Reprogrammable plasmonic topological insulators with ultrafast control

Abstract Topological photonics has revolutionized our understanding of light propagation, providing a remarkably robust way to manipulate light. Despite the intensive research and rapid progress in this field, most of existing studies are focused on designing a static photonic structure to realize a specific topological functionality or phenomenon. Developing a dynamic and universal photonic topological platform to intelligently switch multiple topological functionalities at ultrafast speed is still a great challenge. Here we theoretically propose and experimentally demonstrate an ultrafast reprogrammable plasmonic topological insulator, where the topological propagation route can be dynamically changed at nanosecond-level switching time, which is more than 1×10^7 times faster than the current state-of-the-art, leading to an experimental demonstration of unprecedentedly ultrafast multi-channel optical analog-digital converter. This orders-of-magnitude improvement compared to previous works is due to the innovative use of ultrafast electric switches to implement the programmability of our plasmonic topological insulator, which enables us to precisely encode each unit cell by dynamically controlling its digital plasmonic states while keeping its geometry and material parameters unchanged. Our reprogrammable topological plasmonic platform can be fabricated by the widely-used printed circuit board technology, making it much more attractive and compatible with current highly integrated photoelectric systems. Furthermore, due to its flexible programmability, many existing photonic topological functionalities can be integrated into this versatile topological platform. Our work brings the current studies of photonic topological insulators to a digital and intelligent era, which could open new avenues towards the development of software-defined photoelectric elements in high-speed communications and computation-based intelligent devices with built-in topological protection.