Hierarchical metamaterials for laser-infrared-microwave compatible camouflage

In this paper, a hierarchical metamaterial (HMM) is reported to achieve compatible camouflage for laser, thermal infrared detectors, and radar. The HMM consists of an all-metallic metasurface array (AMMA) integrated with a microwave absorber. The top AMMA plays two roles. First, the gradient metasurface can reduce the specular reflection at the laser wavelength of 1.06 µm to less than 5% by tailoring the wavefronts and redirecting the reflected energy to non-specular angles. Second, the AMMA acts as an infrared shielding and microwave transparent layer, ultralow surface emissivity (∼5%) in the infrared atmosphere window of 3-5 µm and 8-14 µm can be realized, and incident microwave can perfectly pass through the top AMMA and then be absorbed by the bottom microwave absorber. The absorption efficiency is over 90% in the broadband of 7-12.7 GHz up to incident angles of 40° for both TE and TM polarizations. These excellent performances indicate that our proposed HMM has promising applications in multispectral camouflage fields.