Study of localized pulsed laser depassivation by interferometric probe

Optical interferometry has been implemented as a novel approach to monitor sensitively the localized pulsed laser depassivation of iron or stainless steel samples. This new method, complementing the previous transient current measurements and channel flow double-electrode, is based on the time-resolved measurement of the rear surface displacement of the test sample induced by the laser generated ultrasonic wave. The removal of any material, such as the passive film, from the irradiated surface results in an enhancement of the longitudinal component of the laser generated ultrasonic wave, which is manifested in a change of the displacement characteristics of the rear surface of the test sample, monitored by the interferometric probe. Preliminary results, demonstrating the applicability of this novel approach for localized pulsed laser depassivation studies, will be presented and future prospects will be discussed.