Hanle Configuration Research Articles

Double Radio-Optical Resonance in the Hanle Configuration under the Excitation of the D1 Absorption Line in Alkali Metal Atoms

Double Radio-Optical Resonance in the Hanle Configuration under the Excitation of the D1 Absorption Line in Alkali Metal Atoms

Application of coating based on 5 nm octadecylamine-functionalized gold-nanoparticles for protecting the spin-polarization of atoms confined in a vacuum cell

We report on the expressed atomic spin-polarization protection properties of thin layers of Octadecylamine capped gold-nanoparticles applied to the inner surface of an alkali metal vapor cell. The work aims to reveal the potential of using appropriately functionalized gold nanoparticles as a novel approach to forming efficient coatings on the inner surface of vacuum cells for atomic spectroscopy. The performed layer characterization uses parameters of electromagnetically induced transparency/absorption resonances observed in the Hanle configuration. We show at the Rb D2 absorption line that cells with such a coating provide conditions for achieving high-contrast and narrow, bright, and dark resonances, comparable to those reported by others for Octadecyltrichlorosilane coatings. Using visualization software for structural analysis, we represent the possible interaction scenarios between the alkali atoms and the surface building blocks. We demonstrate and discuss the main structural and functional differences introduced by covering the cell surface with passivated nanoparticles instead of directly using molecules to form monolayers. Having gold-nanoparticles in the coating allows preserving at the same time the earlier discovered advantage for high-speed control over the Rb vapor density by light-induced desorption of atoms. That enables significant problem-solving in atomic clocks and magnetometers and eases their considerable miniaturization.

Coherent magneto-optical resonances on the potassium D2 line in Hanle configuration for magnetometry applications

The coherent magneto-optical resonances on the potassium D2 line are investigated from the point of view of magnetometry applications. The measurements are performed in Hanle configuration with potassium excited by circularly polarized laser beam in cell with dimensions 8 mm and buffer gas 30 Torr Ne. The parameters of the resonances registered in fluorescence and transmission are compared. The capability of the laser system to work with magnetically unshielded cell is demonstrated. The registration of bright and dark magneto-optical resonances detected in fluorescence by controlling the optical thickness of potassium vapor is discussed. The influence of the laser power and transverse magnetic field are considered. The experimental results show the potential of the system for magnetic field sensing and calibration.

Coherent magneto-optical resonances in hot potassium vapor

In this communication, we present experimental results on the preparation of magneto-optical resonances in potassium. The magneto-optical resonances are registered in Hanle configuration, i.e. monitoring the atomic fluorescence vs the applied magnetic field scanned around zero value. The excitation of the second resonance line with a wavelength of 404.4 nm leads both to direct fluorescence at 404.4 nm and to a cascade decay with fluorescence at 770.1 nm and 764.5 nm (first resonance line transitions). This transfer is evidenced by the registration of a narrow magneto-optical resonance in the fluorescence. It should also be noted that even after multiple cascade transitions, the resonance observed on the infrared lines has a much better signal/noise ratio compared to that on the excited second resonance line. Therefore, the study of these sub-Doppler-width magneto-optical resonances in hot potassium vapor will be useful for the further development of high-resolution magneto-optical laser spectroscopy.

Highly Efficient Spin-Current Operation in a Cu Nano-Ring.

An all-metal lateral spin-valve structure has been fabricated with a medial Copper nano-ring to split the diffusive spin-current path. We have demonstrated significant modulation of the non-local signal by the application of a magnetic field gradient across the nano-ring, which is up to 30% more efficient than the conventional Hanle configuration at room temperature. This was achieved by passing a dc current through a current-carrying bar to provide a locally induced Ampère field. We have shown that in this manner a lateral spin-valve gains an additional functionality in the form of three-terminal gate operation for future spintronic logic.

Hanle electromagnetically induced absorption in open transitions of the 87Rb D2 line

The influence of the closed transition on the neighboring and open transitions of the 87Rb D2 line, partially resolved under Doppler broadening, is studied at different ellipticities in the Hanle configuration with longitudinal and transverse magnetic field scans. We show that a sign reversal from an electromagnetically induced transparency (EIT) resonance to an electromagnetically induced absorption (EIA) resonance occurs with an increase in ellipticity for the transition in a transverse field scan. This transformation is not observed for a longitudinal field scan. These observations are attributed to the higher amplitude of the EIA resonance for the transition in transverse field scans for elliptical polarized light. The EIA character in the Hanle transmission profile of and transitions is enhanced (weakened) when the laser beam frequency is detuned towards (away from) the transition. We show by computation that at higher ellipticities, a transformation from an EIT to an EIA resonance for the transition occurs at low frequency shifts (towards the transition) in a transverse field scan.

