Shock waves generated by XeCl excimer laser ablation of polyimide in air and water

Pressure transients of several hundred bars with rise times of a few nanoseconds can be created by UV-laser ablation of organic polymers as well as of tissue.1,2 We demonstrate, we beEeve for the first time, that ablation of polyimide by 308-nm XeCl excimer laser radiation generates shock waves at fluences of several times the threshold of ablation. This is a significant finding, because a shock wave, characterized by a picosecond rise time and a supersonic propagation speed, differs qualitatively from an acoustic wave. Our measurements were intended to simulate the ablation of cornea at 193 nm, but are also relevant to material processing of lasers.