Ultrafast laser processing of camouflaged metals by topography inherited multistep removal for information encryption

Surfaces with micro-nanoscale structures show different optical responses, including infrared reflection, thermal radiation, and protective coloration. Direct realization of structure camouflage is important for material functionalities. However, external cloaks or coatings are necessary in structure camouflage, which limits the surface functionality. Here, we propose a novel strategy for the direct structure camouflage through topography inherited removal (TIR) with ultrafast laser, featuring pristine topography preservation and scattering surface fabrication. After multistep TIR, pristine topographies are partially and uniformly removed to preserve the original designed structures. Optical response changes show the suppression of specular reflection by uniformizing reflected light intensity to a low level on the inherited surface. We produce various structure camouflages on large scaled substrates, and demonstrate applications of information encryption in code extraction and word recognition through structure camouflage. The proposed strategy opens opportunities for infrared camouflage and other technologies, such as thermal management, device security, and information encryption.