Position-controlled trapping of nanoparticles and quantum dots on a fiber taper

We investigate numerically and experimentally the properties of a two-color optical fiber taper trap, for which the evanescent field of the modes in the fiber taper give rise to a trapping potential with both radial confinement and confinement along the fiber axis. Experimentally, we use the technique to confine colloidal nanoparticles near the surface of an optical fiber taper, and show that the trapping position of the particles is adjustable by controlling the relative power of two modes in the fiber. We also demonstrate a proof-of-principle application by trapping quantum dots together with gold nanoparticles in a configuration where the trapping fields double as the excitation field for the quantum dots. This scheme will allow the positioning of quantum emitters in order to adjust coupling to resonators combined with the fiber taper.