Topological photonic crystal fibers and ring resonators

With an exact recursive approach, we study photonic crystal fibers and resonators with topological features induced by Aubry-Andre-Harper cladding modulation. We find nontrivial gaps and edge states at the interface between regions with different topological invariants. These structures show topological protection against symmetry-preserving local perturbations that do not close the gap and sustain strong field localization and energy concentration at a given radial distance. As topological light guiding and trapping devices, they may bring about many opportunities for both fundamentals and applications unachievable with conventional devices. (C) 2020 Optical Society of America