Nonlinear Space-time Focusing and Filmentation of Annular Femtosecond Pulses in Dielectrics
Filamentation during simultaneous space-time focusing in bulk fused silica is investigated numerically. We model the use of a pair of concentric gratings to transform a common femtosecond laser pulse with a Gaussian spatial profile into a radially chirped, annular beam shape that is focused into the bulk of silica by a lens. By varying the energy and/or time-chirp of the incident pulse, we capture the pulse dynamics and material response that yields material modification and damage in the nonlinear focus. The results show rich pulse dynamics, enhanced damage/modification site localization, and suggest novel approaches to laser machining of solids.
Journal of the Optical Society of America B
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