Abstract We have observed the Autler–Townes (AT) effect in single- and suspected double-photon magnetic-dipole transitions in the Cesium ground-state magnetic-sublevel manifold. Experiments were performed in a Cesium vapor cell at room temperature. The D1 line was excited by laser radiation to create ground-state optical polarization, and transitions between the ground-state magnetic sublevels were excited by radio-frequency (RF) radiation. Two different excitation geometries were studied: in one case the electric field vector of the linearly polarized laser radiation was parallel to the static magnetic field, whereas in the other case these vectors were perpendicular. The oscillating magnetic field produced by the RF coils was in the plane perpendicular to the electric field vector of the laser radiation. The AT effect was confirmed by its linear dependence on the RF magnetic field amplitude, which is proportional to the Rabi frequency, in the case of single-photon transitions. With increasing RF power we also observed peaks that by their position appeared to correspond to double and even triple photon transitions, which were more pronounced when the DC magnetic field and optical electric field vectors were perpendicular. In the peak at an energy that corresponds to two photons, splitting with a quadratic dependence on the RF magnetic field amplitude could be observed. The experimental measurements are supplemented by theoretical calculations of a model J = 1 ⟶ J = 0 system.
Abstract We have observed the Autler–Townes (AT) effect in single- and suspected double-photon magnetic-dipole transitions in the Cesium ground-state magnetic-sublevel manifold. Experiments were performed in a Cesium vapor cell at room temperature. The D1 line was excited by laser radiation to create ground-state optical polarization, and transitions between the ground-state magnetic sublevels were excited by radio-frequency (RF) radiation. Two different excitation geometries were studied: in one case the electric field vector of the linearly polarized laser radiation was parallel to the static magnetic field, whereas in the other case these vectors were perpendicular. The oscillating magnetic field produced by the RF coils was in the plane perpendicular to the electric field vector of the laser radiation. The AT effect was confirmed by its linear dependence on the RF magnetic field amplitude, which is proportional to the Rabi frequency, in the case of single-photon transitions. With increasing RF power we also observed peaks that by their position appeared to correspond to double and even triple photon transitions, which were more pronounced when the DC magnetic field and optical electric field vectors were perpendicular. In the peak at an energy that corresponds to two photons, splitting with a quadratic dependence on the RF magnetic field amplitude could be observed. The experimental measurements are supplemented by theoretical calculations of a model J = 1 ⟶ J = 0 system.
Autler-Townes (A-T) splitting, known as an AC Stark effect, shows a change of an absorption/emission spectral line of a probe beam when an oscillating field is tuned in resonance with the atomic or molecular transition. The A-T splitting is observed in different three-level atoms and widely investigated in a vapor cell and in a magneto-optical trap (MOT). The A-T splitting plays an important role in the atom-based microwave electric-field measurements where a cascade three-level system involving Rydberg state is adopted. In this work, an A-T splitting is observed in an ultracold cesium Rydberg gas, which is cooled down to about 100 pK and center density is about 1010 cm-3 in a conventional MOT by using the laser cooling technology. We present the A-T spectrum in a ladder three-level atomic system involving a 34D5/2 Rydberg state. The cesium ground state (6S1/2), excited state (6P3/2) and Rydberg state (34D5/2) constitute a Rydberg three-level system. A coupling laser, locked to the Rydberg transition by using a Rydberg electromagnetically induced transparency signal that is obtained from a cesium room-temperature vapor cell, couples 6P3/2 (F'=5) 34D5/2 Rydberg transition. A weak probe laser, stabilized to a ground-state transition by using a polarization spectroscopy, is swept, covering the transition 6S1/2 (F=4) 6P3/2 (F'=5) with a double-passed acousto-optic modulator. The probe and coupling lasers are counter-propagated through the MOT center. The power of probe light is 200 pW, corresponding Rabi frequency p=21.05 MHz. During the experiment, 50 s after turning off the trapping laser, both the coupling and probe beams are switched on and last 100 s. The A-T spectrum as a function of the probe detuning is detected with a single-photon counter module detector. We use Gaussian multiple peak fitting to obtain the positions of the A-T peaks and the A-T splitting. The measured A-T splitting is proportional to the Rabi frequency of the coupling light. We numerically solve the density matrix equations to obtain the A-T spectrum, and the calculations reproduce A-T spectra well. The measured A-T splitting shows good agreement with the theoretical calculation for Rabi frequency of the coupling light c29 MHz. The A-T splitting is less than the calculation for the case of c29 MHz, the deviation is mainly attributed to the increased dephasing rate induced by the strong interaction between Rydberg atoms, whose number increases with the coupling laser Rabi frequency. In this work, the adopted method for the cascade three-level system involving Rydberg state is also suitable for -and V-type cases.
