Single-shot quantitative phase gradient microscopy using a system of multifunctional metasurfaces

Quantitative phase imaging (QPI) of transparent samples plays an essential role in multiple biomedical applications, and miniaturizing these systems will enable their adoption into point-of-care and in vivo applications. Here, we propose a compact quantitative phase gradient microscope (QGPM) based on two dielectric metasurface layers, inspired by a classical differential interference contrast (DIC) microscope. Owing to the multifunctionality and compactness of the dielectric metasurfaces, the QPGM simultaneously captures three DIC images to generate a quantitative phase gradient image in a single shot. The volume of the metasurface optical system is on the order of 1 mm³. Imaging experiments with various phase resolution samples verify the capability to capture quantitative phase gradient data, with phase gradient sensitivity better than 92.3 mrad μm^‑1 and single-cell resolution. The results showcase the potential of metasurfaces for developing miniaturized QPI systems for label-free cellular imaging and point-of-care devices.