Microexplosions in bulk sapphire driven by simultaneously spatially and temporally focused femtosecond laser beams

We report experimental results on the formation of microvoids in bulk sapphire produced through the single-shot illumination of the sample by near-infrared, simultaneously spatially and temporally focused (SSTF) laser beams. Compared with the cases of tightly focused femtosecond Gaussian and flattop beams, the SSTFs produce internal microvoids with significantly larger volumes and without cracks between the interaction sites, which may be beneficial for applications in volumetric data storage and for the studies of exotic, super-dense elemental phases contained in the densified shells surrounding the microvoids.