Dielectric Metasurface for Synchronously Spiral Phase Contrast and Bright-Field Imaging.

Spiral phase contrast imaging and bright-field imaging are two widely used modes in microscopy, providing distinct morphological information about objects. However, conventional microscopes are always unable to operate with these two modes at the same time and need additional optical elements to switch between them. Here, we present a microscopy setup that incorporates a dielectric metasurface capable of achieving spiral phase contrast imaging and bright-field imaging synchronously. The metasurface not only can focus the light for diffraction-limited imaging but also can perform a two-dimensional spatial differentiation operation by imparting an orbital angular momentum to the incident light field. This allows two spatially separated images to be simultaneously obtained, one containing high-frequency edge information and the other showing the entirety of the object. Combined with the advantages of planar architecture and ultrathin thickness of the metasurface, this approach is expected to provide support in the fields of microscopy, biomedicine, and materials science.