Femtosecond laser fabrication metasurface emitter for multispectral camouflage

The powerful electromagnetic capability of metasurface makes it good candidate for thermal emission manipulation towards promising infrared (IR) camouflage and thermal management technology. Here, a metasurface based infrared emitter with multilayer metal-dielectric-metal (MDM) structure is fabricated to simultaneously achieve multi-spectral camouflage as well as radiative cooling. Cross-scale processing on metal-dielectric composite films is successfully achieved by femtosecond laser direct writing (FsLDW), which is proven to be an efficient and feasible technique in metasurface fabrication. The prepared emitter exhibits low emissivity (ɛ3-5 μm=0.32, ɛ8-14 μm=0.31) in the atmospheric windows while high absorption in 10.6 μm so that it can effectively evade the tracking of infrared detectors and laser radar. Besides, the emitter also has high emissivity in the undetected band (ɛ5-8 μm=0.66) to dissipate possible heat accumulation coming from high-temperature working environment or energy absorption of radar laser. The metasurface emitter shows obvious lower surface temperature compared to the metallic Cu film under the same heating voltage, confirming the effective radiative cooling property. The proposed metasurface design and fabrication method empowers new ideas for the generation of optical devices towards multispectral camouflage and radiative cooling compatibility.