High-resolution, high-speed, chromotropic color printing based on fs-laser-induced gold/graphene HSFLs

Through achieving high-spatial-frequency laser-induced periodic surface structures (HSFLs) on a gold/graphene hybrid film, we introduce a high-speed, high-resolution, and wide-gamut chromotropic color printing technique. This method effectively addresses the trade-off between throughput and resolution in laser coloring. To realize Au HSFL, disordered lattice structures and high transmittance of amorphous Au (a-Au) thin film are used to overcome the rapid hot-electron diffusion and loss of plasmonic coherence typically observed on low-loss metal surfaces, respectively. Coupled with crystallization in Au and modulated surface plasmon polaritons by artificial “seed” pre-structure growing in a SiO 2 / Si substrate, HSFL emerged with a period of 100 nm on crystalline Au after single and rapid femtosecond laser scanning. This equips the proposed color printing with high-resolution and high-speed features simultaneously. In addition, the crystallization process is demonstrated to initiate change in the complex refractive index of Au, which causes wide-gamut colors. The chromotropic capability, which facilitates the background color to be tailored in color as well as into desirable shapes independently, enables three-level anti-counterfeiting based on the proposed color printing. Therefore, the proposed color printing is amenable for practical implementation in diverse applications, including security marking and data storage, ranging from nanoscale to large-scale fabrication.