  The conversion of phase variations in an optical wavefield into intensity
information is of fundamental importance for optical imaging technology
including microscopy of biological cells. While conventional approaches to
phase-imaging commonly rely on bulky optical components or computational post
processing, meta-optical devices have recently demonstrated all-optical,
ultracompact image processing methods. Here we describe a metasurface that
exploits photonic spin-orbit coupling to create an asymmetric optical transfer
function for real time phase-imaging. The effect of the asymmetry on
transmission through the device is demonstrated experimentally with the
generation of high contrast pseudo-3D intensity images of phase variations in
an optical wavefield without the need for post-processing. This
non-interferometric method has potential applications in biological live cell
imaging and real-time wavefront sensing.
