ABSTRACT
Laser cleaning based on pulsed laser irradiation of a surface ensures effective removal of surface particulate as small as 0.1 micrometers. For example, the pulsed laser-Irradiation can be used with or without the simultaneous deposition of a thin liquid film on the surface to be laser-cleaned. Laser cleaning with the highest efficiency is obtained by choosing a laser wavelength that is strongly absorbed by the surface to ablate off a water film of thickness on the order of micrometers deposited just before the pulsed laser irradiation. This technique, to be called “laser-steam cleaning,” permits the effective removal of particles smaller than 20 micrometers. Basic theoretical estimates as well as experimental measurements support the hypothesis that the liquid-film enhanced laser cleaning effect involves strong superheating of a thin-layer of liquid in contact with the solid, and this thin-layer undergoes explosion when the incident pulsed laser fluence exceeds a certain threshold value, launching a shock pulse which causes particulates to be ejected.
