  Different imaging modalities are used to extract the diverse information
carried in an optical field. Two prominent modalities include bright field and
phase contrast microscopy that can visualize the amplitude and phase features
of a sample, respectively. However, capturing both of these images on the same
camera typically requires interchanging optical components. Metasurfaces are
ultra-thin nanostructures that can merge both of these operations into a single
miniaturized device. Here, a silicon-based metasurface that supports a Mie
resonance is demonstrated to perform near-infrared phase contrast and bright
field multi-modal microscopy that can be tuned by changing the polarization of
the illumination. We performed experiments using optical fields with phase
variations synthesized by a spatial light modulator and introduced by
propagation through semi-transparent samples, including C. elegans, unstained
human prostate cancer cells and breast tissue. The results demonstrate the
potential of metasurfaces for label-free point-of-care testing.
