HETERODYNE MEASUREMENT OF THE RESONANCE FLUORESCENCE OF A SINGLE-ION

The three-dimensional localization of a single ion to the Lamb-Dicke l imit in a radio-frequency trap has been combined with the technique of heterodyne detection to provide high-resolution spectroscopy of the f luorescent light of the ion. A coherent component with a linewidth of 0.7 Hz, corresponding to elastic scattering of the incident laser ligh t, was observed in the heterodyne signal. The method may be extended t o observe the narrow sidebands related to the secular motion in the tr ap, yielding information on the dynamics of the ion. Quantum propertie s of the fluorescent radiation can be detected by probing higher order field correlations. As an example we investigated the phenomenon of a ntibunching which appears as intensity anticorrelations of the emitted radiation. A measurement of intensity crosscorrelations of the fluore scent light superimposed with a weak local oscillator is expected to p ermit the observation of squeezing in the resonance fluorescence of a single ion.