Dynamic control and manipulation of near-fields using direct feedback.

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.