Shaping and controlling electromagnetic fields at the nanoscale is vital for advancing efficient and compact devices used in optical communications, sensing and metrology, as well as for the exploration of fundamental properties of light-matter interaction and optical nonlinearity. Real-time feedback for active control over light can provide a significant advantage in these endeavors, compensating for ever-changing experimental conditions and inherent or accumulated device flaws. Scanning nearfield microscopy, being slow in essence, cannot provide such a real-time feedback that was thus far possible only by scattering-based microscopy. Here, we present active control over nanophotonic near-fields with direct feedback facilitated by real-time near-field imaging. We use far-field wavefront shaping to control nanophotonic patterns in surface waves, demonstrating translation and splitting of near-field focal spots at nanometer-scale precision, active toggling of different near-field angular momenta and correction of patterns damaged by structural defects using feedback enabled by the real-time operation. The ability to simultaneously shape and observe nanophotonic fields can significantly impact various applications such as nanoscale optical manipulation, optical addressing of integrated quantum emitters and near-field adaptive optics.

纳米级电磁场的整形和控制对于推进用于光通信、传感和计量的高效和紧凑型器件，以及探索光-物质相互作用和光学非线性的基本特性至关重要。主动控制光的实时反馈可以在这些努力中提供显着优势，补偿不断变化的实验条件和固有或累积的器件缺陷。扫描近场显微镜本质上速度很慢，无法提供迄今为止只有基于散射的显微镜才能提供的实时反馈。在这里，我们提出了对纳米光子近场的主动控制，并通过实时近场成像促进直接反馈。我们使用远场波前整形来控制表面波中的纳米光子图案，以纳米级精度演示近场焦点的平移和分裂，不同近场角动量的主动切换，以及使用实时操作实现的反馈校正因结构缺陷而损坏的图案。同时塑造和观察纳米光子场的能力可以显著影响各种应用，例如纳米级光学操纵、集成量子发射器的光学寻址和近场自适应光学。