Multifractal characterization of femtosecond laser-induced herringbone patterns

Analysis of surface structures formed due to femtosecond laser surface ablation is usually done through subjective assessment of the surface images. Here, we analyze the evolution of femtosecond laser-induced surface structures using multifractal analysis. We computed the singularity spectrum to characterize the behavior of laser-induced herringbone patterns. The surface morphology of the ablated surface shows a polarization dependent multifractal nature. The singularity spectrum depicts three distinct morphological phases that sequentially form as a function of the laser pulse number. We objectively characterize the laser-dependent morphological properties of herringbone structures. Multifractal analysis was able to reflect the hierarchy, uniformity, and roughness of the formed structures and their dependence on the pulse number and polarization.