ABSTRACT
Femtosecond laser pulses are easily available from commercial lasers and even attosecond laser pulses are realized in laboratories. This chapter focuses on the ultrashort pulse laser process in the order of 100 short-pulse, which is the most popular pulsewidth in laboratories and industrial research. Femtosecond laser processing cover a wide variation of material like metal, semiconductor, and dielectric materials. The most popular industrial application of the femtosecond laser is micro-machining, such as drilling or cutting, with a negligible heat affected zone. Under the femtosecond irradiation, an interesting phenomenon called laser-induced periodic surface structure happens near the ablation threshold. Even below the threshold for amorphization, it has been reported that amorphous spark ignition can be crystallized with the femtosecond laser irradiation. In the high field of laser pulses, atoms and molecules are easily ionized. As the laser beam is a coherent electromagnetic wave, electrons put in the laser beam get energy from the oscillating electric field.
