Design of an achromatic optical polarization-insensitive zoom metalens

A diffractive lens based on metasurfaces has many advantages such as flatness, small aberrations, and compactness. The focal length can be adjusted by changing the lateral displacement between a pair of conjugate metasurfaces while fixing their axial distance, thereby forming a very compact zoom lens. However, chromatic aberration of diffractive optical elements restricts this system to working at one wavelength. This Letter proposes a metalens design method based on novel three-layer polarization-insensitive nanoposts, which can improve transmission amplitude and satisfy the achromatic zoom function with wavelengths ranging from 1310 nm to 1550 nm. The focal length can be adjusted from 31.2 µm to 19.8 µm, corresponding to extremal wavelength-dependent focal length relative deviation of 8.98%. This achromatic zoom metalens design method could have applications in various fields including augmented reality and integrated optical systems.