Dynamic Detection of Higher-Order Topological Charges of Vortex Beams Using Ring-Shaped Surface Plasmonic Bending Beams

Dynamic detection of the orbital angular momentum (OAM) properties of optical vortex (OV) beams has shown a wide range of applications in on-chip photonics, optical communication, and optical imaging. However, conventional detection technique suffers from issues of low efficiency, limited functionality, and low noise immunity. In this paper, a dislocated circular hole array is designed to generate ring-shaped surface plasmonic bending (R-SPB) beams. The propagation characteristics of R-SPB beams are numerically simulated using the finite difference time domain (FDTD) method. By analyzing the spot shape, size, and split-to-single spot conversion of the R-SPB beams, we are able to dynamically detect the topological charge values, polarization state (left circular polarization and right circular polarization), and positive or negative of the OV beam. We have successfully detected topological charges up to l=+/- 12\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$l{\kern 1pt} {\kern 1pt} { = }{\kern 1pt} \pm 12$$\end{document}. These results demonstrate that an intuitive and convenient method for detecting the higher-order topological charges of OV beam is realized utilizing the R-SPB beam propagation properties. In addition, we found that changing the structural parameters only affects the electric field intensity distribution of the R-SPB but do not impact the detection results. These findings are useful for the development of on-chip OV beam topological charge detectors with multiplexed and highly integrated capabilities.