Academic Seminar (Course)
Online
16.10.2024 - All Day
SEMINAR:Topological Control of Light
Classification of materials based on their physical properties has shaped the development of modern civilisations. Using the right materials together with fine-tuning of their physical properties, has enabled novel engineered devices. Over the last decade, we have witnessed a new materials classification based on topological concepts. We can group materials using integer numbers associated with the symmetry of their electronic band structure. Recently those innovative concepts have been applied for optical systems to investigate topological phases of light on tailored optical materials. However, examples in the literature are passive optical systems with built-in topology. Active control of topology and device applications remains a challenge. This talk explores the topological control of light across different domains, demonstrating how topological singularities can be harnessed to manipulate electromagnetic waves. First, I will show how exceptional points (EPs) singularities in graphene-based terahertz devices enable precise control over light propagation. By tuning a gate voltage, we can modulate both the intensity and phase of terahertz pulses using a topological phase transition while crossing an EP. We were able to reconstruct the complex energy landscape and explore non-Hermitian physics behind the observed topological properties. In a second approach, we apply topological principles to thermal light. By controlling the reflection topology of thermal emitters, we observed a topological phase transition in thermal radiation by varying a single parameter. The critical point of zero reflection is topologically protected, and boundaries between spatial domains host interface states with near-unity thermal emissivity. Together, these examples illustrate rich physics of topological singularities providing new tools for controlling light, from the terahertz regime to thermal radiation, with potential applications in THz communications and thermal management.