Wide-angle and polarization-insensitive broadband absorber based on multilayer metal-dielectric films

Abstract Plasmonic nanostructures and metamaterials have shown great potential for efficient light absorption. In this work, we propose an ultrathin broadband absorber consisting of alternating Al 2 O 3 and Au layers with a total thickness of less than 180 nm. By precisely engineering the layer thicknesses, multiple Fabry–Pérot resonances are excited, enabling strong absorption over a wide spectral range from 150 nm to 500 nm. A peak absorptance of 99.9% is achieved without the need for complex nanofabrication. The absorber exhibits wide-angle stability (0°–60°) and polarization insensitivity, with TE/TM differences below 5%. Numerical analyses reveal that the enhanced local electric field and hybrid resonance coupling in ultrathin dielectric cavities are key to its broadband performance. Owing to its planar architecture, scalability, and cost-effective fabrication compatibility, the proposed design offers a promising solution for ultraviolet detection, thermal photonic control, and integrated optoelectronic devices.