Light–matter interaction drives many systems, such as optoelectronic devices like light-emitting diodes and solar cells, biological structures like photosystem II and potential future quantum devices. The absorption or emission of light typically occurs on the sub-nanometre scale and the involved processes take place on attosecond to picosecond timescales. Light–matter interaction can be studied at atomic space-time scales by using a scanning tunnelling microscope and coupling light into or extracting light from the tunnel junction. Electromagnetic radiation couples with matter through the interaction with charge carriers, leading to excitations such as electronic transitions, collective oscillations, excitons and spin flips. These excitations can be studied with high spatial and temporal resolution using approaches in which light interacts with the tunnel junction itself or with a quantum system in the junction. This Review discusses the powerful union of photonics and scanning probe techniques.

光与物质的相互作用驱动了许多系统，例如光电器件（如发光二极管和太阳能电池），生物结构（如光系统II）和潜在的未来量子器件。光的吸收或发射通常发生在亚纳米尺度上，并且所涉及的过程发生在十亿分之一秒至皮秒的时间尺度上。通过使用扫描隧道显微镜并将光耦合到隧道结中或从隧道结中提取光，可以在原子时空尺度​​上研究光与物质的相互作用。电磁辐射通过与电荷载流子的相互作用与物质耦合，从而导致激发，例如电子跃迁，集体振荡，激子和自旋翻转。可以使用光与隧道结本身或与结中的量子系统相互作用的方法，以高时空分辨率研究这些激发。这篇评论讨论了光子学和扫描探针技术的强大结合。