Lithium tetraborate (Li2B4O7) has aroused interest of scientists since 1960s by the courtesy of the thermoluminescence (TL) property it possesses. Over and above, it found widespread use in surface acoustic wave apparatuses, in sensor sector and in laser technology due to its non linear optical characteristics. For the uses in thermoluminescence dosimetry lithium tetraborate is activated by addition of a variety of metals as dopants. This study comprises the synthesis of lithium tetraborate by two methods (high temperature solid state synthesis and water/solution assisted synthesis) as well as doping and characterization of the material. Lithium tetraborate is readily commercially available in TL dosimetry / hence, the main aim is to specify practical production conditions to pioneer domestic production. In high temperature synthesis, the initial heating was performed at 400oC for 3 hours. Then the samples were heated at 750oC for two hours, intermittently mixed to enhance diffusion and exposed to the same temperature for another two hours. In water/solution assisted synthesis, stoichiometric quantities of reactants were mixed in water by heating and agitating in order to achieve homogenous mixing and good dispersion of the material. The remnant of water was removed from the system by 3 hours initial heating at 150oC. The synthesis stage is followed by doping step where the metals Cu, Ag and In in different proportions were doped in lithium tetraborate by solid state and solution assisted synthesis techniques. Powder X-ray diffraction method was employed for the characterization of the material. The thermal properties of doped and un-doped materials were studied by DTA (Differential Thermal Analyses). Besides, FT-IR (Fourier Transform Infra red) spectrometry analyses were performed in order to detect differences in the bond structure caused by doping The XRD patterns obtained showed that lithium tetraborate production was successful by both high temperature solid state synthesis and solution assisted synthesis Moreover, it was inferred from the XRD results that addition of dopants did not have a sound effect on the crystal structure. Furthermore, the DTA results displayed that addition of different dopants to the structure of lithium tetraborate did not cause any noticeable difference. The extensive TL measurements showed that the TL response of the material produced is affected by production and doping methods.

In this study, differences in glow curves of Mn doped LTB powder samples synthesized with solid and wet synthesis methods and doped by using solid and wet doping techniques were investigated. Firstly, LTB was synthesized by using wet synthesis method which mainly comprises dissolution of reactants in water as solvent. Second way to produce LTB which was used in this study was solid synthesis method. In solid synthesis method, reactants were mixed in powder form. In the second part of the study, LTB produced by two different methods were doped with Mn and additionally Ag, Mg or P by using two different doping techniques. In order to see structural differences between differently synthesized and differently doped LTB samples which contained different amount of dopant powder X-Ray Diffraction (XRD) method was employed. Besides, FTIR (Fourier Transform Infrared) spectroscopy analyses were performed in order to detect differences in the bond structure caused by doping. Additionally, Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) was used to determine the actual amount of dopant in LTB. Also morphological structures of samples were compared by using Scanning Electron Microscopy (SEM). Thermoluminescence measurements were performed with (TLD) Thermoluminescence Dosimeter equipment. XRD and FTIR analysis showed that syntheses of products were done in well success. Addition of dopants did not cause any changes in structural or bonding properties of LTB. It was possible to observe that, synthesis and doping methods and dopant concentration effect the thermoluminescence glow curves of doped LTB.

