Ethanol-assisted ablation of silicon and germanium by temporally shaped femtosecond pulses

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 the adjustment of the photon-electron coupling efficiency by pulse train technology plays an important role in the ablation process.