Wavelength Dependence of Energy Transfer from Femtosecond Laser Double Pulse to Silicon

Femtosecond laser ablation enables precision processing with minimal thermal effects. From the viewpoint of processing efficiency, the ratio of the total energy absorbed by the material to the incident pulse energy should be high. In recent years, an increase in ablation efficiency by GHz bursts mode [1] and dual wavelength pulse irradiation [2] has been reported. We have also recently shown dramatically enhanced energy absorption by mixed irradiation of ultraviolet and infrared pulses [3]. Inspired by these works (but not directly targeting at GHz burst processing), in this study, we theoretically study how the energy absorption by silicon subject to femtosecond double pulses can be increased by optimizing the combination of different wavelengths.