Confining photons to atomic length scales

在高分辨率扫描光学显微镜以及强光-物质耦合方面，将光子定位到原子长度尺度提供了令人着迷的可能性。原子尺度分辨率光谱成像预计将对生命科学以及纳米科学产生巨大影响。另一方面，具有原子尺度模式体积的纳米级光学谐振腔中的强耦合对于量子计算方案的大规模集成和单光子体制下全光数据处理的非线性实现具有重要意义。然而，到目前为止，光定位仅限于bbb10nm范围。本项目将协同结合原子尺度光定位的两个突破性方面，通过实施一种新型扫描显微镜，使用原子受限的MIM腔共振作为光学探针。我们最近成功地制造了具有亚1nm绝缘间隙的单晶金属-绝缘体-金属（MIM）纳米谐振器，并展示了相应的亚1nm光约束。一方面，探针和/或样品的横向扫描将通过记录纳米物体（如单个量子点、（生物）分子和新型2d材料）的发光和拉曼散射，提供具有近原子空间分辨率的光谱映射。由于选择规则的改进，探测场的强梯度有望打开多极光谱通道。另一方面，探针扫描也改变了探针和量子发射体之间的耦合强度，导致从微扰到强甚至可能是超强相互作用的平滑过渡。在强耦合状态下，探针和量子发射器的量子力学纠缠将产生新的成像方式。

Localizing photons to atomic length scales offers fascinating possibilities in terms of high-resolution scanning optical microscopy, as well as in terms of strong light-matter coupling. Atomic-scale resolution spectroscopic imaging is expected to have a huge impact in life science as well as in nano science in general. On the other hand, strong coupling in a nanoscale optical resonator with atomic scale mode volume will be of great interest for large scale integration of quantum computation schemes and the implementation of nonlinearities for all-optical data manipulation in the single-photon regime. However, so far light localization has been limited to the >10 nm range. The present project will synergistically combine both groundbreaking aspects of atomic scale light localization by implementing a new type of scanning microscopy which uses atomically confined MIM cavity resonances as optical probes. We recently succeeded in fabricating single-crystal metal-insulator-metal (MIM) nano resonators with sub-1nm insulating gaps and demonstrated the corresponding sub-1nm light confinement. Lateral scanning of probe and/or sample on the one hand will afford spectroscopic mapping with near-atomic spatial resolution by recording luminescence and Raman scattering of nano objects, such as individual quantum dots, (bio)molecules, and novel 2D-materials. The strong gradients of the probe field are expected to open multipolar spectroscopic channels due to modified selection rules. On the other hand, probe scanning also varies the coupling strength between probe and quantum emitters, causing a smooth transition from the perturbative into the strong and possibly even ultrastrong interaction regime. It is further expected that the quantum mechanical entanglement of probe and quantum emitter in the strong coupling regime will lead to new imaging modalities.