Study on polariton condensates and quantized vortices in engineered potentials via optical modulation and structural fabrication

Abstract

Exciton-polaritons (polaritons) are bosonic quasiparticles resulting from strong light-matter interactions between cavity photons and excitons in a semiconductor microcavity. As half-light and half-matter bosonic particles, polaritons exhibit various macroscopic quantum phenomena such as Bose-Einstein condensation, superfluidity, and quantum vortices. Although polaritons are in a flat two-dimensional system, one can address and control the spatial potential and observe various characteristics of the polariton. In this dissertation, firstly, we realized a strong coupling regime in AlGaAs-alloy based microcavities grown by metalorganic chemical vapor deposition. We observed the Rabi splitting behavior and polariton condensation in the microcavities through the optimization of growth conditions. Secondly, we investigated the dynamics of a polariton vortex in a nonresonant Laguerre-Gaussian beam by controlling the beam size. We measured the multistate condensates according to the beam size and discovered that a polariton vortex can be annihilated as a transition from the rotating excited state into the stationary ground state. Thirdly, we tried to address a complex-valued potential to polariton by implementing two methods. A 1D chain of polariton condensates was created in nonresonant 1D periodic array pumping by a spatial light modulator and beam shaping technique. And photonic bandgap was observed in 1D periodic pillar microcavity by lithography and dry etching techniques. It is expected to address complex-valued potentials in polariton systems by combining two potential engineering methods. Addressing complex-valued potential in polariton systems will be an interesting platform for investigating non-equilibrium and non-Hermitian physics in the solid-state system. Furthermore, it is expected to be helpful in the development and application of polariton-based optoelectronic devices in the future.