Femtosecond laser processing - Industrial applications of ultra-short pulses

Ultra-short pulses are a new laser technology offering a highly original mode of laser-matter interaction compared with conventional, continuous lasers, or those delivering pulses with durations in excess of a nanosecond. Ultra-short laser pulses range in duration from femtoseconds (10 ^-15 s) to picoseconds (10 ^-12 s). These pulses have given rise to some highly innovative applications in materials processing. A distinction is made between femtosecond pulses, usually lasting a few hundred femtoseconds, and picosecond pulses, lasting more than 1 ps. This article does not deal with imaging applications, where the aim is to visualize without modifying the material, a field in which ultra-short technologies also play a role. Nor will we touch on the field of very high energies, used for major research instruments such as the Laser MégaJoule (LMJ). The field of laser processes concerns a modification made to a material, and is aimed more at industrial laser applications. This modification can lead to material removal, known as laser ablation. We'll be focusing on the characteristics of laser-matter interaction in ultra-short mode, and their relevance to the development of applications.

In the case of ultra-short laser pulses, the highly original physics of laser-matter interaction calls for highly specific expertise in process control. Their development has been made possible by numerous laboratory research results, combined with intense scientific publication activity. Even before the 2000s, when femtosecond pulses were first used in ophthalmic surgery, innovative industrial applications were being devised and studied with the resources available. The motivation behind these studies was, and still is, to overcome the technological barriers limiting the scope of the applications concerned. In particular, the "trademark" of femtosecond processes is the very high precision of machining, usually in the order of ten microns, but quite easily reaching a few hundred nanometers, and simultaneously the non-alteration of materials outside the treated zone.

The first phase in the development of femtosecond processes was therefore aimed at reaching the industrial stage. In France, a number of technical centers embarked on this path very early on, against a backdrop of strong competition, mainly from Germany and Japan. Thanks to the development and marketing of laser sources adapted to industrial applications in France from the 2000s onwards, these technologies reached the maturity required to move beyond the initial industrialization stage. The applications concerned were mainly in the medical field, but the industrial production sector also took off very quickly. Femtosecond micromachining...