High energy density deposition inside the bulk of dielectrics via resonance absorption

Ultrafast laser processing of nanochannels and nanovoids in the bulk of dielectrics such as fused silica, glass or sapphire is highly desirable for a number of applications such as stealth dicing, nano-fluidics or nano-photonics. It was demonstrated more than 10 years ago that high angle femtosecond Bessel beams can generate high aspect ratio with only a single laser pulse. However the exact mechanism of energy deposition was still lacking. Indeed, most numerical models were predicting defocussing of the pulse on the plasma, and very weak energy density deposition which was incompatible with the experimental result using an imaging technique developed in [1] .