Physicists classify and understand systems in terms of many properties; color, mass, length and microscopic symmetries are familiar examples. Another interesting feature is a system’s topology, or how its parts connect. As an example, a circular linked necklace can be deformed into an oval or a rectangle without changing the topology, since the links remain connected in the same way. But the necklace can only be made into the topologically distinct straight line if it is cut or its clasp is opened. In the 1980s physicists realized that some physical properties are entirely dictated by a system’s topology.
Our group investigates topological features in optical systems to explore new physics and develop optical devices with built-in protection. For more information, you can read a Quick Study in Physics Today, a Feature article in OSA News, and an exhaustive review in RMP.