Metallic-layer-free multilayer absorber for visible and near-infrared bands

Broadband visible (VIS, 0.4-0.78 μm) and near-infrared (NIR, 0.78-1.1 μm) absorbers that avoid metallic and metal-like materials are attractive for integrated photonics, optical sensing, and energy-related optoelectronics. However, scalable VIS-NIR absorbers without conventional metallic layers or conducting metal-like materials such as indium tin oxide (ITO) remain insufficiently developed. Here, we demonstrate a planar absorber based on sputter-deposited indium antimonide (InSb), Al₂O₃, and SiO₂, where VIS-NIR denotes the full 0.4-1.1 μm operating band. Unlike absorbers that rely on metallic reflectors or conducting metal-like oxide layers, the present structure uses dielectric/semiconductor layers to realize broadband absorption. The device achieves average absorptance values of 91.47% over VIS-NIR, 86.93% in the VIS band, and 96.85% in the NIR band. This work provides a scalable dielectric/semiconductor route toward broadband optical absorbers without metallic or metal-like materials.