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Center For Applied and Computational Mathematics

Thermal and Fluid Processes During Femptosecond Laser Ablation

Faculty:  Anthony Harkin

Summary:

We study the formation mechanism of rims created around femtosecond laser ablated craters on glass. Experimental studies of the surface morphology reveal that a thin rim is formed around the smooth craters and is raised above the undamaged surface by about 50 to 100 nm. To investigate the mechanism of rim formation following a single ultrafast laser pulse, we perform a one-dimensional theoretical analysis of the thermal and fluid processes involved in the ablation process. The results indicate the existence of a very thin melted zone below the surface and suggest that the rim is formed by the high pressure plasma producing a pressure-driven fluid motion of the molten material outwards from the centre of the crater. The numerical solutions of pressure-driven fluid motion of the thin melt demonstrate that the melt can flow to the crater edge and form a rim within the first nanoseconds of the ablation process. The possibility that a tall rim can be formed during the initial stages of the plasma is suggestive that the rim may tilt outwards towards the low pressure region creating a resolidified melt splash as observed in the experiments. The possibility of controlling or suppressing the rim formation is also explored.

Publications:

  1. Thermal and fluid processes of a thin melt zone during femtosecond laser ablation of glass: the formation of rims by single laser pulses, Adela Ben-Yakar, Anthony Harkin, Jacqueline Ashmore, Robert L. Byer and Howard A. Stone, J. Phys. D: Appl. Phys.(40), 1447-1459, (2007).

Collaborators:

Adela Ben-Yakar (University of Texas at Austin)
Howard Stone (Harvard)