Pulse width effect in ultrafast laser processing of materials

A A systematic study of the influence of laser pulse width in ultrafast laser micromachining of silicon and stainless steel was carried out. Experiments were performed using a Ti:sapphire laser with 800 nm and 400 nm ( frequency doubling) wavelengths in an air environment with a pulse duration ranging from 110 fs to 10 ps. Hole drilling and line cutting of silicon and stainless steel were studied. Structural details of the machined area were characterized using a number of techniques such as optical microscopy, atomic force microscopy and stylus profilometry. The effect of pulse width on melting was observed at similar to 2.5 ps for stainless steel and at similar to 5 ps for silicon. Also, the polarization effect on the laser machining is reported. The machined quality using femtosecond laser pulses with high energy fluence was found to be limited by the laser intensity contrast.