Room Temperature Condensation And Engineering Of Exciton-polaritons In Optically-controlled Traps

Exciton-polaritons are quasi-particles built from the strong coupling between semiconductor excitons and cavity photons.As half-light half-matter bosons,exciton-polaritons are ideal testing grounds for the study of macroscopic quantum phenomena,such as Bose-Einstein condensation at elevated temperatures,quantized vortices and superfluidity,due to their extremely small effective masses(typically~10~-55 m_e)and the ability to interact with other carriers via Coulomb forces.The manipulation of their energy states and optical properties via all-optical means has become an important aspect toward the development of advanced polaritonic devices.In this thesis,we focused on the room temperature condensation effect and manipulation of the energy states of exciton-polaritons in all-optically controlled dynamic potential wells.Details of our results are listed as following:(1)Based on the inherited excitonic fraction of exciton-polaritons,we succeeded in injecting dynamic potential barriers for exciton-polaritons via non-resonant optical pumping.(2)We realized the optical injection of parabolic potential wells for exciton-polaritons in one-dimensional ZnO whispering gallery microcavities.We carried out experimental studies on the room temperature condensation behaviors and manipulation of energy states for exciton-polaritons confined in parabolic optical traps,by means of angle-resolved microscopic spectroscopy and real-space imaging technique.(3)We studied the interactions between longitudinal optical phonons and the harmonic oscillator modes of exciton-polaritons,via Raman spectroscopy.We observed the mode competition behaviors of the polaritonic harmonic oscillator modes in optical traps.We carried out theoretical modelling using three-level coupled rate-equation model and obtained consistent results with experimental observations.(4)We succeeded in engineering the profiles of optical traps for exciton-polaritons,via combination of optically-generated dynamic potentials and defect-induced static potentials.Using these techniques,we successfully generated two different kinds of potential traps who have either parabolic or square-well profiles.