Abstract The electromagnetically induced transparency (EIT) profile is utilized to measure the strength of the microwave (MW) frequency magnetic field in a closed lambda system (CLS). In this system, two laser fields couple a common excited state to two ground states via electric dipole-allowed transitions, while the MW magnetic field induces a transition between the ground states through magnetic dipole interactions. The strength of this interaction is characterized by the EIT profile of the probe beam, mediated by atomic vapor. Key parameters, including the EIT profile and its full width at half maximum (FWHM), are employed to determine MW magnetic field strength at frequencies of 3.036 GHz and 6.835 GHz. Analytical models predict sensitivity to the magnetic field strength (B μ ) down to approximately 35 femtotesla (fT), even in the absence of Zeeman splitting.
Abstract The electromagnetically induced transparency (EIT) profile is utilized to measure the strength of the microwave (MW) frequency magnetic field in a closed lambda system (CLS). In this system, two laser fields couple a common excited state to two ground states via electric dipole-allowed transitions, while the MW magnetic field induces a transition between the ground states through magnetic dipole interactions. The strength of this interaction is characterized by the EIT profile of the probe beam, mediated by atomic vapor. Key parameters, including the EIT profile and its full width at half maximum (FWHM), are employed to determine MW magnetic field strength at frequencies of 3.036 GHz and 6.835 GHz. Analytical models predict sensitivity to the magnetic field strength (B μ ) down to approximately 35 femtotesla (fT), even in the absence of Zeeman splitting.
We have investigated some possibilities to use effect of Electromagnetically Induced Transparency (EIT), which is based on quantum interference, for measuring magnetic fields. Multi-frequency laser light is driving atomic transitions (e.g. in a Λ-type excitation scheme), and the atoms are decaying into a super positional dark state, in which the population is trapped, if the frequencies of the applied light fulfills certain conditions. Then the atomic medium becomes transparent for the exciting electromagnetic fields. The observed line width of this "transparency window" is not limited by the natural line width of the involved optical transitions and can be decreased down to a few hundredths of Hertz. As a consequence, this narrow feature can be used as a sensitive probe if the frequencies fulfill the required conditions, which are dependent on the energy positions of the involved atomic levels. These energy positions are influenced by external magnetic fields, thus the observation of EIT can be used to determine external magnetic fields strengths. In our approach a so called Hanle-configuration is used, where only one laser frequency is used to simultaneously excite σ+- and σ--transitions within a single hyperfine transition of the Rb87 Dl-line. In this configuration a resonant Λ-system is formed at zero magnetic field. The detuning from two-photon resonance is caused by a magnetic field scanned in laser propagation direction. Any additional probe magnetic field characteristically changes the width and shape of the EIT transparency window resonance; hence the probe magnetic field can be determined directly from the shape of this resonance.
Abstract A scheme for measuring microwave (MW) electric (E) fields is proposed based on bichromatic electromagnetically induced transparency (EIT) in Rydberg atoms. A bichromatic control field drives the excited state transition, whose absorption shows three EIT windows. When a MW field drives the Rydberg transition, the EIT windows split and six transmission peaks appear. It is interesting to find that the peak-to-peak distance of transmission spectrum is sensitive to the MW field strength, which can be used to measure MW E-field. Simulation results show that the measurement accuracy could be increased by about 4 times, and the minimum detectable strength of the MW E-field may be improved by about 3 times compared with the common EIT scheme. After the Doppler averaging, the minimum detectable MW E-field strength is about 5 times larger than that without Doppler effect. Also, we investigate other effects on the sensitivity of the system.
We present an atom-based approach for determining microwave electric and magnetic fields by using a single rubidium vapor cell in a microwave waveguide. For a 87Rb cascade three-level system employed in our experiment, a weak probe laser driving the lower transition, 5S1/2→5P3/2, is first used to measure the microwave magnetic field based on the atomic Rabi resonance. When a counter-propagating strong coupling laser is subsequently turned on to drive the Rydberg transition, 5P3/2→67D5/2, the same probe laser is then used as a Rydberg electromagnetically induced transparency (EIT) probe to measure the microwave electric field by investigating the resonant microwave dressed Autler-Townes splitting (ATS). By tuning the hyperfine transition frequency of the ground state using an experimentally feasible static magnetic field, we first achieved a measurement of the microwave electric and magnetic field strength at the same microwave frequency of 6.916 GHz. Based on the ideal relationship between the electric and magnetic field components, we obtained the equivalent microwave magnetic fields by fitting the inversion to the measured microwave electric fields, which demonstrated that the results were in agreement with the experimental measurement of the microwave magnetic fields in the same microwave power range. This study provides new experimental evidence for quantum-based microwave measurements of electric and magnetic fields by a single sensor in the same system.
