Abstract
Summary form only given. Pulsed schlieren photography and fast helium-neon laser beam deflection were used to study the hydrodynamics of laser ablation from polymethylmethacrylate (PMMA) and polyethyleneterephthalate (PET) by pulsed KrF laser (248 nm) radiation in atmospheric air, N2, and Ar. The time scales investigated were 0.5 ms to 6 ms. Fluences varied from less than 30 mJ/cm2 to 10 J/cm2. Sound waves, shock waves, reduced density plumes, or optical breakdown plasmas were produced depending on the laser fluence. Below the ablation threshold, sound waves were observed leaving the surface. Above the ablation threshold, a shock wave and a reduced density plume were generated. At low fluences, below 300 mJ/cm 2 for PET, a linear relationship exists between fluence and shock velocity. At higher fluences, above 1 J/cm2 for PET, the shock speeds approach ideal blast wave theory
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