Nanoscale energy deposition in glass by double ultrashort Gauss-Bessel pulses

The main advantage of ultrafast laser-based processing techniques is the capability of structuring the material in three dimensions, even inside the bulk of transparent materials. It allows for a very precise control and versatility of the manufacturing process. The formation of high aspect ratio voids in glass with diameters in the hundreds of nanometres range using only a single ultrafast laser pulse is particularly useful for many applications. Drilling of high aspect ratio nanochannels has been particularly successful when using zeroth-order Bessel beams [1] , [2] . However, depending on the material and illumination geometry, limitations arise on the maximal and minimal nanochannel diameter ( Fig. 1a ). Here, we demonstrate that double pulses drastically improve the efficiency of the drilling ( Fig. 1b ) and absorption measurement allow for deciphering the mechanism.