[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Detection and Tracking of Multiple Individual Nanoparticles in Antiresonant Hollow-Core Fibers

摘要： Directly studying the dynamics of nanoparticles with subwavelength dimensions, for example protein interactions or viral self-assembly, is difficult using conventional light microscopes due to Abbe’s resolution limit. Methods to overcome this limit such as fluorescence microscopy usually require to label particles and suffer from photobleaching in the case of long illumination times. A recent tracking method based on elastic light scattering from nano-objects inside a microstructured fiber which includes a nanometer sized channel managed to circumvent these limitations [1]. However, due to the small channel size, this approach imposes high spatial constraints on the particle motion, impedes the investigation of multi-particle dynamics and allows very little control over the liquid flow inside the fiber. In this work, we demonstrate that antiresonant hollow-core fibers (ARHCFs) open new perspectives for the detection and tracking of unlabeled, individual nanoparticles in statistically large numbers simultaneously. Gold nanospheres of diameters as small as 40nm were introduced into the hollow inner channels of an ARHCF with hexagonally shaped core section of around 30μm in diameter (see Fig. 1a,b). The fiber was integrated into an optofluidic chip system which allows controlling the liquid flow [2], and illuminated by a laser source (wavelength at 532nm). The light scattered off the particles was collected from the transverse direction by a low NA microscope objective (see Fig. 1a) and imaged onto a high speed camera. Applying an appropriate algorithm [3], the obtained data was analyzed and individual particle trajectories deduced (see Fig. 1c). Therefore a single video contains statistical data, e.g. for particle size estimations via the mean squared displacement method for a large number of freely diffusing particles (see Fig. 1d). Since particle tracking for tens of seconds at kHz image rates is possible, this novel method holds strong potential for the investigation of yet unexplored multi-particle dynamics at the nanoscale.