We report an experimental study on the ground-state magnetic resonances of optically pumped cesium vapors at lower temperatures of about 30°C–40°C. A longitudinal static magnetic field is applied along the single laser beam to control the splitting of the Zeeman sublevels of the ground state. When the laser frequency is set to the cesium D1 spectral line (F=3→F′=4), by modifying the transverse radio frequency field, we find that the unusual weaker-absorption and zero-dip resonance phenomena occur in the optical-magnetic resonance (OMR) effects, which is called the cesium optical-RF resonance line reversals and doubling in this paper. We explore a theoretical description for these phenomena by using density matrix equations, and our calculated results are in approximate agreement with the experimental results.
Abstract We utilize an electromagnetically induced transparency (EIT) of a three-level cascade system involving Rydberg state in a room-temperature cell, formed with a cesium 6S1/2–6P3/2–66S1/2 scheme, to investigate the Autler–Townes (AT) splitting resulting from a 15.21-GHz radio-frequency (RF) field that couples the | 66 S 1 / 2 〉 → | 65 P 1 / 2 〉 Rydberg transition. The radio-frequency electric field induced AT splitting, γ AT, is defined as the peak-to-peak distance of an EIT-AT spectrum. The dependence of AT splitting γ AT on the probe and coupling Rabi frequency, Ωp and Ωc, is investigated. It is found that the EIT-AT splitting strongly depends on the EIT linewidth that is related to the probe and coupling Rabi frequency in a weak RF-field regime. Using a narrow linewidth EIT spectrum would decrease the uncertainty of the RF field measurements. This work provides new experimental evidence for the theoretical framework in [J. Appl. Phys. 121, 233106 (2017)].
We demonstrate the single-photon excitation spectra of cesium Rydberg atoms by means of a Doppler-free purely all-optical detection with a room-temperature vapor cell and a 319 nm ultra-violet (UV) laser. We excite atoms directly from 6S1/2 ground state to 71P3/2 Rydberg state with a narrow-linewidth 319 nm UV laser. The detection of Rydberg states is performed by monitoring the absorption of an 852 nm probe beam in a V-type three-level system. With a strong coupling light, we observe the Autler-Townes (AT) doublet, and the dependences of the separation and linewidths on the coupling intensity are experimentally investigated, which is consistent with the prediction based on the dressed state theory. Moreover, the AT splitting can be used to measure the Rabi frequency. In an external magnetic field, the Rydberg spectra of nondegenerate Zeeman sublevels are demonstrated. The splitting of the spectrum is of great significance for studying the characteristics of Rydberg atoms.
We demonstrate the three-photon Autler-Townes (AT) spectroscopy in a cold cesium Rydberg four-level atom by detecting the field ionized Rydberg population. The ground state |6S1/2〉, two intermediate states |6P3/2〉 and |7S1/2〉 and Rydberg state |60P3/2〉 form a cascade four-level atomic system. The three-photon AT spectra and AT splittings are characterized by the Rabi frequency Ω852 and Ω1470 and detuning δ852 of the coupling lasers. Due to the interaction of two coupling lasers with the atoms, the AT spectrum has three peaks denoted with the letters A, B and C. Positions of the peaks and relative AT splittings, γAB and γBC, strongly depend on two coupling lasers. The dependence of the AT splitting, γAB and γBC, on the coupling laser detuning, δ852, and Rabi frequency, Ω852 and Ω1470 are investigated. It is found that the AT splitting γAB mainly comes from the first photon coupling, whereas the γBC mainly comes from the second photon coupling with the atom. The three-photon AT spectra and relevant AT splittings are simulated with the four-level density matrix equation and show good agreement with the theoretical simulations considering the spectral line broadening. Our work is of great significance both for further understanding the interaction between the laser and the atom, and for the application of the Rydberg atom based field measurement.
We have theoretically and experimentally investigated the laser-detected magnetic resonance induced by radio-frequency two-photon processes in Fg=4 of D1 line of cesium atoms. The effective Hamiltonian for the interaction between the two radio-frequency magnetic fields and sublevels at the ground state of Fg=4 is derived. By appropriately selecting the frequencies of the two radio-frequency fields, the Raman two-photon process and the cascade two-photon process can occur, which induce the magnetic resonance detected through laser transmission spectra. The theoretical calculation results fit well with the experimental data. Our results maybe apply for measuring the high bandwidth radio-frequency magnetic fields in space and studying the magnetic-induction tomography.