Ultra-compact and fabrication-tolerant mode multiplexer and demultiplexer based on angled silicon waveguides

An ultra-compact and fabrication-tolerant mode multiplexer (MUX) and demultiplexer (DeMUX) is proposed based on the angled silicon waveguides. The proposed mode (De)MUX is optimized by using the full-vectorial finite element method (FV-FEM) and three-dimensional full-vectorial finite difference time domain method (3D-FV-FDTD). The simulated results show that the optimal mode (De)MUX is with an ultra-compact length of 7.0 mu m, a high mode conversion efficiency of 98.5%, an ultra-low excess loss of 0.05 dB and a low mode crosstalk of -18.2 dB at the operating wavelength of 1550 nm. The fabrication tolerances are also studied for the proposed mode (De)MUX.