Surface coloring by laser irradiation of solid substrates

Laser marking has become a versatile method for industrial product identification because of its applicability to almost all kinds of solid materials in a simple and single-step process. However, traditional laser marking generally produces contrast marks which are often monochromatic. There is increasing interest in color marking by laser processing for decoration and visual attraction. This tutorial provides a digest of the recent advancement of laser coloring technologies for surface coloration. An overview of existing methods for laser coloring is summarized, and three distinct physics mechanisms behind color formation are discussed. It is found that the coloration of diverse solid surfaces originates from laser induced oxidation, surface structuring, and micro/nanoparticles generation. How the laser processing parameters and experimental conditions affect the resulting colors is also presented. The laser coloring technique is capable of producing complete Hue palettes on metal surfaces by the precise control of laser processing parameters and will find much more extensive applications.