Regular uniform large-area subwavelength nanogratings fabricated by the interference of two femtosecond laser beams via cylindrical lens

Inhomogeneity and low efficiency are two important factors that hinder the wide application of laser-induced periodic surface structures. Two-beam interference is commonly used to fabricate gratings with interference periods. This study reports regular and uniform periodic ripples fabricated efficiently by the interference of two femtosecond laser beams via a cylindrical lens. The interference period is adjusted to be an integer multiple of the wavelength of a surface plasmon polariton. Regular and uniform subwavelength nanogratings (RUSNCs) on a silicon wafer of a diameter of 100 mm are fabricated with a scanning velocity of 6-9 mm/s. Bright and pure colors (including purple, blue, and red) are demonstrated on different patterns covered with RUSNGs.