Optical characterisation and manipulation of active microspheres

Abstract

Spherical microcavities are of great interest for both photonic applications and for fundamental physics. In this thesis, a novel active dielectric microsphere emitter coated with colloidal CdTe nanocrystals is studied. In the first experimental part of the thesis, the microsphere emitter was optically characterized in a micro-photoluminescence/micro- Raman setup. Strong enhancement of photoluminescence and Raman scattering was observed due to the optical feedback in the microcavity. At excitation below the bandgap, anti-Stokes photoluminescence was observed due to an efficient phonon-assisted upconversion process. In the second part of the thesis, a novel type of an active microsphere emitter was fabricated for an optical trapping experiment. The microsphere was coated with a several nanometer thick polyelectrolyte multilayer and the layer was additionally softened with a chemical treatment. The elastic polyelectrolyte shell was then coated with a monolayer of CdTe nanocrystals. Controlled radiation force deformed the elastic shell of the microsphere in contact with a substrate.