Laser ablation of Mg, Cu, and Pb using infrared and ultraviolet low-fluence lasers

The modified two-dimensional hydrodynamic code POLLUX has been used to simulate the ablation of magnesium, copper, and lead targets in the early stage of expansion (<100 ns) by 30 ns, 0.248 mu m KrF excimer and 1.064 mu m Nd-YAG lasers at fluences of 3-10 J/cm(2). The results of magnesium ablation using KrF laser with different fluences are compared and found to be in reasonably good agreement with the experimental results. A comparative study of laser ablation for magnesium, copper, and lead has been made by simulation using Nd-YAG lasers at fluence 10 J/cm(2). The temporal evolution of surface temperature of the target, ablated vapor mass, and ionization fraction of plasma plume is studied for each material. The simulated temporal evolution and spatial distribution of electron density, electron temperature, and axial velocity of ablated plume of each material are studied and the results are compared. It is found that the plume expansion follows adiabatic behavior and is slowed down with increasing atomic mass. In addition to that, the effect of laser wavelength on ablation has also been investigated by comparing ultraviolet KrF excimer and infrared Nd-YAG lasers. It is found that shorter-wavelength lasers favor ablation and plasma screening is more effective for longer-wavelength lasers. (C) 2003 American Institute of Physics.