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Optics Letters

Highly sensitive Rydberg atom-based terahertz heterodyne receiver enabled by array-beam excitation

Renhao Xing, Yue-Xiao Yan, Fang Hong-Hua

Published Feb 25, 2026• 1 citation
Publisher

Abstract

Rydberg atom-based precision terahertz (THz) metrology has advanced rapidly in recent years. However, its electric-field sensitivity remains significantly lower than that of state-of-the-art THz receivers, thereby limiting its potential for practical applications. In this work, we enhance the sensitivity of a Rydberg atom-based THz heterodyne receiver at 0.3 THz by employing a 3 × 3 laser-beam array, yielding a 7.6 dB improvement over a single-beam configuration. The achieved electric-field sensitivity reaches 35.8±1.4 n V c m −1 H z −1/2 , approaching the performance of an ideal λ/2 metallic antenna. A minimum-detectable power of −149 dBm is achieved at a 1-Hz bandwidth. Our results suggest a promising approach for future THz radar and communication applications.

DOI
10.1364/ol.583994

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Rydberg atom-based precision terahertz (THz) metrology has advanced rapidly in recent years. However, its electric-field sensitivity remains significantly lower than that of state-of-the-art THz receivers, thereby limiting its potential for practical applications. In this work, we enhance the sensitivity of a Rydberg atom-based THz heterodyne receiver at 0.3 THz by employing a 3 × 3 laser-beam array, yielding a 7.6 dB improvement over a single-beam configuration. The achieved electric-field sensitivity reaches 35.8±1.4 n V c m −1 H z −1/2 , approaching the performance of an ideal λ/2 metallic antenna. A minimum-detectable power of −149 dBm is achieved at a 1-Hz bandwidth. Our results suggest a promising approach for future THz radar and communication applications.
Abstract Terahertz heterodyne receivers with high sensitivity and spectral resolution are crucial for various applications. Here, we present a room-temperature atomic terahertz heterodyne receiver that achieves ultrahigh sensitivity and frequency resolution. At a signal frequency of 338.7 GHz, we obtain a sensitivity of 2.88 ± 0.09 μV⋅cm −1 ⋅Hz −1/2 for electric field measurements. The calibrated linear dynamical range spans approximately 89 dB, ranging from −110 dBV/cm to −21 dBV/cm. We demodulate a 400 symbol stream encoded in 4-state phase-shift keying, demonstrating excellent phase detection capability. By scanning the frequency of the local oscillator, we realize a terahertz spectrometer with Hz level frequency resolution. This resolution is more than two orders of magnitude higher than that of existing terahertz spectrometers. The demonstrated terahertz heterodyne receiver holds promising potential for working across the entire terahertz spectrum, significantly advancing its practical applications.
Broadband and sensitive terahertz (THz) detectors are essential for advancing applications in THz technology. Rydberg atoms were proven to be a promising THz detector, but its detection bandwidth and sensitivity still remain challenging. In this paper, a four-level cesium Rydberg atom system was designed, and it can be operated using electromagnetically induced transparency (EIT). Above all, a high-performance THz detection scheme was demonstrated by introducing frequency detuning of the THz wave relative to the atomic resonance and analyzing the asymmetric splitting between the EIT main peak and the off-resonant Autler–Townes (AT) peak. This method exploits the linear dependence of Rydberg eigenfrequencies on THz detuning and allows us to resolve weak THz electric fields even in the nonlinear regime. Furthermore, the probe laser power was found to influence the EIT signal, with low power producing a narrow but weak signal and high power yielding a stronger yet broader signal; therefore, under a probe power of 20 μW, a minimum detectable field of 2.43 V/m at 108.9 GHz was achieved, while a probe power of 500 μW allowed the detection bandwidth to be extended to 14 GHz. That means that the sensitivity was improved by 50% and the bandwidth was improved by three orders compared with the conventional EIT–AT method. Theoretical modeling results based on the Lindblad master equation are consistent with the experimental results. This frequency-detuning-based strategy offers a physically traceable and scalable approach to advancing quantum-enhanced THz sensing under ambient conditions.
As terahertz (THz) technology rapidly develops, room temperature THz detectors with high sensitivity and wide bandwidth are urgently required. Rydberg atoms are very sensitive to external electric fields, and offer a promising approach for THz detection with exceptional sensitivity. In this paper, we propose a method for measuring the THz field with the frequency of 0.17 THz using 85Rb Rydberg atoms. By analyzing the probe laser transmission spectrum and atomic population, the electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting effect are explained by the presence and splitting of the Rydberg dark states; the THz field, coupling laser and probe laser play a crucial role in the EIT signal; and the EIT spectral transmission will increase when the atomic population of the excited state decreases. Moreover, a method was demonstrated to improve the THz detection sensitivity by changing the eigenfrequencies of the Rydberg dark states with THz detuning. This work finds the relationship between EIT-AT effect and atomic population of Rydberg atoms caused by THz wave and provides what we believe to be a new method to improve the detection efficiency.
Rydberg atoms have great potential in electric field measurement and have an advantage with a large frequency bandwidth from the kHz to the THz scale. However, the sensitivity for measuring a weak MHz electric field signal is limited by the spectroscopic resolution, because the weak electric field induces only a small perturbation of the population and energy-level shift of the Rydberg atoms. Here, we report highly sensitive measurement of a weak MHz electric field using electromagnetically induced transparency with Rydberg atoms in a thermal atomic system. Using the heterodyne method on a 30-MHz electric field, we successfully measure the minimum electric field strength to be $37.3\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{V}/\mathrm{cm}$ with a sensitivity up to $\ensuremath{-}65$ dBm/Hz and a linear dynamic range over 65 dB. Additionally, we measure an amplitude-modulated signal and demodulate the signal with a fidelity over 98%. This work extends the sensitivity of atomic sensors for measuring MHz electric fields, which advances atomic electric field-sensing technology.
With the rapid advancement of terahertz (THz) technology, there is an urgent demand for highly sensitive, broadband THz detectors that can operate at room temperature to support the evolving applications. Due to the high sensitivity of Rydberg atoms to external electric fields, detectors based on Rydberg quantum coherence offer great potential for highperformance THz detection. This paper proposed a ambient temperature electrometry approach for THz detection using probe laser spectroscopy of Rb Rydberg atoms and carry out a comprehensive study of a four-level system involving electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting in Rb cascades. By solving the Lindblad master equation, the influences of the THz electric field, probe laser, and coupling laser on the populations of the ground and Rydberg states were analyzed. Furthermore, the effects of temperature and vapor cell dimensions on the Rb atomic density are examined, revealing their critical impact on detection sensitivity. The results predict that the proposed quantum coherence based THz detection method can achieve a sensitivity as low as 10−9^{-9}−9V/m/Hz1/2^{1/2}1/2at ambient temperature. This paper provides a solid theoretical foundation for the implementation and optimization of Rydbergatom- based quantum coherence techniques for high-sensitivity, ambient temperature THz wave detection.
Realization of practical terahertz wireless communications still faces many challenges. The receiver with high sensitivity is important for THz wireless communications. Here we demonstrate a terahertz receiver based on the cesium Rydberg atoms in a room-temperature vapor cell. The minimum detectable THz electric field is calibrated. With this receiver, the phase-sensitive conversion of amplitude-modulated or frequency-modulated terahertz waves into optical signals is performed. The results show that the atomic receiver has many advantages due to its quantum properties. Particularly, the long distance THz wireless communications is achievable using this receiver. Furthermore, the atomic receiver can be used in the THz wireless-to-optical link.