An investigation of long pulsed laser induced damage in sapphire

The formation of keyhole and transverse section of a laser-cut kerf with slight stripe undulations by a 1064 nm ms pulse laser on (0 0 0 1) sapphire was investigated. The morphologies of keyhole and transverse section surfaces were evaluated by SEM, and the composition of transverse section of laser-cut kerf was evaluated by EDS, XRD and XPS. The time scale for onset of vaporization and the keyhole depth with different laser pulse energies were calculated. The result suggests that the depth of keyhole is approximately directly proportional to laser pulse energy. On sapphire transverse section surface, the element ratio of Al to O deviates from the stoichiometry of sapphire, perhaps due to the oxygen removal from surface.