Laser induced breakdown as a function of pulse duration: From 7 ns to 150 fs

Single-shot laser induced breakdown, in wide band gap materials such as SiO2 and MgF2, has been studied over almost 5 orders of magnitude in duration from 150 fs to 7 ns. A Ti:sapphire chirped pulse amplification system was used in this experiement, so the pulse duration could be continuously adjusted without changing any other parameters. The damage threshold was detected by looking at the plasma formation and the change of material transmission coefficient. The avalanche mechanism was found to dominate over the entire pulse-width range even for 150 fs pulses where we would expect multi-photon processes to take over. A strong departure from the conventional fluence threshold scaling law is observed for pulses shorter than 10 ps, where beyond this point the fluence threshold increases. Also, it is observed for the first time that for short pulses the damage threshold becomes very accurate and less statistical than that for longer pulses.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.