Laser drilling of advanced materials: Effects of peak power, pulse format, and wavelength

The quality of laser-drilled holes is significantly influenced by the laser peak power, pulse format, and wavelength. Three advanced materials are used to demonstrate the importance of choosing the correct laser parameters for a specific material. The materials are: (1) intermetallic single crystal nickel aluminide (NiAl) alloy; (2) N5, a single crystal nickel-based superalloy; and (3) a silicon carbide (SiC) ceramic matrix composite (CMC). The Laser peak power is varied in terms of the pulse duration and format. For low peak powers, long pulse format (pulse lengths on the order of ms), conventional and also shaped-pulse (burst) commercial rod Nd:YAG laser systems were used. For high peak powers, a short pulse format was adopted for the laser used, namely a cw-pumped Q-switched or modelocked/Q-switched Nd:YAG oscillator followed by a cw-pumped multipass amplifier using a face-pumped, total internal reflection Nd:YAG slab as the gain medium. Finally, a KrF excimer laser operating at a 248 nm wavelength was used. The excimer wavelength was chosen to be close to the Nd:YAG fourth harmonic.