publication detail
Nonlinear plasmonic nanostructures for quadratic nonlinear optics
AUTHORS
Document type
Conference papers
Résumé
The increasing interest in metallic nanoparticles (NP) is motivated by their potential applications in photonics, information storage, detection systems, therapeutics, diagnostics, photovoltaic and catalysis. Their size and shape (nanospheres, nanorods, nanostars…) affect significantly their physical and chemical properties, especially 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. Here we use 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. First we report the influence of surface area of gold and silver nanospheres and nanorods on their β values. Diameters ranging from 3 to 80 nm allows to identify the validity domain of a pure dipolar origin of β values. The predominance of surface effects over shape factors is evidenced, leading us to revisit previous studies on the nanorod NLO response. Second, we report the synthesis and characterization of platinum “nanoflowers” (PtNFs) with different controlled sizes. These PtNFs display exceptionally strong first hyperpolarisabilities, higher than those of gold nanoparticles of similar size. Particle surface corrugation is shown to be the dominant factor governing these exceptionally high β values, with a very limited contribution from plasmonic effects that are negligible in the visible range In a third part, we synthesize and investigate the β values of non-centrosymmetric gold nanoprisms (NPrs) . Their β values display a linear dependence with the surface area and strongly depend on the sharpness of NPr corners. These β values of NPs are assigned mainly to the enhancement of electromagnetic fields due to geometrical effects (sharp extremities), in analogy with metallic tip-enhanced Raman spectroscopy