We have made measurements of the spectrum of resonance fluorescence emitted by sodium atoms in an intense, uniform, monochromatic field. The transition used in the experiment was between the
32S21 (
F=2,
mF=2) ground state and the
32P23 (${F}^{\ensuremath{'}}=3$, ${m}_{F}^{\ensuremath{'}}=3$) excited state. A separate light beam, circularly polarized and resonant with this transition, was used to prepare the sodium atoms in the
F=2,
mF=2 magnetic sublevel. This pumping scheme was used to obtain the spectrum for both on- and off-resonance excitations. The measurements are in good agreement with Mollow's calculation. In addition, we describe conditions under which we observed asymmetric spectra similar to those of earlier experiments.
Phase-sensitive detection of resonance fluorescence, i.e., allowing the light emitted from an atom which is undergoing Rabi oscillations in free space to interfere with a coherent local oscillator (LO) beam, has drawn considerable attention throughout the history of quantum optics. Recently, phase-sensitive squeezing spectra for single-atom resonance fluorescence were observed for the first time using strongly-driven long-lived atoms. A measurement of phase-sensitive intensity correlations for this system will be presented. Using physical arguments I will construct the phase-sensitive two-time intensity autocorrelation function, and elucidate the role played by quantum fluctuations in phase-dependent resonance fluorescence.
The experimental conditions under which the intensity correlation function from a single atom undergoing resonance fluorescence may be observed are studied. As was pointed out by Jakeman et al. (1977), even under optimum conditions the number of fluctuations in the atomic beam prevent a direct observation of photon antibunching under the subsequent normalisation scheme used by Kimble et al. (1977). However, a direct observation of photon antibunching is possible in principle by adopting alternative normalisation schemes of the intensity correlation function.