In this presentation, we briefly review the development of optical metalenses from the single metalens to the metalens array and to the metalens systems, especially focusing on the progress of silicon nitride metalenses. We then show the optical properties of silicon nitride films with different refractive index in our lab. With such silicon nitride films, we introduce our researches on the broadband achromatic metalens array, and the microscope meta-objectives with cascade metalenses, showing the visible imaging applications on noncoherent 3D integral imaging and high-resolution biological imaging.
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