Laser-ablated volume and depth as a function of pulse duration in aluminum targets

The ablated depth and volume per laser pulse from an aluminum target were measured for pulse durations that ranged from 80 fs to 270 ps at an average fluence of approximately 100 J/cm2 and a wavelength of 0.8 microm. The ablated volume showed a flat maximum for subpicosecond pulses and a minimum for approximately 6 ps. The crater diameters were rather constant up to pulse durations of approximately 6 ps and increased for larger pulse durations. As a result, the ablated depth also showed a plateau for subpicosecond pulses but decreased monotonically with pulse duration. A physical interpretation of these results and their consequences for laser applications are discussed.