Structural characteristics induced by nanosecond, picosecond, and femtosecond laser pulse in sapphire

The damage threshold and morphology of sapphire crystal (0001) have been investigated by nanosecond (ns), picosecond (ps), and femtosecond (fs) laser pulse at 800 nm based on the mechanical, thermal, and photon-electrical properties of sapphire crystal. The star-like crack which is associated with the point group of sapphire crystal is induced by ns laser pulse, and the cross crack is induced by ps laser pulse and linelike crack is induced by fs laser pulse, which may be related to the preferred dislocation from anisotropic stain tensor.