Tunable whispering gallery quantum-dot-doped mode emission from microspheres

We describe the synthesis of quantum-dot (QD) doped silica microspheres and a method by which it is possible to fine-tune the position of the whispering gallery modes (WGMs) produced by the fluorescence emission of CdSe@ZnS doped silica microspheres (5.06 mum in diameter). The method is based on small perturbations to the sphere's refractive index caused by adsorption of thin layers of polyelectrolytes and modification of the radial position of the nanocrystals within the microsphere by means of deposited silica shells.