Self-induced nonreciprocity from asymmetric photonic topological insulators

Photonic topological insulators and self-induced nonreciprocity based on nonlinear effects in asymmetric structures have garnered increased attention due to their potential applications in quantum information technologies and advanced photonic integrated circuits. In this study, we combine these two fields and present asymmetric photonic crystal designs based on all-dielectric checkerboard structures forming topological interfaces. The resulting topological photonic structures lead to the emergence of a narrowband leaky mode in their linear transmission response, accompanied by an edge state with topological protection. The incorporation of the nonlinear optical Kerr effect in the system results in spectral tunability and transmission nonreciprocity in the induced topological edge states, as the input beam intensity is increased, due to the introduction of asymmetric defects along the interface. We envision that the findings presented in our work will lead to tunable photonic topological insulators with a nonreciprocal response that promise to provide new avenues for the development of next-generation photonic devices and quantum optical technologies.