The effects of microstructure on high-intensity laser-material interaction of aluminum oxide

Alumina is a versatile ceramic with robust properties, allowing applications in numerous areas including medical, optical, aerospace, and industrial applications. Single-crystal alumina (undoped sapphire) and polycrystalline alumina have different optical and mechanical properties, attributed to the differences in microstructure. It is imperative to understand the behavior of these materials under extreme conditions. Laser irradiations with high peak intensities subject the materials to extreme conditions with high loading rates, exerting high pressure proportional to the peak intensity on the surface. This study uses single-shot laser irradiations on single-crystal and polycrystalline alumina to investigate the intrinsic material responses. An ultrafast laser is utilized to perform single-shot irradiations with peak intensities ranging from 10¹² W/cm² to 10¹⁵ W/cm² for understanding laser-induced modifications. The geometrical and morphological properties of the laser-induced features are characterized using Scanning Electron Microscope (SEM), Atomic Force Microscopy (AFM), and optical profilometer. The single-crystal alumina exhibits thermal effects with signs of melting whereas the polycrystalline alumina fractures under high pressure. Geometrical analysis of the laser-induced features reveals the scaling correlation between the laser parameters and material modifications.