Optically Transparent Single‐Layer Frequency‐Selective Surface Absorber for Dual‐Band Millimeter‐Wave Absorption and Low‐Infrared Emissivity

Current research on multispectral stealth material technology focuses on practical functionalities such as optical transparency, flexibility, and lightweight. Herein, an optically transparent and single‐layer frequency‐selective surface (OTSF) absorber for dual‐band millimeter‐wave (MMW) absorption and low‐infrared (IR) emissivity is proposed. By adopting indium tin oxide and polyethylene terephthalate, the proposed OTSF absorber exhibits good optical transparency (76% transmittance in the 400–800 nm range on an average) and flexibility. The OTSF absorber exhibits high absorption at the dual‐band frequency in the MMW range (99.7% at 35 GHz and 89.7% at 103 GHz). In the IR band, the average band emissivity of the OTSF absorber for the midwave IR (MWIR) band (3–8 μm) and the long‐wave IR (LWIR) band (8–15 μm) is measured to be 0.26 and 0.23, respectively. Thermal images of the OTSF absorber clearly show its low‐emission characteristics that are similar to those of metal. The proposed OTSF absorber structure has significant potential for practical applications of MMW–IR multispectral stealth materials.