Fig. 1. SEM images of craters produced by 20 double pulses at a repetition rate of 20 Hz in different mediums: (a) in air, F=0.6  J/cm2; (b) in ethanol, F=0.4  J/cm2; (c) in ethanol, F=0.6  J/cm2.

Fig. 2. Ablation area as a function of the pulse delays at different laser fluences: (a) air, (b) ethanol.

Fig. 3. SEM images of crater morphologies obtained at Δt=500  fs in (a) air and (b) ethanol. Two-dimensional profiles of the craters produced in (c) air and (d) ethanol.

Fig. 4. Ablation area as a function of pulse delays in Ge in the ethanol solution.