La structuration des matériaux à l échelle micro et nano métrique constitue un domaine de recherche et développement très prometteur dont le succès permettra de réaliser le saut technologique tant attendu dans le domaine de la photonique. Du point de vue du matériau, l utilisation des diélectriques de type LiNbO3 ou encore TiO2 qui possèdent des propriétés spécifiques qui différent de ceux des semi-conducteurs est de nature à élargir les performances des composants photoniques à mettre au point. De plus, l utilisation de ces matériaux sous forme de couches minces permet de s affranchir des contraintes et des limitations imposées par le cristal massif. Dans le cadre de ce travail, nous nous intéressons à la réalisation de -structures 1D et 2D par ablation laser nanoseconde dans des couches minces et monocristaux de niobate de lithium ainsi que des couches minces de TiO2. Les couches minces de LiNbO3 ont été déposées par pulvérisation cathodique rf magnétron sur saphir tandis que les couches de TiO2 ont été réalisées par voie sol-gel sur des substrats de verre. Les ablations ont été réalisées avec un laser nanoseconde de type KrF excimer (ATLEX 300 SI Model). L irradiation des échantillons a été effectuée avec un masque de 10 m de diamètre, les fréquences appliquées varient de 10 à 100 Hz et les fluences varient de 0.3 à 2.3 J/cm2. Les structures ablatées ont été observées et analysées à l aide de la microscopie optique fonctionnant en mode Nomarski et de la microscopie -Raman. Nous avons notamment étudié l influence des paramètres d ablation (nombre de pulses, fluence et fréquence de répétition) sur les caractéristiques des structures ablatées. A titre d exemple, des réseaux de 55 trous ont été réalisés avec un nombre de pulse constant (5pulses). et différentes valeurs de fluences (0.88 à 2.093J/cm2). D après les résultats obtenus, nous avons constaté que la forme des trous ainsi que leur profondeur dépendent fortement de la fluence utilisée. Les meilleurs résultats sont obtenus pour les fluences élevées. Pour l étude de l effet du nombre des pulses sur l ablation des couches, nous avons procédé à la réalisation des réseaux de 55 trous avec une fluence constante 1.467J/cm2 et une variation du nombre de pulses de 5 à 15. Le taux moyen d ablation décroît avec l accroissement du nombre de pulses. A noter que préalablement à ces études, nous avons étudié les propriétés optiques de nos couches minces en utilisant la spectroscopie des lignes noires. Les résultats ont montré que les couches sont monomodes et possèdent des pertes optiques de l ordre de 1 dB.cm-1. L objectif final de ce travail est d optimiser le processus expérimental d ablation afin d obtenir des structures sub-micrométriques pour des applications dans le domaine des télécommunications optiques. / Micro and nano structuring of materials constitutes a field of very promising research and development whose success will make it possible to carry out very important progress of photonic technology. From the material point of view, the use of dielectrics such as LiNbO3 or TiO2, which have specific properties different from those of the semiconductors, is likely to widen the performances of the photonic components to be developed. Moreover, the utilization of these materials in the form of thin layers makes it possible to release from limitations imposed by the bulk materials. In this work, we were interested in the realization of -structures 1D and 2D by using nanosecond laser ablation of lithium niobate thin layers and monocrystals as well as thin layers of TiO2. LiNbO3 thin films were deposited by RF magnetron sputtering technique on sapphire while TiO2 layers were carried out by using sol-gel method on glass substrates. Ablations were performed with a nanosecond KrF excimer laser (ATLEX 300 IF Model). The ablation of samples was carried out with a mask of 10 m of diameter. The frequencies applied vary from 10 to 100 Hz and the fluences from 0.3 to 2.3 J/cm2. Structures were observed using optical microscopy functioning in Nomarski mode and analyzed using -Raman spectroscopy. We particularly studied the influence of the ablation parameters (number of pulsate, fluence and repetition rate) on the structure features. For example, 5x5 holes gratings were carried out with a constant number of pulse (5pulses) and various values of fluences (0.88 with 2.093J/cm2). Our results showed that the shape of holes and their depth strongly depend on the fluence used. The best results were obtained for high fluences. For the study of the effect of the number of pulse on the ablation process, we realized a 5x5 holes grating with a constant fluence 1.467J/cm2 and a variation of pulse number from 5 to 15. The average rate of ablation decreases with the increase of the pulse number. Note that, before these studies, we studied the optical properties of our thin films by using m-lines spectroscopy. Results showed that our films are monomodes and have optical losses of about 1 dB.cm-1. The final objective of this work is to optimize the experimental ablation process in order to obtain sub-micrometric structures for applications in the field the photonic

