Study by focused shadowgraphy of the effect of laser irradiance on laser-induced plasma formation and ablation rate in various gases

The influence of laser irradiance on the extent of laser-sample coupling at 1064 nm was investigated in argon, air and helium at atmospheric pressure. Focused shadowgraphy measurements allowed the observation of laser–matter interaction at the nanosecond timescale and to visualize different behaviors in argon, air and helium atmospheres. It was established using shadowgraphy and laser drilling experiments that the growth of ablation rate with laser irradiance changes drastically depending on the irradiance range considered. In addition, laser-induced gas breakdown and laser-supported detonation processes, which have different origins but may both lead to decreased coupling via plasma shielding, could clearly be distinguished.