Robust omnidirectional perfect absorption empowered by angle-immune topological interface states in one-dimensional photonic crystals heterostructures comprising hyperbolic metamaterials

The development of optical absorbers that maintain high performance over a wide angular range is essential for applications such as light energy conversion, high-performance sensing, and efficient thermal management. However, most existing absorbers suffer from strong directional sensitivity, which severely limits their practical applicability. In this paper, we design a robust omnidirectional perfect absorber based on an angle-immune topological interface state (TIS) in a one-dimensional photonic crystal heterostructure comprising hyperbolic metamaterials. By introducing material loss and appropriately tuning the number of periods of the two constituent photonic crystals, we achieve precise impedance matching between them, enabling unity absorption despite the presence of loss. Empowered by the angle-immune field enhancement of the TIS, the proposed absorber exhibits an absorptance exceeding 95% over an ultrawide angular range from 0° to 78.8°. Furthermore, benefiting from the topological protection of the angle-immune TIS, the absorption performance remains robust against layer thickness variations. This work not only provides a viable route toward robust omnidirectional perfect absorption but also advances the development of absorption-based devices with high angular tolerance, including solar cells, photodetectors, and thermal emitters.