Abstract Combination of the electromagnetically-induced-transparency (EIT) effect and Rydberg-state atoms has attracted great attention recently due to its potential application in the photon-photon interaction or qubit operation. In this work, we studied the Rydberg-EIT spectra with room-temperature 87Rb atoms. Spectroscopic data under various experimental parameters all showed that the contrast of EIT transparency as a function of the probe field intensity is initially enhanced, reaches a maximum value and then decays gradually. The contrast of spectral profile at the optimum probe field intensity is enhanced by 2–4 times as compared with that at weakest intensity. Moreover, the signal-to-noise ratio of the spectrum can potentially be improved by 1 to 2 orders of magnitude. We provided a theoretical model to explain this behavior and clarified its underlying mechanism. Our work overcomes the obstacle of weak signal in the Rydberg-EIT spectrum caused by an apparent relaxation rate of the Rydberg polariton and weak coupling transition strength, and provides the useful knowledge for the Rydberg-EIT study.
Abstract Combination of the electromagnetically-induced-transparency (EIT) effect and Rydberg-state atoms has attracted great attention recently due to its potential application in the photon-photon interaction or qubit operation. In this work, we studied the Rydberg-EIT spectra with room-temperature 87Rb atoms. Spectroscopic data under various experimental parameters all showed that the contrast of EIT transparency as a function of the probe field intensity is initially enhanced, reaches a maximum value and then decays gradually. The contrast of spectral profile at the optimum probe field intensity is enhanced by 2–4 times as compared with that at weakest intensity. Moreover, the signal-to-noise ratio of the spectrum can potentially be improved by 1 to 2 orders of magnitude. We provided a theoretical model to explain this behavior and clarified its underlying mechanism. Our work overcomes the obstacle of weak signal in the Rydberg-EIT spectrum caused by an apparent relaxation rate of the Rydberg polariton and weak coupling transition strength, and provides the useful knowledge for the Rydberg-EIT study.
We discuss the interplay between high-contrast Rydberg-state electromagnetically induced transparency (EIT) and optical pumping (OP) in a thermal 87Rb medium. By pumping the population to one single hyperfine state, we can enhance the interaction strength and, in principle, amplify the EIT peak. According to the measurements, the EIT peak height can be improved by a factor of two or reduced by one order of magnitude, and linewidth was slightly narrowed by the pumping effect. The EIT feature is predicted quantitatively using a Doppler-free non-perturbation numerical calculation. In both simulations and measurements, Rydberg-EIT enhancement through OP is dependent on the intensity of the probe field and the optical density. Our work clarifies the underlying mechanisms of optical pumping, making relevant studies useful in developing Rydberg-based electrometry.
The power broadening of a coupling laser can be converted into two-photon detuning by electromagnetically induced transparency (EIT), resulting in a residual Doppler effect. The residual Doppler effect in a ladder-type EIT in a room-temperature atom ensemble is further amplified through a wavelength mismatch effect between the probe and coupling laser beams, which reduces the atomic coupling of light or microwaves. We measured the Rydberg spectra of the electric dipole (E1) and electric quadrupole (E2) microwave transitions, demonstrating that the reduction in the Rydberg EIT signal can be recovered through far-off-resonance E2 microwave transition dressing and achieving an 8-dB enhancement in the Rydberg EIT signal. The frequency-dependent dressing of the E2 transition enables the shift of the dressed Rydberg states to be tuned, thereby providing a scalable approach to optimize the interaction between the Rydberg state and microwave field.
