A quantitative analysis of single pulse ultraviolet dry laser cleaning

Particles as small as 0.3 mu m in diameter have been successfully removed from a glass surface using a single ultraviolet pulse from a frequency doubled copper vapor laser (255.3 nm). Quantitative analysis of the particle density before and after laser irradiation shows that laser cleaning occurs after a fluence threshold is reached. The cleaning efficiency after threshold follows a nonlinear trend with respect to fluence. A model is presented which reveals that the cleaning efficiency is a function of the irradiance distribution of the beam used. Results of modeling thermal expansion of the substrate and particles, and particle adhesion do not confirm a thermal expansion mechanism for laser cleaning in this study, in contrast with other recent reports. (C) 1999 American Institute of Physics. [S0021-8979(99)06223-4].