High-Performance Nanosensors Based on Plasmonic Fano-like Interference: Probing Refractive Index with Individual Nanorice and Nanobelts

We propose two different configurations for which the Fano-like interference of longitudinal plasmon resonances occurring at individual metallic nanoparticles can be easily employed in refractive index sensing: a colloidal suspension of nanospheroids (nanorice) and a single nanowire with rectangular cross section (nanobelt) on top of a dielectric substrate. We numerically study the performance of the two in terms of their figures of merit, which are calculated under realistic conditions. For the case of nanorice, we explicitly incorporate the effect of size dispersity into the simulations. Our obtained results show that the application of the proposed configurations seems to be not only feasible but also very promising

High-Contrast Fano Resonances in Single Semiconductor Nanorods

Fano resonances in plasmonics have received widespread attention for their distinctly narrow asymmetric line shapes. A variety of configurations have been considered, either requiring complex metallic nanostructures or being extremely faint if originated in simple single nanoparticles. Here we report on the emergence of high-contrast, strongly asymmetric Fano line shapes in the light scattered from semiconductor nanorods. Numerical calculations are carried out for the scattering cross sections of finite semiconducting nanorods, with dimensions such that the lowest-order (transverse) Mie resonances coexist with the lowest-order guided modes. Such intense narrow Fano resonances are strongly/weakly asymmetric in TE/TM polarization and overlap with the Mie-like background. A physical interpretation is presented stemming from the (strong or weak) interference of the far-field angular patterns of Mie resonances (indeed, of both magnetic and dielectric dipole character) with narrow Fabry–Perot (guided mode) resonances, the latter calculated through a 1D line current model. A quasi-analytical expression is developed for the scattering cross sections that reproduce fairly well the Fano numerical line shapes, along with a generalized Fano formula, with fitting factors confirming their high asymmetry and contrast. These high-contrast, strongly asymmetric Fano resonances herein obtained could be potentially exploited in nanophotonics and sensing in the visible and near-IR, eased by simplified fabrication requirements of shape (nanorod) and material (semiconductor)

Nanowire Antenna Emission

We experimentally demonstrate the directional emission of polarized light from single semiconductor nanowires. The directionality of this emission has been directly determined with Fourier microphotoluminescence measurements of vertically oriented InP nanowires. Nanowires behave as efficient optical nanoantennas, with emission characteristics that are not only given by the material but also by their geometry and dimensions. By means of finite element simulations, we show that the radiated power can be enhanced for frequencies and diameters at which leaky modes in the structure are present. These leaky modes can be associated to Mie resonances in the cylindrical structure. The radiated power can be also inhibited at other frequencies or when the coupling of the emission to the resonances is not favored. We anticipate the relevance of these results for the development of nanowire photon sources with optimized efficiency and/or controlled emission by the geometry

The evolving Interreligious Vision of Raimon Panikkar

Conferència a càrrec de Gerard Hall de l'Australian Catholic University sobre l'evolució del pensament interreligiós de Raimon Panikka

Optical Mie Scattering by DNA-Assembled Three-Dimensional Gold Nanoparticle Superlattice Crystals

Programmable assemblies of gold nanoparticles engineered with DNA have intriguing optical properties such as Coulomb-interaction-driven strong coupling, polaritonic response in the visible range, and ultralow dispersion dielectric response in the infrared spectral range. In this work, we demonstrate the optical Mie resonances of individual microcrystals of DNA–gold nanoparticle superlattices. Broadband hyperspectral mapping of both transmission and dark-field scattering reveal a polarization-insensitive optical response with distinct spectral features in the visible and near-infrared ranges. Experimental observations are supported by numerical simulations of the microcrystals under a resonant effective medium approximation in the regime of capacitively coupled nanoparticles. The study identifies a universal characteristic optical response which is defined by a band of multipolar Mie resonances, which only weakly depend on the crystal size and light polarization. The use of gold superlattice microcrystals as scattering materials is of interest for fields such as complex nanophotonics, thermoplasmonics, photocatalysis, sensing, and nonlinear optics