The atomic-vapor cell is a vital component for Rydberg atomic microwave sensors, and impacts on overall capability of Rydberg sensors. However, the conventional analysis approach on effect of vapor-cell length contains two implicit assumptions, that is, the same atomic population density and buffer gas pressure, which make it unable to accurately capture actual response about effect of Rydberg-atom-based sensor performance on different Rydberg atom populations. Here, utilizing a stepped cesium atomic-vapor cell with five different dimensions at the same atomic population density and buffer gas pressure, the height and full width at half maximum of electromagnetically induced transparency (EIT) signal, and the sensitivity of the atomic superheterodyne sensor are comprehensively investigated under conditions of the same Rabi frequencies (saturated laser power). It is identified that EIT signal height is proportional to the cell length, full width at half maximum and sensitivity grow with the increment of cell length to a certain extent. Employing the coherent integration signal theory and atomic linear expansion coefficient method, theoretical analysis of the EIT height and sensitivity are further investigated. The results could shed new light on understanding and design of ultrahigh-sensitivity Rydberg atomic microwave sensors and find promising applications in quantum measurement, communication, and imaging.
The atomic-vapor cell is a vital component for Rydberg atomic microwave sensors, and impacts on overall capability of Rydberg sensors. However, the conventional analysis approach on effect of vapor-cell length contains two implicit assumptions, that is, the same atomic population density and buffer gas pressure, which make it unable to accurately capture actual response about effect of Rydberg-atom-based sensor performance on different Rydberg atom populations. Here, utilizing a stepped cesium atomic-vapor cell with five different dimensions at the same atomic population density and buffer gas pressure, the height and full width at half maximum of electromagnetically induced transparency (EIT) signal, and the sensitivity of the atomic superheterodyne sensor are comprehensively investigated under conditions of the same Rabi frequencies (saturated laser power). It is identified that EIT signal height is proportional to the cell length, full width at half maximum and sensitivity grow with the increment of cell length to a certain extent. Employing the coherent integration signal theory and atomic linear expansion coefficient method, theoretical analysis of the EIT height and sensitivity are further investigated. The results could shed new light on understanding and design of ultrahigh-sensitivity Rydberg atomic microwave sensors and find promising applications in quantum measurement, communication, and imaging.
The atomic-vapor cell is a vital component for Rydberg atomic microwave sensors, and impacts on overall capability of Rydberg sensor. However, the conventional analysis approach on effect of vapor-cell length contains two implicit assumptions, that is, the same atomic population density and buffer gas pressure, which make it unable to accurately capture actual response about effect of Rydberg-atom-based sensor performance on different Rydberg atom population. Here, utilizing a stepped cesium atomic-vapor cell with five different dimensions at the same atomic population density and buffer gas pressure, the height and full width at half maximum of Electromagnetically Induced Transparency(EIT) signal, and the sensitivity of the atomic superheterodyne sensor are comprehensively investigated at the same Rabi frequences(saturated laser power) conditions. It is identified that EIT signal height is proportional to the cell length, full width at half maximum and sensitivity grow with the increment of cell length to a certain extent. Based on the coherent integration signal theory and atomic linear expansion coefficient method, theoretical analysis of the EIT height and sensitivity are further investigated. The results could shed new light on the understanding and design of ultrahigh-sensitivity Rydberg atomic microwave sensors and find promising applications in quantum measurement, communication, and imaging.
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.
