Periodical ripples on metal and semiconductor by femtosecond laser irradiation

Formation of periodical surface ripple is widely observed in laser processing such as laser annealing, laser-induced chemical vapor deposition and laser etching. The ripple structures are closely related with the material properties and wavelengths used. Such structures were reported on the transparent material using a visible femtosecond laser pulse. In the paper, the ripple structure formed on Ni, Ag and GaP by the irradiation of ultra-short laser pulse of a Ti:sapphire laser is described. Pulse duration and repetition rate of the laser is 130 fs and 10 Hz, respectively. The laser beam was focused on the target using a lens of the focal length of 150 mm. The incident angle was varied from 0 degree to about 45 degree by rotating the sample mounted on an angle-tilting stage. The number of the laser pulse was varied from three to one hundred.