Rydberg-atom antennas have the remarkable advantages of non-destructive and high sensitivity for RF telecommunications. However, current implementations are carried out on the optical platform of the laboratory, which exhibits low levels of equipment miniaturization and lacks mobility and integration for movement from the laboratory to outdoor testing. This article proposes a portable atomic antenna with a waveguide-integrated metallic mesh resonator (MMR) to synergize these methods, aiming for system integration and improving sensitivity for deep-space exploration applications. We developed modular 852 nm and 509 nm fiber systems, laser frequency locking architecture. Thus, a portable atomic antenna is realized with a smaller volume (0.1 × 0.25 × 0.3 m3), lighter weight (26 kg), and narrow probe laser linewidth (5.4 kHz). Experimental investigations were conducted at 8.3 GHz using a vapor cell in the resonators. Spectral measurements indicate that the MMR provides enhancement factors of 24.5 dB. The MMR achieves continuous frequency reconfiguration across 7.49-8.78 GHz by mechanical tuning while significantly reducing field distortions compared to traditional pin-based tuning systems. When MMR was used for Rydberg atomic heterodyning, the sensitivity improved significantly 14:3 nv/cm/√Hz, which is a 24.5 dB improvement in sensitivity than when MMR was not used. This research represents a significant low-SWaP advancement toward the practical application of Rydberg atomic antennas.
Rydberg-atom antennas have the remarkable advantages of non-destructive and high sensitivity for RF telecommunications. However, current implementations are carried out on the optical platform of the laboratory, which exhibits low levels of equipment miniaturization and lacks mobility and integration for movement from the laboratory to outdoor testing. This article proposes a portable atomic antenna with a waveguide-integrated metallic mesh resonator (MMR) to synergize these methods, aiming for system integration and improving sensitivity for deep-space exploration applications. We developed modular 852 nm and 509 nm fiber systems, laser frequency locking architecture. Thus, a portable atomic antenna is realized with a smaller volume (0.1 × 0.25 × 0.3 m3), lighter weight (26 kg), and narrow probe laser linewidth (5.4 kHz). Experimental investigations were conducted at 8.3 GHz using a vapor cell in the resonators. Spectral measurements indicate that the MMR provides enhancement factors of 24.5 dB. The MMR achieves continuous frequency reconfiguration across 7.49-8.78 GHz by mechanical tuning while significantly reducing field distortions compared to traditional pin-based tuning systems. When MMR was used for Rydberg atomic heterodyning, the sensitivity improved significantly 14:3 nv/cm/√Hz, which is a 24.5 dB improvement in sensitivity than when MMR was not used. This research represents a significant low-SWaP advancement toward the practical application of Rydberg atomic antennas.
Abstract Rydberg atom-based sensors using the atomic heterodyne technique demonstrate prominent performance on sensing sensitivity and thus have significant potential for radar, electronic reconnaissance, and communication applications. Here, we propose a local oscillator (LO) embedded field enhancement resonator to improve the sensitivity and integration of Rydberg atomic heterodyne sensors. In this approach, a vapor cell filled with cesium atoms is placed into the resonance structure for electric (E) field measurements. By integrating parallel-plate waveguide (PPWG) antennas and the resonator, the LO signal can be directly guided to the resonator using coaxial cable instead of the use of external antennas radiating through free space, allowing for a more flexible and practical Rydberg atom-based heterodyne technique. Based on the off-resonant Rydberg atomic heterodyne approach, for a radio frequency (RF) signal at 638 MHz, it is found that the sensitivity is 43 μ V/cm Hz Hz in the absence of the resonator, while in the presence of our resonator, the sensitivity is down to 854.36 nV/cm Hz Hz , indicating 50 times or 34 dB improvement capacity of the proposed resonator. This type of enhancement resonator is expected to benefit Rydberg atomic heterodyne applications in practical environments.
The Rydberg atomic heterodyne technique and resonant structures represent two prominent approaches that can notably enhance the sensing sensitivity of Rydberg atomic receivers in the atomic and microwave domains, respectively. However, current implementations exhibit low levels of integration, particularly in the VHF band. This article introduces local oscillator (LO) port-integrated resonators (LOIRs) to synergize these methods, aiming to improve sensitivity and system integration in Rydberg atom-based receivers. Through an analysis of the electric field distribution in the split-ring resonator (SRR), we developed two types of LOIRs: the standing wave type LOIR (SIR) and the traveling wave type LOIR (TIR). Experimental investigations were conducted at 264 MHz using a vapor cell containing cesium atoms in the resonators. Spectral measurements indicate that the SIR and TIR provide enhancement factors of 45.8 and 45.3 dB, respectively. When employing the SIR and TIR for Rydberg atomic heterodyning, sensitivity significantly improved to 104.34 and 105.54 (nV/cm)/Hz, respectively. Furthermore, in comparison to the SRR setup in the atomic heterodyne scenario, the LO power consumption decreased to 22.4% and 3.7% with the SIR and TIR, respectively. This research represents a significant advancement toward the practical application of Rydberg atomic receivers.
