Stimulated emission in aluminum laser-induced plasma: An experimental study

The stimulated emission (SE) in aluminum laser-induced plasma pumped in resonance with the 3s²3p-3s²4s aluminum transition at 266.04 nm is investigated experimentally. It is shown that the population inversion between the 3s²3p and 3s²4s states can be created by weak pumping at several microjoule to millijoule pulse energies and result in high gain. The intensity of the SE at 396.15 nm is related to the number density of Al atoms via absorption measurements. It is found that the SE in forward and backward directions with respect to the pumping laser is different in terms of the line shape and intensity that is attributed to inhomogeneity in a gain coefficient across the plasma plume.