Neuromorphic photonics has recently emerged as a promising hardware accelerator, with significant potential speed and energy advantages over digital electronics, for machine learning algorithms such as neural networks of various types. Integrated photonic networks are particularly powerful in performing analog computing of matrix-vector multiplication (MVM) as they afford unparalleled speed and bandwidth density for data transmission. Incorporating nonvolatile phase-change materials in integrated photonic devices enables indispensable programming and in-memory computing capabilities for on-chip optical computing. Here, we demonstrate a multimode photonic computing core consisting of an array of programable mode converters based on metasurface made of phase-change materials. The programmable converters utilize the refractive index change of the phase-change material Ge-Sb-Te during phase transition to control the waveguide spatial modes with a very high precision of up 64 levels in modal contrast. This contrast is used to represent the matrix elements, with 6-bit resolution and both positive and negative values, to perform MVM computation in neural network algorithms. We demonstrate an optical convolutional neural network that can perform image processing and classification tasks with high accuracy. With a broad operation bandwidth and a compact device footprint, the demonstrated multimode photonic core is very promising toward a large-scale photonic processor for high-throughput optical neural networks.
Zhejiang Key Laboratory of 3D Micro/Nano Fabrication and Characterization, Department of Electronic Science and Engineering, School of Engineering, Westlake University（西湖大学工程学院电子科学与工程系三维微纳加工与表征浙江省重点实验室）；Westlake Center for Micro/Nano Fabrication, Westlake University（西湖大学微纳加工中心）；Eastern Institute of Technology（宁波东方理工大学）
Spatio-spectrally tailored multimode metasurface lasers in the visible range
Friedrich Schiller University（弗里德里希·席勒大学）；Fraunhofer-Institute of Applied Optics and Precision Engineering IOF（弗劳恩霍夫应用光学和精密工程研究所）；Max Planck School of Photonics（马克斯·普朗克光子学院）
Programmable metasurfaces for future photonic artificial intelligence
Colorado School of Mines（科罗拉多矿业学院）；Université Côte d’Azur（蔚蓝海岸大学）；LAAS, Université de Toulouse（图卢兹大学LAAS实验室）；Université de Rennes（雷恩大学）；Department of Physics, Colorado School of Mines（科罗拉多矿业学院物理系）；Department of Electrical and Computer Engineering, Boston University（波士顿大学电气与计算机工程系）
Autonomous multifunctional image processing via programmable multimode lasing
Tsinghua University（清华大学）；Key Laboratory of Photonic Control Technology, Ministry of Education, Tsinghua University（教育部光子控制技术重点实验室，清华大学）；State Key Laboratory of Precision Space-time Information Sensing Technology（精密时空信息传感技术国家重点实验室）；The University of Hong Kong（香港大学）；City University of Hong Kong（香港城市大学）
Reconfigurable Linear Optical Transformations in a Single Integrated Multimode Waveguide
MESA+ Institute for Nanotechnology, University of Twente（特文特大学 MESA+ 纳米技术研究所）；Institute of Photonics and Quantum Electronics (IPQ), Karlsruhe Institute of Technology (KIT)（卡尔斯鲁厄理工学院光子与量子电子学研究所）
Arbitrary control over multimode wave propagation for machine learning
School of Applied and Engineering Physics, Cornell University（应用与工程物理系，康奈尔大学）；NTT Physics and Informatics Laboratories, NTT Research, Inc.（NTT物理与信息实验室，NTT研究公司）；E. L. Ginzton Laboratory, Stanford University（E. L. Ginzton实验室，斯坦福大学）；Kavli Institute at Cornell for Nanoscale Science, Cornell University（康奈尔大学纳米科学研究所）；Department of Electrical and Computer Engineering, Boston University（波士顿大学电气与计算机工程系）；Department of Electrical Engineering and Computer Science, University of California（加州大学电气工程与计算机科学系）；Department of Applied Physics, Yale University（耶鲁大学应用物理系）
Dynamically Tunable Membrane Metasurfaces for Infrared Spectroscopy
University of Wisconsin-Madison（威斯康星大学麦迪逊分校）；Istanbul University（伊斯坦布尔大学）；Argonne National Laboratory（阿贡国家实验室）；Australian National University（澳大利亚国立大学）
Cascaded Metasurface Interferometer for Multipath Interference with Classical and Quantum Light
Paderborn University（帕德博恩大学）；Beijing Institute of Technology（北京理工大学）；Johannes Kepler University（约翰内斯·开普勒大学）；Julius-Maximilians-University of Würzburg（维尔茨堡朱利叶斯-马克西米利安大学）；Vorarlberg University of Applied Sciences（福拉尔贝格应用科学大学）；Sapienza Università di Roma（罗马大学）；Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院）
Programmable Non-Hermitian Synchronization of Light on a Silicon Photonic Processor
KTH Royal Institute of Technology（瑞典皇家理工学院）；University of Michigan（密歇根大学）；University of Vaasa（瓦萨大学）；Institute of Science Tokyo（东京科学大学）；Huazhong University of Science and Technology（华中科技大学）
Tuning Plasmonic Metasurfaces via Phase Change Material Substrates for Modulating Reactivity in Light-Driven Reactions
Friedrich-Schiller-Universität Jena（耶拿弗里德里希·席勒大学）；Australian National University（澳大利亚国立大学）；Xi’an University of Posts and Telecommunications（西安邮电大学）；University of Applied Sciences Landshut（兰茨胡特应用科学大学）
Electro-optically tunable second-harmonic generation in lithium niobate metasurfaces boosted by Brillouin zone folding induced bound states in the continuum
State Key Laboratory of Photonics and Communications, School of Information and Electronic Engineering, Shanghai Jiao Tong University（上海交通大学信息电子工程学院光子与通信国家重点实验室）；Department of Electronics and Nanoengineering, Aalto University（阿尔托大学电子与纳米工程系）
Electrically-programmable frequency comb for compact quantum photonic circuits
Institute of Nuclear Sciences, Hacettepe University（哈杰泰普大学核科学研究所）；Department of Physics, Quaid-i-Azam University（奎德-阿扎姆大学物理系）；Department of Physics, Recep Tayyip Erdogan University（雷杰普·塔伊普·埃尔多安大学物理系）；Department of Nanoscience and Nanotechnology, Faculty of Arts and Science, Burdur Mehmet Akif Ersoy University（布尔杜尔·梅赫梅特·阿克夫·埃尔索伊大学文理学院纳米科学与纳米技术系）
