Three-mode multiplexed device based on tilted- branch bus structure using silicon waveguide

We propose a new design of a silicon chip for (de)multiplexing three optical modes based on a tilted-branch bus structure using silicon waveguide. Input lights at fundamental, first-order, and second-order modes in three-dimensional space are simultaneously demultiplexed and converted to three fundamental modes at three individual output ports. The device is designed and optimized via numerical simulation using three-dimensional beam propagation method (3D-BPM). Successful three-mode demultiplexing can be achieved over 150 nm wavelength band of telecom winodws with insertion loss smaller than 1.45 dB and crosstalk below -16 dB. The proposed device also features with a small footprint (8 μm × 950 μm) and a large fabrication tolerance against chip-size variations while maintaining the desired optical performance.