ALPhANOV

The research work presents silicon laser processing with GHz bursts (emission wavelength at 1.6 um) for uniform column growth throughout the bulk of a 1 mm sample. Different burst configurations and burst parameters are explored for repeatable uniform column growth. While 2 pulse per burst was observed to be better compared to single pulse in terms of column growth, the energy distribution within the 2 pulses too have an effect on such modifications. Thanks to the optimization of different parameters, columns are generated with writing speeds such as 7 μm/s even in the absence of substrate glass.

We report on a comparative study of MHz and GHz bursts for femtosecond laser structuring of electrodes (graphite-silicon composite and high nickel content NMC coatings). Influences of average power, burst length and intra repetition rate on the matter removal rate were investigated for drilling and grooving with both holes and grooves reaching the metallic collector. Removal rates and resulting machining qualities, investigated by SEM, were compared between single pulse (SP) and bursts (clocked at 40 MHz and 1.28 GHz). Fastest processing conditions for which SP and burst machining qualities are comparable were identified by SEM. In accordance with an ablation model, results indicate that removal rates depend strongly on the burst duration and slightly on the intra-repetition rate. MHz and GHz burst modes can decrease the processing time by a factor up to respectively 4 and 5.

We report on in bulk modifications induced by Bessel-beam irradiation in Sodalime glass with a single GHz-burst. By coupling a single pulse probe with a burst pump, clear understanding of the accumulation regimes can be established. A comparison is also made between the bulk modification generated by MHz- and GHz-burst.

Femtosecond laser processing in GHz-burst regime offers enhanced control of thermal effects, enabling faster and more precise material modification. This work highlights three implementations demonstrating its versatility: (i) fabrication of moulds for microfluidic devices, (ii) high-throughput drilling of through-glass vias (TGVs), and (iii) surface treatment of 3D parts using a robot-assisted fibre-delivered system. All demonstrations use a 50-W, 1030-nm Satsuma X laser (Amplitude). For microfluidics, GHz-burst machining produces moulds with sub-10-µm accuracy and surface roughness below 300 nm, reducing production time to under an hour and cost to a few hundred euros. For microelectronics, the technique drills high-aspect-ratio holes (AS > 150) in fused silica in under 12 ms per hole, greatly improving throughput. Finally, the low pulse energy of GHz bursts enables stable fibre delivery. A hollow-core fibre mounted on a robotic arm transported up to 20 W while performing surface treatments on a 3D stainless-steel part.