Electrodynamics in complex systems: Application to near-field probing of optical microresonators

This paper discusses recent theoretical efforts to develop a general and flexible method for the calculation of the field distributions around and inside complex optical systems involving both dielectric and metallic materials. Starting from the usual light-matter coupling Hamiltonian, we derive a self-consistent equation for the optical field in arbitrary optical systems composed of N different subdomains. We show that an appropriate solving procedure based on the real-space discretization of each subdomain raises the present approach to the rank of an accurate predictive numerical scheme. In order to illustrate its applicability, we use this formalism to address challenging problems related to nonradiative energy transfers in near-field optics. In particular, we investigate in detail the detuning of a microresonator probed by a near-field optical probe.</p

Near-zone field effect of FIR laser radiation on tunnel current through the Schottky barrier under plasma reflection condition

Far infrared (FIR) radiation of high-power pulsed laser incident normal to the surface of GaAs/metal tunnel structures with a self-consistent Schottky barrier gives rise to a change in the tunnel conductance. It has been shown that the observed photoresistive effects are caused by ponderomotive forces of the radiation field on the free electron plasma in the junctions. The change of tunnel conductance rises linearly with increasing intensity at low power levels and proceeds into a strongly superlinear dependence at high intensities. It is shown that this superlinearity is a result of an enhancement of the local radiation field in the near zone of diffraction by inhomogeneities at the metal-semiconductor interface and depends strongly on the roughness of the metal electrode. Experimental results are compared to a nonlinear extension of the theory of electron redistribution due to the radiation pressure

Laterally-resolved study of the Au/SiNx/GaAs(100) interface

We report a microscopic study of the Au/5 Angstrom SiNx/GaAs Schottky barrier based on scanning near-field optical microscopy. Photocurrent yield microimages taken at different photon energies reveal non-topographic features. Taking into account their dependence on photon energy and bias, such features are consistent with lateral variations of the local density of states related to defects. The results, therefore, confirm that lateral variations must be considered when analyzing semiconductor interfaces and of the corresponding devices. (C) 1998 Elsevier Science B.V

Self assembled film thickness determination by focused ion beam

The thickness evolution of multilayer film is investigated by focused ion beam (FIB) in the domain of polymer multilayers. This method, currently used in the modification and the characterisation of integrated circuits, proves it is possible to determine the polymer film thickness. Sample cutting and its observation of the cross section are performed in the FIB without leaving the vacuum chamber. Two main conclusions can be drawn: (1) the roughness of the film increases with the number of layer deposit, (2)the film growth changes from non linear (called exponential) to linear beyond 300 nm (70 layers

Caractérisation de multicouches de polyélectrolytes par réflectométrie laser, microscopie à force atomique et microscopie de fluorescence en champ proche

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Microscopie en champ proche par réflexion

This communication presents two techniques for high resolution surface analysis. In the first one, the illumination beam is totally reflected under the object surface, which must be transparent. The evanescent wave confined on the surface is frustrated locally by a dielectric probe of nanometric dimension which scans the objetc. A horizontal resolution of 10 nm and a vertical one of 1 nm have been obtained. In the second one, more adapted to metallic objects, the surface is illuminated by the near-field of the stylus, in which the reflected beam is Partially launched. First results dealing with the characterization of the dielectric stylus are presented.Cette communication présente deux techniques permettant l'analyse de surface haute résolution. Dans la première, le faisceau d'éclairage est réfléchi totalement sous la surface de l'objet, nécessairement transparent. L'onde évanescente qui l'accompagne est frustrée localement par une pointe diélectrique de dimension nanométrique balayant la surface. Une résolution de 10 nm horizontalement et de 1 nm verticalement a été obtenue. Dans la seconde, qui permet d'étudier un objet opaque, celui-ci est éclairé par le champ proche émis par la pointe, dans laquelle le faisceau réfléchi est partiellement réinjecté. Les premiers résultats concernant la caractérisation de la pointe sont présentés

Study of Film Growth Properties of Self-Assembled Polyelectrolyte Films of Higher Thickness : Reflectometric and Focused Ion Beam Analyses

International audienceThis work addresses the use of fixed-angle laser reflectometry to follow in situ the deposition of self-assembled polyelectrolyte films in a large domain of thickness. It is shown theoretically and illustrated experimentally that the reflectometric output can be interpreted in terms of refractive index and thickness way above the usual range which covers the earlier deposition steps of the polymers (i.e., 30-50 layers, depending on the film composition). Thick films containing up to 320 deposition steps (160 bilayers) were made in the reflectometric cell with the polymer pair poly(allylamine, hydrochloride) and poly(styrene sulfonate) on a silica substrate. They were imaged with AFM, and their thickness was measured using the focused ion beam (FIB) technique. In the course of construction, the reflectometric data started to alternate more or less regularly between positive and negative values, exhibiting absolute values at the extrema which decreased progressively. This phenomenon was coherent with simulated data, once the diffusion of the incident beam and the change of refractive index were taken into account. The phenomenon gives an opportunity to evaluate the composition and the mean thickness of the film during the growth, which is confirmed by comparison with the FIB measurements

Croissance et stabilité de films auto-assemblés de polyélectrolytes

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