Nanostructures with quantized angular momentum in the strong light-matter coupling regime

• Main Author: Sigurdsson, Helgi
• Other Authors: Timothy Liew C. H.
• Format: Theses and Dissertations
• Language: English
• Published: 2016
• Subjects: DRNTU::Science::Physics::Atomic physics::Solid state physics; DRNTU::Science::Physics::Atomic physics::Quantum theory; DRNTU::Science::Physics::Optics and light
• Online Access: https://hdl.handle.net/10356/69068
• Institution: Nanyang Technological University

A great deal of both theoretically and experimental investigation is currently being devoted into the regime of strong light-matter coupling in optically confining systems. In this strong coupling regime, bare matter particle states are heavily influenced by photon modes trapped within the system. The matter particles are said to become "dressed" in the optical field, picking up the properties of the photons therein. A large portion of this thesis is devoted to a type of such phenomena, the exciton-polariton, a quasiparticle which arises due to strong coupling between quantum well excitons and microcavity photons. Exciton-polaritons are exciting candidates for a number of practical optoelectronic applications. Being spin-1 quasiparticles with high natural nonlinearities inherited from their excitonic part, and fast scattering dynamics from their photonic part, they open the possibility of a new era in spin-dependent devices with great speed and efficient signal processing. In terms of waveguide geometries, they can propagate coherently over hundreds of microns with small losses. This coherence can be sustained indefinitely as exciton-polaritons can form an analog of a driven-dissipative Bose-Einstein condensate, a macroscopic quantum fluid so to speak. In this thesis we explore novel angular momenta effects, arising in such systems, through both numerical and analytical methods. In the case of exciton- and exciton-polariton Bose-Einstein condensates, unique types of quantum vortices appear due to the particle spin structure. These vortex states have quantized angular momentum and offer new possibilities in topologically robust elements in future applications. Here, the advantage of using exciton-polaritons comes from the fact that they can be easily controlled and monitored through the application of an optical field. Angular phenomenon arising in quantum rings are also studied in the regime of light-matter coupling. Both electron- and exciton states become "field-dressed" in a strong, external, circularly polarized electromagnetic field. In quantum ring structures, the field-dressed particle states reveal the onset of an artificial U(1) gauge associated with breaking of time-reversal symmetry, analogous to the well known Aharonov-Bohm effect.