Water matrix-based metamaterial absorber with multi-band regulation performance for optical windows

Metamaterial absorbers are required to exhibit multi-band regulation performance to address the increasingly complex electromagnetic environment. However, existing designs face challenges in reconciling multi-band regulation with optical transparency, which is a key requirement for applications such as optical windows. This work presents a metamaterial absorber integrating ITO-patterned metasurfaces and a water matrix, achieving a wide microwave working bandwidth, low infrared thermal radiation, and optical transparency. Combined with the analysis of optical transmission characteristics, the energy multiple absorption mechanism is proposed from the perspective of energy flow to elucidate the energy dissipation process behind the broadband absorption. Through simulations and experimental validation, the metamaterial absorber achieves an absorption rate exceeding 0.9 across the 6.0 to 39.4 GHz frequency range, with a relative absorption bandwidth of approximately 147.1 %. Due to the introduction of the fluid medium water, the metamaterial absorber can remove the backplane and achieve an optical transmittance of 51.38 %, while the infrared thermal radiation can be effectively regulated. These findings may offer a new strategy for designing optical windows for electronic communication devices and detectors with multi-band regulation performance.