High-precision Rydberg atom EIT spectroscopy has significant application value in studying the interactions between Rydberg atoms, the energy level structure of Rydberg atoms, and the precise measurement of electric fields. Therefore, it is of great importance to study the parameters influencing atomic EIT spectroscopy. In this paper, a theoretical model for the generation of a two-photon three-level EIT spectrum is established, and the influence of the coupling light's Rabi frequency and corresponding power on the EIT spectrum is theoretically explored. The changes in the EIT spectrum's amplitude and FWHM caused by variations in the coupling light power are experimentally verified. Furthermore, the effect of the overlap between the probe light and the coupling light in the atomic vapor cell on the EIT spectrum is investigated. The results show that as the laser power increases, the amplitude of the EIT spectrum first increases and then decreases, while the FWHM increases. The optimal coupling light laser power of 35 mW is determined using the quality factor. A decrease in the overlap of the two lasers leads to a reduction in the EIT spectrum's amplitude. This study provides a reference for selecting coupling light parameters and improving the accuracy of electric field measurements using Rydberg atoms.
High-precision Rydberg atom EIT spectroscopy has significant application value in studying the interactions between Rydberg atoms, the energy level structure of Rydberg atoms, and the precise measurement of electric fields. Therefore, it is of great importance to study the parameters influencing atomic EIT spectroscopy. In this paper, a theoretical model for the generation of a two-photon three-level EIT spectrum is established, and the influence of the coupling light's Rabi frequency and corresponding power on the EIT spectrum is theoretically explored. The changes in the EIT spectrum's amplitude and FWHM caused by variations in the coupling light power are experimentally verified. Furthermore, the effect of the overlap between the probe light and the coupling light in the atomic vapor cell on the EIT spectrum is investigated. The results show that as the laser power increases, the amplitude of the EIT spectrum first increases and then decreases, while the FWHM increases. The optimal coupling light laser power of 35 mW is determined using the quality factor. A decrease in the overlap of the two lasers leads to a reduction in the EIT spectrum's amplitude. This study provides a reference for selecting coupling light parameters and improving the accuracy of electric field measurements using Rydberg atoms.
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.
The interaction between an electric field and the energy levels of Rydberg states results in the Stark effect, which can be used for quantum detection by measuring the frequency shift in electromagnetically induced transparency (EIT) spectra. By using the functional relationship between the frequency shift and the electric field, it is possible to measure the electric field in question. However, the mismatch between the probe laser and the polarization direction of the coupled laser leads to errors in the measurement of the frequency shift, affecting the accurate measurement of the electric field. In this work, the Schrödinger equation is solved by perturbation method to derive the functional relationship between the energy offset and the electric field strength. Then, the functional relationship between the energy offset and the electric field strength is brought into the solution of the density matrix equation, and the influences of the polarization direction of the detected light and coupled light on the EIT-Stark mathematical model are analyzed. Then an internal electrode method is used to prevent shielding effects caused by alkali metal atoms adhering to the surface of the atomic vapor cell, thereby enabling the application of the electric field. The calibration of the Rydberg state polarisation rate is achieved by using a standard source and measuring the frequency shift of the EIT spectrum. Finally, the effects of polarisation mismatch on the measurement results of EIT spectrum and the electric field are verified by modulating the laser polarization direction. The experimental data show that when the polarization directions of the probe laser and coupled laser are parallel to each other, it is the most matched polarization direction for the lasers, the peak value of the EIT spectrum is the largest, and the maximum relative error of the electric field measurement is 1.67%. When the angle between the polarisation directions of the probe light and the coupled light laser is 45°, the laser polarisation mismatch is the most severe, the EIT spectral peak is the lowest and the maximum relative error of the electric field measurement is 10.24%.
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.
Through the cascade excitation of 852-nm continuous-wave (CW) laser and 509-nm nanosecond pulsed laser, the electromagnetically-induced transparency (EIT) spectroscopic signals of ladder-type three-level cesium atoms with Rydberg state are obtained by using a room-temperature cesium vapor cell. The power of 509-nm pulsed laser beam is ~176 W, while the pulse repetition frequency ranges from 300 kHz to 100 MHz and can be continuously adjusted. The laser pulse duration runs from 1 to 100 ns and can be continuously adjusted. The relationship between Rydberg EIT spectroscopic signals and 509-nm nanosecond pulsed laser parameters is investigated experimentally. By changing the pulse repetition frequency and the pulse duration of the 509-nm nanosecond pulsed laser, the comb-like Rydberg atomic spectrum is obtained by using a room-temperature cesium vapor cell. Within a certain range of repetition frequency and pulse duration, the envelope of spectral lines shows a regular pattern, and the spacing between the transmission peaks is consistent with the pulse repetition frequency. By changing the 509-nm laser pulse repetition frequency and pulse duration, atoms with the specific velocity group can be excited to Rydberg state. Reducing the repetition frequency of the 509-nm pulsed coupling laser can further increase the number of atoms in the Rydberg state in comparison with the case of finite velocity group pumping of cesium atoms by a continuous-wave laser. When the repetition frequency of the 509-nm pulsed laser approaches the EIT linewidth, the number of cesium Rydberg atoms can be increased by up to 10 times. In the parameter optimization process, the dynamic characteristics of pulsed excitation in multi-level atoms, as well as the interaction characteristics between arbitrarily shaped laser pulses and multi-level atomic systems, should be considered. Pulsed laser pumping can achieve the interaction between the laser field and atomic group with a specific velocity, and its developed atomic frequency comb spectra can be used for electric and magnetic field measurements. The multi-peak structure of the spectrum can be used to more accurately determine the intensity, frequency, and phase of the microwave electric field by measuring spectral variations. This high-sensitivity and high-resolution measurement capability is crucial for precisely measuring microwave electric fields. The pulsed coupling laser can excite atoms in a specific velocity group to the Rydberg state. High-density Rydberg atoms can improve the signal-to-noise ratio of the measured spectrum, which has potential applications in quantum sensing and quantum measurement based on Rydberg atoms.