Strontium pyrophosphate is a promising phosphate that is used widely in the industry as a result of its luminescent, fluorescent, dielectric, semi-conductor, catalyst, magnetic and ion exchange properties. Thermoluminescent dosimetry (TLD) is one of such areas. Recent researches in METU on thermoluminescence property of strontium pyrophosphate showed that strontium pyrophosphate could give enough intensity for radiation dosimetry when doped with oxides of some rare-earth elements. In this study strontium pyrophosphate was synthesized and the product was doped with copper-silver, copper-indium and manganese-praseodymium ions by solid-state reaction. In addition to these processes, characterization and the investigation of thermoluminescence properties of strontium pyrophosphate with and without dopants was conducted. Stoichiometric quantities of strontium carbonate and ammonium dihydrogen phosphate were weighed, mixed and ground by agate mortar. Afterwards, the mixture was heated at 900&amp / #730 / C for 14.5 hours. For doping process, synthesized strontium pyrophosphate and different amounts of copper oxide, indium oxide, silver nitrate, manganese oxide and praseodymium oxide were weighed and powdered together. Then, mixture was heated at 950&amp / #730 / C for 11 hours. For characterization of strontium pyrophosphate samples with and without dopants / X-ray Diffraction (XRD) was implemented. Fourier Transform Infrared Spectroscopy (FTIR) was used to determine whether the bond structures were affected from doping or not. Thermal properties of the samples were investigated with the help of Differential Thermal Analysis (DTA). Morphology of compounds was observed by Scanning Electron Microscope (SEM). Afterwards thermoluminescence (TLD) studies were carried out. XRD pattern of samples showed that the intensity of hkl-310 peak of strontium pyrophosphate increased with the inclusion of metal oxides, however none of the characteristic peaks of metal oxides was observed. Addition of metal oxides caused no change in FTIR meaning that the anionic part of matrix compound, which is strontium pyrophosphate, has structural stability. Thermal analysis and morphological investigation of this material were performed. TLD results were different for each sample, which has different content. The most significant peak, which is suitable for radiation dosimetry was observed at 160&amp / #730 / C in the glow curve with the sample doped with 7% manganese oxide and 1% praseodymium oxide.

Les sources laser accordables se distinguent par leur capacité à changer leur longueur d’onde d’émission de façon continue dans le temps. Elles sont utilisées dans de nombreuses applications comme les télécommunications, la spectroscopie et la tomographie optique cohérente. Elles sont caractérisées principalement par une faible largeur de raie instantanée, une grande fréquence de balayage et une large plage d’accord. Les avantages des sources accordables ouvrent la voie vers d’autres types d’applications comme la caractérisation des impulsions ultra-courtes par exemple. Généralement, ces impulsions sont caractérisées via des méthodes non linéaires, lentes et trop compliquées à mettre en place. Nous avons donc proposé une nouvelle approche basée sur les sources accordables pour la caractérisation des impulsions ultra-courtes. En utilisant un laser à semi-conducteur accordable linéairement, type SG-DBR (Sampled-Grating Distributed Bragg Reflector), nous pouvons balayer en une seule mesure tout le spectre optique des impulsions sous test. Le signal de battement entre la source accordable et le laser pulsé permet de mesurer l’amplitude et la phase spectrales des différents modes ce qui nous donne accès à la forme temporelle de l’impulsion. L’avantage de notre approche est que tout le processus de caractérisation se fait en une seule mesure très rapide. En effet, la grande fréquence de balayage du laser accordable permet d’avoir des temps de mesure très faibles (< 10 μs), ce qui offre la possibilité d’avoir des mesures en temps réel. De plus, grâce à la large plage d’accord, cette technique est complétement indépendante de l’impulsion sous test, elle ne nécessite aucune connaissance au préalable des différentes propriétés de cette dernière telles que la fréquence de répétition, le nombre de modes ou la fréquence de chaque mode / Optical swept sources are distinguished by the ability to change their output wavelength in a continuous manner over time. They are used in many applications such as telecommunications, spectroscopy and optical coherence tomography. They are mainly characterized by a narrow instantaneous linewidth, a high sweep rate and a wide tuning range. The advantages of swept sources open the way to other types of applications such as the characterization of ultrashort pulses for example. Generally, these pulses are characterized using nonlinear methods which are slow and too complicated. We have proposed a novel approach based on swept sources for the characterization of ultrashort pulses. By using a linearly wavelength-swept semiconductor laser like SG-DBR (Sampled-Grating Distributed Bragg Reflector), we can scan the entire optical spectrum of the pulses under test in a single measurement. The beat signal between the swept source and the pulsed laser is then used to measure the spectral amplitude and phase of all modes which gives access to the temporal shape of the pulse. The main advantage of our approach is that the entire characterization process is done in a single fast measurement. Indeed, the high sweep rate of the swept source offers the possibility of having real time measurements. In addition, thanks to the wide tuning range, this technique is completely independent of the pulse under test, it requires no prior knowledge of the various properties of the pulse such as the repetition frequency, the number of modes or the frequency of each mode

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