Optical trapping dynamics of nanoparticles by resonant optical response

For the purpose of precise manipulation of single nanoparticles by optical trapping, we demonstrated optical trapping of nanoparticles enhanced depending on the wavelength of excitation laser. The optical trapping dynamics of quantum dot (QD) nanoparticles at the focal spot was evaluated by fluorescence correlation spectroscopy (FCS). The simultaneous irradiation with excitation and near-infrared lasers increased the average transit time of QDs at the focal spot, which depended on the laser power and the wavelength of the excitation laser. This suggests that the particle motion of QD nanoparticles is constrained at the laser focus due to enhancement of optical trapping based on the resonant optical response.