Ethanol assisted ablation of silicon and germanium by temporally shaped femtosec

A surprising phenomenon can be discovered by using femtosecond double-pulse ablation of silicon and germanium in ethanol. The ablation areas present an oscillation increase phenomenon when the pulse delay increases from 200 fs to 1 ps in the fluence range of 0.5–0.6 J/cm2. In contrast, the ablation areas exhibit an oscillation decrease phenomenon as the pulse delay increases when the laser fluence F < 0.5 J/cm2, which is consistent with the results of the experiment in air. It is considered that