Extreme UV metalens consisting of ring meta-atoms

Abstract

Designing lenses for wavelengths below 121 nm is challenging due to the strong absorption of optical materials. This study introduces a metalens composed of ring-shaped silica nano-elements that efficiently focus extreme ultraviolet (EUV) radiation. Each ring features an air or vacuum core ($n=1$) surrounded by silica with a refractive index $n<1$, optimized for EUV operation. Finite-difference time-domain (FDTD) simulations demonstrate a phase coverage of 1.85 $\pi$, high EUV transmission, and an optical efficiency of 83.6%. These results represent a significant advancement over existing EUV metalenses, and underscore the potential of this design for compact and efficient EUV optical systems.