Séminaire de Nicolas Bonod
All-Dielectric Mie-Resonant Nanophotonics : tailoring light at the nanoscale with low-order Mie resonances
Mardi 12 octobre 2021, 11h00Passat
All-Dielectric Mie-Resonant Nanophotonics : tailoring light at the nanoscale with low-order Mie resonances
par Nicolas Bonod
Institut Fresnel, Aix Marseille Univ, CNRS, Centrale Marseille
Semi-conductor based nanoparticles can resonantly interact with light thanks to the excitation of Mie resonances. The interest of dielectric Mie scatterers is that they feature both electric and magnetic low order resonances. The resonant light scattering can be used, for example, in the far field to create a palette of structural colours and in the near field to design all-dielectric optical antennas with fluorescence emission rates. One of the main interests of dielectric Mie scatterers compared with plasmonic particles is their ability to strongly enhance the fields inside the scatterers, i.e. inside the high refractive index material, which turns out to be of crucial importance for designing non-linear all dielectric metasurfaces. We will show that doubly resonant silicon particles can enhance by more than two orders of magnitude the FWM signal compared with that obtained with a silicon film. It is therefore possible to generate visible light when exciting silicon particles in the near infrared with laser beams.
Besides experimental investigations, we have been working on the development of a modal formalism to retrieve and explain the optical response of photonic structures in terms of their eigen-frequencies. For that purpose, we derived the exact modal expansion of the T- and S- scattering operators in the harmonic domain. Spectral anomalies such as dips and peaks in the scattering spectrum can be analysed thanks to the eigen-frequencies of the scatterer. Resonances can result in a strong minimum of the scattering efficiency that are called anapoles. We will show how the modal expansion of the T-matrix can explain the existence of anapoles. More recently, we extended this modal approach to the time domain to retrieve the times dynamics of optical cavities. We consider the fundamental case of a dielectric slab excited by a pulse and show how the exact analytic expressions of the reflected and transmitted fields can be obtained thanks to the eigen-frequencies of the slab.
