We present an inverted ladder cesium Rydberg atom excitation scheme with a probe transition of 6S1/2→7P1/2 (459 nm) and coupling transition of 7P1/2→nD3/2 (⩾1038 nm) for electric field sensing, as an alternative to schemes that use the D1 and D2 probe laser transitions and green light coupling laser transitions. We investigate the transition from enhanced absorption (EA) to electromagnetically induced transparency for different probe Rabi frequencies and conduct experiments to validate Autler–Townes splitting of the nD3/2→(n+1)P1/2 and nD3/2→(n−2)F5/2 Rydberg transitions in the presence of on-resonance microwave fields, for a proof-of-concept demonstration of microwave field sensing using EA in an inverted ladder scheme. Finally, we demonstrate 459 nm probe laser stabilization to the hyperfine lines in a saturated absorption spectroscopy configuration, and laser stabilization of the 1038 nm coupling laser to an EA spectral feature in a counter-propagating probe and coupling laser configuration. Under stabilization, Allan deviations of less than 200 kHz for τ< 50 s are achieved for both the probe and coupling lasers.
We present an inverted ladder cesium Rydberg atom excitation scheme with a probe transition of 6S1/2→7P1/2 (459 nm) and coupling transition of 7P1/2→nD3/2 (⩾1038 nm) for electric field sensing, as an alternative to schemes that use the D1 and D2 probe laser transitions and green light coupling laser transitions. We investigate the transition from enhanced absorption (EA) to electromagnetically induced transparency for different probe Rabi frequencies and conduct experiments to validate Autler–Townes splitting of the nD3/2→(n+1)P1/2 and nD3/2→(n−2)F5/2 Rydberg transitions in the presence of on-resonance microwave fields, for a proof-of-concept demonstration of microwave field sensing using EA in an inverted ladder scheme. Finally, we demonstrate 459 nm probe laser stabilization to the hyperfine lines in a saturated absorption spectroscopy configuration, and laser stabilization of the 1038 nm coupling laser to an EA spectral feature in a counter-propagating probe and coupling laser configuration. Under stabilization, Allan deviations of less than 200 kHz for τ< 50 s are achieved for both the probe and coupling lasers.
We investigate the effect of dressing the dark state in a ladder scheme of electromagnetically induced transparency (EIT) involving a Rydberg state by an optical field. We show that similarly to microwave dressing, the dressing by a laser field induces an Autler–Townes splitting of the EIT resonance which results in an absorption dip while scanning the frequency of the dressing laser. Experimental results show that the full width at half-maximum of the dressing-induced dip can become very narrow as the coupling laser power increases, while the probe transmission change Δ T P exhibits a non-monotonic trend. Numerical simulation using the Lindblad master equation attributes this evolution to a transition from the saturated to the linear regime of absorption. This laser dressing approach enables high-resolution, sub-Doppler measurements in room-temperature environments, providing a precise method for probing hyperfine structures in alkali metal atoms with enhanced clarity. Furthermore, we demonstrate frequency stabilization of a home-made 1064 nm laser to the dressing signal, achieving a stability of 1.5×10 −9 at τ ≈30s.
Abstract We present the electromagnetically induced transparency (EIT) spectra of cold Rydberg four-level cascade atoms consisting of the 6S1/2 → 6P3/2 → 7S1/2 → 60P3/2 scheme. A coupling laser drives the Rydberg transition, a dressing laser couples two intermediate levels and a weak probe laser probes the EIT signal. We numerically solve the Bloch equations and investigate the dependence of the probe transmission rate signal on the coupling and dressing lasers. We find that the probe transmission rate can display an EIT or electromagnetically induced absorption (EIA) profile, depending on the Rabi frequencies of the coupling and dressing lasers. When we increase the Rabi frequency of the coupling laser and keep the Rabi frequency of the probe and dressing laser fixed, flipping of the EIA to EIT spectrum occurs at the critical coupling Rabi frequency. When we apply a microwave field coupling the transition 60P3/2 → 61S1/2, the EIT spectrum shows Autler–Townes splitting, which is employed to measure the microwave field. The theoretical measurement sensitivity can be 1.52 × 10−2 nV⋅cm−1⋅Hz−1/2 at the EIA–EIT flipping point.
