Influence of 2.09-μm pulse duration on through-silicon laser ablation of thin metal coatings

A robust Ho:YAG chirped pulse amplifier with a simple dispersion management was developed for material processing applications. The amplifier produces 3.2 ps pulses centered at 2.09 μm with energies up to 1.6 mJ. At 10 kHz repetition rate this results in 16 W of average power. Both pulse stretching and compression in the amplifier is realized within a single chirped volume Bragg grating. With the developed amplifier we study laser ablation of a gold layer through a carrier substrate and, particularly, the effect of pulse duration on the process. A balance between nonlinear effects within the carrier and interaction with the thin ablation layer makes few picosecond pulses most suitable for non-thermal ablation. Furthermore, since only a few-microjoules of pulse energy is required for de-bonding, the developed 16 W amplifier can be potentially operated at MHz repetition rates for high throughput.