Spiral Metalens for Phase Contrast Imaging

Abstract Spiral phase contrast imaging offers an excellent opportunity to observe non‐labeled biological samples with slight variations in refractive index or thickness. However, the overall system covering previous works is still complex and bulky, hindering miniaturization and compatibility with conventional systems. Furthermore, high‐resolution imaging, particularly for observing biological specimens such as cellular structures, requires several refractive optical elements like objectives and relay optics which dramatically increases the system form factor. Here, it is demonstrated that a metalens, in which the phase profile is a sum of the hyperbolic phase and spiral phase with a topological charge of 1, performs 2D isotropic edge‐enhanced imaging. The metalens achieves a submicrometer resolution of up to 0.78 µm operated under visible broadband range in conjunction with a compact form factor. Furthermore, experiments with biological samples can additionally prove the feasibility of practical usage. Capitalizing on compactness and high‐resolution characteristics, it is believed that the scheme provides a stepping stone to biomedical imaging technologies and analog computing.