Optical transparent metamaterial emitter with multiband compatible camouflage based on femtosecond laser processing

Abstract

Infrared (IR) camouflage has garnered growing attention with progress in IR detection technology. The emergence of metamaterial with powerful electromagnetic field regulation ability provides an effective solution for thermal emission manipulation in IR camouflage. However, the intricated micro/nano machining technology of metamaterial greatly limits its moving toward practical application, and single-band IR camouflage makes it difficult to resist multiband cooperative detection systems. Here, a flexible, fine, and mask-free femtosecond laser direct writing (FsLDW) technology was introduced to pattern on ultra-thin metals. Based on this efficient technique, the optically transparent metamaterial emitter with multiband compatible camouflage is fabricated. The emitter is demonstrated to achieve high reflectance (R_3–5 µm = 0.79 and R_8–14 µm = 0.70) in the dual-band atmospheric window and low reflectance (R_1.06 µm = 0.3, R_1.55 µm = 0.1) for IR and laser stealth. In addition, the high emissivity (ɛ_5–8 µm = 0.64) for the nonatmospheric window effectively dissipates the accumulated heat, showing promising prospects in radiative cooling by comparison with Ag at the same heating power. This work offers a clue for coordinated control of multiband electromagnetic waves and heat through simple structural design, which is expected to promote its camouflage applications and thermal management in the military.