Adaptive long wave-infrared camouflage using an all-dielectric metasurface

All-dielectric metamaterials consisting of high-index, sub-wavelength, and periodically decorated arrays allow for efficient manipulation of electromagnetic permittivity and permeability with lower losses at the optical frequencies. In this study, we propose a planar multilayer structure composed of dielectric interlayers (Al2O3/Ge/ITO/Soda Lime Glass) to achieve perfect and broadband absorption of mid- and long-infrared (IR) wavelengths. Analyzing the spectral properties of the designed structure proved that it possesses exquisite importance in thermal application when considering the IR signature reduction in the long wavelength range, as well as the reduced radiated energy dissipation along with the undetected band and the requirements for IR camouflage. This intrinsic merit of dielectric metamaterials stems from their inherent selective absorption/emission. In that respect, Kirchhoff's law states that the emissive and absorptive powers of all bodies are similar for radiation of the same wavelength at the same temperature. The temperature difference may occur not only from the properties of the surfaces but also from the optical properties of materials and environmental conditions. Studying the thermal camouflage at different background temperatures found that the camouflage material substantially reduces the contrast between the target and the background. Beyond that, extensive assessments validated that the contrast in the resulting short tips is due to the differences in the reflective properties of the material and the background. Our simulations and experiments lay the groundwork for structuring cost-effective all-dielectric thermal camouflage metaplatforms with high performance and the strong potential to be employed in practical military and defense applications.