Diffraction-limited high-efficiency extreme ultraviolet metalens at 13.5 nm wavelength based on nanohole array in molybdenum membrane.

Extreme ultraviolet (EUV) light with a 13.5 nm wavelength plays a crucial role in many fields, such as microelectronics manufacturing and material science. However, conventional transmissive meta-optics designs for EUV light face great challenges due to the strong absorption of most materials and the near-unity real part of the refractive indices, which usually prevent waveguiding and effective refraction. Here, we numerically demonstrate the focusing of EUV light at 13.5 nm by the elaborately designed molybdenum (Mo) metalens based on the nanohole array. Compared with other candidate materials, Mo-based metalens sustains efficient propagation of the 13.5 nm EUV light through nanoholes milled on the membrane, leading to the focal spot with a diffraction-limited size of 46 nm and a focusing efficiency of 27.8%. In addition, the dependence of the focusing efficiency on the self-supporting Si or Si3N4 membrane is investigated. The proposed Mo-based metalens for the focusing of the 13.5 nm EUV light holds promising applications in semiconductor lithography, high-resolution imaging, and ultrafast spectroscopy. [ABSTRACT FROM AUTHOR]