Bessel filamentation in glass
Résumé
Glass processing is an important technological problem since this class of material generates an increasing number of applications (solar calls, flat panel displays, microfluidics, optofluidics). In this context, the ability of femtosecond laser pulses to deposit energy in the bulk of transparent material is an important benefit for drilling, cleaving or index writing. At high intensities, femtosecond pulses in glass undergo Kerr self-focusing and interact with laser-generated free-electron plasma. Gaussian beams usually undergo strong spatio-temporal distortions during propagation in dielectrics.
We investigate the propagation dynamics of Bessel filaments. They exhibit a regime that is distortion-free even at high intensity. To develop applications, it requires thorough comparisons between experiments and simulations. We have developed a novel 3D beam imaging technique allowing for direct and quantitative comparison between numerical and experimental beam fluence distributions in glass. We also report on the domain of existence of stationary femtosecond Bessel beams in dielectrics and the emergence of instabilities from studies both in near and far field. Applications to femtosecond laser processing will be reported.