The use of Rydberg atoms for radio frequency electric field sensing has emerged as a promising alternative to traditional antenna-based designs that enables all-optical readout. However, the need for atomic vapor cells comprised of dielectric materials can adversely affect the electric field distribution at the probing volume. Here we describe the effects of electric field inhomogeneity on measured optical electromagnetically induced transparency (EIT) spectra. This is accomplished using custom-designed waveguide-embedded atomic vapor cells with stub tuners that allow control of the degree of electric field inhomogeneity within the cell. We describe the resulting broadening of the measured EIT feature and the associated reduction in magnitude, which results in an overall reduced sensitivity of the resulting measurement.
The use of Rydberg atoms for radio frequency electric field sensing has emerged as a promising alternative to traditional antenna-based designs that enables all-optical readout. However, the need for atomic vapor cells comprised of dielectric materials can adversely affect the electric field distribution at the probing volume. Here we describe the effects of electric field inhomogeneity on measured optical electromagnetically induced transparency (EIT) spectra. This is accomplished using custom-designed waveguide-embedded atomic vapor cells with stub tuners that allow control of the degree of electric field inhomogeneity within the cell. We describe the resulting broadening of the measured EIT feature and the associated reduction in magnitude, which results in an overall reduced sensitivity of the resulting measurement.
Highly excited Rydberg atoms in a room-temperature vapor cell are promising for developing a radio-frequency (RF) electric field (E-field) sensor and relevant measurement standards with high accuracy and sensitivity. The all-optical sensing approach is based on electromagnetically-induced transparency and Autler-Townes splitting induced by the RF E-field. Systematic investigation of measurement uncertainty is of great importance for developing a national measurement standard. The presence of a dielectric vapor cell containing alkali atoms changes the magnitude, polarization, and spatial distribution of the incident RF field. In this paper, the field distortion of rubidium vapor cells is investigated, in terms of both field strength distortion and depolarization. Full-wave numerical simulation and analysis are employed to determine general optimization solutions for minimizing such distortion and validated by measuring the E-field vector distribution inside different vapor cells. This work can improve the accuracy of atom-based RF E-field measurements and contributes to the development of related RF quantum sensors.
We investigate a technique for detecting radio frequency (RF) electric fields in a cesium (Cs) vapor cell at room temperature by collecting charges from ionized Rydberg atoms and compare its performance with the established method of electromagnetically induced transparency (EIT). By applying a known RF field, we measure the response from both the electrical (ionization current-based) and optical (EIT-based) readouts. The ionization current-based method yields a sensitivity of 22 μ V m−1 Hz−1/2, while the EIT-based method achieves 3.7 μ V m−1 Hz−1/2. The sensitivity of the ionization current-based method is limited by the 2.2 k Ω resistance between the collection electrodes, attributed to a thin Cs film on the inner surfaces of the vapor cell. Controlling or eliminating the Cs layer can significantly improve the sensitivity of this ionization approach.
A Rydberg atom is a special type of atom characterized by a high principal quantum number. Electric field sensors based on Rydberg atoms have received widespread attention due to their high polarizability. However, there is currently little research on the use of Rydberg atoms for direct current (DC) or low-frequency electric fields, mainly due to the shielding effect of atomic vapor cells in low-frequency electric fields, which makes accurate measurement of the electric fields extremely challenging. In this paper, we construct a Rydberg ladder configuration by using probe laser at 852 nm and coupling laser at 510 nm in a room-temperature cesium vapor cell with integrated electrode plates, thereby enabling the realizing of a Floquet-EIT (electromagnetically induced transparency) spectrum dressed by a radio frequency (RF) field in the presence of a DC electric field. We further study the influence of DC electric field on spectral characteristic. Experimentally, it is observed that when only the RF electric field is applied, the EIT spectrum displays solely even-order sidebands. Furthermore, when both the RF field and the DC electric field are simultaneously present, the first-order sideband signal of the Floquet-EIT is observed. As the intensity of the DC electric field increases, the amplitude of the first-order sideband gradually increases. However, increasing the DC electric field to a sufficient magnitude induces sideband interference, which leads the sideband amplitudes to decrease. Furthermore, increasing the RF frequency can alleviate the interference effects induced by the DC electric field on the first-order sideband. Finally, comparing the relative standard deviation of the sideband amplitudes of the Floquet-EIT spectra with the frequency shifts of the DC-Stark spectra under weak DC electric fields, we find that the measurement accuracy of the former is significantly superior to that of the latter. This work makes use of a Cs atomic vapor cell with an integrated electrode to avoid shielding effects. By observing Floquet-EIT spectra, the response of the spectra to DC electric fields is investigated. This experiment provides novel insights into the quantum sensing measurements of DC and low-frequency electric fields.
