Ce travail de thèse a pour objectif la création d’indice optique local et contrôlé dans une matrice vitreuse à travers la mise au point et le développement de procédés de synthèse de nanoparticules (NPs) de sulfure de zinc (ZnS) dans un verre d’oxydes. Nous avons commencé par l’élaboration par voie de fusion d’un verre d’oxydes de composition initiale très simple. Nous avons ensuite examiné la problématique de la synthèse et du contrôle de croissance des NPs de ZnS dans nos échantillons dans trois matrices différentes et par trois traitements : recuit thermique, insolation UV ou par un traitement simultané (recuit thermique + insolation UV). Les propriétés optiques des verres dopés NPs ZnS fabriqués ont été caractérisées par diverses techniques (absorption UV visible, photoluminescence, FTIR, Raman, XPS, mesure d’indice). Il ressort de ces caractérisations que nous arrivons à fabriquer des NPs dans les trois matrices dont la taille peut aller de 1.8 à 7 nm. La dispersion sur les distributions de taille dépend de la matrice, du traitement post-fusion et de sa durée ainsi que de la concentration initiale en dopant. Nous avons également été amené à synthétiser et à étudier des nanopoudres de ZnS. Le procédé de sélection de taille révèle qu’il est possible d’obtenir au moins trois distributions étroites de tailles bien distinctes. Des filtres optiques UV à bande étroite peuvent ainsi être réalisés pour une longueur choisie en contrôlant la taille des NPs ZnS. Des applications prospectives des NPs ZnS pour le nano marquage et la photo dégradation de polluants modèles présents dans l’eau ont été illustrées / Our efforts have been devoted to the development of simple approach to synthesize ZnS nanoparticules (NPs) by melting process in a glassy matrix with the aim to create a controlled optical index variation. In this thesis, we present the formation of ZnS NPs in the glassy matrix and study of their optical properties. The nanocomposite incorporating ZnS in the host medium was prepared using the melting process from a mixture of the raw materials. We have prepared various glass samples with ZnS NPs size ranging from 1.8 à 7 nm. These samples were treated (heat treatment ± UV insulation with 244 nm laser) and characterized by UV-Vis absorption, FTIR, photoluminescence spectroscopy, Raman measurements and XPS. The refractive index measurements of these nanostructured composite glasses have been carried out and show an important increase with ZnS concentrations and treatments. We also present the elaboration of small and monodisperse ZnS nanopowder with size ranging from 3 to 100 nm by a simple, low-cost and mass production chemical method. The NPs were characterised by X-ray powder diffraction (XRD), UV-vis absorption and photoluminescence spectroscopy. The photocatalytic activity of ZnS nanopowders was investigated by using different colorant water dispersed. ZnS NPs appear to be a good candidate for potential environmental applications such as water purification. We also present application of fluorescent ZnS nanoparticles as cellular biomarkers. Fluorescent microscopy images of osteoblastic MC3T3-E1 cells revealed that the ZnS nanoparticles were biocompatible and were penetrated cells and nucleus regardless of their size. Hence, the ZnS NPs can be good candidates for drug delivery and bio-imaging applications

The study on refractive index modification of transparent materials with ultrashort laser pulses is presented in this work. Based on experimental data it was demonstrated, that using ultrashort pulses, generated with Yb:KGW laser system, it is possible to produce modified refractive index zones in the fused silica glass, that possess birefringence. This effect is caused by nanogratings that form in the bulk of the material. Homogeneity of the modified zones is determined by the accumulation effects, mainly the number of pulses that affect each area. Refractive index variations can be created also in crystalline material such as lithium niobate. Depending on the writing pulse parameters different types of modifications can be created: permanent modification that is caused by crystal amorphization and non-stable modifications that originate from the photorefractive properties of the crystal. Latter modifications can be used for three-dimensional, rewritable data recording. Highly efficient photonic elements, such as volume Bragg gratings, recorded in fused silica and lithium niobate crystal are