Génération de second harmonique de milieux diélectriques : du tensioactif en solution à la microparticule de silice optiquement piégée

Abstract : This thesis reports an experimental study of harmonic radiation from various dielectric media. We both study second harmonic generation on interfaces and hyper Rayleigh scattering in solutions. We present the first step for the realization of the following project : the study of the second harmonic generation on an optically trapped soapy bubble. To do so, two main axis of investigation are developped. Firstly, we study the harmonic response of two commonly used surfactants such as TTAB, a cationic one and SDS carrying a negative charge. This study consits of understanding the main component of a soapy bubble. We investigate how harmonic intensity is modified with an increase of soap concentration. These experiements are carried both in volume and at the air/water interface. The harmonic scattered intensity shows similar features for SDS and TTAB, as a sudden drop appearing at the critical micelar concentration. However, on the surface, the two oppositely charged surfactants give a radically different evolution of second harmonic signal versus their concentration. Indeed, the water molecules of the surroundings behaves in an opposite manner with negative or positive charged surfactants. The second axis of research that we work on in this thesis, is on a novel experimental development. We combine an optical tweezer to trap microsized particles with a femtosecond laser probe to generate the second harmonic. This is a first step in order to trap a bubble and study it with second harmonic generation. This non linear inverted confocal microscope is used to study harmonic profil of an silica bead stuck on a sample. This study gives a glance of the complexity of the correlation between linear optics effects on the laser probe beam and the created harmonic intensity. We also perform experiments on a trapped particle and we measure the harmonic response of an unique particle
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Lucile Sanchez. Génération de second harmonique de milieux diélectriques : du tensioactif en solution à la microparticule de silice optiquement piégée. Optique [physics.optics]. Université de Lyon, 2018. Français. ⟨NNT : 2018LYSE1298⟩. ⟨tel-02044255⟩

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