Topological states enable robust transport within disorder-rich media through integer invariants inextricably tied to the transmission of light, sound, or electrons. However, the challenge remains to exploit topological protection in a length-scalable platform such as optical fiber. We demonstrate, through both modeling and experiment, optical fiber that hosts topological supermodes across multiple light-guiding cores. We directly measure the photonic winding number invariant characterizing the bulk and observe topological guidance of visible light over meter length scales. Furthermore, the mechanical flexibility of fiber allows us to reversibly reconfigure the topological state. As the fiber is bent, we find that the edge states first lose their localization and then become relocalized because of disorder. We envision fiber as a scalable platform to explore and exploit topological effects in photonic networks.
We demonstrate a new method for taking a single shot measurement of a photonic topological invariant. The simplicity of this method is highlighted through our characterization of topological photonic crystal fiber.
We reveal imaginary coupling components in the coupled-mode theory for evanescently coupled cavities with gain and loss. We show how exceptional points are resolved and restored in such systems where their effects are generally inevitable.
We review recent research of exceptional point degeneracies in on-chip coupled cavities, including our experimental demonstration with electrically pumped photonic crystal lasers and extended coupled-mode theory. We also discuss extra properties of such non-Hermitian systems.
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