Lithium niobate(LiNbO3)has been widely used in optical frequency converter, electro-optical modulator¡Asurface acoustic waveguide filter¡Aand photorefractive recording due to its ease of growth, high nonlinear coefficient, and excellent optical quality. We think that we can utilize second harmonic generation (SHG) and laser scanning system to construct a reflective SHG system .From this system we can obtain PPLN poling pattern, then we can check the growth condition correctly or not. Compare to traditional method, this approach has the advantage of fast and non-invasive test. Besides, we can find crystal axis of crystal by changing the angle of incidence light and using additional half plate.

Este trabalho consiste na caracterização ótica de monocristais de LiNbO3: Er+3, visando a possibilidade deste sistema ser meio ativo para laser. Os resultados obtidos para absorção e emissão foram satisfatórios, sendo bastante compatíveis com os do modelo teórico adotado. O tempo de vida de luminescência das transições 4S3/2 - 4I15/2 e 4F9/2 - 4I15/2 foi medido, à temperatura ambiente e de nitrogênio líquido, mostrando que elas são possíveis candidatas a transições laser. Também foi feito um estudo sobre o comportamento das concentrações das impurezas indesejáveis OH- e Fe2+, através de tratamento térmico. O controle dessas concentrações foi feito através das técnicas de RPE e absorção ótica e os resultados mostraram que é perfeitamente possível eliminar tais impurezas de uma forma totalmente controlada. / This work consists in the optical characterization of LiNbO3:Er3+ single crystals, aiming to verify the possibility of this system being an active media for laser. The absorption and emission results were satisfactory, being compatible enough with the theoretical model adopted. The luminescence lifetime of the 4S3/2 - 4I15/2 e 4F9/2 - 4I15/2 transitions was measured at the ambient and liquid nitrogen temperature, showing that they are possible candidates for laser transitions. The behavior of the undesirable OH- and Fe2+ impurities was also studied through thermal treatment. The control of these concentrations was done using the EPR and optical absorption techniques and the results showed it is possible to eliminate such impurities in a totally controlled way.

Este trabalho consiste na caracterização ótica de monocristais de LiNbO3: Er+3, visando a possibilidade deste sistema ser meio ativo para laser. Os resultados obtidos para absorção e emissão foram satisfatórios, sendo bastante compatíveis com os do modelo teórico adotado. O tempo de vida de luminescência das transições 4S3/2 - 4I15/2 e 4F9/2 - 4I15/2 foi medido, à temperatura ambiente e de nitrogênio líquido, mostrando que elas são possíveis candidatas a transições laser. Também foi feito um estudo sobre o comportamento das concentrações das impurezas indesejáveis OH- e Fe2+, através de tratamento térmico. O controle dessas concentrações foi feito através das técnicas de RPE e absorção ótica e os resultados mostraram que é perfeitamente possível eliminar tais impurezas de uma forma totalmente controlada. / This work consists in the optical characterization of LiNbO3:Er3+ single crystals, aiming to verify the possibility of this system being an active media for laser. The absorption and emission results were satisfactory, being compatible enough with the theoretical model adopted. The luminescence lifetime of the 4S3/2 - 4I15/2 e 4F9/2 - 4I15/2 transitions was measured at the ambient and liquid nitrogen temperature, showing that they are possible candidates for laser transitions. The behavior of the undesirable OH- and Fe2+ impurities was also studied through thermal treatment. The control of these concentrations was done using the EPR and optical absorption techniques and the results showed it is possible to eliminate such impurities in a totally controlled way.

