Topological supermodes in photonic crystal fibre*

A challenge in photonics is to create a scalable platform in which topologically protected light can be transmitted over large distances. Here we design, model, and fabricate photonic crystal fibre (PCF) characterised by a topological invariant. The fibre is made using a stack-and-draw technique in which glass capillaries are stacked, molten, and drawn to desired size. We directly measure the bulk winding-number invariant and image the associated boundary modes predicted to exist by bulk-boundary correspondence. In contrast to length limitations of both planar waveguides and resonance-based metamaterials, topological photonic crystal fibre (TopoPCF) guides visible light over metre length scales. Due to optomechanical coupling, bending these long waveguides allows us to explore the non-monotonic effects of on-site disorder for topological states. Based on the robustness of quantum and nonlinear states within topological waveguides, we envision future technologies exploiting our scalable fibre platform.