Study of laser pulse width dependence on ablation of thin film and plasma plume propagation

Effect of laser pulse width on plasma plume formation and its expansion into the background gas is investigated for thin film sample under the rear ablation geometry, employing 10 ns, 200 ps and 100 fs laser pulses respectively. The plasma plume is diagnosed with multiple diagnostics like fast imaging, spectroscopy and Langmuir probe. We observe that the plume directionality, splitting and expansion significantly depend on the laser pulse width. The plume expansion behavior is explained by appropriate models. We also observe that the laser pulse width along with the film thickness plays a major role in deciding the nature of plasma plume expansion. (author)