Tailoring nonreciprocal topological edge states with all-dielectric nonlinear metasurfaces

Recently, photonic topological insulators have gained great attention due to their potential in many different optics and photonics applications including waveguide systems, next-generation photonic integrated circuits, and quantum information technologies [1-2]. In our study, an all-dielectric metasurface platform with checkerboard geometry is proposed to investigate the effect of Kerr optical nonlinearity that can lead to nonreciprocity in the topological edge state propagation. The transmission spectra show that our topological metasurface can serve as a bandpass filter in the optical frequency regime. However, introducing a lattice mismatch in this 2D photonic crystal causes an ultra-narrow leak mode in the transmission spectra. Furthermore, based on the energy dispersion diagram of the superlattice-type structure, it is proven that the leak mode has topological edge mode characteristics. In addition, the Kerr optical nonlinearity causes a nonreciprocal behavior in the edge mode due to asymmetric field excitation. Finally, the effect of a dielectric defect on the topological edge state is investigated. The modulation and control of light using such nonreciprocal and nonlinear metasurface design can provide a considerable boost to the developing field of quantum optics and photonics.