Light with an optical orbital angular momen-
tum (OAM) has attracted an increasing amount of interest
and has found its way into many disciplines ranging from
optical trapping, edge-enhanced microscopy, high-speed
optical communication, and secure quantum teleportation
to spin-orbital coupling. In a variety of OAM-involved
applications, it is crucial to discern different OAM states
with high fidelity. In the current paper, we review the latest
research progress on OAM detection with micro- and
nano-optical structures that are based on plasmonics,
photonic integrated circuits (PICs), and liquid crystal
devices. These innovative OAM sorters are promising to
ultimately achieve the miniaturization and integration of
high-fidelity OAM detectors and inspire numerous appli-
cations that harness the intriguing properties of the twisted
light.

• Detection of photonic orbital angular momentum with micro- and nano-optical structures