Metasurface-enhanced Newton's rings interferometer-enabled local curvature detection

Curvature detection can reveal significant characteristics of target areas, playing a pivotal role in micro–nano fabrication. The Newton's rings experiment is one of the classical methods for detecting curvature; however, it has several limitations. First, stress-induced deformation damages the convex lens. Second, its applicability is restricted to spherical surfaces. Here, a flexible and low-damage metasurface-enhanced Newton's rings interferometer is proposed to enable the local curvature detection within a micrometer range. Since the metasurface performs differential operation on the pattern of Newton's rings, the three-dimensional local surface of convex lens is directly obtained by bias imaging. As a result, we can calculate the curvature of the target curve on the surface with an error of 2.1 %. Furthermore, such approach was also experimentally demonstrated to realize local curvature detection of aspherical objects such as transparent liquids. It is believed that the proposed scheme can open up more possibilities for applications involving metasurfaces.