Abstract Quantum electrometric sensing properties of a four-level system are theoretically investigated for microwave (MW) field measurement in thermal Rydberg atoms. In the considered system, the phenomenon of electromagnetically induced transparency (EIT) is invoked to study the impact of microwave (MW) field strength on its optical response. The amplitude of the MW electric field is obtained directly by measuring the height and frequency of EIT peaks. Further, for MW frequency measurement, the probe spectra are examined for red and blue MW detuned cases. It is found that the responsiveness of 133Cs for MW electric field as well as frequency is relatively higher than 87Rb. The overall sensitivity of both these atoms can be enhanced by the convenient setting of the system and field parameters.
Significant progress has been made in atom-based measurements of length, time, gravity and electromagnetic fields in recently years. Rydberg atom-based microwave electric field measurement, using electromagnetically induced transparency (EIT) in room temperature alkali-metal vapors, has been extensively investigated and aroused the broad interest. This approach may establish a new standard for the measurements of microwave (MW) and radio frequency (RF) electric fields.In this review, we describe the work on a new method of measuring electric fields based on quantum interference by using either cesium or rubidium atoms contained in a dielectric vapor cell. Rydberg atoms with principal quantum number n >>1 have large direct current (DC) polarizabilities and microwave transition dipole moments, thereby making them extremely sensitive to external electric fields. Using the Rydberg three-level EIT to detect the level splitting and shift that is induced by the external field, we can realize a rapid and robust self-calibration method of measuring the electric field in a frequency range from 0.01 GHz to 1000 GHz. For the MW electric field (frequency range > 1 GHz), the MW field causes the Rydberg states to split, known as an Autler-Townes splitting (A-T) effect when the applied microwave can resonate with adjacent Rydberg states. The MW coupled A-T splitting is proportional to the applied electric field strength, from which the field strength is measured. Using the EIT window, a high sensitivity of 3 μV·cm-1·Hz-1/2 and small electric field of 1 μV/cm are expected to be achieved with a modest setup, and the limitations of the sensitivity are also addressed in the review. For the RF field at frequency mj EIT lines, and avoided crossings formed with the fine-structure levels of equal mj and different J's, which is used to calibrate and measure the RF field amplitude. On the other hand, the dependence of the EIT-line strength on the RF field polarization provides a fast and robust polarization measurement of RF fields based on matching experimental data with a theoretical simulation. The measurements of minimum strengths and sensitivity of RF fields based on Rydberg atoms are one order magnitude below the values obtained by traditional antenna methods. The atom-based field measurement paves the way for determining fields through calibration-free, invariable atomic properties and miniaturization. We also propose its various potential applications in the future.
We propose a technique for frequency locking a laser to the Zeeman sublevel transitions between the 5P3/2 intermediate and 32D5/2 Rydberg states in 87Rb. This method allows for continuous frequency tuning over 0.6 GHz by varying an applied external magnetic field. In the presence of the applied field, the electromagnetically induced transparency (EIT) spectrum of an atomic vapor splits via the Zeeman effect according to the strength of the magnetic field and the polarization of the pump and probe lasers. We show that the 480 nm pump laser, responsible for transitions between the Zeeman sublevels of the intermediate state and the Rydberg state, can be locked to the Zeeman-split EIT peaks. The short-term frequency stability of the laser lock is 0.15 MHz, and the long-term stability is within 0.5 MHz. The linewidth of the laser lock is ∼0.8 and ∼1.8 MHz in the presence and absence of the external magnetic field, respectively. In addition, we show that in the absence of an applied magnetic field and adequate shielding, the frequency shift of the lock point has a peak-to-peak variation of 1.6 MHz depending on the polarization of the pump field, while when locked to Zeeman sublevels, this variation is reduced to 0.6 MHz. The proposed technique is useful for research involving Rydberg atoms, where large continuous tuning of the laser frequency with stable locking is required.