Broadband polarization-insensitive achromatic metalens with high focusing efficiency

Broadband achromatic metalenses exhibit significant potential for practical applications due to their superior focusing and imaging performance. Nevertheless, designing achromatic metalenses that simultaneously achieve high focusing efficiency and minimal focal length shift across a wide bandwidth remains an unresolved challenge. In this work, we present a polarization-insensitive achromatic metalens operating in the near-infrared band (1.26–1.66$\mu m$), composed of annular zinc selenide ($\mathrm{ZnSe}$) nanopillars on a barium fluoride ($\mathrm{Ba}{F}_2$) substrate. Numerical simulation results demonstrate that the designed metalens achieves a remarkably small maximum focal shift of merely 2.89 % relative to the designed focal length of 9.4 $\mu m$, while maintaining an average efficiency of 79.77 % across the entire operational bandwidth (1.26–1.66 $\mu m$). Compared to previously reported near-infrared achromatic metalenses, our design shows significant improvements in suppressing focal shift and enhancing focusing efficiency. Furthermore, the predefined operational bandwidth fully covers the entire optical communication range (1.26–1.625$\mu m$), indicating that the proposed achromatic metalens could serve as a promising solution for near-infrared communication systems.