Minimizing the luminescence lifetime while maintaining a high emission quantum yield is paramount in optimizing the excitation cross-section, radiative decay rate, and brightness of quantum solid-state light sources, particularly at room temperature, where non-radiative processes can dominate. In that sense, plasmon-based optical nanoantennas can feature strongly enhanced and confined optical fields to enhance excitation probabilities and fluorescence decay rates. Their morphology and their coupling to luminescent emitters can be engineered to minimize non-radiative losses and optimize their overall brightness.
We demonstrate here that short DNA strands are an excellent template to introduce individual fluorescent molecules in dimers of gold nanoparticles in order to achieve single photon emission with decay rates enhanced by more than two orders of magnitude (M. P. Busson et al, Nat. Commun. 3, 962 (2012)). The coupling between single dye molecules and plasmonic gap antennas can be further optimized by selecting nanostructures where the transition dipole of the emitter is aligned with the gold particle dimer axis (M. P. Busson & S. Bidault, Nano Lett. 14, 284 (2014)). Furthermore, by using dimers of 60 and 80 nm diameter gold particles, we demonstrate the assembly of nanostructures exhibiting single-photon emission with lifetimes that can fall below 10 ps and typical quantum yields in a 45−70% range (S. Bidault et al, ACS Nano 10, 4806 (2016)). These data are in excellent agreement with theoretical calculations and demonstrate that millions of bright fluorescent nanostructures, with radiative lifetimes below 100 ps, can be produced in parallel.
A trimer of gold particles 50 nm in diameter is illuminated in oblique incidence by a plane wave. It is shown that one can fully focus light in only one nanogap and that the localization of the hot spot between the two nanogaps is controlled via the angle of incidence of the illuminating plane wave. The physical mechanism of this surprising phenomenon is unveiled. It relies on the excitation of opposite and in phase modes. Furthermore, balancing of the fundamental modes of the system permits to extinguish the dipolar moment of a metallic particle.
Photonic jets can be produced by the illumination of a micrometer dielectric particle by an optical plane wave, and are
characterized by a narrow elongated focal volume. Bessel beams have been widely studied in recent decades and are
commonly referred to as being "diffractionless" over long distances. The Bessel beam aspects of photonic jets are
investigated in this manuscript. In particular, we show that photonic jets take their properties from Bessel propagative
beams, but more complex phenomena are involved.
The electromagnetic backscattered response of a metallic nanoparticle located close to a dielectric microsphere
illuminated by a plane wave or a focused beam is theoretically investigated. It is demonstrated that the main contribution
of the microsphere consists in increasing the excitation field. Furthermore, investigation of dipolar emission close to the
microsphere shows a redirection of the radiated field in the backward direction.
We discuss the compound set of two dielectric microspheres to confine light in a three dimensional region of dimensions
on the order of the wavelength when the spheres are illuminated by a plane wave. This simple configuration enables the
reduction of the longitudinal dimension of so called photonic jets, together with a strong focusing effect. The beam
shaped in that way is suitable for applications requiring high longitudinal resolutions and/or strong peak intensities.