Security printing with laser-induced plasmonic colors

Nathalie Destouches

University Jean Monnet, Saint Etienne

Security printing with laser-induced plasmonic colors

Plasmonic colors have garnered significant attention in recent years due to their anticipated profound impact on various industrial sectors. These colors, stemming from the resonant interaction between light and metallic nanostructures, offer stability over time and can be fabricated as thin films. The ability to control the shape and organization of metallic nanostructures further provides spectral sensitivity to light polarization, enabling the development of innovative applications.

Laser-induced printing of a color image on a Ag:TiO2 thin film observed in reflection with polarized light for angle 1 (left), or 2 (middle) or in transmission under non-polarized light.

This presentation explores the diverse physical and chemical mechanisms induced by lasers on plasmonic metasurfaces composed of silver nanoparticles embedded in a TiO₂ thin film. Under continuous wave (cw), nanosecond, or femtosecond¹ laser exposure, silver nanoparticles undergo reshaping, shrinking, or growth, and self-organize along subwavelength gratings. Various laser-induced self-organized nanostructures are identified and their origins are elucidated through optical models. Once formed, these self-organized nanostructures exhibit intriguing dichroic optical properties, whose origin, elucidated through electromagnetic modeling, lies in the hybridization of resonant modes.² These singular optical properties present opportunities for innovation, particularly in high-end anti-counterfeiting applications. Laser-induced printed image multiplexing emerges as a recently developed inkless technique, providing high flexibility to print multiplexed colored images observable independently under natural light by altering the viewing angle.³

References

1. Destouches, et al. Laser-empowered metasurfaces for white light image multiplexing Adv. Func. Mater. 2010430 (2021)
2. D. Le, et al. Understanding and exploiting the optical properties of laser-induced quasi-random plasmonic metasurfaces ACS Appl. Opt. Mater., accepted (2024)
3. Dalloz, et al. Anti-counterfeiting white light printed image multiplexing by fast nanosecond laser processing Adv. Mater., 34, 2104054 (2022)

Konuşmacı hakkında

Nathalie Destouches is Professor at University Jean Monnet, Saint-Etienne, France. She leads projects at the interface between materials science and photonics and she is particularly interested in the interaction of light with plasmonic metasurfaces. She coordinates the Erasmus Mundus Joint Master Degree Photonics for Security Reliability Sustainability and Safety. Her main scientific contributions have led to the development of plasmonic photochromic materials, to the elucidation of different laser-triggered mechanisms in plasmonic films, to the explanation of the electromagnetic response of random plasmonic metasurfaces, to the simulation of metallic nanoparticle growth under dynamic laser irradiation, or to the explanation of special thermal behavior in dynamic laser processes. These fundamental studies led to the development of laser printing of color and multiplexed images in collaboration with a leading security document company.