Structuring features of micro- and nano-ripples induced by oblique incident linear polarized femtosecond laser irradiating metal surface

The periodic ripple structures with micro- and nano-scales on the metal surface are fabricated experimentally by using an oblique incident linear polarized femtosecond laser pulses with 800nm wavelength. The structuring features show a material difference in the s- and p-polarized laser irradiations. Besides the ripples are perpendicular to the polarized direction of applied laser, in the p-polarized laser irradiation the interspace between ripples increases with the incident angle when it exceeds a threshold angle, and differently the interspace is unaltered with the incident angle in the s-polarized laser irradiation. Especially, when the incident angle is larger than the threshold angle, the spacial structured cycle (SSC) is larger than the wavelength of incident lase. Meanwhile, with the incident fluence increasing, the threshold is become small.