Ultrafast laser-induced periodic-surface structure: Formation mechanisms and applications in laser marking

Abstract : Ultrafast laser radiation has a strong potential for surface structuring on ultimate scales due to a strongly localized character of energy deposition. Additionally, the appearance of periodic surface patterns with subwavelength dimensions, usually known as laser-induced periodic surface structure (LIPSS), is an inherent and quasi-universal phenomenon, onsetting for fluences around the phase transformation threshold. Depending on laser parameters and material properties, these self-formed structures develop with varying periodicity and amplitudes. We propose here a study concerning the effect of energy coupling on LIPSS formation. We generated LIPSS on various materials with different electronic configuration in order to investigate the influence of the electron-phonon coupling strength and thermal diffusion efficiency on the specific contrast of LIPSS. Representative metals (simple, transition, noble) with a large range of coupling strengths were exposed to ultrafast laser excitation and the patterning surface was investigated ex-situ by atomic force microscopy, and scanning electron microscopy. The relative strength and the electron temperature dependence of the electron-phonon coupling in the metals are identified as key factors affecting the initial energy redistribution and the dimensional size of the region undergoing transient melting and resolidification. It appears that growth of the contrast and increase of the ripples height are correlated to the evolution of the constant of coupling and to the amount of material experiencing solid-to-liquid transitions. Additionally, in order to be able to control the interaction process and the subsequent pattern resulting from relaxation and organisation processes, a thorough understanding of excitation, melting and solidification mechanism is required. We propose hydrodynamic simulation of laser-matter interaction to calculate laser energy deposition, electron-ion nonequilibrium stage and material heating [1]. Time history of ripples formation and growth is discussed in this context of matter transformation phases using a capillarity approach. The combined models account for fast variations in optical properties and electron-phonon coupling which may transiently change the coupling conditions of the target material, influencing in turn the width of the thermally affected layer thickness. Apart from the comprehension effort related to laser excitation mechanisms, the objective is to assist and validate experiments allowing to design matter transformation scales and patterns in designing user-defined matter transformations with predictable properties for a wide range of metals by taking advantage of their behavior under nonequilibrium conditions. To this end and, in the context of present requirements of high precision patterning of materials, this presentation indicates as well an application related to laser-induced marking, authentification and traceability of applications products. This is based on the optical response of subwavelength structures and the possibility to color code. Due to the ripples periodicity in the range of visible spectrum, a complex colorization process of the material has been performed to impress defined information colors on the surface [2]. This process based on the control of the laser-driven nanostructure orientation allows gathering variable information in a minimal surface, providing a high efficient way to perform identifying codes.
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Communication dans un congrès
The 12th International Symposium on Laser Precision Microfabrication, Jun 2011, Takamatsu, Japan
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https://hal-ujm.archives-ouvertes.fr/ujm-00597720
Contributeur : Jean-Philippe Colombier <>
Soumis le : mercredi 1 juin 2011 - 16:34:02
Dernière modification le : mercredi 25 juillet 2018 - 14:05:31

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  • HAL Id : ujm-00597720, version 1

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Jean-Philippe Colombier, Florence Garrelie, Florent Pigeon, Razvan Stoian, Mourad Bounhalli, et al.. Ultrafast laser-induced periodic-surface structure: Formation mechanisms and applications in laser marking. The 12th International Symposium on Laser Precision Microfabrication, Jun 2011, Takamatsu, Japan. 〈ujm-00597720〉

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