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Analysis of the periodic nanostructures generated by means of laser color marking of Ti: sapphire seconds in stainless steel

Grant number: 19/12837-9
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): November 01, 2019
Effective date (End): October 31, 2020
Field of knowledge:Interdisciplinary Subjects
Principal Investigator:Jarbas Caiado de Castro Neto
Grantee:Bárbara dos Santos Migliato
Home Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

The proposed project aims to study the interaction of the femtosecond laser with the material, whose purpose is the generation of color during the marking process through the formation of periodic nanostructures on the surfaces of the materials (called ripples). Femtosecond lasers generate ripples on the interaction surfaces, unlike nanosecond lasers that generate oxide formation on the surface of the material, causing changes in its microstructure and influencing mainly its optical properties. One of the main factors in the interaction of ultra-short pulse lasers with the material is absence of the thermal factor during the sample marking process. Modifications to material surfaces using ultrashort pulses via formation of polarization-dependent structures are responsible for the generation of specific color patterns. These periodic nanostructures created on the surface of the material are undulations typically smaller than the wavelength of the laser. A method based on laser induced nanostructure orientation control, allows accumulating a large amount of information on a minimal surface, proposing new applications for color laser marking. The use of ultrashort pulsed lasers in materials processing has aroused the interest of scientific research and the laser color marking market in the face of the promising and innovative applications of this technology. Characterized by the extremely short duration of the pulse of emitted light, between 10 (-12) and 10 (-15) seconds, allow to submit to the surface of the material reached a high energy for a very short time producing interesting effects. From a certain energy level, this type of laser induces periodic and oriented structures of small undulations of the order of nanometers in the surface of materials. Such periodic structures form diffraction gratings, which have the property of reflecting the incident white light producing colors respectively depending on the angle of view. In order to apply this property to the control of the coloring of surfaces of various materials of industrial interest, contributing to the scientific, technological and national innovation development, it is proposed the development of a process of pulsed laser marking in the range of femtoseconds to produce oriented nanostructures on the surface of materials, resulting in the visualization of specific color patterns on these surfaces. The objective of the present project is to optimize the process of generation of periodic nanostructures obtained with femtosecond laser pulses, so that the formation of ripples can be controlled with precision considering the effects of diffractive optics. The goal of this work is to obtain color codes for marking especially in stainless steel, a material widely used in industrial applications.