A polarization-independent electro-optically tunable add/drop filter utilizing non-polarizing novel relaxed beam splitters has been developed in LiNbO3 at the 1.55μm wavelength regime. The operation of this filter is based on passive directional coupler type beam splitters and strain-induced phase-matched TE↔TM polarization mode converters on an asymmetric Mach-Zehnder interferometer waveguide configuration. Fabrication parameters for channel waveguides, relaxed beam splitters and polarization mode converters were optimized individually then integrated to produce the final device. Single mode channel waveguides for both TE and TM polarizations were realized by the diffusion of 7μm wide Ti strips into LiNbO3 substrate. Relaxed beam splitters were produced using Ti diffused waveguides in a directional coupler configuration with 3.5mm long coupling region, 0.6º bending angle, and separation gap of 11μm and 13μm between waveguides. Tunable TE↔TM polarization mode converters with 99.8%

A polarization-independent electro-optically tunable add/drop filter utilizing non-polarizing novel relaxed beam splitters has been developed in LiNbO3 at the 1.55μm wavelength regime. The operation of this filter is based on passive directional coupler type beam splitters and strain-induced phase-matched TE↔TM polarization mode converters on an asymmetric Mach-Zehnder interferometer waveguide configuration. Fabrication parameters for channel waveguides, relaxed beam splitters and polarization mode converters were optimized individually then integrated to produce the final device. Single mode channel waveguides for both TE and TM polarizations were realized by the diffusion of 7μm wide Ti strips into LiNbO3 substrate. Relaxed beam splitters were produced using Ti diffused waveguides in a directional coupler configuration with 3.5mm long coupling region, 0.6º bending angle, and separation gap of 11μm and 13μm between waveguides. Tunable TE↔TM polarization mode converters with 99.8%

In the present thesis, diamond-like carbon thin films were deposited on Si(100) and LiNbO3 substrates by a planar capacitor plasma-enhence-chemical-vapor-deposition system. The reaction gases were C2H2,CH4,O2 and mixed with Ar (95¢M) and H2(5¢M).The influence of the growth of the thin film from different substrates and three different source gases flow ratios have been studied. The bi-layers structure of SAW(Surface Acoustic Wave) device was then fabricated. The interdigital transducers (IDTs) were fabricated on the bi-layers structure. The conditions of the DLC thin film of the bi-layers structure was varied in order to discuss its effects on SAW devices. In addition to Raman analyses, SEM and AFM have been employed to characterize the DLC thin film quality. From the experimental results of Raman spectrum analysis reveals that the DLC film has wide and flat spectrum region at wavelength of 1585~1600cm-1 of G-band and 1390cm-1 of D-band .It indicates that the DLC film contains much graphite sp2 bonds and a small part of amorphous DLC sp3 bonds. The optimal deposition conditions of the DLC film have been found for the reaction gas of C2H2 and Ar, from which the insertion loss of the SAW filter shows the quality better than from the others. SEM and AFM analyses shows that the roughness of the DLC film is below 10 nm and the faces of the DLC films are flat to be made into devices.

In this study, we use the reactive rf magnetron sputtering method with deposition parameters of RF power of 370W, sputtering pressure of 15 mTorr, substrate temperature of 400¢J, nitrogen concentration (N2/N2+Ar) of 30% and 40%, to deposit highly c-axis orientation AlN thin films on Z-cut LiNbO3 and ST-cut quartz piezoelectric substrate, respectively. The material characteristics of AlN films deposited on Z-cut LiNbO3 and ST-cut quartz substrate with different thickness were obtained by means of the analyses of XRD, SEM and AFM. Besides, the interdigital transducers (IDTs) were fabricated on the bi-layers structure. The AlN film thickness of piezoelectric bi-layers structure was varied in order to discuss its effect on SAW devices and the temperature coefficient of frequency (TCF) of AlN. From the experimental results, it reveals that the center frequency and TCF of SAW filters increase with the increased AlN thin film thickness. Besides it can be concluded that poly-crystalline AlN exhibits a positive temperature coefficient of frequency (TCF).

Em processos de crescimento de cristais pelo método de Czochralski, é observado que um campo elétrico aplicado ao cristal durante o processo de crescimento modifica a quantidade de dopante incorporada ao cristal. É desenvolvido um modelo, baseado na teoria de Burton, Prim e Slichter, levando-se em consideração as duas classes de material envolvidas, os óxidos e os semicondutores, e os efeitos produzidos pelo campo elétrico, eletromigração, subresfriamento constitucional, Efeito Peltier e efeito Seebeck. Resultados experimentais obtidos em crescimentos de LiNbO3:Cr2O3 e Si:Al são usados para aplicações do modelo / In crystal growth processes through the Czochralski method, it is observed that an electrical field applied to the crystal during the growth process modifies the quatity of the dopant incorporated to the crystal. A model is developed based on Burton, Prim and Slichter´s theory, taking into consideration two classes of materials, the oxides and the semiconductors, and the effects produced by the electrical field, electromigration, constitutional supercooling, Peltier Effect, Seebeck Effect. Experimental results obtained from the growth of the LiNbO3:Cr2O3 e Si:Al singlecrystals are used to the model application

