Broadband Achromatic Metalenses With High Focusing Efficiency Based on Inverse Design

In this letter, we propose a broadband achromaticmetalens that exhibits high focusing efficiency within the wave-length range of 1270-2070 nm and is insensitive to polarization.Within the operating wavelength range, the metalens displaysa focal length shift of only +/- 0.5 mu m and exhibits excellentachromatic properties. The average focusing efficiency of themetalens is 56%, with a maximum focusing efficiency of 70.7%.Compare with no metalens, the metalens can enhance thetransmissivity of incident light by approximately 10%. And theaverage full width at half maximum (FWHM) of this structure is0.5526 mu m. In the design process, we propose a new algorithm.The concept behind this method has significant implications forother inverse design algorithms.