Measurement sensitivity is crucial for the practical application of Rydberg atomic microwave superheterodyne receiver systems in communication, radar, and navigation. Based on laser-atom-microwave interaction mechanisms, the influence of laser powers and local-oscillator (LO) microwave field intensity on measurement sensitivity is systematically studied in this paper. Measurement sensitivity is analyzed through electromagnetically induced transparency (EIT) spectral characteristics, specifically EIT amplitude and full-width-half-maximum (FWHM),larger amplitudes and narrower FWHM indicate improved signal-to-noise ratios. For a 60D-state Rydberg atomic system with fixed probe and coupling laser beam waists (800 µm and 875 µm), optimal parameters are determined: probe laser power of 60 µW(Rabi frequency: 2π×7.02 MHz), coupling laser power of 40 mW (Rabi frequency: 2π×0.66 MHz), and LO microwave Rabi frequency of 2π×8.34 MHz. Experimental results demonstrate a 4.6 dB sensitivity enhancement, advancing from −137.5dBm/Hz to −142.1 dBm/Hz at 3.21 GHz microwave field. This improvement is attributed to precise alignment of laser-atom and microwave-atom interactions, bridging the gap toward quantum sensitivity limits.
The spectra of Rydberg atoms are of great significance for studying the energy levels of Rydberg atoms and the interaction between neutral atoms, especially, the high-precision spectra of Rydberg atoms can be used to measure the energy level shifts of Rydberg atoms resulting from the dipole-dipole interactions in room-temperature vapor cells. In this paper we report the preparation of cesium Rydberg states based on the cascaded two-photon excitation of 509 nm laser and 852 nm laser in opposite, and the measurements of the fine structure of cesium Rydberg states. In this experiment, the 509 nm laser is generated by the cavity-enhanced second-harmonic generation from 1018 nm laser with a periodically-poled KTP crystal and has a maximum power of about 1 W, and the 852 nm probe laser is provided by an external-cavity diode laser with a maximum output power of 5 mW and a typical linewidth of 1 MHz. By scanning the frequency of 509 nm coupling laser, it is presented that the Doppler-free spectra based on electromagnetically-induced transparency (EIT) of 509 nm coupling laser and 852 nm probe laser. The velocity-selective EIT spectra are used to study the spectral splitting of 6S1/26P3/257S(D) ladder-type system of cesium Rydberg atoms in a room-temperature vapor cell. The powers of 852 nm probe laser and 509 nm coupling laser are 0.3 upW and 200 mW, respectively. Their waist radii are both approximately 50 m. The intervals of hyperfine splitting of the intermediate state 6P3/2(F'=3, 4, 5) and fine splitting of 57D3/2 and 57D5/2 Rydberg states are measured by a frequency calibrating. Concretely, the velocity-selective spectrum with a radio frequency (RF) modulation of 30 MHz is used as a reference to calibrate the Rydberg fine-structure states in the hot vapor cell, where the RF frequency precision is smaller than a hertz on long time scales and the EIT linewidth is smaller than 13 MHz. The experimental value of the fine structure splitting of 57D3/2 and 57D5/2 Rydberg states is (354.72.5) MHz, that is in consistence with the value of 346.8 MHz calculated by Rydberg-Ritz equation and quantum defects of 57D3/2 and 57D5/2 Rydberg states. The experimental values of hyperfine splitting of intermediate state 6P3/2(F'=3, 4, 5) are also coincident with the theoretical calculated values. The dominant discrepancy existing between the experimental and calculated results may arise from the nonlinear correspondence of the PZT while the 509 nm wavelength cavity is scanned, and the measurement accuracy influenced by the spectral linewidth. The velocity-selective spectroscopy technique can also be used to measure the energy level shifts caused by the interactions of Rydberg atoms.