RESUMO
The spontaneous emission rate of a fluorophore provides a direct probe of the photonic local density of states at the fluorophore position. Here we exploit this capability to map the plasmonic modes of gold nanoparticles by imaging the fluorescence intensity in combined regular arrays of identical gold and fluorophore-doped polymer nanoparticles. By varying the distance between gold and polymer particles across the array, the fluorophore emission generates an optical Moiré pattern corresponding to a magnified spatial map of the plasmonic mode, which can be directly imaged with an optical microscope. Our results are corroborated by supplementary theoretical model calculations.
RESUMO
We study dielectric/metal thin film multilayers designed for the coupling of dielectric waveguide modes and surface plasmons. The coupling as identified in calculated dispersion relations for extended multilayers is confirmed by measured angle-resolved reflectance data. By lateral structuring of the multilayers the mutual coupling of dielectric and plasmonic modes is directly observed by fluorescence based microscopy. For a light wavelength of 514nm we find a coupling length of 15microm. Our results highlight the potential of hybrid dielectric/metal waveguides for integrating surface plasmon based photonic circuitry or sensing elements into conventional optical devices.
Assuntos
Microscopia de Fluorescência/instrumentação , Óptica e Fotônica , Ressonância de Plasmônio de Superfície/instrumentação , Corantes/farmacologia , Eletrônica , Desenho de Equipamento , Luz , Metais/química , Microscopia de Fluorescência/métodos , Microscopia de Polarização/instrumentação , Microscopia de Polarização/métodos , Modelos Estatísticos , Modelos Teóricos , Dispositivos Ópticos , Polímeros/química , Ressonância de Plasmônio de Superfície/métodosRESUMO
In this paper, we report on the observation of multipolar surface plasmon excitation in lithographically designed gold nanotriangles, investigated by means of far-field extinction microspectroscopy in the wavelength range of 400-1000 nm. Several bands are observed in the visible and near infrared regions when increasing the side length of the triangles. The assignment of these peaks to successive in-plane multipolar plasmon modes is supported by calculations using the discrete dipole approximation method. We show that the lowest three multipolar excitations are clearly resolved in the visible and near infrared range. These new spectral features could be very promising in nanooptics or for chemosensing and biosensing applications.
