Scalable‐Manufactured Plasmonic Metamaterial with Omnidirectional Absorption Bandwidth across Visible to Far‐Infrared

Abstract Broadband, omnidirectional light absorption in the infrared range is critical for emerging aerospace and ground applications, such as machine vision, autonomous vehicle technology, and aerospace telescope. Broadband absorbers (BBAs) need to possess strong absorption through thin structures for high signal‐to‐noise ratios, as well as manufacturing scalability and service reliability in harsh environment for practical applications. Such requirements rule out many known absorbing materials such as carbon nanotubes that are intrinsically lossy and fragile. Achieving strong light‐matter interaction in the mid‐ and long‐wavelength infrared ranges has been extremely challenging despite long‐standing research efforts. Here, an aerospace‐grade, ≈2.0 µm‐thick hierarchical coral‐structured titanium nitride (coral‐TiN) plasmonic metamaterial is experimentally realized with over 90% omnidirectional absorption across the visible to the long‐wavelength infrared range (0.25–25 µm) using a scalable fabrication method. The broadband optical control of the coral‐TiN BBA is achieved by the superposition of the hybridized plasmonic mode in the visible and near‐infrared, the cavity mode in the short‐wavelength infrared as well as the propagating surface plasmon polariton mode in the mid‐ and long‐wavelength infrared. With conformal alumina coating, the plasmonic absorber demonstrates outstanding reliability in rigorous aerospace‐grade tests under harsh mechanical and thermal environmental conditions.