Dipolar and quadrupolar plasmon LASER modes for core-shell

International audience; Spasers are based on a combination of the localized plasmon field properties of the metallic material with an amplification medium [1]. The optical properties of these compound systems are based on a compensation of the metallic losses trough the optical gain of the amplification medium. Recently it was demonstrated experimentally that coating a gold nanoparticle with a silica shell containing Oregon Green 488 allows to overcome the loss-of-surface plasmon resonance [2]. One of the consequences of the compensation of the losses is an extremely large enhancement of the local field amplitudes (giant resonances). Rising the gain leads to a singularity stricking the tran…