Dispersion Design Method of Metasurface Based on Semi‐Inverse Phase Matching

Simultaneously modulating the phase and dispersion of the light field is one of the specific functions of metasurfaces. Classic dispersion design methods for metasurfaces, including forward and inverse methods, cannot simultaneously achieve high interpretability from theoretical equations and optimizability via feedback of the output field. In this article, a semi‐inverse design method based on phase matching is proposed. This method achieves dispersion design by matching theoretical phase and phase responses of meta‐atoms, while iteratively adjusting the physical parameters in theoretical equations based on the far‐field energy distribution. The working parameters of the metasurface and the combination of meta‐atoms (instead of the shapes of the meta‐atoms), are optimized iteratively to make the output field match the design. Using the proposed method, three broadband devices are presented. The first is an achromatic metalens working in 850–1800 nm, achieving high efficiency greater than 70% within 1100–1800 nm. The second is a spectral router working in 850–1550 nm with an average efficiency of 75%. The third is a metalens with abnormal dispersion working in 1200–1800 nm with ≈80% diffraction efficiency. The proposed method is versatile and can be applied in the field of applied optics such as achromatic imaging and spectral routing.