Angle-insensitive transmission and absorption with a PT phase transition via coupled interface states in hybrid one-dimensional photonic crystal heterostructures

This is the authors' abstract. We don't add key points for this paper.

Non-Hermitian systems offer novel methods for manipulating electromagnetic waves, including applications in sensing and mode conversion, attracting significant research interest. In this work, we propose a hybrid photonic crystal comprised of two topologically distinct heterostructures with angle-insensitive band gaps. This hybrid photonic crystal can sustain two topological interface states (TISs), and is considered as an optical non-Hermitian system. By precisely tuning of the coupling between these TISs, we achieve perfect wave transmission, revealing a parity-time (PT) phase transition, as evidenced by the evolution of the transmission spectra. Remarkably, the perfect transmission of waves remains resilient against fluctuating incident angles, ensured by the angle-tolerant photonic band gaps of the heterostructures. Additionally, we explore another hybrid photonic crystal heterostructure featuring two interface channels supporting the TIS and the Tamm plasma polariton. As the coupling between these two modes strengthens, two distinct resonance peaks emerge. Gradually reducing this coupling results in the merging of these peaks into a single peak. As the PT phase transition case, perfect wave absorption can be realized. Notably, the frequency shifts of the transmission and absorption peaks remain minimal, demonstrating a remarkable stability with an angle variation from 0 ^∘{} to 90 ^∘{} (Δf=1.44pt0exTHz). These results further expand and complement the ongoing exploration of non-Hermitian topological physics.