Specifications of nanosecond laser ablation with solid targets,aluminum, silicon rubber,and polymethylmethacrylate (PMMA)

The ablation parameters such as threshold fluence,etch depth,ablation rate and the effect of material targets were investigated under the interaction of laser pulse with low intensity.The parameters of the laser system are:laser pulse energy in the range of 110-140 m J,wavelength 1064 nm and pulse duration 20 ns.By macroscopic estimation of the outward images of the ablation and data obtained,we can conclude that the photothermal and photoionization processes have more influence for aluminum ablation.In contrast,for polymer samples,from the macroscopic observation of the border pattern at the irradiated spot,and also the data obtained from the experiment results,we deduce that both chemical change due to heating and photochemical dissociation were effective mechanisms of ablation.However,concerning the two polymer samples,apart from considering the same theoretical ablation model,it is conceived that the photomehanical specifications of PMMA are involved in the ablation parameters.The threshold fluence for an ablation rate of 30 laser shots were obtained as 12.4,24.64,and 11.71 J cm-2,for aluminum,silicon rubber and polymethylmethacrylate (PMMA) respectively.The ablation rate is exponentially decreased by the laser-shot number,especially for aluminum.Furthermore,the etch depth after 30 laser shots was measured as 180,630 and 870 μm,for aluminum,silicon rubber and PMMA,respectively.