Antoine Moreau
Université Clermont Auvergne
Antoine Moreau is an Assistant Professor at Clermont Auvergne University, in France. He is a specialist of modeling and numerical methods in electromagnetic optics. Since a one-year stay as an visiting scholar in David Smith's group at Duke University, he has focused on plasmonics. More precisely, he has studied film-coupled nanocubes and gap-plasmon resonators (MIM structures) as well as the impact of spatial dispersion in metals on their optical response. Optimization of photonic structures is another subject that has attracted his attention. Finally, he is happy you are reading his biography.
Drude's model is at the very heart of plasmonics, providing the almost unique way to take into account the response of metals. In 2012, a landmark experiment showed that Drude's model is not able to accurately give the... [ view full abstract ]
Drude's model is at the very heart of plasmonics, providing the almost unique way to take into account the response of metals. In 2012, a landmark experiment showed that Drude's model is not able to accurately give the resonance of nanospheres closely coupled to a metallic film because it neglects the repulsion between electrons inside the metal. Since then, a lot of progress has been made from a theoretical and numerical point of view, by using a hydrodynamic model to better describe the response of metals.
Numerical tools solving the equations of the hydrodynamic model are now available for multilayers or even complex geometries. For multilayered structures, the solution being analytical, it is possible to generalize the scattering matrix formalism to take into account spatial dispersion very easily. A code implementing this technique has been recently made available. For complex geometries, numerical tools have been recently developed: while some authors have proposed comsol add-ons, recently, a Galerkin-discoutinuous method has been developed and tested. Using the above mentioned numerical tools, it is possible to build on the idea that nonlocality cannot be neglected when plasmonic guided modes with high wavevectors are excited. Analytical calculations indeed show that the influence of spatial dispersion is controlled by a parameter proportional to the square of the wavevector. Physically this means that when the effective wavelength of the guided modes shrinks down to a scale close to the free mean path of electrons, then spatial dispersion has a real influence on the guided mode.
We have been working in the direction of proposing feasible experiments that would allow to measure accurately the nonlocal parameters. Using the most realistic and conservative material and model parameters, we came up with several designs that should be sensitive to nonlocaliy. This includes prism couplers, grating couplers in high-index dielectrics, nanoslit arrays and patch antennas.
Our work not only paves the way for future much needed experiments, it gives a much more accurate idea of what the limits of Drude's model actually are and in which situation issues are likely to arise.
