Short pulsed laser machining: How short is short enough?

Machined feature quality is examined, and the effects of laser pulse width (and thus peak power or intensity) are investigated for the following four laser systems: (1) a millisecond-class, free-running Nd:YAG; (2) a 100-nanosecond-class, Q-switched Nd:YAG laser; (3) a 100-picosecond-class, mode locked Nd:YAG laser; and (4) a 100-femtosecond-class, Ti:sapphire chirped pulse amplification laser. The effect of shorter laser wavelength is also examined by using the second harmonic wavelength of the Nd:YAG laser in the Q-switched and the mode locked pulse formats. Hole drilling and cutting of superalloy, ceramic, and composite materials are studied. The machined feature quality is improved as the pulse width becomes shorter and the peak intensity becomes higher. The shorter wavelength provides another significant improvement. Finally, an attempt is made to view these quality improvements in the context of process throughput and cost of ownership.