Metasurface-Based Hierarchical Structures: Excellent Electromagnetic Wave Absorbers with Low-Infrared Emissivity Layer

Derived from the increasing demand for radar and infrared camouflage integration, a two-layer hierarchical structure that combines coating and a square patch-based metasurface is designed. Under deep subwavelength thickness, the infrared stealth layer (IRSL) can markedly reinforce microwave absorption layer (MAL) performance. More than 90% of the electromagnetic wave energy in the 3.7-5.1 GHz and 12.8-18 GHz bands can be absorbed. The hierarchical structure expands the effective absorption bandwidth of the exposed coatings from 0 to 6.6 GHz, and the maximum reflection loss increases from -8 to -40 dB. Moreover, the emissivity in the midinfrared range is maintained at an extremely low value of 0.281. The delay of magnetic resonance is found in the simulation model, indicating that strong magnetic resonance is formed in coatings after covering the IRSL. Meanwhile, the absorption peaks of the coatings are controlled by low-pass filter metasurfaces. These two factors contribute to the enhancement effect of IRSL on MAL and break the boundary between radar and infrared stealth. Herein, an original solution for tuning multispectral electromagnetic (EM) waves is provided and it has broad application prospects in advanced compatible camouflage material.