Changes in the Intensity Distribution of the Laser Pulse due to Non-linear Optical Interaction with Air and Its Effects on Laser Ablation

Femtosecond laser processing has paved the path to ultrahigh precision fabrication, such as three-dimensional optical devices and micro/nanostructures [1] . To further expand the capabilities of this technology, laser processing using advanced light sources with pulse durations of several to tens of femtoseconds is being explored [2] . For example, the peak intensities reaching 10 14 W/cm 2 have been shown to allow for highly deterministic processing of dielectric materials [3] . However, such high intensities result in non-trivial modulation of the laser propagation by non-linear optical phenomena, such as a self-focusing and air ionization before the laser pulse reaches the material. Such effects may prove detrimental to not only the overall controllability of applications, but also to fundamental studies. While these effects have been experimentally shown not to affect the deterministic qualities which make such short-pulse ablation attractive [4] , we show here that it is possible to numerically calculate, and hence, predict, such effects.