Realtime study of plume ejection dynamics in silicon laser ablation under 5 ns pulses

We present results of nanosecond laser ablation of silicon over a broad range of laser intensities, investigated by studying the time evolution of the ablation plume ejection, which, as measured by transmission of a probe beam, consists of a fast ejection phase followed by a delayed slow ejection phase. Experimental results indicate that different physical processes dominate at different ablation stages. The laser intensity threshold for the appearance of the slow ejection is similar to 30 GW/cm(2). The plume kinetics parameters extracted from our experiments agree well with estimations based on blast wave and homogeneous nucleation theories, providing a physical explanation for the observed ablation rate dependence on the laser light intensity. (c) 2006 American Institute of Physics.