Observation of normal-mode splitting for an atom in an optical cavity

Abstract

An investigation of the spectral response of a small collection of two-state atoms strongly coupled to the field of a high-finesse optical resonator is described for mean number N\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\le}10 atoms. For weak excitation, a coupling-induced normal-mode splitting is observed even for one intracavity atom, representing a direct spectroscopic measurement of the so-called vacuum Rabi splitting for the atom-cavity system.