The early detection of laser-induced damage

An imaging technique has been developed that, for the first time in a single non-damaging laser pulse, allows enough information about the surface under test to be obtained to enable accurate predictions to be made as to the spatial locations of the first damage sites. The technique is based upon using high resolution schlieren imaging to monitor the deflection of a pulsed probe (dye) laser beam incident on the test surface a few hundred nanoseconds after the surface has been heated by a non-damaging pulse from the main (KrF excimer) laser. It is found for all samples tested (metals semiconductors, dielectrics) that the areas of greatest probe beam deflection are the first ones to damage. Furthermore it is found, in multiple shot experiments, that to a good approximation the order in which areas damage is proportional to the amount of probe beam deflection.