Metamaterial-enabled arbitrary on-chip spatial mode manipulation

摘要

On-chip spatial mode operation,represented as mode-division multiplexing(MDM),can support high-capacity data communications and promise superior performance in various systems and numerous applications from optical sensing to nonlinear and quantum optics.However,the scalability of state-of-the-art mode manipulation techniques is significantly hindered not only by the particular mode-order-oriented design strategy but also by the inherent limitations of possibly achievable mode orders.Recently,metamaterials capable of providing subwavelength-scale control of optical wavefronts have emerged as an attractive alternative to manipulate guided modes with compact footprints and broadband functionalities.Herein,we propose a universal yet efficient design framework based on the topological metamaterial building block(BB),enabling the excitation of arbitrary high-order spatial modes in silicon waveguides.By simply programming the layout of multiple fully etched dielectric metamaterial perturbations with predefined mathematical formulas,arbitrary high-order mode conversion and mode exchange can be simultaneously realized with uniform and competitive performance.The extraordinary scalability of the metamaterial BB frame is experimentally benchmarked by a record high-order mode operator up to the twentieth.As a proof of conceptual application,an 8-mode MDM data transmission of 28-GBaud 16-QAM optical signals is also verified with an aggregate data rate of 813 Gb/s(7%FEC).This user-friendly metamaterial BB concept marks a quintessential breakthrough for comprehensive manipulation of spatial light on-chip by breaking the long-standing shackles on the scalability,which may open up fascinating opportunities for complex photonic functionalities previously inaccessible.