Metasurface-enabled detection of photonic angular momentum: a review

The photon angular momentum (PAM), encompassing spin angular momentum (SAM) and orbital angular momentum (OAM), serves as a means for multi-channel or high-throughput optical communication. The detection of PAM has garnered significant attention due to its importance in quantum information, telecommunications, and optical manipulation. However, traditional PAM detection methods rely on polarization elements, phase plates, or spatial light modulators combined with multiple optical components, resulting in complex and bulky detection systems. Furthermore, the traditional techniques struggle to achieve simultaneous detection of SAM and OAM and the detection of high-order OAM modes. Recently, ultra-thin and compact metasurfaces with remarkable electromagnetic modulation performance present a novel solution to the limitations of traditional detection methods. Metasurfaces have emerged as powerful tools for detecting both SAM and OAM. In this paper, we discuss the development of PAM detection approaches based on metasurfaces, including fundamental concepts, limitations of traditional methods, applications in separate and simultaneous detection of SAM and OAM, and future prospects.