Thesis defense of Bernd Michael Berger
- Defense
Control of Orbital Angular Momentum of Exciton Polariton Condensates
The goal of this work is to investigate the use of exciton polariton vortices for all optical information processing. To achieve this goal, we develop a novel technique based on sorting orbital angular momentum states of light, which allows for detecting and temporally tracing vortices in a light beam. We successfully implement and benchmark this technique and apply it to demonstrate the spontaneous formation of exciton polariton vortices inside all optically excited annular trapping potentials in a GaAs based microcavity. Subsequently we investigate the temporal dynamics of this formation process, which is strongly dependent on excitation power. Our experimental results show the simultaneous and statistically independent formation of vortex modes with topological charges m = −1 and m = +1. We gain further insight into the temporal dynamics of all arising modes by theoretically modeling our experimental results. Furthermore, in some cases vortices show spin-orbit coupling between their orbital angular momentum and their spin, which corresponds to the circular polarizations σ+ and σ-. In the final stage of our experiments, we experimentally verify the theoretical prediction that the topological charge of exciton polariton vortices may be flipped by perturbing them with a pulsed laser. Thereby we demonstrate the potential use of exciton polariton vortices as all-optical information storage.