Simulation of Multiwavelength Achromatic Metalens in the Extreme Ultraviolet

The advancement of lithography, mass spectrometry and other technologies is increasingly requiring the highquality focusing of extreme ultraviolet (EUV) beams. Traditional transmissive optics are not suitable for focusing EUV beams due to the strong absorption of most materials. However, rapid developments of metasurfaces have led to breakthroughs in the research of EUV metalenses. Based on the hole-type unit structure proposed recently, we demonstrated the dual-wavelength achromatic metalens in the EUV working for wavelengths of 46.9 and 69.8 nm with a numerical aperture 0.05. Then the dispersion manipulation for the achromatic metalens is extended to three wavelengths 46.9, 60, and 69.8 nm. The simulation results suggest that the maximum relative focal shift from the designed focal length is 0.008 %, and the diffraction-limit focusing is achieved for all working wavelengths. This work could expand the means of the EUV optical field modulation.