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RESEARCH PRODUCT

Contribution à l'étude de la formation des images optiques en microscopie champ proche optique: effet de la sonde en deux dimensions

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This work consists in the development of a theoretical tool for the purpose to undertake numerical simulations able to take into account the coupling between the probe and the object. The first part, concerns the combination of the differential method and the algorithms T and S, to overcome numerical problems which appear in the cases where the size of system (probe - object) is more realistic. The developed global model is two-dimensional and applied in polarization TE under the normal diffraction condition. We have used the developed model to study the formation of optical image by monomodes and multimodes probes. The obtained optical images at constant height, have allowed us to study the installation of guided modes, and then to study the influence of the apex shape and size. By calculating the transfer functions in the case of monomodes probes we have observed that this function of transfer can exist only in particular cases ( e.g. of size of objects, distance probe-object, incidence angle etc...) and that in general a pseudo-function of transfer remains accessible. To validate our results, we have studied more complicated (structured) probes, possessing a core, a sheath and possibly a metallic coating. With a very good qualitative agreement with experimental results recorded at constant intensity mode, it is interesting to observe that the attacked probe is more efficient than the etched probe. By extending our study to the infrared near-field, the study of spectroscopy map about the detection of an absorbent object embedded in a dielectric layer confirms the former results : the probe modify slightly the spectroscopic signature. This application shows the pertinence of the theoretical model and its large applications in any spectral domain.