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PROCESSUS DE MIGRATION MOLECULAIRE PHOTO-INDUITE EN MILIEU POLYMERE. APPLICATION A LA REALISATION DE NANOSTRUCTURES ORGANISEES OPTIQUEMENT.

Abstract : This work deals with the study of a new all optical structuration process of azo-polymer films. We show that the irradiation with normal incidence of an azo-polymer film by a uniform laser beam whose wavelength is in the absorption band of the azo-molecules, can lead to the formation of a quasi hexagonal surface relief grating at the surface of the polymer film.
After a brief review of different methods of micro and nanostructuration as well as the properties of azo-polymer films in the case of the surface relief gratings formation, we study in the first part of this manuscript the influence of several experimental parameters on the spontaneous formation of these photoinduced structures, among them the light polarization direction and the irradiation power.
The different results obtained in our case are then compared with different photo-assisted structuration processes already proposed and whose physical origins are clearly established, in order to determine the key parameters governing the formation of these hexagonal structures as well as their origins.
In the second part, different experiments are performed in order to evaluate the validity of effects so called “optical feedback effect” observed in liquid crystal light valve systems is performed.
The interpretation of the photoinduced hexagonal structuration process appears to be difficult: it is not excluded that an optical feedback phenomenon could be at the origin of the structuration process, but at the present, according to the different experiments performed, a new and original phenomenon of structuration adapted to azo-polymers films cannot be excluded in order to fully explain the different results obtained.
Finally, the last part of this manuscript is devoted to the implementation of these hexagonal structures in photonic devices and more particularly in organic electroluminescent diodes, in order to control their light emission properties. More particularly, as a first step, in the case of an optical pumping, we show that due to Bragg scattering it is possible to enhance the external efficiency by recovering a part of the light initially guided in the diode structure. Due to the hexagonal orientation of the photoinduced structures, the improvement of diode efficiency, followed by modification of the emission spectra as well, appears to be more important than the one observed when using a one dimensional grating structure.
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Submitted on : Friday, November 3, 2006 - 12:13:20 AM
Last modification on : Monday, January 13, 2020 - 5:46:02 PM
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  • HAL Id : tel-00111028, version 1

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Christophe Hubert. PROCESSUS DE MIGRATION MOLECULAIRE PHOTO-INDUITE EN MILIEU POLYMERE. APPLICATION A LA REALISATION DE NANOSTRUCTURES ORGANISEES OPTIQUEMENT.. Physique Atomique [physics.atom-ph]. Université Paris Sud - Paris XI, 2003. Français. ⟨tel-00111028⟩

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