Laser Induced Dielectric Material Modifications Using Burst Of Spatio-Temporally Focused Laser Pulses

Femtosecond laser pulses are widely used for in-bulk dielectric material modifications, with a large range of applications in micro- and nano-photonics, or micro- and nano-fluidics. The conventional focusing of a single gaussian pulse leads to a teardrop-shaped energy deposition, limiting the precision of the energy deposition location, and restricting the geometry of the absorbing area. These problems could be overcome by combining two methods: using a burst of laser pulses exhibiting a spatial chirp. The first method relies on the possibility to produce tens of pulses in 100 ps timescale [2] , which is shorter than thermal and hydrodynamics relaxation timescales. It is then possible to accumulate accurately the energy within the material, pulse after pulse. The second method, called Simultaneous Spatial and Temporal Focusing (SSTF), is a promising technique in which the pulse duration diminishes in the course of propagation [3] . The SSTF technique also leads to a pulse-front tilt (PFT), which extends the transverse dimension of the beam, and constitutes another degree of freedom to control the interaction geometry.