Inverse Design of Photonic Topological Insulators with Extra‐Wide Bandgaps

Abstract

An intelligent approach for inversely designing topological photonic crystals (PCs) with time‐reversal symmetry (TRS) at any desired frequency is presented. By accurately controlling the frequencies of dipolar and quadrupolar modes, PCs with double Dirac cones and their band inversion are successfully realized through topology optimization. Novel patterns for topological trivial and nontrivial PCs with extra‐wide bandgaps are created for the realization of spin‐locked unidirectional propagation and robust transport of topological edge states. The systematic design reveals the evolution of the geometry of dielectric materials within unit cells of topological trivial and nontrivial PCs from low to high frequencies. Finally, the geometric rules of topological trivial and nontrivial PCs are extracted and analyzed for the ease of design and fabrication.