Comparison of Structural Colors Achieved by Laser-Induced Periodic Surface Structures and Direct Laser Interference Patterning

Engraving surfaces with holographic features is not only used for decorative applications, but also for protecting products from counterfeit and piracy. This structural coloration can be produced on large areas at high-throughput using laser-based methods such as Direct Laser Interference Patterning and Laser-Induced Periodic Surface Structuring (LIPSS). In this contribution, both technologies were used to generate diffraction gratings on stainless steel with different processing parameters. Then, the resulting spectral reflectances were quantitatively compared and correlated to topographical characteristics determined by scanning electron microscopy and atomic force microscopy. Overall, the DLIP treated samples showed up to 42% higher diffuse reflectivity than the LIPSS samples when illuminated with a green laser diode. However, the LIPSS textures were less spectral dependent, probably due to their broader distribution of spatial periods and structure heights. These findings could also be appreciated with the naked eye as the samples patterned with LIPSS have a matte aspect with a homogeneous coloration, whereas the DLIP samples had a glossy appearance with brighter colors.