Rydberg atom based sensors allow for SI traceable measurements and show promise for applications in the field of communication and radar technologies. In this article, we investigate the bandwidth and sensitivity of a Rydberg atom-based sensor in a rubidium vapor cell using Rydberg electromagnetically induced transparency (EIT) spectroscopy. We employ a radio-frequency (RF) heterodyne measurement technique in combination with an optical homodyne setup to extend the achievable range between sensitivity and bandwidth in a Rydberg sensor. While the bandwidth of Rydberg sensors are limited by the transit time of atoms and the Rabi frequency of the coupling field, achieving higher bandwidth through smaller beam sizes is thought to compromise sensitivity due to reduced EIT signal strength. Using optical homodyne detection, we demonstrate that sensitivity is preserved while achieving a response bandwidth of 8 MHz. In addition, using the Rydberg sensor, we receive digital communication signals and present error vector magnitude (EVM) measurements as a function of varying symbol rates and bandwidth of the Rydberg sensor. Furthermore, the sensor's performance is compared with a conventional RF mixer. We establish that the bandwidth of a Rydberg sensor when receiving a pure tone is not the same as the bandwidth of the sensor when receiving a modulated signal. This difference results from the spreading of symbols in the frequency domain, leading to a reduction of the signal to noise ratio (SNR) and an accumulation of noise over the total span of the modulated signal.
Quantum microwave measurement techniques based on Rydberg atoms exhibit exceptional potential in microwave communication, sub-wavelength imaging and quantum metrology, due to the inherent advantages of self-calibration, minimal interference with external electric fields, and a broadband range of measurable frequencies. However, the current measurement sensitivity is not yet comparable to that of classical receivers. One contributing factor is the low utilization of atoms within the vapor cell, which remains a significant challenge to enhance substantially. To address this problem, scholars have proposed a variety of optical domain methods to enhance sensitivity. For example, increasing vapor cell length, utilizing multi-photons excitation or repump lasers. Despite these advancements, the study of the influence of laser beam diameter on the sensitivity is insufficient, and the lack of a comprehensive experimental investigation is not conducive to the practical application and optimization of the receiver. In this study, we investigate the impact of varying probe laser diameters on receiver sensitivity using a beam expander to adjust the diameter from 600 μm to 3 mm. Modifying the beam diameter could alter the light-atom interaction area in the vapor cell, offering a feasible approach to adjust the utilization of the atoms. Our findings indicate that under the experimental conditions, the sensitivity could be enhanced by expanding the beam diameter, where the sensitivity is changed from 299 nV cm-1 Hz-1/2 to 127 nV cm-1 Hz-1/2. These results could provide valuable insights for designing and optimizing ultrahigh-sensitivity Rydberg atomic receivers and facilitating applications in meteorology, communication, and quantum precision measurement.
Engineered, metamaterial vapor cells are useful for high-sensitivity Rydberg atom-based radio frequency (RF) sensors. We present recent advancements on a photonic crystal receiver (PCR) fabricated using MEMS technology for sensitive RF field detection. Beyond the established operational principles leveraging electromagnetically induced transparency (EIT) within alkali atom ensembles, we describe critical factors impacting the performance of the PCR, namely the generation of electric fields arising from Cesium atom interactions with the vapor cell materials. Through X-ray Photoelectron Spectroscopy (XPS) analysis of the glass and silicon components, we determine the amount of Cesium that is adsorbed to the glass and silicon surfaces. The insights into surface adsorption and its control are crucial for improving the stability and practical applicability of PCR-based RF sensors, as well as other types of MEMS vapor cells.
Abstract Rydberg atom-based sensors use atoms dressed by lasers to detect and measure radio frequency electromagnetic fields. The absorptive properties of the atomic gas, configured as a Rydberg atom-based sensor, change in the presence of a radio frequency electromagnetic field. While these sensors are reasonably sensitive, the best conventional radio frequency sensors still outperform Rydberg atom-based sensors with respect to sensitivity. One approach to increase the sensitivity of Rydberg atom-based sensors is to engineer the vapor cell that contains the atomic gas. In this work, we introduce a passive, all-dielectric amplifier integrated into a Rydberg atom-based sensor vapor cell. The vapor cell is a combination of a slot waveguide and a photonic crystal. The structural features of the vapor cell yield a power amplification of ~ 24 dB. The radio frequency electromagnetic field is coupled adiabatically into the slot waveguide and slowed to increase the interaction between the radio frequency field and the atoms to effectively amplify the incoming signal, i.e., increase the Rabi frequency on the radio frequency transition. The work shows the utility of vapor cell engineering for atom-based quantum technologies and paves the way for other such devices.