Design of a wide-band nearly perfect absorber based on multi-resonance with square patch

• The design demonstrates a high absorber operating well at wide angles of incidence.
• The bandwidth of the absorption can be improved by using multi-square patches structure.
• The MA with four square patches structure is only 1.7 mm, and the FWHM bandwidth achieves 2 GHz.
• The MA can be easily fabricated with a standard optical lithography process.

A multi-resonance structure design of nearly perfect absorber (PA) was proposed based on square patch at microwave frequencies. One-layer square patch metamaterial has an absorption of 99.9%. The multi-layer metamaterials can extend the bandwidth of nearly perfect absorber. By stacking several such structural layers with different geometrical dimensions, the bandwidth of this strong absorption can be effectively enhanced due to the hybridization of magnetic polarizations in different layers. Numerical simulations reveal that the multi-layer metamaterials with different resonance frequencies can extend the absorption bandwidth. The full bandwidth at half-maximum (FWHM) bandwidth is improved to 2 GHz with 4-layers square patch structure. The simulated and experimental results are coincided well. The mechanism of nearly perfect absorption is explained in detail.