Effect of thermal stresses on fused silica surface on the laser induced damage

Abstract

To study the effect of the thermal stresses on the optics, experiment is performed to measure the damage threshold of the two fused silica samples with one annealed to eliminate thermal stresses while the other not. The measurement includes the effects of the thermal stresses on the initial damage threshold of the fused silica, the damage growth threshold, and the damage growth laws. The results show that the damage threshold decreases as the thermal stresses increase, and the damage induced by the laser is accelerated by the thermal stresses. For the same laser intensity, the damage growth factor is higher for the area with higher thermal stresses, but the damage growth still obeys the exponential increase rule and no obvious effect of the thermal stresses is found on the damage growth threshold. The study here will determine to some extent whether the technology of the CO2 laser pretreatment can be applied to the large-aperture optics or not.