Composite structure of Ge/ZnO multilayer films with Au metasurface for enhanced infrared reflection and compatible microwave transparency

Suppressing target infrared radiation signatures and enhancing their environment-adaptive camouflage capability have remained key research objectives in infrared thermal management technologies, this study proposes a metasurface-based composite multilayer film (CMF) composed of germanium (Ge)/zinc oxide (ZnO) multilayers (MLF) and an Au square periodic array (ASPA), achieving high infrared reflectivity and high microwave transmittance through synergistic design. For the infrared band, alternating Ge/ZnO layers with optimized thicknesses satisfy Bragg reflection conditions, leveraging constructive interference between high/low refractive index materials to achieve broadband high reflectivity. The ultrathin Au periodic array acts as an auxiliary reflector, suppressing transmission losses via the intrinsic infrared reflectivity of metals and dense subwavelength arrangement, thereby broadening the reflection bandwidth. For the microwave band, specially designed ultrathin Au metasurfaces achieve impedance matching with free space, demonstrating high-efficiency microwave transmission. Experimental and simulation results demonstrate that the proposed composite structure achieves average infrared reflectance of 94.1 % in the 3–5 µm band and 89.1 % in the 8–14 µm band, while exhibiting efficient transmission characteristics exceeding 85 % in the 2–15 GHz frequency range and maintaining relatively high transmittance efficiency of 75–85 % in the 15–18 GHz band. By integrating infrared interference and microwave metasurface resonance, this work resolves the incompatibility of conventional materials in thermal management and communication, offering a novel approach to designing multifunctional integrated satellite materials for thermal control and signal transmission.