We trap and cool a well-defined small number of neutral cesium in a magneto-optical trap utilizing methods of laser cooling. In order to couple the atoms to the resonator photons we transport the atoms to the center or the resonator. The transport happens by an optical "conveyor belt". The "conveyor belt" is formed by two counter-propagating laser beams and acts as a dipole trap on the atoms. We can detune the relative frequency of the two counter-propagating laser beams and thereby shift the interference pattern of the dipole trap. Doing so we can shift the atoms inside the dipole trap with a high precision and place them inside the resonator (see picture of setup on left side).

The coupling of a single atom to the resonator field is measured by the change of probe-laser transmission through the cavity. The atom-field coupling can result in a strong suppression of the probe-laser transmission as soon as a single atom is inside the resonator (see transmission data below).