Design of broadband achromatic metalens in the visible

As an important parameter for evaluating optical devices, chromatic aberration is an enduring research hotspot in optics. The traditional bulk lens relies on the polished surface profile on the transparent optical material to achieve the required gradual phase change. Compared with the traditional lens, the metalens can achieve the effect of focusing the beam with a more suitable small size standard. In this paper, the geometric phase method is used to realize the phase shift required by the surface of the achromatic metalens through the unique design of the nano-unit column array. In order to be applied to the optical path of multi-wavelength phase microscopy imaging, the metalens designed in this paper effectively eliminates chromatic aberration in the visible light band from 500 nm to 595 nm and improves the imaging resolution. It also satisfy the needs of modern optical devices for ultra-light, ultra-thin and easy portability, and can be used in a variety of optical instruments, aerospace and military fields.