Patent ID: 7875414

Claim:
A method of forming a periodic structure, comprising: irradiating a surface of a material with a linearly polarized single laser beam of a femtosecond laser, of which a fluence is above but nearly as low as ablation threshold; and executing an overlapped scanning in which the laser beam is scanned on the material surface with a laser scanning speed being set such that the number of pulses of the laser beam irradiated on an identical position of the material surface is within a range of 10 to 300, so as to cause the ablation on the material surface at a section where interference has taken place between a p-polarization component of an incident beam and a p-polarization component of a surface scattered wave generated along the material surface, and to thereby form a periodic structure on the material surface, wherein the periodic structure has ripples spacing near a wavelength of the incident beam in a direction perpendicular to a polarization direction of the incident beam.