Xiang Jinlong, Tao Zhiyuan, Li Xingfeng, Zhao Yaotian, He Yu, Guo Xuhan, Su Yikai
State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
Light Sci Appl. 2022 Jun 1;11(1):168. doi: 10.1038/s41377-022-00859-9.
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.
片上空间模式操作，即模式分割复用（MDM），可支持高容量数据通信，并有望在从光学传感到非线性和量子光学等各种系统及众多应用中展现卓越性能。然而，当前最先进的模式操纵技术的可扩展性不仅受到特定的面向模式阶数的设计策略的显著阻碍，还受到可能实现的模式阶数的固有局限性的影响。最近，能够对光波前进行亚波长尺度控制的超材料已成为一种有吸引力的替代方案，可用于以紧凑的尺寸和宽带功能操纵导模。在此，我们提出了一种基于拓扑超材料构建块（BB）的通用且高效的设计框架，能够在硅波导中激发任意高阶空间模式。通过简单地用预定义的数学公式对多个完全蚀刻的介电超材料微扰的布局进行编程，可以同时实现任意高阶模式转换和模式交换，且性能均匀且具有竞争力。超材料BB框架的非凡可扩展性通过高达二十阶的创纪录高阶模式算子在实验上得到了验证。作为概念应用的证明，还验证了28 - 波特16 - QAM光信号的8模式MDM数据传输，总数据速率为813 Gb/s（7%前向纠错）。这种用户友好的超材料BB概念通过打破长期以来在可扩展性方面的束缚，标志着片上空间光综合操纵的一个典型突破，这可能为以前无法实现的复杂光子功能开辟迷人的机会。
