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A brief perspective on light scattering in dense and cold atomic rubidium is presented. We particularly focus on the influence of auxiliary applied fields on the system response to a weak and nearly resonant probe field. Auxiliary fields can strongly disturb light propagation; in addition to the steady state case, dynamically interesting effects appear clearly in both the time domain, and in the optical polarization dependence of the processes. Following a general introduction, two examples of features found in such studies are presented. These include nonlinear optical effects in (a) comparative studies of forward- and fluorescence-configuration scattering under combined excitation of a control and probe field, and (b) manipulation of the spatial structure of the optical response due to a light shifting strong applied field.

We report a combined experimental and theoretical simulation of multiply scattered light dynamics in an ultracold gas of 85Rb atoms. Measurements of the spectral dependence of the time-decay of the scattered light intensity, following pulsed excitation with near resonance radiation, reveals that the decay for long times is nearly exponential, with a decay constant that is largely independent of detuning from resonance. Monte Carlo simulations of the multiple scattering process show that, for large detunings, near resonance scattering of Fourier components of the excitation pulse plays a significant role in the effect. This interpretation is supported by the observations, and successful modelling, of beating between Rayleigh scattered light at the excitation carrier frequency with the Fourier components of the excitation pulse that overlap significantly with the atomic resonance.

A combined experimental and theoretical investigation of time- and alignment-dependent propagation of light in an ultracold atomic gas of atomic {sup 85}Rb is reported. Coherences among the scattering amplitudes for light scattering off excited hyperfine levels produce strong variations of the light polarization in the vicinity of atomic resonance. Measurements are in excellent agreement with Monte Carlo simulations of the multiple scattering process.

We report experimental observations of polarization-dependent coherence loss occurring in strong-field multiple scattering of light in ultracold atomic 85Rb. A measure of coherence in multiple light scattering is the degree of contrast of the coherent backscattering enhancement from the vapour. For resonance saturation parameters up to 9, we see light-polarization-dependent modification of the backscattering enhancement, suggesting that inelastic atomic light scattering and dynamic atomic magnetization may play important roles in the multiple scattering process for 85Rb.

We report a combined experimental and theoretical investigation of near resonance light scattering from a high-density and ultracold atomic $^{87}$Rb gas. The atomic sample, having a peak density $\sim 5\cdot10^{13}$ atoms/cm$^{3}$, temperature $\sim$ 65 $\mu$K and initially prepared in the F = 1 lower energy $^{87}$Rb hyperfine component, is optically pumped to the higher energy F = 2 hyperfine level. Measurements are made of the transient hyperfine pumping process and of the time evolution of scattering of near resonance probe radiation on the $F = 2 \rightarrow F' = 3$ transition. Features of the density, detuning, and temporal dependence of the signals are attributed to the high density and consequent large optical depth of the samples., Comment: Submitted to Physical Review A. This is V.2, completely revised from earlier V.1. 13 pages, 14 figures

We calculate the differential cross section of polarized light scattering from a cold and dense atomic ensemble. The regularities in the transformation of the cross section when increasing the size of the atomic ensemble are analyzed numerically. We show that for typical experimental conditions, an approximate scaling law can be obtained. Very good agreement is found in a comparison with experimental data on the size dependence of a dense and cold cloud of 87$Rb atoms., Comment: Submitted to Journal of Modern Optics, Special issue on the Proceedings of the Colloquium on the Physics of Quantum Electronics

We report on the study of the noise properties of laser light propagating through a cold 87Rb atomic sample held in a magneto-optical trap. The laser is tuned around the Fg = 2 \rightarrow Fe = 1, 2 D1 transitions of 87Rb. We observe quadrature-dependent noise in the light signal, an indication that it may be possible to produce squeezed states of light. We measure the minimum and maximum phase-dependent noise as a function of detuning and compare these results to theoretical predictions to explore the best conditions for light squeezing using cold atomic Rb.

We report sensitive detection of parametric resonances in a high-density sample of ultracold $^{87}\text{R}\text{b}$ atoms confined to a far-off-resonance optical dipole trap. Fluorescence imaging of the expanded ultracold atom cloud after a period of parametric excitation shows significant modification of the atomic spatial distribution and has high sensitivity compared with traditional measurements of parametrically driven trap loss. Using this approach, a significant shift of the parametric resonance frequency is observed and attributed to the anharmonic shape of the dipole trap potential.

We report measurements of near-resonance light scattering from an ultracold sample of $^{87}\text{R}\text{b}$ atoms formed in a magneto-optical trap (MOT). Time-dependent measurements of scattering of probe radiation tuned in the vicinity of the $F=1\ensuremath{\rightarrow}{F}^{\ensuremath{'}}=0$ hyperfine transition of the ${D}_{2}$ resonance line reveal dynamics due to Zeeman optical pumping on this transition in competition with diffusive light scattering in the optically dense sample. Zeeman mixing effects due to small residual magnetic fields also play an important role in the scattered light dynamics and reveal surprising sensitivity to the field strength. The various processes are examined as a function of probe-laser power, detuning from atomic resonance, and the presence or absence of the spatially inhomogeneous MOT quadrupole field.

Proximity of the light localization threshold can be detected through time evolution of forward or diffusely scattered light. We report experimental and theoretical results of time-dependent light scattering (F=1 - F'=0) in dense, ultracold 87Rb.

We report effects influencing enhancement (E) in coherent backscattering (CBS) of resonance radiation from ultracold Rb, and may have strong influence on efforts to observe strong localization. Theoretical results predict destructive interference in CBS, E

We report a combined theoretical and experimental study of the spectral and polarization dependence of near resonant radiation coherently backscattered from an ultracold gas of 85Rb atoms. Measurements in an approximate 6 MHz range about the 5s 2S1/2 → 5p2P3/2, F=3 → F' =4 hyperfine transition are compared with simulations based on a realistic model of the experimental atomic density distribution. In the simulations, the influence of heating of the atoms in the vapor, magnetization of the vapor, finite spectral bandwidth, and other nonresonant hyperfine transitions are considered. Good agreement is found between the simulations and measurements.