Thèse soutenue

Mesure et modélisation de la génération de seconde harmonique de nanoparticules d'or de symétrie d'ordre 3

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Auteur / Autrice : Thanh Ngoc Nguyen
Direction : Timothée TouryAlexandre Vial
Type : Thèse de doctorat
Discipline(s) : Optique et nanotechnologies
Date : Soutenance en 2013
Etablissement(s) : Troyes
Ecole(s) doctorale(s) : Ecole doctorale Sciences pour l'Ingénieur (Troyes, Aube)

Résumé

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We made metallic nanoparticles with C3v symmetry properties of 160 nm typical size. Although they are made only with gold, their non centrosymmetrical shape permit second harmonic generation. Their size has been optimized for plasmon resonance and non linear response. Gold nanostars have been made by electron beam lithography. The inter-distance is sufficiently large to allow collecting the SHG emission of individual particle. The effective χ(2) values of nanostars (44 pm/V off-resonance second order susceptibility, 480 pm/V at resonance), triangles (33 pm/V offresonance, 370 pm/V) and cylinders (7 pm/V off-resonance, 25 pm/V at resonance) point out the leading role of contour shape for significant efficiencies. The SHG response has been precisely assessed with a polarization analysis. We developed several models for the SHG response in which the nonlinear induced dipoles sources are located at the tip of star arms. The (exact or approximative) symmetry and the size of the star were taken into account. Our models show a very good agreement with experimental results. Efficiency of SHG has been measured according to pump wavelength