Study on periodic structures on Si surface induced by femtosecond laser

In order to study periodic structures on Si surface induced by femtosecond laser, the relationship between the ripple period and the incident laser wavelength was analyzed. After theoretical analysis and experimental verification, the ripple period of monocrystalline silicon was calculated to be about 800nm. The ripple structures irradiated by 1kHz femtosecond pulses (center wavelength of 800nm, pulse width of 35fs) were studied. The results show that a set of liner ripple structure with parallel and equal spaces is found on the silicon surface irradiated by pulse laser under the condition that power density is slightly higher than damage threshold of the workpiece. The period of ripples is about 750nm by measurement, close to the center wavelength of laser. When the polarization direction of incident laser is changed by a rotatable Glan-Taylor prism, the direction of periodic ripples is changed accordingly. The direction of ripple is perpendicular to the electric vector direction of the femtosecond laser. The processing images show that the irradiated area is much cleaner than the non-irradiated area. The investigation is significant for further study of laser-induced periodic surface structures.