publication detail
Metallic nanoparticles for quadratic nonlinear optics : size and shape effects
AUTHORS
Document type
Conference papers
Résumé
Metallic nanoparticles (NP) are being investigated for a wide range of applications, such as photonics, information storage, electronic and optical detection systems, therapeutics, diagnostics, photovoltaic and catalysis. Many investigations have been focused on controlling the size and shape of metallic nanoparticles, such as nanospheres, nanorods, nanostars and so on, as there factors affect significantly their physical and chemical properties, especially their linear and nonlinear optical response. The quadratic nonlinear optical properties of metallic NPs are generally defined by their hyperpolarizability β values, measured via the Harmonic Light Scattering technique in colloidal NP solutions. As a result, large magnitudes of NPs hyperpolarizabilities have been reported. In this work we used a fundamental laser source at 1.064 nm, the second harmonic wavelength at 532 nm coming close to plasmonic resonances of Au and Ag nanoparticles. In the first part of this work we propose a systematic investigation of the influence of the gold NP surface area on their quadratic nonlinear optical properties of metallic NPs, defined by their hyperpolarizability β values. Gold and silver nanospheres, with diameters ranging from 3 to 80 nm are investigated, in order to reach the limit of validity of the purely dipolar origin of beta values. Moreover, by studying gold (Fig. 1a) and silver nanorods (Fig. 2a) with different surface areas, we will evidence the predominance of these surface effects over shape factors, leading us to revisit previous studies on the NLO properties of these nanorods.