On-Chip Active High-Q Slow Light Topological Cavities

Topological photonic waveguides for lossless transport through edge states have enabled the design of cavities with sharp bends in a closed-loop configuration, where the confinement of photons in topological cavities has typically been controlled by varying the cavity size. Here, a slow light topological cavity is presented, where the light confinement and the quality (Q) factor are controlled through engineered dispersion of the slow light waveguide mode and its group velocity, introducing a new degree of freedom to design high-Q photonic cavities. It is experimentally demonstrated that topological slow light in valley photonic crystals with bearded interfaces enhances light-matter interactions, resulting in improved cavity Q-factor. In addition, active Q-factor control of slow light topological cavities is achieved through optical excitation of the silicon cavity chip, offering promising applications in communications, sensing, and polaritonics.