Optics and Photonics Society of Iran

In this research, a silicon wafer has been irradiated by femtosecond laser pulses. Laser fluence is studied as an important parameter. The reflection spectrum of the surface at three different fluencies 1, 3 and 9 KJ/m² has been recorded after 1-minute irradiation. The results are shown that at low laser fluence the efficient ablation did not take place and the surface reflection did not change. However, when the laser fluence reaches to ionic plasma formation threshold, the laser ablation is occurring that cause spikes formation on the silicon surface. The changes in the surface structure result in reflection decreases. In conclusion, by laser irradiation of silicon surface with laser fluence more than the threshold the black silicon is fabricated which due to its high absorption can improve the manufacture of solar cell technology.