Introduction: Rydberg atoms are ideal for measuring electric fields due to their unique physical properties. However, low-frequency electric fields below MHz can be challenging due to the accumulation of ionized free electrons on the atomic vapor cell’s surface, acting as a shield. Method: This paper proposes a Cavity-enhanced three-photon system (CETPS) measurement scheme, which uses a long-wavelength laser to excite the Rydberg state, reducing atomic ionization and enhancing detection spectrum resolution. A theoretical model is proposed to explain the quantum coherence effect of the light field, measured electric field, and the atomic system. Result: The results show that the proposed scheme significantly increases the electromagnetically induced transparency (EIT) spectral peak and narrows the spectral width, resulting in the maximum slope increasing by more than an order of magnitude. Discussion: The paper also discusses the impact of the Rabi frequency of the two laser fields and the coupling coefficient of the optical cavity on the transmission spectrum amplitude and linewidth, along with the optimal configuration of these parameters in the CEPTS scheme.
Introduction: Rydberg atoms are ideal for measuring electric fields due to their unique physical properties. However, low-frequency electric fields below MHz can be challenging due to the accumulation of ionized free electrons on the atomic vapor cell’s surface, acting as a shield. Method: This paper proposes a Cavity-enhanced three-photon system (CETPS) measurement scheme, which uses a long-wavelength laser to excite the Rydberg state, reducing atomic ionization and enhancing detection spectrum resolution. A theoretical model is proposed to explain the quantum coherence effect of the light field, measured electric field, and the atomic system. Result: The results show that the proposed scheme significantly increases the electromagnetically induced transparency (EIT) spectral peak and narrows the spectral width, resulting in the maximum slope increasing by more than an order of magnitude. Discussion: The paper also discusses the impact of the Rabi frequency of the two laser fields and the coupling coefficient of the optical cavity on the transmission spectrum amplitude and linewidth, along with the optimal configuration of these parameters in the CEPTS scheme.
Rydberg atoms, leveraging their unique properties, have been increasingly investigated and applied in the field of electric field measurement, demonstrating significant advantages. Nevertheless, challenges persist in measuring low-frequency electric fields below kHz, including difficulties in field loading and weak field effects. To address these issues and enable the measurement of weak low-frequency electric fields below kHz, we propose a novel measurement scheme based on a Double-Dark State Three-Photon System (DDSTPS). The proposed scheme overcomes the shielding effect of the glass vapor cell by employing a built-in electrode plate sampling technique and adjusting the electric field loading method. A three-photon double-dark-state system model was established, utilizing an inverted Y-type system structure. This configuration ensures that the dark state generated during the excitation of the atomic ground state is further excited to the intermediate state through photon interactions. The increased population of atoms in the intermediate state significantly enhances the resolution of the transmission spectrum. Compared to conventional two-photon three-level systems, the proposed scheme improves the maximum slope of the electromagnetically induced transparency (EIT) spectral peak by 122.53% and reduces the full width at half maximum (FWHM) of the spectral peak by more than half. When compared to experimental data from two-photon systems, the FWHM is narrowed by a factor of eight, substantially improving the resolution of the EIT spectrum and further advancing the performance of Rydberg atom-based electric field measurements. In addition, this study investigates the response of DDSTPS under low-frequency electric fields and analyzes its optimal operational region.
The high polarizability of Rydberg atoms enables the multi-parameters measurement of electromagnetic fields. In this paper, we report on an atomic antenna based on Rydberg atoms in a room temperature vapor cell. The EIT is a destructive interference spectroscopy with a narrow linewidth and can be used to detect small electric fields through Autler-Townes splitting or Stark shifts. In our experiments, we employ cascade-type two-photon excitation electromagnetically induced transparency (EIT) spectroscopy to measure the shift of the Rydberg energy level. We introduce a low-frequency electric field (~kHz frequency) using a built-in electrode technique in the cesium cell. The interaction between the Rydberg atom and electric field induces the Stark shifts, where the amplitude of the electric field is converted into corresponding two-photon detuning by the EIT effect. Furthermore, the amplitude of the low-frequency electric field is converted into an intensity signal of EIT probe beam. Under weak field conditions, it is an approximate linear relationship between EIT transmission signal and input electric field amplitude, enabling measurement of waveform, amplitude, and frequency. We have demonstrated optical measurements of low-frequency electric field using Rydberg atoms. By increasing the power of probe beam and coupling beam, the EIT can increase the response bandwidth from ~MHz to hundreds of MHz. This provides a scalable approach for measuring high-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.
An enhanced measurement of the microwave electric (MW E) field by using intracavity Rydberg atoms is proposed. Based on electromagnetically induced transparency (EIT), the intracavity atomic system exhibits two EIT windows, resulting in two narrow peaks in the cavity transmission. The peak-to-peak distance is sensitive to MW fields and can be used to probe MW E-field strength. Simulation results show that the detectable minimum strength of the MW fields is nearly eight times smaller than that without a cavity. Due to cavity coupling, the transmission spectrum is greatly narrowed, which improves the measurement resolution substantially. The numerical results show that the spectrum resolution is increased by more than 20 times. Furthermore, the cavity-enhanced measurement scheme seems to be robust against the changes in the control field strength and shows a broadband tunability.
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.
Rydberg atoms are highly excited atoms with large principal quantum number n, big sizes (~n2) and long lifetimes (~n3). Rydberg atoms are very sensitive to an external field due to the large polarizabilities of Rydberg atoms (~n7). Electromagnetically induced transparency (EIT) of Rydberg atom provides an ideal method to detect Rydberg atoms without destroying atoms, and can be used to measure the external direct current and radio frequency (RF) field. In this paper, we study the EIT effect of a cesium ladder-type three-level atom involving Rydberg state exposed to a weak RF field. The ground state (6S1/2), the excited state (6P3/2) and Rydberg state (48D5/2) constitute the Rydberg three-level system, in which the probe laser couples 6S1/2(F=4)6P3/2(F'=5) transition, whereas the coupling laser scans across the 6P3/248D5/2 Rydberg transition. The coupling laser (510 nm laser, propagating in the z-axis direction and linear polarization in the y-axis direction) and the probe laser (852 nm laser, linear polarization in the y-axis direction) counter-propagate through a 50-mm-long cesium vapor cell at room temperature, yielding Rydberg EIT spectra. Rydberg EIT signal is detected as a function of the detuning of the coupling laser. When a weak RF (80 MHz) electric field polarized in the x-axis direction is applied to a pair of electrode plates located on both sides of the cesium cell, the EIT spectrum of Rydberg 48D5/2 shows the Stark splitting and the even order harmonic sidebands. The experimental results are analyzed by using the Floquet theory. The simulation results accord well with the experimentally measured results. Furthermore, we also investigate the influence of the self-ionization effect of Rydberg atom on the Stark spectrum by changing the RF frequency. We put forward a proposal to avoid the effect of ionization by placing electrode plates in the cesium cell. In the weak RF-field domain, mj=5/2 Stark line crosses mj=1/2, 3/2 sidebands, these cross points provide an antenna-free method of accurately calibrating the RF electric field based on Rydberg atoms.