface plasmon resonance (SPR) centered around 470nm (for silver NPs) and around 800nm (for copper NPs). Emission measurements were performed pumping the samples with a cw laser (980nm; 80mW). Bands associated to Er3+ frequency upconversion centered around 530, 550 and 670nm were observed due to the transitions 2H11/2 -> 4I15/2, 4S3/2 -> 4I15/2 e 4F9/2 -> 4I15/2, respectively. For the samples containing silver NPs, for 1,0 and 2,0% of AgNO3, it was observed a higher enhancement of the green emission (530 and 550nm), with the increasing of the annealing time, when compared to the emission at 670nm. The samples with 0,5 and 1,0% of Au2O3 showed higher enhancement of the emission centered at 670nm, when compared to the emissions at 530 and 550nm. For the samples with copper NPs, the Er3+ emissions were uniformly affected by the presence of the NPs, and have lower intensity than the other ones. The study of the variation of the fluorescence intensity with the pump laser power indicated that two photons are involved in the frequency upconversion process in the presence and in the absence of the metallic NPs. The observed enhancements in the luminescence are probably due to the local field enhancement in the proximities of the rare-earth ions, due to the small size observed for the NPs (2-10nm). Thus, the presence of metallic NPs plays an important role in the enhancement and/or quenching of the Er3+ frequency upconversion, given new properties to glasses which are of great interest for application in photonic devices.