broadbandabsorbing

Broadband absorbing refers to the ability of a material, coating, or nanostructured surface to absorb electromagnetic radiation across a wide spectral range, typically spanning from the visible through the near-infrared and into the mid-infrared. The goal is to minimize reflectance and transmission over the target band, converting incident energy into heat or other forms. Broadband absorbers rely on multiple design strategies that extend beyond narrowband resonances, including impedance matching, graded refractive index profiles, and the incorporation of lossy or strongly scattering elements.

Common approaches include metamaterial or metasurface absorbers with subwavelength resonators arranged to cover broad frequencies, multilayer coatings with progressively increasing losses, nanostructured surfaces that trap light via random or fractal geometries, and porous or carbon-based materials with intrinsic absorption across wide bands.

Materials and examples include carbon blacks, graphene-based layers, metal-dielectric composites, and dielectric nanostructures such as silicon or TiO2 with textured surfaces. Fabrication methods include chemical vapor deposition, lithography, and electroplating; challenges include angular and polarization dependence, thermal management, and cost.

Applications include solar energy harvesting, thermal detectors and bolometers, infrared camouflage and sensing, and electromagnetic interference shielding. Researchers also explore broadband absorbers for stealth technologies and optical sensors with wide dynamic range.