Anatomy and Thermal History of Laser Self-Focusing Damage Tracks in Glass

Laser induced self-focusing damage tracks in glass are analyzed. The damaged regions consist of long cylinders of altered refractive index, containing occasional bubbles and partly surrounded by arrays of small cracks. An analysis of the refractive index change in the subfracture damage tracks and the presence of bubbles leads to estimates of a minimum temperature reached by heating of the glass in the tracks. A calculation of minimum stresses developed during laser-beam heating gives a good account of the orientation of the observed cracks.