X-ray emission from femtosecond laser micromachining

Summary form only given. Ultrafast lasers are rapidly becoming important tools in the micromachining and microprocessing of solids. Extremely short laser light pulses in the femtosecond regime lead to qualitatively different interactions with solids compared with light pulses of much longer duration. Pulse energies from high-repetition-rate solid state lasers deployed in femtosecond laser machining commonly range from /spl sim/0.1 /spl mu/J to /spl sim/1 mJ; with typical repetition rates in the 1-250 kHz regime. Focussing these light pulses to small spot sizes lead to very high peak intensities (/spl sim/10/sup 14/-10/sup 16/ W/cm/sup 2/), even for relatively compact (amplified) micromachining lasers. The characterization of hard photon emission, including in the X-ray region, is important for laser plasma characterization as well as in terms of workplace environmental considerations. Our investigations utilized an amplified Ti:sapphire laser system with pulses of 120 fs duration, up to 300 /spl mu/J in pulse energy, and operating at a 1 kHz repetition rate.