Spin selection in single-frequency two-photon excitation of alkali-metal atoms

Rajasree, Krishnapriya Subramonian; Gupta, Ratnesh Kumar; Gokhroo, Vandna; Kien, Fam Le; Nieddu, Thomas; Ray, Tridib; Chormaic, Síle Nic; Tkachenko, Georgiy

doi:10.1103/physrevresearch.2.033341

Cited by 11 publications

(8 citation statements)

References 54 publications

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“…For 762 nm light, the output power was 1.23 mW whereas 1.3 mW was used in the model. Note that we had particularly high losses in the ONF likely due to the fact that it was 5 years old and had been used extensively for several earlier experiments [5,6,20]. After the experiment, we removed the fiber from the setup and imaged it using a scanning electron microscope; large deposits were clearly visible on it and we assume that these were Rb.…”

Section: Resultsmentioning

confidence: 99%

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Machine learner optimization of optical nanofiber-based dipole traps for cold $^{87}$Rb atoms

Gupta,

Everett,

Tranter

et al. 2021

Preprint

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In two-color optical nanofiber-based dipole traps for cold alkali atoms, the trap efficiency depends on the wavelength and intensity of light in the evanescent field, and the initial laser-cooling process. Typically, no more than one atom can be trapped per trapping site. Improving the trapping efficiency can increase the number of filled trapping sites, thereby increasing the optical depth. Here, we report on the implementation of an in-loop stochastic artificial neural network machine learner to trap 87 Rb atoms in an uncompensated two-color evanescent field dipole trap by optimizing the absorption of a near-resonant, nanofiber-guided, probe beam. By giving the neural network control of the laser cooling process, we observe an increase in the number of dipole-trapped atoms by ∼ 50%, a small decrease in their average temperature from 150 µK to 140 µK, and an increase in peak optical depth by 70%. The machine learner is able to quickly and effectively explore the large parameter space of the laser cooling control to find optimal parameters for loading the dipole traps. The increased number of atoms should facilitate studies of collective atom-light interactions mediated via the evanescent field.

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Section: Resultsmentioning

confidence: 99%

“…For Rb atoms, few such wavelengths exist, and compensation can only be achieved for pure linear or pure circular polarization of the trapping fields, and only for some upper energy levels [15]. Notably, pure polarization cannot be achieved in the evanescent field of the ONF [16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Machine learner optimization of optical nanofiber-based dipole traps for cold $^{87}$Rb atoms

Gupta,

Everett,

Tranter

et al. 2021

Preprint

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“…We prepared an ensemble of trapped cold 87 Rb atoms using a standard magneto-optical trap (MOT) setup [13]. The average temperature of the atomic cloud was ∼200 μK, with a density of 10 10 atoms cm −3 .…”

Section: Methodsmentioning

confidence: 99%

“…We focus our discussion on ONFs, which provide tight confinement of light beyond the Rayleigh range and also serve as an ideal channel for light propagation. ONFs have been used to efficiently probe, manipulate and trap cold, alkali atoms [6][7][8][9][10] with recent works extending atom and ONF studies to the observation of a quadrupole transition in 87 Rb atoms [11], the demonstration of quadrature squeezing of nanofibreguided light [12], and a determination of the polarization dependency of spin selection in laser-cooled atoms [13].…”

Section: Introductionmentioning

confidence: 99%

Rubidium atom spectral lineshapes in high intensity light fields near an optical nanofibre

Gokhroo

Kien

Chormaic

2022

J. Phys. B: At. Mol. Opt. Phys.

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The integration of cold atomic systems with optical nanofibres (ONFs) is an increasingly important experimental platform. Here, we report on the spectra observed during a strongly driven, single-frequency, two-photon excitation of cold rubidium atoms near an ONF. At resonance, two competitive processes, namely a higher excitation rate and stronger pushing of atoms from the nanofibre due to resonance scattering, need to be considered. We discuss the processes that lead to the observed two-peak profile in the fluorescence spectrum as the excitation laser is scanned across the resonance, noting that the presence of the ONF dramatically changes the fluorescence signal. These observations are useful for experiments where high electric field intensities near an ONF are needed, for example when driving nonlinear processes.

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“…This Cs transition is well known as a dipole-forbidden but a quadrupole-allowed transition. In evaluating the rate of OAM transfer involving a quadrupole transition we had to consider the relevant selection rules which involve both spin and OAM [26].…”

Section: Introductionmentioning

confidence: 99%

Quadrupole absorption rate for atoms in circularly-polarized optical vortices

Bougouffa

2021

Preprint

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Twisted light beams, or optical vortices, have been used to drive the circular motion of microscopic particles in optical tweezers and have been shown to generate vortices in quantum gases. Recent studies have established that electric quadrupole interactions can mediate an orbital angular momentum exchange between twisted light and the electronic degrees of freedom of atoms. Here we consider a quadrupole atomic transition mediated by a circularly-polarized optical vortex. We evaluate the transfer rate of the optical angular momentum to a Cs atom involving the 6 2 S 1/2 → 5 2 D 5/2 quadrupole transition and explain how the polarization state and the topological charge of the vortex beam determine the selection rules.

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Spin selection in single-frequency two-photon excitation of alkali-metal atoms

Cited by 11 publications

References 54 publications

Machine learner optimization of optical nanofiber-based dipole traps for cold $^{87}$Rb atoms

Machine learner optimization of optical nanofiber-based dipole traps for cold $^{87}$Rb atoms

Rubidium atom spectral lineshapes in high intensity light fields near an optical nanofibre

Quadrupole absorption rate for atoms in circularly-polarized optical vortices

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