Graphene-based dual-mode modulators
Gongcheng Yue, Zhengkun Xing, Haofeng Hu, Zhenzhou Cheng, Guo-Wei Lu, Tiegen Liu
Abstract
Mode-division multiplexing (MDM) has attracted broad attention as it could effectively boost up transmission capability by utilizing optical modes as a spatial dimension in optical interconnects. In such a technique, different data channels are usually modulated to the respective carriers over different spatial modes by using individual parallel electro-optic modulators. Each modulated channel is then multiplexed to a multi-mode waveguide. However, the method inevitably suffers from a high cost, large device footprint and high insertion loss. Here, we design intensity and phase dual-mode modulators, enabling simultaneous modulations over two channels via a graphene-on-silicon waveguide. Our method is based on the exploration of co-planar interactions between structured graphene nanoribbons (GNs) and spatial modes in a silicon waveguide. Specifically, the zeroth-order transverse electric (TE 0 ) and first-order transverse electric (TE 1 ) modes are modulated separately and simultaneously by applying independent driving electrodes to different GNs in an identical modulator. Our study is expected to open an avenue to develop high-density MDM photonics integrated circuits for tera-scale optical interconnects.