Angle‐Independent Terahertz Absorption Based on Topological Interface States in a Graphene‐Embedded 1‐D Photonic Heterostructure Containing Hyperbolic Metamaterials

This theoretical study investigates angle‐independent absorption based on topological interface states (TIS) in a graphene‐embedded 1D photonic crystal (PC) heterostucture containing hyperbolic metamaterials (HMMs). The angle‐independent nature of TIS interface states arises from the angle‐invariant photonic bandgaps (PBGs) in 1D PCs containing HMMs. The absorption within the (PBG) region protected by TIS is examined. The findings reveal a strong angle‐insensitive absorption property in terms of resonance frequency, absorption magnitude, and response to an external magnetic field. In the case of a cascade structure designed to achieve dual‐mode absorption, the lower‐energy mode demonstrates significantly stronger angle‐insensitive behavior compared to the single‐mode case. However, a minor performance decay is observed for higher‐energy modes. The proposed design provides opportunities for exploring perfect omnidirectional Terahertz absorbers.