Electromagnetically-induced-absorption resonance with high contrast and narrow width in the Hanle configuration

The method for observing the high-contrast and narrow-width resonances of electromagnetically induced absorption (EIA) in the Hanle configuration under counter-propagating pump and probe light waves is proposed. Here, as an example, we study a ‘dark’ type of atomic dipole transition in D1 line of 87Rb, where usually the electromagnetically induced transparency can be observed. To obtain the EIA signal one should properly choose the polarizations of light waves and intensities. In contrast to regular schemes for observing EIA signals (under a single traveling light wave in the Hanle configuration or under a bichromatic light field consisting of two traveling waves), the proposed scheme allows one to use buffer gas for significantly improving the properties of the resonance. Also the dramatic influence of atomic transition openness on the contrast of the resonance is revealed, which is advantageous in comparison with cyclic atomic transitions. The nonlinear resonances in a probe-wave transmitted signal with contrast close to 100% and sub-kHz widths can be obtained. The results are interesting in high-resolution spectroscopy, nonlinear and magneto-optics.

Postselection of a polarization basis in intensity correlations under electromagnetically induced transparency

We report on switching the intensity correlation or anticorrelation by changing the polarization basis for measuring light that has already propagated through the electromagnetically induced transparency (EIT) medium of the 5S1/2 (F = 2) − 5P1/2 (F ′ = 1) transition of 87Rb atoms. When a linearly polarized laser beam interacts with the EIT medium in the Hanle configuration, selection of the polarization basis after the optical field has already interacted with the atoms was found to significantly affect the intensity-intensity correlation of the two orthogonal polarization components. We compared the second-order correlation functions of two postselected polarization bases (linear and circular), and the polarization basis effect on the second-order correlation functions as a function of the applied magnetic field was numerically calculated using an eight-level atomic model.

Transformation of Ramsey electromagnetically induced absorption into magnetic-field induced transparency in a paraffin-coated Rb vapor cell

We report on magnetic-field induced transparency (MIT) based on Ramsey electromagnetically induced absorption (EIA) in a paraffin-coated Rb vapor cell. Changing the laser polarization from linear to circular in the presence of a weak residual transverse magnetic field to the laser propagation, the narrow absorption due to the Ramsey EIA transformed into the transparency due to MIT of the 5S1/2 (F = 2)-5P3/2 (F' = 3) transition of 87Rb in the paraffin-coated Rb vapor cell. The spectral widths of the EIA and MIT in the Hanle configuration were measured to be 0.6 mG (425 Hz) and 1.2 mG, respectively. MIT depended on the long preservation time of the ground-state coherent spin states and the transverse magnetic field. From the numerical results, the crossover between the Ramsey EIA and the MIT could be illustrated as the superposition of both signals.

Pulse propagation dynamics in the presence of a continuous-wave field

We present theoretical results for the propagation dynamics of an electromagnetic field pulse through rubidium vapor, while another field, a continuous-wave electromagnetic field, is present. The frequencies of both electromagnetic fields are resonant with the transition between the ground and excited state hyperfine levels of Rb, Fg → Fe = Fg ± 1. Detuning from resonance is done by the magnetic field oriented along the light propagation direction (Hanle configuration). When both the electromagnetic fields are simultaneously interacting with Rb atoms, either electromagnetically induced transparency or absorption is induced. Propagation dynamics was obtained solving the set of Maxwell–Bloch equations for the interacting atoms with two electromagnetic fields. Motivated by recent results (Brazhnikov et al 2011 Eur. Phys. J. D 63 315–25; Brazhnikov et al 2010 JETP Lett. 91 625–9; Kou et al 2011 Phys. Rev. A 84 063807), we have analyzed the influence of experimental parameters, laser polarization, and mutual phases between lasers, which can lead to optical switching, i.e. the transformation from electromagnetically induced absorption to transparency and vice versa.

