Quantum optics of a single atom

In this paper recent experiments performed in our laboratory are reviewed dealing with the investigation of quantum phenomena in the radiation interaction of single atoms. The first part describes experiments in single mode cavities using the one-atom maser or micromaser and in the second part experiments with ion traps are summarized. The latter experiments concentrate on the investigation of resonance fluorescence. In addition new experimental proposals using ultracold atoms in cavities and traps are discussed. In those future experiments the interplay between atomic waves and light waves is important and leads to new phenomena in radiation-atom interaction.