Ultrafast lasers for materials microprocessing

The field of ultrafast optical science, including the generation, amplification and manipulation of ultrashort laser pulses (∽ 1 ps or less), has seen dramatic growth in the recent years. Ultrafast lasers have found diverse applications from probing ultrafast, transient chemical reactions to inertial confinement nuclear fusion studies. Materials processing such as laser drilling and cutting is one of the promising potential applications of ultrafast lasers. Ultrashort laser pulses have opened up many new possibilities in laser-matter interaction and materials processing. The extreme short pulse width makes it easy to achieve very high peak laser intensity with low pulse energies. The laser intensity can reach 1014–– 1015 W/cm2 with a pulse < 1 mJ when a sub-picosecond pulse is focused to a spot size of a few tens of micrometers. The extremely high intensity and short laser-matter interaction times lead to a highly non-equilibrium state in the material under irradiation, where electrons are driven to much higher temperatures than ions. The short duration means that the hydrodynamic motion of the matter under laser irradiation can be ignored, and there is essentially no fluid dynamics to consider during the laser-matter interaction.