Neste trabalho, apresentamos resultados da caracterização Magneto-Óptica de íons terras-raras (Nd3+ e Yb3+) em monocristais de niobato de lítio (LiNbO3). Medidas de Dicroísmo Circular Magnético (MCD) e de Emissão Circularmente Polarizada em Presença de Campo Magnético (MCPE) foram realizadas pela primeira vez nesses sistemas. Os resultados foram obtidos à temperatura de 2K, e em campos magnéticos de até 5 T. Através desses estudos, foi possível identificar os números quânticos cristalinos (&#956) dos subníveis Zeeman desses íons. A partir da dependência do sinal de MCD com a intensidade de campo magnético, determinou¬se o fator giromagnético efetivo g// do estado fundamental de cada íon, obtendo-se os valores: g//Nd = (1,4 &#177 0,1) e g//Yb = (4,7 &#177 0,1). Esses valores foram confirmados através de medidas de espectroscopia de Ressonância Paramagnética Eletrônica (EPR), realizadas a baixa temperatura (4-8 K), em banda X. Os espectros de EPR foram tomados em função da orientação relativa do campo magnético externo com o eixo c cristalino dos cristais, em 3 planos perpendiculares entre si. Os espectros de EPR mostram a existência de diferentes sítios ocupados pelos íons terras-raras. O sítio mais populado tem simetria axial, e para esse centro determinaram-se os fatores g efetivos g//Nd = (1,440 &#177 0,005) e g//Nd = (2,959 &#177 0,004), para o íon Nd3+, e g//Yb = (4,705 &#177 0,008) e g//Yb = (2,693 &#177 0,005) para o íon Yb3+. Espectros de MCD e MCPE obtidos para um cristal de rubi ilustram as convenções utilizadas e atestam que o sistema experimental funciona adequadamente. Os espectros obtidos nessa amostra também são originais, tendo sido resolvidas as transições permitidas com luz circularmente polarizada entre os subníveis Zeeman correspondentes aos níveis de energia 4A2 e &#8254E (2E) do íon Cr3+. / In this work we present Magneto-Optícal characterizations of rare-earth ions (Nd3+ e Yb3+) in lithium niobate (LiNbO3) single crystals. Magnetic Circular Dichroism (MCD) and Magnetic Circularly Polarized Emission (MCPE) measurements were performed for the first time on those systems. Spectra were obtained at 2K and at magnetic field strength up to 5T. From these studies, it was possible to assign the crystal quantum number (&#956) of the Zeeman sublevels of these ions, so that the sign and allowance of the electronic transitions could be predicted. From the dependence of suitable MCD spectral lines on the magnetic field strength, the effective parallel gyromagnetic factor (g//) of the ground state for each of the rare earth ions has been determined to be: g//Nd = (1,4 &#177 0,1) e g//Yb = (4,7 &#177 0,1). These values are in dose agreement to those obtained by means of Electron Paramagnetic Resonance (EPR) spectroscopy, at 4-8 K, and at X-band frequency. EPR spectra were recorded as a function of the external magnetic field orientation relative to the c crystalline axis in three mutual perpendicular planes. These spectra show evidence of multiple sites occupied by the rare-earth ions. For the most intense line seen in the spectra of each ion, it could be clearly assigned a site with axial symmetry, with effective g factors of g//Nd= (1,440 &#177 0,005) and g//Nd = (2,959 &#177 0,004), for the Nd3+3+ ion, and g//Yb = (4,705 &#177 0,008) and g//Yb= (2,693 &#177 0,005) for the Yb3+ ion. MCD and MCPE spectra recorded for a ruby crystal shows the experimental conventions used so far in this work, as well as assure that the experimental system works properly. These results are original ones, by means of which, the spectral transitions between the Zeeman sublevels of the 4A2 and &#8254E (2E) of the Cr3+ ions in ruby could be resolved.