engleski

Laser generated solitons on vortex filaments on ta surface

In the non-stationary laser vapourization a shear layer of molten metal is generated and vortex filaments on the micron-scale are observed. The Shock waves generated in the process of material removal cause the cascade splitting and generation of the vortex filament bush. Torsion of the vortex filaments generates the solitons that travel in radial direction (along the filaments). The soliton in the central zone of the bush are three dimensional and travel in helicoidal way, while the solitons in the side zones are two dimensional and travel by "slipping" along the filaments. This indicates that torsion tau, is not constant in all the branches of the bush but has maximum in the central zone and vanishes (tau=0) in the side zones. Two dimensional solitons are described by modified Korteweg-de Vries equation in parameter kappa (curvature), while three dimensional ones are described by the non-linear Schrodinger equation in complex parameter Psi. These experiments clearly demonstrate that spectrum of structures may appear as a consequence of nonlinear dynamics in the liquid molten layer of metal in the process of non-stationary vapourization, caused by the single laser pulse. They offer a possibility to relatively simply generate the unusual structures and bring them to study. Finally, they also show that the process of laser vapourization is more complex than usually assumed from the aspect of surface dynamics of the target.

soliton; vortex filaments; mkdv; NLS

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