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2Femtosecond laser printing of structural colors for information encryption and anti-counterfeit labeling
V. Lapidas1*, A. Zhizhchenko1, S. Shevlyagina1, A. Cherepakhin1, A. Kuchmizhak12
1-Institute of Automation and Control Processes, Far Eastern Branch, Russian Academy of Sciences,
5 Radio Str., Vladivostok, Russia 2- Pacific Quantum Center, Far Eastern Federal University, Vladivostok, Russia
Structural colors, as a result of light interaction with nanoscale structures, offer a promising alternative to pigments, as they are non-fading and resistant to UV and heat. However, achieving precise control over color tones and saturation at the submicron level currently requires expensive and limited lithographic techniques for creating pixelated nanostructures. To address this, researchers have explored direct laser-based approaches for cost-effective fabrication of structural color. One method involves using focused laser beams to induce dewetting of gold films deposited on Fabry-Perot filters, forming plasmonic nanoparticles [1]. However, this approach suffers from a lack of control over the color, as the nanoparticles are formed randomly, and their size depends on the initial gold film thickness. Our work presents an alternative method that overcomes these limitations. Here, instead of random dewetting, we utilized unique and highly controllable thermomechanical behavior of fs-laser-irradiated thin noble metal film to demonstrate template-free high-resolution color printing at a superior lateral resolution up to 50000 dots per inch (dpi). Diverse ablative and ablation-free scenarios of surface nanotexturing can be simultaneously realized on the top noble-metal film of the MIM sandwich allowing wide tunability of the color tone and saturation. Ability to produce properly arranged subwavelength arrays of isolated hollow nano-bumps supporting reach plasmonic behavior was also utilized to demonstrate the security labeling with facile optical readout [2].
This work was supported by Russian Science Foundation (grant. 21-72-20122).
200 fs/ 515 nm
Wavelength / nm Density / Saturation
Figure 1. Direct laser printing of structural colors. (a) Schematic of the proposed fs-laser printing of high-resolution structural color images of the surface of top Au layer coating 75 -nm thick Al2O3 spacer and 200-nm thick Ag reflecting mirror. (b) Color palette illustrated by a series of bright-field optical images of the laser-patterned pixels (10x10 ^m2) fabricated by varying the incident pulse energy and nanostructure periodicity. Insets provide top-view SEM images of representative surface morphologies marked by numbers. (c) Measured (solid curves) and calculated (dashed curves) reflectance spectra of the representative nanotextured surfaces as well as pristine sandwich structure. (d) Correlated SEM and bright-field optical images showing optical appearance of isolated nanobumps of variable size printed at 500 nm periodicity. (e) Tuning the color saturation by increasing the density of nanobumps (top panels) and nanoholes (bottom panels) as illustrated by correlated SEM and optical images. (f) Reflectance spectra of the color palette pixels represented as coordinates in the HCV color space.
[1] A.S. Roberts, S.M. Novikov, Y. Yang, Y. Chen, S. Boroviks, J. Beermann, S.I. Bozhevolnyi, Laser writing of bright colors on near-percolation plasmonic reflector arrays, ACS Nano, Vol. 13, pp. 71-77, (2018).
[2] V. Lapidas, A. Zhizhchenko, E. Pustovalov, D. Storozhenko, A. Kuchmizhak, Direct laser printing of high-resolution physically unclonable function anti-counterfeit labels, Applied Physics Letters, Vol. 120, p. 261104, (2022).
