Highly angle-tolerant and polarization-independent topological interface modes in the THz band via centrosymmetric photonic crystals

Achieving angle-tolerant resonances is an open problem in communication technology, especially in the THz band, due to material constraints and losses. We demonstrate polarization-independent and highly angle-tolerant topological interface modes (TIMs) for the first two odd photonic band gaps (PBGs) indicated as g1 and g2, within the (0-6) THz range, using simple all-dielectric one-dimensional (1D) centrosymmetric photonic crystals (CPCs). By a novel, to the best of our knowledge, phase-gradient cancellation (PGC) method, we achieve remarkable TIMs stability for both TE and TM polarizations under wide-angle variation up to 89° against three critical perturbations: by inserting a defect at random positions, by aperiodic disorders, and by inserting the defect at the interface. This wide-angle tolerance against perturbations allows for alignment-free integration of photonic devices such as LiDAR and VR optics, where conventional structures require active polarization control. The structure is fabricable using existing fabrication technology and can serve as a promising and stable platform to explore rich physics in topological photonic integrated settings.