Surface Coloring and Plasmonic Information Encryption at 50000 dpi Enabled by Direct Femtosecond Laser Printing

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.nanolett.4c03576.

• Details on the materials and methods used; (Figure S1) Optical properties of the MIM structures with variable thicknesses of Al₂O₃ layers; (Figure S2) Hollow structure of the nanobumps revealed by SEM image of the cross-section cut made using focused ion beam milling; (Figure S3) Evolution of the laser-printed nanostructure morphology produced on the top Au layer of the MIM structure at elevated applied pulse energy; (Figure S4) Bright-field optical images of the brown and black color pixels produced at large laser pulse energies; (Figure S5) Reference SEM image and corresponding bright-field optical images of the recorded picture visualized at NA = 0.65 and 0.1; (Figure S6) Color palette realized upon patterning of the MIM sandwich by varying applied pulse energy and nanostructure periodicity using a laser beam focused at NA = 0.42; (Figure S7) Calculated distributions of the E_x EM-field component near the nanobump arrangements with different interstructural distances and different orientation with respect to the polarization direction of the normally incident plane wave at 540 nm excitation wavelength as well as averaged amplitude of this EM-field E_x component as a function interstructural distance calculated for structures arranged at 45° with respect to polarizer/analyzer orientations; (Figure S8) Bright-field optical image of the QR-code before and after the deposition of 1-μm thick SiO₂ (PDF)