We have experimentally demonstrated the strong coupling between single atoms and the higher-order Hermite-Gaussian transverse modes in a high-finesse optical microcavity. Compared to the usual low-order symmetric transverse modes, multiple lobes and the asymmetric spatial pattern of the titled modes provide more information about the motion of single atoms in the cavity. The motional information can be extracted from the measured transmission spectra, which includes the velocities and the positions of the atoms in vertical and off-axis directions. The scheme has great potential in time-resolved atom-cavity microscopy and in tracking the three-dimensional single atom trajectory in real time.
We present an alternative route to track the motion of a single atom traversing a high-finesse optical cavity by means of the coherence statistics of photon antibunching. Here the single atom strongly couples to the high-order transverse Laguerre-Gaussian (LG) mode (e.g.,
LG01) of optical cavity, instead of the high-order transverse Hermite-Gaussian (HG) mode, which is beneficial to the single-atom trajectory measurement utilizing such a photon antibunching effect. With this aim, we characterize the position-dependent quantum correlations of the transmitted light in such a cavity quantum electrodynamics (QED) system subject to various kinds of the LG modes, finding that the photon antibunching effect is closely related to the position of the atom in the transverse plane and therefore the degree of the antibunching carries the information about the position of the atom within the cavity. The numerical results of the second-order correlation function agree well with the analytical calculations. Thanks to the tilted transverse
LG01 mode of the cavity, which is inclined to the vertical direction by an angle of $\ensuremath{\sim}{15}^{\ensuremath{\circ}}$, the LG-mode cavity QED architecture helps us to eliminate the degenerate trajectory of the single atom falling through the cavity and to obtain a unique atomic trajectory. In a $10\text{\ensuremath{-}}\ensuremath{\mu}\mathrm{s}$-long time interval as an example, our in-depth analysis displays that the atomic position with the spatial resolution of $\ensuremath{\sim}4.0\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{m}$ in the vertical direction (axis
x) can be achieved. The present study is useful for well understanding and researching both the robust generation of single-photon source and the precision measurement of single-atom trajectory.
Abstract. We experimentally investigate the interaction between one and two atoms and the field of a high-finesse optical resonator. Laser-cooled caesium atoms are transported into the cavity using an optical dipole trap. We monitor the interaction dynamics of a single atom strongly coupled to the resonator mode for several hundred milliseconds by observing the cavity transmission. Moreover, we investigate the position-dependent coupling of one and two atoms by shuttling them through the cavity mode. We demonstrate an alternative method, which suppresses heating effects, to analyze the atom-field interaction by retrieving the atom from the cavity and by measuring its final state.
The motion of individual cesium atoms trapped inside an optical resonator is revealed with the atom-cavity microscope (ACM). A single atom moving within the resonator generates large variations in the transmission of a weak probe laser, which are recorded in real time. An inversion algorithm then allows individual atom trajectories to be reconstructed from the record of cavity transmission and reveals single atoms bound in orbit by the mechanical forces associated with single photons. In these initial experiments, the ACM yields 2-micrometer spatial resolution in a 10-microsecond time interval. Over the duration of the observation, the sensitivity is near the standard quantum limit for sensing the motion of a cesium atom.
We demonstrate the trajectory measurement of the single neutral atoms deterministically using a high-finesse optical microcavity. The single atom strongly couples to the high-order transverse vacuum TEM
10 mode, instead of the usual TEM
00 mode, and the parameters of the system are $({g}_{10},\ensuremath{\kappa},\ensuremath{\gamma})=2\ensuremath{\pi}\ifmmode\times\else\texttimes\fi{}(20.5,2.6,2.6) \text{MHz}$. The atoms simply fall down freely from the magneto-optical trap into the cavity modes, and the trajectories of the single atoms are linear. The transmission spectra of atoms passing through the TEM
10 mode are detected by single-photon counting modules and are well fitted. Thanks to the tilted cavity transverse TEM
10 mode, which is inclined to the vertical direction
${45}^{\ifmmode^\circ\else\textdegree\fi{}}$, it helps us to eliminate the degenerate trajectory of the single atom falling through the cavity and to obtain a unique atom trajectory. An atom position with a high precision of $0.1 \ensuremath{\mu}\text{m}$ in the off-axis direction (axis
y) is obtained, and a spatial resolution of $5.6 \ensuremath{\mu}\text{m}$ is achieved in a time interval of $10 \ensuremath{\mu}\text{s}$ along the vertical direction (axis
x). The average velocity of the atoms is also measured from the atom transits, which determines independently the temperature of the atoms in a magneto-optical trap, $186\ifmmode\pm\else\textpm\fi{}19 \ensuremath{\mu}\text{K}$.