Ramsey effect of coherent population trapping in anti-relaxation-coated Rb vapor cells

We examine experimentally and theoretically the Ramsey effects on the coherent population trapping (CPT) resonance in a paraffin-coated Rb vapor cell. The observed CPT spectrum in the Hanle configuration of the 5S1/2(F = 2)−5P1/2(F′ = 1) transition of 87Rb atoms consists of a narrow structure with a spectral width of 0.10 mG due to the wall-induced Ramsey effect and a broad structure with a spectral width of 23 mG due to the transit effect. Considering the velocity distribution of atoms and the number of wall-atom collisions, we numerically calculated the transmittance of the laser beam as a function of the longitudinal magnetic field. The experimental results of the CPT Ramsey interference were in good agreement with the theoretical results, and the dependences of the CPT Ramsey effects on the atom-laser interaction time were investigated in detail.

Magnetic-field-induced absorption with sub-milligauss spectral width in paraffin-coated rubidium vapor cell

We investigated the switching between the transmittance and absorption of the 5S1/2(F=2)→5P1/2(F′=1) transition of Rb87 in a paraffin-coated Rb vapor cell in the Hanle configuration. When the laser polarization was changed from linear to circular, the coherent population trapping (CPT) spectrum, with a spectral width of 0.12 mG due to the Ramsey effect, transformed into a narrow absorption spectrum with a sub-milligauss spectral width of 0.2 mG. The CPT and narrow absorption spectra were numerically calculated for both polarizations by considering the degenerate magnetic sublevels of the 5S1/2–5P1/2 transition in the antirelaxation-coated atomic vapor cell. This narrow absorption spectrum was revealed to be magnetic-field-induced absorption due to the residual transverse magnetic field and preservation time of the ground-state coherent spin states.

Degenerate two-level system in the presence of a transverse magnetic field

The effect of a transverse magnetic field (TMF) on the absorption spectra of degenerate two-level systems in the ${D}_{2}$ line of ${}^{87}$Rb is investigated both analytically and numerically. We compare the effect of the TMF on the absorption of a $\ensuremath{\sigma}$ polarized pump in the Hanle configuration with that of a ${\ensuremath{\sigma}}^{\ensuremath{-}}$ probe in the presence of a ${\ensuremath{\sigma}}^{+}$ pump in the pump-probe configuration, and we show that the absorption spectra in both configurations is split in the presence of a TMF and that the splitting is proportional to its magnitude. The population redistribution in the ground state due to the TMF is reinforced by collisional effects, leading to increased splitting of the coherent population trapping (CPT) dip in the absorption spectrum. We explain the appearance of the splitting by setting the quantization axis along the total magnetic field. Then, in the Hanle configuration, the direction of the quantization axis changes as the longitudinal magnetic field is scanned, so that the laser polarization also changes. This leads to the creation of new two-photon detuned $\ensuremath{\Lambda}$ subsystems. The evolution of the populations and coherences of the ground-state Zeeman sublevels is illustrated using the angular momentum probability surface. In addition to being split, the CPT dip in the pump-probe configuration is also shifted by the longitudinal magnetic field, so that the effects of the longitudinal and transverse magnetic fields can be distinguished from each other.

Narrow structure in the coherent population trapping resonance in sodium

We present a detailed study of coherent population trapping (CPT) in the Hanle configuration in sodium atoms confined inside a glass cell and irradiated with a broadband multimode dye laser light resonant with the ${D}_{1}$ line. The presence of several modes spaced by tens of MHz is effective in inhibiting hyperfine optical pumping, thus reducing losses and allowing for efficient trapping. A narrow resonance, whose width is of the order of 1 mG, is observed superimposed on the electromagnetically induced transparency (EIT) resonance. Such a structure is more than two orders of magnitude narrower than the broader one, with significantly reduced power broadening. In order to describe this phenomenon, we developed a theoretical model, based on numerical solutions of density matrix equations, which takes into account the peculiarity of CPT induced by broadband multimode laser light. Results are shown to be in very good agreement with the experimental data. In this framework, the small width and the small amount of power broadening exhibited by this narrow spectral structure are related to the time spent by the atoms to re-enter the laser beam volume after collisions that preserve the orientation. This study offers insight into the mechanisms of atoms depolarization caused by collisions with the cell walls and represents a starting point for the development of techniques for the diagnostics of cell-coating parameters and new applications in metrology and magnetometry.

