Fano resonances in plasmonic core-shell particles and the Purcell effect

TL;DR

This paper explores Fano resonances in plasmonic core-shell particles and their impact on the Purcell effect, revealing how electromagnetic mode interference influences light scattering and emission rates.

Contribution

It provides an analytical overview of Fano resonances in coated spheres and demonstrates their effect on spontaneous emission modification via the Purcell effect.

Findings

Fano resonances arise from interference between electromagnetic modes.

The Purcell factor can exhibit Fano or Lorentzian line shapes.

Mode interference significantly affects light scattering and emission rates.

Abstract

Despite a long history, light scattering by particles with size comparable with the light wavelength still unveils surprising optical phenomena, and many of them are related to the Fano effect. Originally described in the context of atomic physics, the Fano resonance in light scattering arises from the interference between a narrow subradiant mode and a spectrally broad radiation line. Here, we present an overview of Fano resonances in coated spherical scatterers within the framework of the Lorenz-Mie theory. We briefly introduce the concept of conventional and unconventional Fano resonances in light scattering. These resonances are associated with the interference between electromagnetic modes excited in the particle with different or the same multipole moment, respectively. In addition, we investigate the modification of the spontaneous-emission rate of an optical emitter at the presence of a plasmonic nanoshell. This modification of decay rate due to electromagnetic environment is referred to as the Purcell effect. We analytically show that the Purcell factor related to a dipole emitter oriented orthogonal or tangential to the spherical surface can exhibit Fano or Lorentzian line shapes in the near field, respectively.