Fresnel diffraction lithography

Lithography plays a vital important role in modern information technologies. Patterning at the nanoscale in a handy way is highly desired for both scientific and industrial purposes. In this work, we propose a convenient nanolithography method based on Fresnel diffraction patterns. We start with the explanation of the "dense-inside-sparse-outside" Fresnel diffraction fringes resulted from apertures of finite extent, using the fast Fourier transform algorithm by appropriately choosing the number of uniformly spaced samples. Moderately focusing the diffraction patterns via high-numerical-aperture objectives (we term the method “Fresnel diffraction lithography”), the rotationally symmetric patterns with a minimum feature size of ~190 nm, and the scanning lines with a width of ~350 nm are realized, respectively, though the calculation using vectorial diffraction theory suggests a better resolution when perfectly focused. This method shows good tolerance to defocus and does not require complex lens combinations or micro/nano-diffraction optical elements, may therefore find applications in widespread areas, e.g., functional metasurfaces, as a novel and low-cost nano-patterning technology with sub-wavelength resolution and high flexibility.