Detecting the motional state of single atoms in a high-finesse optical cavity by heterodyne spectroscopy

Summary form only given. We observe the quantized motion of single atoms strongly coupled to a high-finesse optical cavity and investigate dynamics of cavity-assisted atom cooling. Single caesium atoms are trapped in a blue-detuned standing-wave intracavity dipole trap, formed by a lock laser which is used to stabilize the cavity resonance frequency. A probe laser is coupled into the cavity mode and its transmission spectrum is monitored by means of photon-counting heterodyne spectroscopy [2].Measured heterodyne spectra of single atoms in the cavity are shown in Fig. 1 for two different lock-laser intensities and compared with theoretical models. The motional Raman sidebands are offset from the carrier beat signal at 1 MHz by the atomic vibrational frequency (±ν). They show asymmetric lineshapes due to the anharmonicity of the dipole potential.We investigate the dependence of the positions and lineshapes of the motional Raman sidebands on experimantal parameters such as the cavity-atom detuning, and lock-laser intensity. Information on the atomic temperature, cooling and heating rates, as well as the atomic position in the cavity with respect to an antinode of the cavity probe field are found by comparing the observed spectra with theoretical predictions [1]. In addition, this technique can also be used to analyze the cooling dynamics of a cavity-assisted EIT cooling scheme which has been recently studied and demonstrated in [3,4].