Les progrès récents de la microscopie en champ proche ont amélioré les connaissances de la physique sub-micronique. La microscopie en champ proche optique permet aujourd'hui de mesurer des propriétés optiques avec une résolution de quelques nanomètres. Ce travail de thèse est basé sur la réalisation et la compréhension du fonctionnement d'un microscope en champ proche optique, en mode transmission. Ce microscope utilise une sonde métallique qui vient localement diffuser le champ électromagnétique qui règne à la surface de l'échantillon. Cette méthode de détection du champ proche optique permet d'obtenir des résolutions rarement atteintes. Avec ce microscope nous étudions de nombreux phénomènes physiques, tant du point de vue fondamental que de leurs applications. Nous traiterons succinctement des autres approches de microscopie à sonde locale, notamment de la microscopie en champ proche optique qui est à l'origine de notre travail. Ceci nous permettra d'introduire la description du montage spéci fique que nous avons réalisé, à laquelle nous avons joint quelques explications et résultats d'expériences, ceux-ci permettant de tester les modèles qui ont été développés ces dernières années au laboratoire a n d'expliquer l'origine du signal dans notre con figuration. Dans une troisième partie nous traiterons des contrastes en champ proche optique par le biais des expériences que nous avons réalisées, avec ce montage fonctionnant en transmission, sur un système modèle ainsi que sur des agrégats et des multi-couches magnétiques. Enfi n, la quatrième et dernière partie de ce travail est exclusivement consacrée à la caractérisation de la localisation de l'exaltation du champ électromagnétique dans des structures métalliques aléatoires et à la validation des modèles théoriques développés a n d'expliquer ces exaltations.

Résumé : voir conclusion - pp. 118 à 120 du pdf joint

Résumé => Voir Pdf (2ème pièce jointe), pages 121-123

Non disponible

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3678. Adviser: Kent D. Choquette. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--Lehigh University, 2009. / Adviser: Thomas L. Koch.

This dissertation contains studies on several aspects of the media and system in the optical data storage. The main subjects that have been examined are magneto-optical (MO) media, phase-change (PC) media and the optical system used for recording and readout. In the studies of MO media, we examined the optical characteristics of magnetic garnets fabricated by sol-gel method and looked at how multilayer design can enhance MO effect. In the investigation of PC media, we developed a new technique to estimate thermal coefficients of erasable PC media, which allowed us to model the thermal profile during the writing and erasing process. In the investigation of the system, we designed and fabricated a variable leaky polarizing beamsplitter used in a dynamic tester for testing different optical disks throughout the wavelength range of 440nm-690nm. We also analyzed the application of partial response equalization and maximum likelihood sequence estimation in MO readout for high density recording.

This dissertation contains studies on several aspects of the media and system in the optical storage. The main subjects that have been examined are magneto-optical (MO) media, phase-change (PC) media and the optical system used for testing and characterizing these media. In the studies of MO media, we examined the thermomagnetic properties of the TbFeCo film and observed the dynamic behavior of its magnetization reversal. We introduced a novel technique to estimate the thermal coefficients, i.e., thermal conductivity and specific heat of each layer in the MO multilayer stack. In the investigation of PC media, we focused on studying the properties of the light scattered from the bare substrates and the disks coated with the PC media. Relationship between the scattering properties and disk noise spectral density has been found by comparing the results from the scattering measurements and noise measurements. Also, we introduce a novel method to study the crystallization process of PC media, by means of heating up a sample with periodic mark array recorded on it. Shining a laser beam on the mark array and monitoring the signal from one of the 1st orders diffracted beam, we can examine the process of the crystallization and tell the difference between growth-dominated and nucleation-dominated PC media. In the investigation of the system, we designed and implemented a scatterometer which is used to measure the scattered light from the sample.

This dissertation presents the measurement of optical phase in the media and systems of optical data storage, polarization dependence of signals from periodic one-dimensional arrays of magnetic domains in magneto-optical media and crystalline domains in amorphous phase-change media, and optical characterization of multilayer stacks used as optical data storage media. Digital signals in optical data storage systems can be encoded in the intensity, polarization or phase of the carrier beam. Both surface structure and material property variations can create a phase modulation at the exit pupil. Current optical data storage systems do not make use of this phase modulation and its recovery could increase the strength of the generated signal. We experimentally describe a variant of Zernike's phase-contrast microscope to measure the small phase object, an interferometer to measure the relative optical phase on reflection between amorphous and crystalline regions of the phase-change media of optical data storage, and a method to measure optical phase information in disk system. In order to increase the data density in optical data storage, the wavelength becomes shorter and the numerical aperture of the objective lens becomes higher. In the interaction of the focused beam with a grooved, multilayer disk, the different response to s- and p-polarized light upon reflection from the disk results in different complex-amplitudes and has strong impact on readout and servo signals for the two fundamental components of polarization. Polarization dependence of signals from periodic one-dimensional arrays of magnetic domains in magneto-optical (MO) media and crystalline domains in amorphous phase change (PC) media are studied by theoretical calculation and experiment. Currently, many different multilayer stacks are designed to enhance the contrast of readout signal, reduce noise, increase the storage density and speed, or improve media reliability. A good understanding of the range of values of the optical constants should help to improve the accuracy of optical and thermal design of the storage media. The refractive index n and the absorption coefficient k of these materials vary to some extent with the film thickness and with the film deposition environment. We report the observed variations of optical constants among samples of differing structure and among samples fabricated in different laboratories.

Nulling stellar interferometry may enable the discovery of earth-like planets around other stars. In nulling mode, the zero order fringe is destructive and on axis, thus canceling light from a bright source and detecting dimer off-axis features. To create deep on-axis nulls, the phase must be shifted half a wave achromatically over a broad band. The phase shift is created by adding optical path thickness with dielectric plates. Plates of different materials can balance dispersion. The nulling solutions found for TPF (infrared) and for SIM (visible) are promising. This dissertation describes the implementation of a nulling beam combiner test bed and presents data characterizing its performance. Although the implementation was limited so that a broad band null of 10E-4 was not attained, the test bed revealed the extreme challenges of this technique and provided very valuable lessons that will enable future implementations to be successful and more precise. The nulling beam combiner testbed was implemented in the laboratory as a Michelson interferometer with the goal of achieving a stabilized, l0E-4 null over a spectral region from 600 nm to 800 nm. The beam combiner system has three tiers of control. Tier 1 controls phase achromaticity by tilting optical plates and is a static control loop. Tier 2 sweeps through the white light fringe and then searches for the null as the air path drifts over minutes. Tier 3 stabilizes the null with a 300 hertz servo loop. A scheme for active control of the optical thicknesses was developed. The phase as a function of wavelength was measured by performing PSI on a spectrally dispersed fringe. The phase was fit to a model to solve for the optical thicknesses. The optical thicknesses were then adjusted to match the ideal thicknesses of an optimized solution. This process of measuring and adjusting the optical thicknesses is performed iteratively to achromatize the phase. The stabilizing servo loop sensed on a grey fringe at a short wavelength. At the shorter wavelength, the fringe was 90 degrees out of phase with the main pass band resulting in a grey fringe. The grey fringe intensity is more sensitive to OPD changes.