Polarization method for controlling a sign of electromagnetically-induced transparency/absorption resonances

We propose a new easy method to control a sign of the subnatural resonances of electromagnetically-induced transparency and absorption in the Hanle configuration under counterpropagating light waves. The analytical results for a three-level atomic Λ-scheme are corroborated by numerical calculations for various atomic transitions. The results can be applied in nonlinear optics, optical communications and magnetometry.

Electromagnetically induced absorption with sub-kHz spectral width in a paraffin-coated Rb vapor cell

We report on electromagnetically induced absorption (EIA) with sub-kHz spectral width in a paraffin-coated Rb vapor cell in the Hanle configuration of the 5S(1/2)(F=2)-5P(3/2)(F'=3) transition of 87Rb atoms. Using a linearly polarized laser, the spectral width of the Hanle EIA spectrum was measured to be 0.55 mG (390 Hz). The narrow spectral width was due to the maintaining of atomic coherence between ground states while atoms collided with the anti-relaxation coated wall of the Rb vapor cell. Under a weak transverse residual magnetic field, the angle between the transverse residual magnetic field and the direction of linear polarization affected the magnitude of the narrow Hanle EIA spectrum. This is because of the change of atomic magnetic momentum due to the weak transverse residual magnetic field around the zero value of the longitudinal magnetic field.

Sign reversal of Hanle electromagnetically induced absorption with orthogonal circularly polarized optical fields

We study by computation and experiment an electromagnetically induced absorption resonance in the Hanle configuration with a transverse magnetic field on a closed Fg → Fe = Fg+1 transition with co-propagating orthogonal circularly polarized probe and coupling optical fields. At high coupling field intensities, the Hanle resonance changes sign due to a shift in atomic population from Zeeman sublevels associated with a probe field cyclic transition to sublevels associated with a coupling field cyclic transition at zero magnetic field. We also show that a similar sign reversal does not occur for π-polarized and σ-polarized coupling fields.

Effect of ellipticity on Hanle electromagnetically induced absorption and transparency resonances with longitudinal and transverse magnetic fields

The effect of incident light field ellipticity on the electromagnetically induced absorption (EIA) and electromagnetically induced transparency (EIT) resonances has been studied experimentally and computationally in Hanle configuration with longitudinal and transverse magnetic fields. We identify the Zeeman coherences that influence the resonance profile and study the role of coherence-transfer from excited to ground state via spontaneous emission as a function of ellipticity for the F{sub g}=2{yields}F{sub e}=3 transition of {sup 87}Rb. The EIT resonance observed with the light field locked on the F{sub g}=1{yields}F{sub e}=2 transition of {sup 87}Rb is an influence of the nearby F{sub g}=1{yields}F{sub e}=0 closed and F{sub g}=1{yields}F{sub e}=1 open transitions. With increase in ellipticity the observed EIA and EIT resonances diminish in amplitude for a longitudinal magnetic field and are enhanced for a transverse magnetic field. We computationally account for these observations and discuss the factors that influence the EIA and EIT resonance amplitudes as a function of ellipticity and show that for a transverse field scan the ellipticity dependence of the EIA resonance amplitude can be accounted for without invoking the Doppler effect unlike for a longitudinal field scan. We also show that the maximum in the EIA resonance amplitude obtained for nonzeromore » ellipticities with a longitudinal magnetic field depends on the closedness of the atomic system.« less

Analytical solution of microwave transition spectral lines for 87Rb atoms in a Hanle configuration

This paper theoretically investigates the microwave transition spectrum of 87Rb atomic D1 line with specially prepared atomic state in a Hanle configuration. The approximate analytical results have shown that the 0–0 transition spectral line has the highest contrast and can be applied to microwave frequency standards.

Effect of the polarization of counterpropagating light waves on nonlinear resonances of the electromagnetically induced transparency and absorption in the Hanle configuration

A polarization method has been proposed for transforming the nonlinear electromagnetically induced transparency resonance into the electromagnetically induced absorption resonance (and vice versa) in the Hanle configuration in the field of counterpropagating waves. Numerical calculations have been performed for the Fg = 2 → Fe = 1 and Fg = 2 → Fe = 3 transitions in the 87Rb atom. The qualitative analysis of the effect has been performed for the three-level Λ scheme of the atomic energy levels. The main theoretical conclusions are in qualitative agreement with our experimental data for 87Rb. The results can be applied in magnetometry and nonlinear optics.