On-chip orbital angular momentum detection using a catenary grating metasurface

Abstract

Vortex lights with optical orbital angular momentum have shown great promise in the areas of optical communication, optical manipulation and quantum optics. However, traditional methods for detecting the topological charge of vortex beams, such as interference and diffraction, are still challenging in miniaturization of the detection system and perfect matching of wave vectors. Here, a detection approach is proposed for measuring the topological charge of Laguerre–Gaussian (LG) vortex beams based on a catenary grating metasurface. According to the wave vector matching principle, the LG vortex beam can be coupled into surface plasmon polariton (SPP) waves propagating in different directions by using the well-designed catenary grating structure. The positive and negative topological charges can be distinguished by different arrangement of the catenary gratings. Additionally, the propagation angle of the launched SPP waves increases with the value of the topological charge. We believe that the proposed device would have broad application prospects in high compact photonic integrated circuits.