Abstract
We report a discrete dipole approximation approach to analyse the perturbations induced by silver nano-particles on the decay dynamics of a point-like emitter placed in their proximity. Due to the excitation of localized surface plasmons, metallic nano-particles behave like optical antennas and are able to convert localized fields into free-propagating optical radiation, and vice versa. Field localization and enhancement induce strong changes on the decay dynamics of dipoles located in the perturbed electromagnetic environment, and these can be faithfully quantified within the framework of classical electromagnetism in terms of total, radiative and non-radiative decay rates. The method is tested on benchmark cases, i.e., nanospheres and nano-shells, and it is then applied to analytically-unsolvable shapes such as sharp nano-cones and oxide-covered small nano-antennas. Numerical results reveal 105-order enhancements in the total decay rate of the dipole when located very near to the sharp tip, both with and without a thin Ag2O layer. Moreover, the counter-intuitive behaviour of the cone response in relation to the distance between the metal and the source of the radiation is discussed. Applications span from strong coupling studies to time-resolved fluorescence spectroscopy.
Highlights
Since the pioneering work of Purcell in 1946 [1], it has been widely known in the field of fluorescence spectroscopy that the rate of the emission process can be modified by placing a quantum emitter (QE), such as an atom or a molecule, in a structured polarizable environment [2 - 5]
The plasmonics community has looked with increasing interest at the possibility of handling the modification of spontaneous emissions through the conscious and controlled use of localized and delocalized surface plasmons, this favouring the growth of radiative decay-rate engineering (RDE) [9] which has become a central issue in nano-photonics
Metallic nano-structures and nano-patterned surfaces provide, a unique way to increase the radiative decay rate of fluorophores, and it has been shown that unusual effects on fluorophores, such as increasing or decreasing the rates of radiative decay or resonance energy transfer (RET), can be achieved [10]
Summary
Since the pioneering work of Purcell in 1946 [1], it has been widely known in the field of fluorescence spectroscopy that the rate of the emission process can be modified by placing a quantum emitter (QE), such as an atom or a molecule, in a structured polarizable environment [2 - 5]. Due to the highly confined electromagnetic resonances following from the response of free electrons [12], metallic nano-particles or nano-structures are able to strongly perturb the electromagnetic fields in their surroundings and to modify both the excitation and the emission rates of proximate fluorophores, chromophores and QDs [21]. Despite these experimental examples, the problem of the electromagnetic coupling between a plasmonic object and a source of radiation located in its proximity continues to raise numerous open questions in molecular plasmonics, especially for complex nano-particle shapes that do not lend themselves to an analytical treatment.
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call