Control over a phase state of the laser plume ablated by femtosecond laser: Spatial pulse shaping

The conditions required for the formation of a fully atomized laser-ablated plume using subpicosecond laser pulses was discussed. The local thresholds for the different material transformations under the action of short powerful laser pulses were also formulated. It was found that the low-intensity wings were responsible for low-threshold phase transformations of the target and this was the major source of particulates in the ablated plumes. It was suggested that by truncating these wings with simple aperture and positioning the target in the image plane of that aperture, particulates can be eliminated from the plume.