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Dipolar emission and absorption in the near-field of nanostructures
Etienne Castanie, doctorant Crédits : ESPCI ParisTech
One part of this work is the experimental study of the local density of electromagnetic states (LDOS) spatial fluctuations on semi-continuous gold films. Those random films are known to exhibit localized surface modes when they are close to the percolation threshold. First we dispersed fluorescents nanosources on random films of increasing gold filling fraction, then we measured the sources decay rate statistics. We have shown that the LDOS spatial fluctuations reach a maximum when localized modes appear. We also designed a new experimental setup which allows us to record LDOS maps by using a fluorescent nanosource glued to an AFM tip. We made a proof of concept of this apparatus on test samples.
Another part of this work was the theoretical study of the optical response of a metallic nanoparticle. We have shown that the decay rate of an electric dipole in the near-field of a metallic nanoparticle is modified when microscopic interactions are taken into account. We also studied the dependance of the absorption cross-section of a metallic nanoparticle on its environment, and showed that the absorption cross-section is not a intrinsic property. We confirmed this result with a simple example which allowed us to calculate orders of magnitude.