Figure 1: Schematic of the setup and the optical ion-trapping sequence.
(a) We start by Doppler cooling the ion from two directions (blue arrows, from left and bottom) and repumping (red arrow, from right) from one direction in a linear rf trap (depicted as four quadrupole electrodes; not to scale). After carrying out a coarse compensation of stray electric fields (see Methods), we turn off the cooling lasers followed by the repumping laser to assure pumping into the electronic ground state |S1/2›. The d.c. potential is chosen to be defocusing along the y axis, but focusing along the z- and x-axes, symbolized by the outwards (red) and inwards (black) pointing arrows, respectively. The distorted shape surrounding the ion symbolizes its driven rf micromotion, superimposed on the harmonic motion within the time-averaged trapping potential. (b) We turn on the dipole trapping laser (green) and switch off the rf trap (the deactivated rf drive is indicated by the translucent electrodes). That is, we provide confinement by optical dipole and d.c. potentials only. After a duration Δt, we turn on the rf trap, the cooling and the repumping laser again while we turn off the dipole trapping laser. In the case of successful optical trapping, we finally detect the ion with a CCD camera via resonant fluorescence in the rf trap (see a).
