Optical and Electronic Study of Hybrid Light-Matter States

Abstract

Hybrid light-matter states are quantum states that result from an efficient combination of light and matter. This combination is efficient when the two constituents exchange their energy faster than the overall energy dissipation. For such efficiency, devices have to be designed and structured to maximise the energy exchange. When an efficient energy exchange between light and matter is achieved, new quasiparticles are formed. One type of these particles are the exciton-polaritons, which result from an efficient energy exchange between excitons and a confined light field. Over the past 40 years, exciton-polaritons have been extensively studied in conventional semiconductors integrated with devices that confine a light field. However, only in the last five years have exciton-polaritons have been realised in semiconductors with a thickness at the monolayer limit. This was first observed at low temperatures and later extended to observations at room temperature. These devices performing at room temperature and at the nanoscale are promising for future technologies. Exciton-polaritons may play an important role due to their combined light and matter properties that provide them with the strong non-linearities necessary for quantum communications among other applications. However, one crucial step for the use of exciton-polaritons in real applications is the control over their formation. Recent reports elucidate ways to control the excitation of exciton-polaritons at room temperature, using semiconductor transistors integrated with light confinement devices. This control over the excitation of exciton-polaritons is the main focus of the work presented in this thesis. Previous reports have focused their research in controlling either the light confinement or the excitonic properties of the semiconductor material in separate ways. In this work both have been carefully controlled, allowing for an extended manipulation of exciton-polariton states. The results presented here set a substantial advance on the manipulation of exciton-polaritons in devices operating at room temperature and using 2-dimensional semiconductor materials in tuneable optical microcavities. These results may lead to applications in future quantum technologies through switchable quantum states.