OAM Modes Generator and Multiplexer by Silicon Waveguides

Based on an integrated silicon platform, we propose a device for generating and multiplexing optical orbital angular momentum modes(OAM), which is consisted of asymmetric directional couplers and trench waveguides. Asymmetric directional coupler is composed of single-mode and multi-mode waveguides . According to the principle of phase matching, the fundamental mode TE(00 )is coupled to the second-order mode via an asymmetric directional coupler. Single-trench waveguide can support two orthogonal eigenmodes. By adjusting the phase difference of two orthogonal eigenmodes to make them degenerate, they can be converted into orbital angular momentum modes with topological charges of +1, 0, -1, and multiplexed in the second trench. We simulate and analyze the characteristics of the device using three-dimensional finite difference domain method (3D-FDTD). The simulation results show that the device can realize the generation and multiplex of orbital angular momentum modes with topological charges +1, 0, -1. The proposed device is very compact with a footprint of 92 mu mx5.3 mu m and an insertion loss of 0.359 dB. The structure woks on a wavelength range from 1.48 mu m to 1.57 mu m. The structure is simple and easy to integrate, having a good application in OAM multiplexing system.