High-precision spectra of Rydberg atoms are of significance in studying the interaction between Rydberg atoms, the energy level structure of Rydberg atom, and the precision measurement of the electromagnetic field. To enhance the measurement sensitivity, it is necessary to achieve the high contrast, high signal-to-noise ratio, and narrow linewidth of the spectra of the Rydberg atoms. In this work, the cavity-enhanced spectra of Rydberg atoms are studied theoretically and experimentally. Comparing with the free-space spectra of Rydberg atoms, the contrast and the signal-to-noise ratio are enhanced by 11.5 times, with the linewidth unchanged. Under the condition of two-photon resonance, both the electro-magnetically induced transparency and the double-resonance optical-pumping process can suppress the absorption of the probe laser, thereby improving the impedance matching of the cavity. As the intracavity probe laser intensity turns stronger, the contrast and signal-to-noise ratio can be improved further, and the improvement depends on the transmission of the probe laser through the atom vapor. It is expected that the contrast and signal-to-noise ratio can be improved by a factor of 23 through optimizing the temperature of the cesium atom vapor. This work provides an important reference for improving the contrast of the spectra of Rydberg atoms and the sensitivity of Rydberg-based precision measurements.
We present Rydberg-state electromagnetically-induced-transparency (EIT) measurements examining the effects of laser polarization, magnetic fields, laser intensities, and the optical density of the thermal 87 Rb medium. Two counter-propagating laser beams with wavelengths of 480 nm and 780 nm were employed to sweep the spectrum across the Rydberg states |33 D 3/2 〉 and |33 D 5/2 〉. An analytic transmission expression well fits the Rydberg-EIT spectra with multiple transitions under different magnetic fields and laser polarization after accounting for the relevant Clebsch-Gordan coefficients, Zeeman splittings, and Doppler shifts. In addition, the high-contrast Rydberg EIT can be optimized with the probe laser intensity and optical density. Rydberg EIT peak height was achieved at 13%, which is more than twice as high as the maximum peak height at room temperature. A quantitative theoretical model is employed to represent the spectra properties and to predict well the optimization conditions. A Rydberg EIT spectrum with high contrast in real time can be served as a quantum sensor to detect the electromagnetic field within an environment.
Light propagation through an ensemble of ultracold Rydberg atoms in an electromagnetically-induced-transparency (EIT) configuration is studied. In strongly interacting Rydberg EIT media, nonlinear optical effects lead to a nontrivial dependence of the degree of probe-beam attenuation on the medium density and on its initial intensity. We develop a Monte Carlo rate equation model that self-consistently includes the effect of the probe-beam attenuation to investigate the steady state of the Rydberg medium driven by two laser fields. We compare our results to recent experimental data and to results of other state-of-the-art models for light propagation in Rydberg EIT media. We find that for low probe field intensities, our results match the experimental data best if a density-dependent dephasing rate is included in the model. At higher probe intensities, our model deviates from other theoretical approaches, because it predicts a spectral asymmetry together with line broadening. These are likely due to off-resonant excitation channels, which, however, have not been observed in recent experiments. Atomic motion and coupling to additional Rydberg levels are discussed as possible origins for these deviations.
Abstract We study electromagnetically induced transparency (EIT) in a room-temperature cesium vapor cell using wavelength-modulated probe laser light. In the utilized cascade level scheme, the probe laser drives the lower transition 6 S 1 / 2 ( F = 4) → 6 P 3 / 2 ( F ’ = 5), while the coupling laser drives the Rydberg transition 6 P 3 / 2 → 57 S 1 / 2 . The probe laser has a fixed average frequency and is modulated at a frequency of a few kHz, with a variable modulation amplitude in the range of tens of MHz. The probe transmission is measured as a function of the detuning of the coupling laser from the Rydberg resonance. The first-harmonic demodulated EIT signal has two peaks that are, in the case of large modulation amplitude, separated by the peak-to-peak modulation amplitude of the probe laser times a scaling factor λ p / λ c , where λ p and λ c are the probe- and coupling-laser wavelengths. The scaling factor is due to Doppler shifts in the EIT geometry. Second-harmonic demodulated EIT signals, obtained with small modulation amplitudes, yield spectral lines that are much narrower than corresponding lines in the modulation-free EIT spectra. The resultant spectroscopic resolution enhancement is conducive to improved measurements of radio-frequency (RF) fields based on Rydberg-atom EIT, an approach in which the response of Rydberg atoms to RF fields is exploited to characterize RF fields. Here, we employ wavelength modulation spectroscopy to reduce the uncertainty of atom-based frequency and field measurement of an RF field in the VHF radio band.