Plasmonically controlled lasing resonance with metallic-dielectric core-shell nanoparticles.

We experimentally demonstrate the capability of tailoring lasing resonance properties by manipulating the coupling between surface plasmons and photons in random lasing media composed of metallic-dielectric core-shell nanoparticles and organic dyes. It is revealed that core-shell nanoparticle-based systems exhibit optical feedback features distinctive from those containing pure metallic nanoparticles, provided that the scattering strength is weak enough. The pump threshold increases with an increment in the shell thickness, which can provide a direct proof that the local field enhancement plays a central role in the emergence of coherent feedback. The anomalous behavior in both threshold and optical feedback is discussed in terms of the modification of fluorescent properties of fluorophores close to metallic surface.