Observations of Moving Self-Foci in Sapphire

Abstract
Observations of the time development of damage tracks in sapphire are explained in terms of a backward-moving self-focused spot. The detailed characteristics of the dynamics of the track evolution depend on the temporal shape of the incident laser pulse. Both qualitative and semiquantitative features of the observed phenomena are explained using a theory which shows that the results are consistent with a combination of both electrostrictive and electronic self-focusing mechanisms.