ABSTRACT
The most significant goal of nanophotonics is the development of high-speed quantum emitting devices operating at ambient temperature. In this regard, plasmonic nanoparticles-on-mirror are potential candidates for designing high-speed photon sources. We introduce a novel hybrid nanoantenna (HNA) with CdSe/CdS colloidal quantum dots (QDs) based on a silver nanocube in a metal cup that presents a nanoparticle-in-cavity coupled with an emitters system. We use focused ion beam nanolithography to fabricate an ordered array of cups, which were then filled with colloidal nanoparticles using the most simple drop-casting and spin coating methods. The spectral and time-resolved studies of the samples with one or more nanocubes in the cup reveal a significant change in the radiation characteristics of QDs inside the nanoantenna. The Purcell effect causes an increase in the fluorescence decay rate (≥30) and an increase in the fluorescence intensity (≥3) of emitters in the HNA. Using the finite element method simulations, we have discovered that the proximity of the cups wall affects the oscillation modes of the gap plasmon, which, in turn, leads to changes in the electric field enhancement inside the nanoantenna gap. Additionally, substantial variations in the behavior of the gap plasmons at different polarizations of the exciting radiation have been revealed. The proposed nanoantenna can be useful in the development of plasmonic sensors, display pixels, and single-photon sources.
ABSTRACT
Recent advances in nanotechnology and optics have paved the way for new plasmonic devices. One of them are nanopatch antennas that are simple and, at the same time, effective devices for localizing the electromagnetic field on a scale of less than 10 nm and can be used in photonic integrated circuits as effective sources of photons, including single-photon sources. In the present study, we investigate the radiative characteristics of a submonolayer of colloidal CdSe/CdS quantum dots that form island structures in a resonator: a cubic silver nanoparticle on an aluminum mirror. For detecting plasmonic nanoparticles on glass or metal surfaces, we propose a new technique involving a tunable laser and a confocal microscope. We provide a comparative study of the luminescence enhancement factors for QDs in the NPAs upon off-resonance excitation and at a wavelength close to the resonance; a significant difference in the luminescence enhancement factors (by order of magnitude) is demonstrated. A 60-fold reduction in the spontaneous emission time, as well as an increase in the radiation intensity by a factor of 330, has been obtained in the experiments. The increase in the spontaneous emission rate demonstrated for the quantum dots is explained by the Purcell effect. Full-wave simulations of electromagnetic fields were carried out for the model of the developed nanopatch antenna; luminescence enhancement factors and radiative efficiencies were calculated as well.
