Line-shaped laser lithography for efficient fabrication of large-area subwavelength nanogratings
Kang Xu, Lingyu Huang, Shaolin Xu
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 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>∼</mml:mo> </mml:mrow> <mml:mi>λ</mml:mi> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>/</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>9</mml:mn> </mml:mrow> </mml:math> ) nanograting on 10 nm Au film) were generated based on the Marangoni effect. An ultra-uniform large-area ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>6</mml:mn> </mml:mrow> <mml:mo>×</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>15</mml:mn> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">m</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msup> </mml:mrow> </mml:math> ) nanograting with a width of 132 nm and a length-to-width ratio of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>∼</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>45</mml:mn> </mml:mrow> <mml:mo>,</mml:mo> <mml:mspace width="negativethinmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>500</mml:mn> </mml:mrow> </mml:math> 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.