A topological nanobeam microcavity*

Photonic crystals in a waveguide can give rise to nanobeam microcavities, where the lateral confinement is given by the waveguide mode, and axial confinement is created by introducing a trivial defect in the photonic crystal. These cavities tend to have small mode volumes and reasonably high quality factors, limited mostly by surface roughness introduced during the fabrication.
If we use a dimerized photonic crystal waveguide, we can create a topological defect by interfacing two sections with different winding numbers. This defect will introduce axial confinement. This topology-induced confinement is robust agains disorder and fabrication-induced roughness. We will discuss the tradeoffs involved in the design of these topological microcavities, and their implementation in a silicon-on-insulator platform.