Toward High-Speed Nanoscopic Particle Tracking via Time-Resolved Detection of Directional Scattering

Owing to their immediate relevance for high precision position sensors, a variety of different sub-wavelength localization techniques has been developed in the past decades. However, many of these techniques suffer from low temporal resolution or require expensive detectors. Here, a method is presented that is based on the ultrafast detection of directionally scattered light with a quadrant photodetector operating at a large bandwidth, which exceeds the speed of most cameras. The directionality emerges due to the position dependent tailored excitation of a high-refractive index nanoparticle with a tightly focused vector beam. A spatial resolution of1.1nmand a temporal resolution of8kHzis reached experimentally, which is not a fundamental but rather a technical limit. The detection scheme enables real-time particle tracking and sample stabilization in many optical setups sensitive to drifts and vibrations.