We present an electromagnetically induced transparency and Aulter-Townes (EIT-AT) spectrum of a Rydberg three-level atom that is dressed with a microwave field in a room-temperature cesium cell. The EIT is a quantum coherent effect produced by the interaction of atoms with electromagnetic waves, which leads to the decrease of the absorption for a weak resonant probe laser. AT splitting refers to the phenomenon, that the absorption line splits when an electromagnetic field that is in resonance or near resonance acts on the transition of atoms. Rydberg atoms are extremely sensitive to an external electric field due to their large polarizabilities and microwave transition dipole moments, which can be used to measure the external field. In this work, a Rydberg three-level EIT is used to detect Rydberg atom and AT splitting induced by the microwave field. Cesium levels 6S1/2, 6P3/2 and 50S1/2 constitute a Rydberg three-level system, in which a weak probe laser locking to the transition from 6S1/2 to 6P3/2 couples ground-state transition and the strong coupling laser resonates on the Rydberg transition from 6P2/3 to 50S1/2. The two Rydberg levels 50S1/2 and 50P1/2 are coupled with the microwave field at a frequency of 30.852 GHz, leading to the AT splitting of EIT line and forming an EIT-AT spectrum, which is used to measure the electric field amplitude of microwave. In order to further study the EIT-AT splitting characteristics of the Rydberg levels, we carry out a series of measurements by changing the microwave field. The experimental results show a broadened EIT-AT signal for the weak field range and the four-peak spectrum for the strong field, which is attributed to the inhomogeneity of the microwave field. The microwave in cesium cell, emitted by a function generator, shows inhomogeneous behavior such that the atoms interacting with the laser field experience the different fields, leading to the line broadened and multi-peak EIT-AT spectra. For the microwave transition of nS1/2-nP1/2 in this paper, a pair of EIT-AT lines should be obtained for an electric field value. The broadening of the EIT-AT spectrum and the multi-peak structure here are due to the inhomogeneity of the microwave field measurement. We propose a method to increase the spatial resolution by reducing the length of cesium cell. The result in this work provides a method of measuring the field amplitude and monitoring the distribution of microwave electric field, meanwhile the spatial resolution of the measurements can be improved by reducing the size of the cell.
We present nonlinear spectra of four-level ladder cesium atoms employing 6S 1/2 → 6P 3/2→ 7S 1/2 → 30P 3/2 scheme of a room temperature vapor cell. A coupling laser drives Rydberg transition, a dressing laser couples two intermediate levels, and a probe laser optically probes the nonlinear spectra via electromagnetically induced transparency (EIT). Nonlinear spectra are detected as a function of coupling laser frequency. The observed spectra exhibit an enhanced absorption (EA) signal at coupling laser resonance to Rydberg transition and enhanced transmission (ET) signals at detunings to the transition. We define the enhanced absorption (transmission) strength, H EA (H ET), and distance between two ET peaks, γ ET, to describe the spectral feature of the four-level atoms. The enhanced absorption signal H EA is found to have a maximum value when we vary the dressing laser Rabi frequency Ω d, corresponding Rabi frequency is defined as a separatrix point, Ω dSe . The values of Ω dSe and further η = Ω dSe /Ω c are found to depend on the probe and coupling Rabi frequency but not the atomic density. Based on Ω dSe , the spectra can be separated into two regimes, weak and strong dressing ranges, Ω d ≲ Ω dSe and Ω d ≳ Ω dSe , respectively. The spectroscopies display different features at these two regimes. A four-level theoretical model is developed that agrees well with the experimental results in terms of the probe-beam absorption behavior of Rabi frequency-dependent dressed states.
Rydberg atoms, with large principal quantum number, exhibit certain properties, such as long lifetimes and strong interactions with fields and other atoms, which have been extensively investigated recently. One of the properties is the electromagnetically induced transparency (EIT) of Rydberg ladder system, which can be used to measure the radio frequency (RF) field with high sensitivity. In this paper, we investigate the quantum coherent effect of cesium Rydberg atom in a three-level ladder system involving the ground state (6S1/2), the excited state (6P3/2) and 49S1/2 Rydberg state in room temperature vapor cell. The probe laser (852 nm) drives the transition of 6S1/2(F=4)→6P3/2(F'=5), while the coupling laser (510 nm) couples the Rydberg transition of 6P3/2 (F'=5)→nS1/2. A typical electromagnetically induced transparency spectrum is obtained when the weak probe laser is scanned through the transition of 6S1/2(F=4)→6P3/2(F'=5) and the coupling laser tuning to Rydberg transition. The two-photon RF spectra are observed when the RF field with a frequency of ～16.9 GHz couples the Rydberg transition of 49S1/2→47D3/2, where the EIT signal is split into two EIT peaks due to the interaction between the RF field and Rydberg atoms. The dependences of EIT splitting on the power of RF field are investigated. The results show that the EIT splitting increases with the power of RF field, which can inversely be used to measure the RF field with a higher spatial resolution in the future.
We present an atom-based approach for determining microwave electric and magnetic fields by using a single rubidium vapor cell in a microwave waveguide. For a 87Rb cascade three-level system employed in our experiment, a weak probe laser driving the lower transition, 5S1/2→5P3/2, is first used to measure the microwave magnetic field based on the atomic Rabi resonance. When a counter-propagating strong coupling laser is subsequently turned on to drive the Rydberg transition, 5P3/2→67D5/2, the same probe laser is then used as a Rydberg electromagnetically induced transparency (EIT) probe to measure the microwave electric field by investigating the resonant microwave dressed Autler-Townes splitting (ATS). By tuning the hyperfine transition frequency of the ground state using an experimentally feasible static magnetic field, we first achieved a measurement of the microwave electric and magnetic field strength at the same microwave frequency of 6.916 GHz. Based on the ideal relationship between the electric and magnetic field components, we obtained the equivalent microwave magnetic fields by fitting the inversion to the measured microwave electric fields, which demonstrated that the results were in agreement with the experimental measurement of the microwave magnetic fields in the same microwave power range. This study provides new experimental evidence for quantum-based microwave measurements of electric and magnetic fields by a single sensor in the same system.