Security labeling and optical information encryption enabled by laser-printed silicon Mie resonators.

Area of Science:

• Materials Science
• Nanotechnology
• Optics

Background:

• Counterfeiting poses a significant societal threat, necessitating advanced anti-counterfeiting technologies.
• Existing security labels often struggle to balance high information density, robust protection, and cost-effective, scalable manufacturing.

Purpose of the Study:

• To propose a novel, scalable, and cost-effective method for fabricating security labels using femtosecond-laser patterning.
• To demonstrate optical information encryption capabilities for anti-counterfeiting applications.

Main Methods:

• Direct reproducible femtosecond-laser patterning of amorphous silicon (α-Si) films on glass substrates.
• Fabrication of Raman-active hemispherical silicon nanoparticles (NPs) with controlled diameters.
• Two-temperature molecular dynamics simulations to understand NP formation mechanisms.
• Development of information encryption strategies using NP arrangement and laser-induced modifications.

Main Results:

• Precise control over NP diameter, enabling tuning of Mie resonance across the visible spectrum.
• Formation of α-Si NPs explained by laser-induced molten layer rupture under negative pressure.
• Creation of hidden security labels with high information density (up to 60,000 dots per inch).
• Demonstrated encryption strategies including laser-induced crystallization and mixing resonant/non-resonant NPs.

Conclusions:

• Femtosecond-laser patterning offers a simple, inexpensive, and scalable route to advanced security labels.
• The developed technology utilizes Earth-abundant materials and commercial equipment, ensuring practical applicability.
• This method provides robust anti-counterfeiting solutions with high information capacity and facile readout.