We report a scheme for enhancing microwave electric field measurement by cavity-assisted Rydberg electromagnetically induced transparency in the 87Rb coherent atomic system. The vacuum Rabi splitting appears when the probe field is strongly coupled with intracavity atoms. The cavity-assisted electromagnetically induced transparency with dual-peak profile is observed as a strong coupling laser is further introduced into the optical ring cavity. The optimal atomic density, resulting in an appropriate vacuum Rabi splitting interval and cavity-assisted electromagnetically induced transparency amplitude, is determined for the coupling effect criterion of the probe field and intracavity atoms. Finally, the cavity-assisted electromagnetically induced transparency is employed to accurately measure the microwave electric field strength, and a measurement sensitivity factor of about 2 is improved owing to an enhanced photon–atom interaction. This study is beneficial for the development of compact, broadband, and self-calibrating microwave receivers.
We report a scheme for enhancing microwave electric field measurement by cavity-assisted Rydberg electromagnetically induced transparency in the 87Rb coherent atomic system. The vacuum Rabi splitting appears when the probe field is strongly coupled with intracavity atoms. The cavity-assisted electromagnetically induced transparency with dual-peak profile is observed as a strong coupling laser is further introduced into the optical ring cavity. The optimal atomic density, resulting in an appropriate vacuum Rabi splitting interval and cavity-assisted electromagnetically induced transparency amplitude, is determined for the coupling effect criterion of the probe field and intracavity atoms. Finally, the cavity-assisted electromagnetically induced transparency is employed to accurately measure the microwave electric field strength, and a measurement sensitivity factor of about 2 is improved owing to an enhanced photon–atom interaction. This study is beneficial for the development of compact, broadband, and self-calibrating microwave receivers.
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.
The collective effects of intracavity Rydberg atoms are investigated and proposed to detect microwave (MW) electric (E) fields with collective Rabi splitting (CRS). When a cavity field drives atoms from ground states to their excited states and a control field further drives them to Rydberg states where a MW field couples Rydberg states, the cavity transmission exhibits a four-peak characteristic, and two side peaks represent the CRS. It is interesting to find that the frequency splitting of CRS changes linearly with the MW-field strength, which can be used to probe MW E-field strength. In the strong coupling regime, the collective effect of Rydberg atoms broadens the CRS peak distance and could improve the detection sensitivity by about 7 times under the given conditions, compared with the common electromagnetically induced transparency scheme. The effects of atomic density and control-field strength on the CRS spectrum are also discussed.
Atom in Rydberg state has large polarizability, large electric dipole and low ionization threshold field. It is very sensitive to electric field, therefore it can be used to measure the amplitude of electric field, especially the microwave electric field. The new developed scheme is based on quantum interference effects (electromagnetically induced transparency and Autler-Townes splitting) in Rydberg atoms. Instead of the direct amplitude measurement, this method tests the Rabi frequency value of the transmission spectrum which is determined by the microwave electric field strength and the corresponding atom nature. The minimum measured strengths of microwave electric fields are far below the standard values obtained by traditional antenna methods. Compared with the traditional methods, this new scheme has several advantages, such as self-calibration, non-perturbation to the measured field and independence of the probe length. Besides, this scheme can also be used to measure the polarization direction of microwave electric field and realize sub-wavelength imaging. Through adjusting the wavelength of coupling laser, a broadband 1-500 GHz microwave electric field measurement can be achieved. This new scheme is benefitial to conducting the continue electric field measurement and the miniaturization of the test equipment. In this paper, the researches about using Rydberg atom to measure electric field with high precision are reviewed. The basic theory and experimental techniques are introduced. Finally, we discuss a promising method of using Rydberg atom interferometer to detect the accumulated phase in the process of interaction between electric field and Rydberg atoms. This method converts amplitude measurement into phase test, which may improve the precision and sensitivity.
The Rydberg-based microwave detection is an all-optical technology that uses the strong coherent interaction between Rydberg atoms and microwave field. Different from the traditional microwave meter, the Rydberg atomic sensing is a new-type microwave detector that transforms the microwave spectrum into a coherent optical spectrum, and arouses increasingly the interests due to its high sensibility. For this kind of sensor, the coherence effect induced by coupling atoms with microwave plays a key role, and the decoherence may reduce the sensitivity. A multi-level Rydberg atomic scheme with optimized quantum coherence, which enhances both the bandwidth and the sensitivity for 4 GHz microwave sensing, is demonstrated experimentally in this work. The enhanced quantum coherence of Rydberg electromagnetically induced transparency (EIT) and microwave induced Autler-Townes (AT) splitting in EIT windows are shown using optical pumping at D1 line. The enhanced sensitivity at 3.4 GHz with 0.3 GHz bandwidth can be realized, based on the enhanced EIT-AT spectrum. The experimental results show that in the stepped Rydberg EIT system, the spectral width of EIT and microwave field EIT-AT can be narrowed by optical pumping (OP), so the sensitivity of microwave electric field measurement can be improved. After optimizing the EIT amplitude and adding single-frequency microwaves, the sensitivity of the microwave electric field measurement observed by the AT splitting interval is improved by 1.3 times. This work provides a reference for utilizing atomic microwave detection.
Abstract We present a mechanism for improving the sensitivity of microwave (MW) electric field (E-field) measurement using dual-MW-dressed electromagnetically induced transparency in a 5 S 1/2 –5 P 3/2 –56 D 5/2 –57 P 3/2 85 Rb atomic coherent system. An auxiliary MW (A-MW) field is introduced into the MW E-field measurement system, which consists of a probe, coupling lasers, and a target MW (T-MW) field. When the A-MW field frequency is tuned to be the same as the T-MW field and its power is adjusted to a suitable range, the T-MW field strength can be read out effectively. Finally, the sensitivity of MW E-field measurement is improved by about two orders of magnitude compared to that without an A-MW field. In addition, this mechanism is proven to be applicable for all frequency bands covered by Rydberg energy levels. This work opens up a novel pathway for the realization of high-sensitivity MW E-field measurement with Rydberg atoms.
The Rydberg-based microwave detection is an all-optical technology that uses the strong coherent interaction between Rydberg atoms and microwave field. Different from the traditional microwave meter, the Rydberg atomic sensing is a new-type microwave detector that transforms the microwave spectrum into a coherent optical spectrum, and arouses increasingly the interests due to its high sensibility. For this kind of sensor, the coherence effect induced by coupling atoms with microwave plays a key role, and the decoherence may reduce the sensitivity. A multi-level Rydberg atomic scheme with optimized quantum coherence, which enhances both the bandwidth and the sensitivity for 4 GHz microwave sensing, is demonstrated experimentally in this work. The enhanced quantum coherence of Rydberg electromagnetically induced transparency (EIT) and microwave induced Autler-Townes (AT) splitting in EIT windows are shown using optical pumping at D1 line. The enhanced sensitivity at 3.4 GHz with 0.3 GHz bandwidth can be realized, based on the enhanced EIT-AT spectrum. The experimental results show that in the stepped Rydberg EIT system, the spectral width of EIT and microwave field EIT-AT can be narrowed by optical pumping (OP), so the sensitivity of microwave electric field measurement can be improved. After optimizing the EIT amplitude and adding single-frequency microwaves, the sensitivity of the microwave electric field measurement observed by the AT splitting interval is improved by 1.3 times. This work provides a reference for utilizing atomic microwave detection.