PhD defence by Frederik Schröder

Abstract

Photonics is the science of light (= photon) and matter, such as electronic states. Information and communication technologies rely on data being encoded in states of light, exploiting photonic technologies. The rapid increase in data traffic poses new challenges. Energy consumption by data centres for information and communication technologies already accounts for a significant amount of carbon emissions. Moreover, increased data traffic increases the risk of security breaches. This demands research for novel photonic components for both energy-efficient data processing and quantum technologies.

Many photonic technologies rely on light being trapped or confined to enhance light-matter interactions. Trapping light is intuitive: It can, for example, be achieved with mirrors, reflecting light back and forth. Recently, researchers demonstrated that light can be confined on length scales smaller than the wavelength of light in dielectric structures, realising extreme dielectric confinement cavities.

Two-dimensional materials have aroused much interest recently. They consist of individual sheets, which can be thinned so that only a single layer remains. These sheets are as thin as a few atoms! An important class of these 2D materials are the transition metal dichalcogenides, which are direct bandgap semiconductors in the case of a single layer. Due to the reduced dimensionality, the optical response of these materials is strong.

In this research project, light-matter interactions between extreme dielectric confinement cavities and two-dimensional semiconductors are studied. One of the main findings is that light confined in these cavities and excitons in two-dimensional semiconductors interact strongly with each other, forming new hybridized states (called exciton-polaritons). This enables further research on exploiting these structures for energy-efficient light sources and novel single-photon sources for quantum technologies.

Supervisors

• Principal supervisor: Associate Professor Nicolas Stenger, DTU Electro, Denmark
• Co-supervisor: Professor Martijn Wubs, DTU Electro, Denmark
• Co-supervisor: Senior Researcher Philip T. Kristensen, DTU Electro, Denmark
• Co-supervisor: Professor Jesper Mørk, DTU Electro, Denmark

Evaluation Board

• Associate Professor Søren Raza, DTU Electro, Denmark
• Professor Ursula Wurstbauer, University of Münster, Germany
• Associate Professor Marcin Syperek, Wroclaw University of Science and Technology, Poland

Master of the Ceremony

• Senior researcher Mikkel Heuck, DTU Electro, Denmark