Investigation of trapped rubidium atoms through frequency-modulation- induced coherent transient effects

Pietiläinen, A.; Kujala, M.; Ikonen, Erkki

doi:10.1364/josab.15.002823

Cited by 10 publications

(4 citation statements)

References 30 publications

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“…For many decades, coherent transient phenomena have been used to characterize decays and dephasing in resonantly driven two-level systems [1,2]. A rich variety of systems, with their own particularities, ranging from NMR [3,4] to electromagnetic resonances in atoms [5][6][7][8], molecules [9][10][11][12] and nuclei [13,14], have been used. A simple situation arises when an electromagnetic wave is sent through a sample composed of atomic (or molecular) scatterers.…”

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Cooperative Emission of a Coherent Superflash of Light

et al. 2014

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We investigate the transient coherent transmission of light through an optically thick cold strontium gas. We observe a coherent superflash just after an abrupt probe extinction, with peak intensity more than three times the incident one. We show that this coherent superflash is a direct signature of the cooperative forward emission of the atoms. By engineering fast transient phenomena on the incident field, we give a clear and simple picture of the physical mechanisms at play.PACS numbers: 42.50. Md, 42.25.Dd For many decades, coherent transient phenomena have been used to characterize decays and dephasing in resonantly driven two-level systems [1,2]. A rich variety of systems, with their own particularities, ranging from NMR [3,4] to electromagnetic resonances in atoms [5][6][7][8], molecules [9][10][11][12] and nuclei [13,14], have been used. A simple situation arises when an electromagnetic wave is sent through a sample composed of atomic (or molecular) scatterers. The abrupt switch off of a monochromatic quasiresonant excitation leads to free induction decay in the forward direction [9]. Temporal shapes and characteristic decay times of free induction decay depend on quantities such as laser frequency detuning [5], optical thickness [8,15], and on the presence of inhomogeneous broadening [9] and nonlinearities [16]. For an optically thick medium, since the incoming light is almost completely depleted by scattering in the stationary regime, the free induction decay signal takes the form of a coherent flash of light [8]. Its duration is reduced with respect to the single scatterer lifetime by a factor of the order of the optical thickness [8]. Consequently, its experimental observation, using standard optical transitions (lifetime in the nanosecond range), is rather challenging [17]. In this Letter, we solve this issue by performing free induction decay on the intercombination line of a cold strontium atomic gas. We gain physical insight into coherent transmission, and observe a coherent superflash of light, i.e., a transmitted intensity larger than the incident one [see Fig. 1(c)]. The superflash is due to strong phase rotation and large amplitude of the forward scattered field which are directly measured in our experiment.Related effects have been observed in Mössbauer spectroscopy experiments, where a temporal phase change in the γ radiation can lead to transient oscillations of the intensity transmitted through a sample [13,14]. These oscillations are rather small, typically of the order of 1%. This is because the γ emitter used has a short coherence time. Note that no superflash was ever observed. In a refined "γ echo" experiment, a coincidence detection made it possible to shift the phase of the emitter at a specific time during its exponential decay, leading to a revival of the forward transmitted intensity [18]. Laser spectroscopy is, however, a much easier and flexible tool. First, the temporal or spectral properties of the source can be tuned almost at will, and second, a dilute cold atomic gas c...

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Cooperative Emission of a Coherent Superflash of Light

et al. 2014

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“…A specific realization for rubidium atoms [27,28] is illustrated in Fig. 5 for a transversal decay of ξ = 0.4 μm (about half the wavelength of the cycling frequency) and a confining region of ∼ =14 μm (i.e., = 7 μm).…”

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confidence: 99%

Emergence of currents as a transient quantum effect in nonequilibrium systems

Granot

Marchewka

2011

Phys. Rev. A

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Most current calculations are based on equilibrium or semi-equilibrium models. However, except for very special scenarios (like ring configuration), the current cannot exist in equilibrium. Moreover, unlike with equilibrium scenarios, there is no generic approach to confront out-of-equilibrium currents. In this paper we used recent studies on transient quantum mechanics to solve the current, which appears in the presence of very high density gradients and fast transients. It shows that the emerging current appears instantaneously, and although the density beyond the discontinuity is initially negligible the currents there have a finite value, and remain constant for a finite period. It is shown that this nonequilibrium effect can be measured in real experiments (such as cooled rubidium atoms), where the discontinuity is replaced with a finite width (hundreds of nanometers) gradient.

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“…[7,9] Multiple passes around the loop allow large changes in phase to be accumulated, and the self-injection-locking maintains a high output power. We expect such controlled light to be useful in applications such as adiabatic population transfer, [10] coherent transients, [11,12] atom optics, [13,14] ultracold collisions, [15] radio-frequency spectrum analyzers based on spectral hole burning, [16] optical coherent transient programming and processing, [17] and high-bandwidth spatial-spectral holography. [18] II.…”

Section: Introductionmentioning

confidence: 99%

Generation of arbitrary frequency chirps with a fiber-based phase modulator and self-injection-locked diode laser

et al. 2007

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We present a novel technique for producing pulses of laser light whose frequency is arbitrarily chirped. The output from a diode laser is sent through a fiber-optical delay line containing a fiberbased electro-optical phase modulator. Upon emerging from the fiber, the phase-modulated pulse is used to injection-lock the laser and the process is repeated. Large phase modulations are realized by multiple passes through the loop while the high optical power is maintained by self-injection-locking after each pass. Arbitrary chirps are produced by driving the modulator with an arbitrary waveform generator.

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Investigation of trapped rubidium atoms through frequency-modulation- induced coherent transient effects

Cited by 10 publications

References 30 publications

Cooperative Emission of a Coherent Superflash of Light

Cooperative Emission of a Coherent Superflash of Light

Emergence of currents as a transient quantum effect in nonequilibrium systems

Generation of arbitrary frequency chirps with a fiber-based phase modulator and self-injection-locked diode laser

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