Abstract Radio frequency antennas based on Rydberg atom vapor cells can in principle reach sensitivities beyond those of any conventional wire antenna, especially at lower frequencies where very long wires are needed to accommodate the increasing wavelength. They also have other desirable features such as consisting of nonmetallic, hence lower profile, elements. This paper presents a detailed theoretical investigation of Rydberg antenna sensitivity, elucidating parameter regimes that could cumulatively lead to a sensitivity increase 2–3 orders of magnitude beyond that of currently tested configurations. The key insight is to optimally combine the advantages of two well-studied approaches: (i) three laser ‘2D star configuration’ setups that, when enhanced with increased laser power, to some degree compensate for atom motion-induced Doppler broadening, and (ii) resonant coupling between a pair of near-degenerate Rydberg levels, tuned via a local oscillator to the incident signal of interest. The advantage of the star setup is subtle because it only restores the overall sensitivity to the expected Doppler-limited value, compensating for additional significant off-resonance reductions where differently moving atom sub-populations destructively interfere with each other in the net signal. An additional unique advantage of local oscillator tuning is that it leads to vastly narrower line widths, as low as ∼10 kHz set by the intrinsic Rydberg state lifetimes, rather than the typical ∼10 MHz scale set by the core state lifetimes. Intuitively, with this setup the two Rydberg states may be tuned to act as an independent high-q cavity, a point of view supported by a study of the frequency-dependence of the antenna resonant response. There are a number of practical experimental advances, especially larger ∼1 cm laser beam widths, required to suppress various extrinsic line broadening effects and to fully exploit this ‘Rydberg superheterodyne’ response.
Highly sensitive detection of VHF band fields poses a challenge for Rydberg atomic sensing since resonant detection requires exciting atoms to extremely high energy states. We demonstrate a PCB-based electrically tunable resonator (PETR) for enhancing the sensing sensitivity of the Rydberg atomic sensor to VHF band fields. In this approach, the sub-wavelength PETR is made of PCB, which offers improved mechanical strength and miniaturization. During the measurements, a parallel-plate waveguide is utilized as the radio frequency (RF) fields launcher to eliminate unintentional scattering from the surroundings. By adjusting the bias voltage applied to the tuning varactor of the PETR, we can continuously tune the resonant frequencies from 187 MHz to 293.6 MHz, corresponding to a relative bandwidth of 44%. There is a fluctuation in the enhancement factor of the PETR, ranging from 17.6 to 60.1, which is primarily caused by misalignment between the laser beam and the resonant area. Furthermore, employing the off-resonant Rydberg atomic heterodyne technique, we investigated the sensitivity of the system. In the absence of the PETR, the sensitivity for a RF signal at 250.5 MHz was found to be 24.36 μV/cm√Hz. However, with the presence of our PETR, the sensitivity significantly improved to 433.26 nV/cm√Hz, indicating a remarkable enhancement capacity of 56.23 times or 35 dB. This enhancement resonator holds great potential for improving Rydberg atomic sensing, particularly in the VHF band.
High-sensitivity amplitude and frequency detection of microwave electric fields is of significant importance in various fields, including communications, microwave quantum technology, aerospace, medicine, and meteorology. Rydberg atom-based sensors promise traceable standards and high sensitivity for detecting weak electric fields and enhancing sensing sensitivity, mainly by using superheterodyne technology and resonant structures. Detecting high-frequency (HF) band fields with high sensitivity using Rydberg atom sensors is a significant challenge due to the requirement of exciting atoms to extremely high energy states for resonant detection. We demonstrate the off-resonant Rydberg atomic superheterodyne architecture with additional resonators for greatly enhancing the sensing sensitivity to HF band fields. In this approach, we propose a miniaturized square spiral resonator with an electrical size of$0.011~\lambda $at 15.54 MHz. To reduce the electric-field-screening effect of the adsorption of alkali metal atoms, we use a monocrystalline sapphire cesium (Cs) vapor cell. By utilizing the off-resonant alternating current (ac) Stark effect, the initial sensitivity of the Rydberg atom sensor without the resonator is measured to be10.39μV/cmHzat room temperature. With the addition of the miniaturized square spiral resonator, the sensitivity significantly improved to2.60nV/cmHz, which has been inaccessible so far with atomic sensors. Here, we provide an enhancement of 72 dB, which is three orders of magnitude improvement in sensitivity than when the resonator is not used. This enhancement resonator extends Rydberg atomic high-sensitivity sensing to the HF band and shows great potential, especially in shortwave radio reception.
In this article, we propose a new paradigm of room-temperature Rydberg atomic receiver for high frequency (HF) band sensing with high sensitivity. The proposed Rydberg atomic HF band receiver is implemented via a multilayered split-ring resonator (MSRR) and an atomic vapor cell. The MSRR is constructed by a five-layered printed circuit board within a deep-subwavelength size, providing a strongly enhanced electric field of the incident radio-frequency (RF) field. Using a quantum-optical readout of AC level shifts of field-sensitive atomic Rydberg states, the enhanced intra-cavity RF field significantly improves the sensitivity of the atomic receiver. In the measurement, we characterize the AC-stark shift in the frequency and power spectrum of the incident RF field. Furthermore, the sensitivity of the whole system is presented by utilizing the off-resonant Rydberg atomic heterodyne technique. In the absence of the MSRR, the sensitivity for an RF signal at 20.51 MHz was found to be 27.46 μV/cm √Hz. However, with the presence of our MSRR, the sensitivity significantly improved to 29.09 nV/cm √Hz, indicating a remarkable enhancement capacity of 944 times or 60 dB. This research holds great potential for high-sensitivity Rydberg atomic sensing, particularly in the HF band.