Phase-dependent fluctuations of resonance fluorescence beyond the squeezing regime

Z. H. Lu

H. M. Castro-Beltrán, Luis Gutiérrez, Levente Horvath

O de los Santos-Sánchez, H M Castro-Beltrán

Abstract We study phase-dependent fluctuations of the resonance fluorescence of a single Λ-type three-level atom in the regime near coherent population trapping, i.e. alongside the two-photon detuning condition. To this end, we employ the method of conditional homodyne detection (CHD) which considers squeezing in the weak driving regime, and extends to non-Gaussian fluctuations for saturating and strong fields. In this framework, and using estimated parameter settings of the resonance fluorescence of a single trapped 138 Ba + ion, the light scattered from the probe transitions is found to manifest a non-classical character and conspicuous asymmetric third-order fluctuations in the amplitude-intensity correlation of CHD.

Matthew J. Collett, Daniel F. Walls, P. Zoller

H. M. Castro-Beltrán, R. Román-Ancheyta, Luis Gutiérrez

Electron shelving gives rise to bright and dark periods in the resonance fluorescence of a three-level atom. The spectral signature of such blinking is a very narrow inelastic peak on top of the two-level atom spectrum. Here, we investigate theoretically phase-dependent fluctuations (e.g., squeezing) of intermittent resonance fluorescence in the frameworks of balanced and conditional homodyne detection (BHD and CHD, respectively). In BHD, the squeezing is reduced significantly in size and Rabi frequency range compared to that for a two-level atom. The sharp peak is found only in the spectrum of the squeezed quadrature, splitting the negative broader squeezing peak for weak fields. CHD correlates the BHD signal with the detection of emitted photons. It is thus sensitive to third-order fluctuations of the field, produced by the atom-laser nonlinearity, that cause noticeable deviations from the second-order BHD results. For weak driving, the third-order spectrum is negative, enlarging the squeezing peak but also reducing the sharp peak. For strong driving, the spectrum is dominated by third-order fluctuations, with a large sharp peak and the sidebands becoming dispersive. Finally, the addition of third-order fluctuations makes the integrated spectra of both quadratures equal in magnitude in CHD, in contrast to those by BHD. A simple mathematical approach allows us to obtain very accurate analytical results in the shelving regime.

Ao D, Guo G

The resonance flnoresenoe from a two-level atom driven by a realistic laser field with phase fluctuation is discussed using a phase-diffusion model. It is shown that when phase fluctuation of the pump laser beam inoreses the squeezing effects in the resonance fluorescence decrese, and the region of the sub-Poisson distribution of the field in the homodyne detection of the resonance fluorescence becomes less.