Pulse pair generation from coherently prepared atomic ensembles

Abstract

We report a detailed investigation on the generation of pulse pairs during the readout of a coherence grating stored in a cold atomic ensemble. The pulse shapes and the split of the retrieved energy between the two pulses are studied as a function of the relative intensities of the two reading fields, and a minimum is observed for the total retrieved energy. We introduce a simplified analytical theory for the process, considering a three-level atomic system, which explains all the most striking experimental features.PACS. 42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption -32.80.Qk Coherent control of atomic interactions with photons

Nonlinear coupling between two Zeeman coherence gratings stored in cold atoms

“…The fact that the total energy extracted from the medium reaches a minimum value for comparable intensities of the grating writing beams, i.e., for I W 1 ≈ I W 2 , reflects the maximization of the contributions of higher-order processes. It is worth mentioning that a similar saturation behavior was observed previously in the generation of a pair of pulses from a single coherence grating [19,20]. However, in the present case the saturation is not induced by the reading beam but is rather stored as the nonlinear coupling between two coherence gratings.…”

“…This simple experimental configuration allowed us to demonstrate the nonlinear coupling between the two stored gratings and to describe its saturation dynamics in terms of the above-mentioned simplified LS picture. It is worth mentioning that cross-saturation effects in LS processes have been observed previously in the double reading of a stored grating and were explained as originating from the contribution of higher-order wave-mixing processes [19,20]. However, in the present case the saturation is induced in the writing process and is therefore stored in the atomic medium as multiple coupled Zeeman coherence gratings.…”

Readout spectroscopy of an atomic memory

“…Once the information is stored in the atomic ensemble, there are different equivalent ways to read it, through the mapping to different optical fields [19]. In the following we explore the two most common configurations: forward or backward readouts.…”

“…[2,6,12,14]), and is discussed in detail for our system in Ref. [19]. The reading field also originates from the same laser as the W ,W fields with their relative frequencies tuned by means of two independent acousto-optical modulators (AOMs), as detailed in the experimental setup schematically shown in Fig.…”

“…The P field is emitted then as a pulse with a shape studied in detail in previous references [16,19,20] from our group, focused on the situation with R on resonance. Figure 3 provides examples of such retrieved pulses for a single intensity of the reading field, but with three different detunings δ.…”