demonstrated. The technique, allowing the evaluation of refractive index change applying Bragg gratings, is described. Also modification influence on nonlinear processes that appear in fused silica such as filament formation and supercontinuum generation is experimentally investigated. / Darbe pristatomi eksperimentiniai bei teoriniai rezultatai, susiję su skaidriųjų terpių lūžio rodiklio pokyčio indukavimu. Parodoma, kad lydytą kvarcą veikiant Yb:KGV lazerine sistema generuojamais impulsais, jame galima sukurti modifikuoto lūžio rodiklio sritis. Šios sritys pasižymi dvejopu šviesos lūžimu, atsirandančiu dėl medžiagos tūryje besiformuojančių nanogardelių, o modifikuotų sričių vienalytiškumas priklauso nuo akumuliacinių efektų. Pakitusio lūžio rodiklio sritis taip pat galima formuoti ir ličio niobato kristale. Priklausomai nuo spinduliuotės parametrų, šiame kristale galima įrašyti stabilius modifikuoto lūžio rodiklio darinius, o taip pat ir nestabilias modifikacijas, atsirandančias dėl fotorefrakcinio reiškinio. Pastarąjį efektą galima panaudoti daugkartiniam informacijos įrašymui. Pademonstruoti efektyvūs fotoniniai elementai, tūrinės Brego gardelės, įrašytos tiek lydyto kvarco, tiek ličio niobato kristalo tūryje. Pateikiama metodika, skirta lazerio indukuoto lūžio rodiklio pokyčiui nustatyti matuojant Brego gardelių difrakcinius efektyvumus. Taip pat tyrinėjama kaip modifikuoti dariniai lemia superkontinuumo ir šviesos gijos formavimosi reiškinius lydytame kvarce.

Sub-surface modification using a frequency doubled Ti: Sapphire femtosecond (fs) laser at 1kHz repetition rate, producing 100-fs pulse duration at 400nm, is studied in order to fabricate optical components within non-photosensitised polymethyl methacrylate (PMMA). This thesis explores the feasibility of producing three-dimensional optical devices in bulk polymers and polymer optical fibre (POF) using fs laser direct-writing techniques. For effective and optimal structuring, the laser writing parameters and focusing conditions, such as focusing depth, translation speed, and accumulated fluence are investigated by means of photo-modification thresholds; structural changes in dimensions and morphologies; and the magnitude of the refractive index modulation. The highest refractive index change is 3.2x10^(-3) achieved by using a dry (non-immersion) 0.45-NA objective for a single laser scan. Variations in damage threshold with focusing depths are attributed to a combination of material absorption or surface scattering of light due to contamination or surface imperfections, as well as oxygen diffusion and spherical aberration. Distortion of the laser-induced feature size and shape due to spherical aberrations is controlled and compensated by adjusting the laser power near the damage threshold. Permanent refractive index structures with cross-sectional dimensions of 2μm by 0.9μm and 3μm by 1.4μm are demonstrated at depths of 300μm and 500μm below the surface, resulting in the axial/ lateral ratio of 2.2 and 2.1, respectively. A novel phenomenon relevant to effects of translation speed on the fs laser modification is observed for the first time. As translation speeds reduce from 1.2 to 0.6mm/s, the optical damage threshold power decreases by 6μW, whilst other writing conditions remain constant. However, the damage threshold increases by 74μW with decreasing speeds from 0.6 to 0.35mm/s. This significant increase in threshold power enables inscription of refractive index gratings <5μm below the surface, because irradiation on the surface or near the surface initiates ablation rather than refractive index changes, and this forms a limit for writing useful structures. Compensating for this limit by using appropriate writing parameters highlights the potential of fabricating three-dimensional integrated optical circuits in thin (100μm) polymer substrates. Finally, highly localised fabrication of long period gratings into step-index single mode polymer fibres is demonstrated by removing distortion effects due to the curved surface. The distortion is compensated by sandwiching the fibre with two flat PMMA sheets, between which index-matching oil (n=1.5) is injected. This arrangement enables precise laser micro-structuring with flat interfaces and continuous inner material. The first demonstration of a 250-μm-period fibre grating, resulting in attenuation bands in the visible spectral region at 613, 633, 728, 816, 853, 877 and 900nm, is presented.