Nonvolatile optical memory via recoil-induced resonance in a pure two-level system

Abstract

We report on the storage of light via the phenomenon of recoil-induced resonance in a pure twolevel system of cold cesium atoms. We use a strong coupling beam and a weak probe beam to couple different external momentum states of the cesium atom via two-photon Raman interaction which leads to the storage of the optical information of the probe beam. We have also measured the probe transmission spectrum, as well as the light storage spectrum which reveals very narrow subnatural resonance features showing absorption and gain. We have demonstrated that this memory presents the unique property of being insensitive to the reading process, which does not destroy the stored information leading to a memory lifetime limited only by the atomic thermal motion.

Atomic memory based on recoil-induced resonances

“…2). The time of tens of microseconds for the decay is related to the diffusion time of atoms between fringes of the coherence grating printed in the ensemble, as already pointed out in [17]. The measured signal is then also given by the modulus squared of ρ III(FWM) 12…”

“…The experiment is performed in the absence of the trapping and repumping beams as well as the MOT quadrupole magnetic field, with the trapping beams and the quadrupole magnetic field being switched off 1 ms before the repumping beam in order to pump the atoms in the hyperfine 6S 1/2 (F = 4) ground state. The residual magnetic field is compensated by three pairs of independent Helmholtz coils, whose current is adjusted by using a microwave spectroscopic technique [17], which allows the residual field to be reduced to less than 10 mG. The simplified experimental scheme is shown in Fig.…”

“…This is the main result of this section: our theoretical model shows in a very direct manner that the reading process does not destroy any information stored in the atomic medium and the retrieved signal is completely indifferent to the moment t = t 2 at which the reading process begins and depends only on the time frame of the writing phase, t 1 . In this way, we provide a theoretical picture that explains the core experimental observations reported in [17]. We now proceed to take a closer look at each mode generated from the atomic memory.…”

“…To obtain the transmission signal, we need to look at the plane waves seeded in the k p direction. Those arise from the terms containing δ( p (17). Explicitly, we have:…”

“…In another context, we have also recently demonstrated the storage of light based on the external atomic degrees of freedom, both using the non-localized degrees of freedom associated with the RIR phenomenon [17], as well as the quantized energy levels of atoms localized in a 1D optical lattice [18]. This new type of memory using the atomic external degrees of freedom is particularly attractive since it is less sensitive to external magnetic and electric fields.…”