Dynamics of material removal in ultrashort laser ablation of dielectrics

Summary form only given. Non-thermal and thermal processes are evidenced in near infrared, ultrashort (sub-ps and ps) pulse laser ablation of wide band-gap dielectrics with accent on the etch phases in the case of laser irradiated sapphire (c-Al/sub 2/O/sub 3/) depending on the laser parameters controlling the ablation process: number of pulses, laser fluence and pulse duration. The mechanism and dynamics of ion expulsion are studied using a combination of time-of-flight mass spectrometry and pump-probe techniques. Mechanistic arguments concerning the energy and momentum distribution in the plume in different irradiation conditions are used to distinguish between non-thermal and thermal processes that lead to laser ablation.