Metamaterial-enabled arbitrary on-chip spatial mode manipulation

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.

All-optical silicon microring spiking neuron

With the rapid development of artificial intelligence and machine learning, brain-inspired neuromorphic photonics has emerged as an extremely attractive computing paradigm, promising orders-of-magnitude higher computing speed and energy efficiency compared to its electronic counterparts. Tremendous efforts have been devoted to photonic hardware implementations of mimicking the nonlinear neuron-like spiking response and the linear synapse-like weighting functionality. Here, we systematically characterize the spiking dynamics of a passive silicon microring neuron. The research of self-pulsation and excitability reveals that the silicon microring can function as an all-optical class Ⅱ resonate-and-fire neuron. The typical refractory period has been successfully suppressed by configuring the pump power above the perturbation power, hence allowing the microring neuron to operate with a speed up to roughly sub-gigahertz. Additionally, temporal integration and controllable inhibition regimes are experimentally demonstrated for the first time, to the best of our knowledge. Our experimental verification is obtained with a commercial CMOS platform, hence offering great potential for large-scale neuromorphic photonics integration.