On-Chip Photon Angular Momentum Absolute Measurement Based on Angle Detection.

Photon angular momentum (AM) has been widely studied due to its unique properties. The accurate detection of photon AM is very important in its wide applications. Though various on-chip AM detectors based on surface plasmon polaritons (SPPs) have been proposed, most of them can only realize relative measurement. For example, most photon orbital angular momentum (OAM) detectors measure the high order OAM via measuring the relative interval between the intensity spots of the SPPs excited by the target order OAM beam and the reference order (usually 0th order) OAM beam. In this paper, we propose a simple on-chip photon AM detector. It can realize absolute measurement of photon OAM via angle detection, whose measurement result does not depend on the measurement of any reference OAM beam. At the same time, it can also recognize photon spin angular momentum (SAM). The proposed detector provides a new way for absolute measurement of photon AM, which may have some potential applications in the field of integrated photonic device.