A Design Proposal for A Broadband Mode (De)multiplexing Synthesizer Based on A 3×1 Multimode Interference Coupler and A Y-junction Using Silicon Waveguides

Abstract

This paper proposes a new design for a mode (de)multiplexing synthesizer with broad bandwidth, high mode conversion efficiency and large fabrication tolerance on a silicon-on-insulator (SOI) platform. By using a 3×1 multimode interference (MMI) coupler, a sinusoidal symmetric Y junction coupler and two linear butterfly-shaped phase shifters, mode synthesis from the fundamental mode TE0 and the first-order mode TE1 to the fundamental mode TE0 is achieved by numerical simulation. The phase evolution in the structure is discussed in detail. Performance analysis of the mode synthesizer is carried out numerically. Simulation results by using three dimension beam propagation method (3D-BPM) incorporated with effective index method (EIM) show high performance of the device whose maximal mode conversion efficiency can be up to 93.32% (i.e., insertion loss can be less than 0.3 dB) in the whole C-band. In addition, the proposed mode synthesizer has large fabrication tolerance. For example, the width deviations of the multimode interference coupler can be as large as 20 nm. The proposed device is suitable for applications to on-chip photonics integrated circuits