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In this paper, the contaminants on the substrate surfaces are cleaned using Q-switched pulse laser irradiation, which with pulse duration typically about 20ns and wavelength typically in the 1064nm or 532nm. A new mechanism for laser cleaning is proposed, which based on opto-acoustic effect that breakdown of the air above the target is obtained by a laser beam, and a laser-induced shock wave is produced to remove the various pollutants on the solid substrate surfaces.This method is much more effective than traditional conservative cleaning techniques including the continuous wave laser cleaning, there are many advantages for this new laser cleaning technology, such as the dry treatment, non-contact, non-damage to the substrate, no environmental pollution, and energy-economic, and so on. We make the theoretical analysis for this physical model of cleaning contaminant in detail and provided some experimental results and photographs.

The shape and energy distribution of laser beam directly define its applications in laser processing. In order to cater for different laser processing requirements, the input beam always needs to be transformed. The transformation between the solid beam and ring beam can be realized by the axicon-based optical devices. A beam transformation optical system, which uses a pair of positive axicon and negative axicon is designed and analyzed. The novelty of the optical system is not only that they can focus the laser beam on a ring pattern or solid beam pattern, but also that they can change the diameter of patter easily by adjusting the separation of the two conical lenses. The optical system is analyzed based on the geometry optical theory. By adjusting the separation of the convergent conical lens and the divergent conical lens, different shapes and the energy distributions are gained. At last, a measurement method of the beam profile is introduced which based on charge coupled device (CCD) The results show that the axicon-based beam transformations raise the effectiveness of laser and have a wide application prospect in laser processing field.