Multiwavelength Achromatic Metalens in Visible by Inverse Design

Achromatic metalenses are promising alternatives to traditional lenses, allowing the miniaturization of optical systems. However, the limitation due to the group delay range of the meta-atoms that can be fabricated requires a trade-off relationship between the working bandwidth, numerical aperture (NA), and aperture of the achromatic metalens operating in a continuous spectrum. Considering that light sources used in most optical systems to illuminate or display images in most optical systems generate multiwavelength light with a narrow bandwidth, an efficient end-to-end inverse design framework for multiwavelength achromatic metalenses is implemented. As a proof of concept, an achromatic metalens with an NA of 0.3 and a diameter of 115 µm at four visible wavelengths and arbitrary linear polarization is designed and experimentally demonstrated. The measured results show a maximum focal length shift of 5.2778%. The proposed strategy avoids complicated physical models, enabling the integration of complex functionalities into a single metasurface, thereby driving the design of efficient and emerging devices.