Broadband light absorbers based on multilayer metal-insulator-metal structures

We study optical properties of multilayer resonant metal-insulator structures. It is shown that a simple three-layer metal-insulator-metal (MIM) structure can provide near-perfect absorption of light (more than 90%) in a 732 nm-wide wavelength range. We demonstrate that by making the MIM structure slightly more complex by adding additional layers and optimizing their thickness, it is possible to broaden the near-perfect absorption band by almost a factor of two, covering the visible, near ultraviolet and near-infrared wavelength ranges with an average absorption level of 98.5%. Both structures provide a considerably low sensitivity to changes in the angle of incidence of the incident light. The obtained results can be applied for solar energy harvesting, photovoltaics and thermophotovoltaics, absorption filtering, and sensing.