Line-shaped laser lithography for efficient fabrication of large-area subwavelength nanogratings

Abstract

Subwavelength nanogratings for optical modulation have attracted significant attention for efficient large-area fabrication. We developed a far-field laser nanofabrication method, called line-shaped laser lithography, to ablate thin films with separated line-shaped ultrafast laser pulses on substrates into multiple nanogratings. The millimeter pulse length and high-speed scanning for a single-pulse ablation ensure exceptionally high large-area fabrication efficiency. Moreover, nanogratings with a sub-100 nm linewidth (e.g., a 57 nm linewidth ( ∼ λ / 9 ) nanograting on 10 nm Au film) were generated based on the Marangoni effect. An ultra-uniform large-area ( 6 × 15 m m 2 ) nanograting with a width of 132 nm and a length-to-width ratio of ∼ 45 , 500 was achieved in only 1.5 s. In particular, diversified nanogratings can be obtained by designing scanning strategies, including moiré, blaze-like, Dammann, and 2D nanogratings, revealing light modulations in diffraction and beam splitting.