The large electric dipole moment of the Rydberg atom allows for strong coupling with weak electric fields, and is widely used in electric field measurements because of its reproducibility, precision and stability. The combination of Rydberg atoms and electromagnetically induced transparency (EIT) technology has been used for detecting and characterizing radio-frequency (RF) electric fields. In this work, by selecting probe light (852 nm), dressed light (1470 nm), and coupled light (780 nm), the Rydberg state (49P3/2) of Cs atom is prepared by using a three-photon excitation scheme through using all-infrared light excitation of Rydberg atoms. We experimentally observe the EIT spectra of the Rydberg states decorated by radio-frequency electric fields, which optically detects Rydberg atoms. The effect of the amplitude and frequency of the RF electric field on the spectrum is explored in light of changes in the EIT spectrum. The results show that in the region of weak electric field, only the ac Stark energy shift and spectral broadening occur. As the electric field is further enhanced, the sideband phenomenon occurs in both the primary peak and secondary peak of the EIT. In the region of strong field, the Rydberg energy level produces a series of Floquet states with higher-order terms, as well as state shifting and mixing, resulting in asymmetry in the spectra of the EIT sideband peaks. The effect of frequency on the shielding effect of the Cs vapor cell is further discussed based on the shift of the main peak of the EIT. The demodulation of the electric field in a range of 50 Hz–1 kHz with a fidelity of 95% is achieved by modulating the low-frequency electric field to the RF electric field. The results can provide valuable references for spectral detection and traceable measurements of low-frequency electric fields.
In Rydberg quantum electric field sensing, the amplitude and linewidth of electromagnetically induced transparency (EIT) spectra significantly impact the accuracy of electric field measurements. This paper discusses the influence of atomic density on the amplitude and linewidth of EIT spectra in a vapor cell within a three-level ladder system driven by two-photon excitation. Due to the adsorption of alkali metal atoms on the inner surface of the vapor cell, the study utilizes light-induced atomic desorption effects to regulate the atomic density using LED light. This approach, combined with probe and coupling lasers, results in the formation of high-amplitude, low-linewidth EIT spectra. Based on the Rydberg atom sensing measurement system constructed in this study, when the number of atoms per cubic meter is less than 1.5×10 24 , a decrease in the optical depth at the bottom of the EIT leads to a reduction in amplitude and an increase in linewidth. When the number of atoms per cubic meter exceeds 4×10 24 , a decrease in the peak value at the top of the EIT results in a reduction in amplitude, with a slight decrease in linewidth. By adjusting the atomic density within the vapor cell through the power of desorption light and optimizing the laser Rabi frequency parameters, the atomic number density is maintained between 1.5×10 24 and 4×10 24 per cubic meter, yielding high-amplitude, low-linewidth EIT spectra. Additionally, the influence of introducing 365 nm desorption light on the accuracy of the constructed electric field measurement system is analyzed and corrected.
Significant progress has been made in atom-based measurements of length, time, gravity and electromagnetic fields in recently years. Rydberg atom-based microwave electric field measurement, using electromagnetically induced transparency (EIT) in room temperature alkali-metal vapors, has been extensively investigated and aroused the broad interest. This approach may establish a new standard for the measurements of microwave (MW) and radio frequency (RF) electric fields.In this review, we describe the work on a new method of measuring electric fields based on quantum interference by using either cesium or rubidium atoms contained in a dielectric vapor cell. Rydberg atoms with principal quantum number n >>1 have large direct current (DC) polarizabilities and microwave transition dipole moments, thereby making them extremely sensitive to external electric fields. Using the Rydberg three-level EIT to detect the level splitting and shift that is induced by the external field, we can realize a rapid and robust self-calibration method of measuring the electric field in a frequency range from 0.01 GHz to 1000 GHz. For the MW electric field (frequency range > 1 GHz), the MW field causes the Rydberg states to split, known as an Autler-Townes splitting (A-T) effect when the applied microwave can resonate with adjacent Rydberg states. The MW coupled A-T splitting is proportional to the applied electric field strength, from which the field strength is measured. Using the EIT window, a high sensitivity of 3 μV·cm-1·Hz-1/2 and small electric field of 1 μV/cm are expected to be achieved with a modest setup, and the limitations of the sensitivity are also addressed in the review. For the RF field at frequency mj EIT lines, and avoided crossings formed with the fine-structure levels of equal mj and different J's, which is used to calibrate and measure the RF field amplitude. On the other hand, the dependence of the EIT-line strength on the RF field polarization provides a fast and robust polarization measurement of RF fields based on matching experimental data with a theoretical simulation. The measurements of minimum strengths and sensitivity of RF fields based on Rydberg atoms are one order magnitude below the values obtained by traditional antenna methods. The atom-based field measurement paves the way for determining fields through calibration-free, invariable atomic properties and miniaturization. We also propose its various potential applications in the future.