Optical pumping magnetometer single probe rubidium isotope differential detection device and method

Abstract

This application relates to a differential detection device and method for rubidium isotopes in a single probe of an optically pumped magnetometer, belonging to the field of optically pumped magnetometer technology. The device includes: a laser module, a single atomic gas cell, a magnetic field modulation module, a photoelectric detection module, and a signal processing module. The laser module is used to split a tunable narrow-linewidth laser into two laser beams via a beam splitter, and then combine the two laser beams into a coaxial beam that is incident on the single atomic gas cell. The single atomic gas cell is filled with a mixture of rubidium-85 and rubidium-87 vapor and a buffer gas. The magnetic field modulation module is used to apply a static bias magnetic field and a high-frequency modulated magnetic field to the single atomic gas cell, causing the rubidium isotopes to undergo Zeeman level splitting. The photoelectric detection module is used to collect the light intensity signals corresponding to the two laser beams emitted from the single atomic gas cell. The signal processing module is used to receive the electrical signal converted by the photoelectric detection module, perform differential processing based on the Zeeman resonance signal, and obtain the corrected magnetic field measurement value.

Description

Technical Field

[0001] This application relates to the field of optically pumped magnetometer technology, specifically to a rubidium isotope differential detection device and method for a single probe of an optically pumped magnetometer. Background Technology

[0002] Optical pumped magnetometers achieve high-precision magnetic measurements based on the atomic Zeeman effect and are widely used in fields such as geomagnetic exploration, aerospace magnetic navigation, and biological magnetic imaging. Alkali metal rubidium has become the mainstream working material due to its clear energy levels and suitable room temperature vapor pressure.

[0003] The relevant technologies are mainly based on magnetic measurements using single isotopes. However, this approach has drawbacks such as sensitivity to common-mode interference, limitations in temperature compensation, and uncontrollable pressure drift, resulting in low accuracy of magnetic measurements. Summary of the Invention

[0004] In view of this, this application provides a rubidium isotope differential detection device and method for a single probe of an optically pumped magnetometer. The main purpose is to solve the problem that the related technologies based on single isotope magnetic measurement have defects such as sensitivity to common-mode interference, limitations in temperature compensation, and uncontrollable pressure drift, which lead to low accuracy of magnetic measurement.

[0005] According to the first aspect of this application, a rubidium isotope differential detection device for a single probe of an optically pumped magnetometer is provided, comprising: a laser module, a single atomic gas cell, a magnetic field modulation module, a photoelectric detection module, and a signal processing module; The laser module is used to output a tunable narrow linewidth laser. The tunable narrow linewidth laser is split into two laser beams by a beam splitter, and the two laser beams are combined into a coaxial beam and incident on the single atom gas cell. The two laser beams are used to match the resonance absorption spectra of rubidium 85 and rubidium 87, respectively. The individual atomic gas chamber is filled with a mixture of rubidium 85 and rubidium 87 vapors and a buffer gas. The individual atomic gas chamber is used to receive the coaxial beam, so that the rubidium 85 and rubidium 87 resonate with the two laser beams respectively. The magnetic field modulation module is used to apply a static bias magnetic field and a high-frequency modulation magnetic field to the individual atom gas cell, so that the rubidium 85 and rubidium 87 generate Zeeman level splitting. The photoelectric detection module is used to collect the light intensity signals corresponding to the two laser beams emitted from the single atomic gas cell, and convert the light intensity signals into electrical signals. The light intensity signals include reflected s-polarized light corresponding to rubidium 85 and transmitted p-polarized light corresponding to rubidium 87. The signal processing module is used to receive the electrical signal converted by the photoelectric detection module, extract the Zeeman resonance signals corresponding to rubidium 85 and rubidium 87 from the electrical signal, perform differential processing on the Zeeman resonance signals, and obtain the corrected magnetic field measurement value.

[0006] According to a second aspect of this application, a method for differential detection of rubidium isotopes in a single probe of an optically pumped magnetometer is provided. The method is applied to the aforementioned differential detection device for rubidium isotopes in a single probe of an optically pumped magnetometer, and includes: Two laser beams are combined into a coaxial beam and incident into a single atomic gas chamber. The two laser beams are used to match the resonant absorption lines of rubidium 85 and rubidium 87. The single atomic gas chamber is filled with a mixture of rubidium 85 and rubidium 87 vapor and a buffer gas. The single atomic gas chamber is used to receive the coaxial beam, so that rubidium 85 and rubidium 87 resonate with the two laser beams respectively. A static bias magnetic field and a high-frequency modulated magnetic field are applied to the individual atomic gas cell, causing the Zeeman level splitting of the rubidium 85 and rubidium 87. The light intensity signals corresponding to the two laser beams emitted from the single atomic gas cell are collected, and the light intensity signals are converted into electrical signals; The Zeeman resonance signals corresponding to rubidium 85 and rubidium 87 are extracted from the electrical signal, and differential processing is performed on the Zeeman resonance signals to obtain the corrected magnetic field measurement values.

[0007] According to a fourth aspect of this application, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the optically pumped magnetometer single-probe rubidium isotope differential detection method of the second aspect. According to a fifth aspect of this application, an electronic device is provided, including a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, wherein the processor executes the computer program to implement the optically pumped magnetometer single-probe rubidium isotope differential detection method of the second aspect.

[0008] By means of the above technical solution, this application provides a rubidium isotope differential detection device and method for a single probe of an optically pumped magnetometer. Compared with the prior art, the device in this application may include: a laser module, a single atomic gas cell, a magnetic field modulation module, a photoelectric detection module, and a signal processing module; the laser module is used to output a tunable narrow linewidth laser, which is split into two laser beams by a beam splitter, and the two laser beams are combined into a coaxial beam and incident on the single atomic gas cell. The two laser beams are respectively used to match the resonance absorption spectra of rubidium-85 and rubidium-87; the single... Each atomic gas chamber is filled with a mixture of rubidium 85 and rubidium 87 vapors and a buffer gas. Each individual atomic gas chamber receives the coaxial laser beam, causing the rubidium 85 and rubidium 87 to resonate with the two laser beams respectively. A magnetic field modulation module applies a static bias magnetic field and a high-frequency modulation magnetic field to each individual atomic gas chamber, causing the rubidium 85 and rubidium 87 to split into Zeeman levels. A photoelectric detection module acquires the light intensity signals corresponding to the two laser beams emitted from the individual atomic gas chamber and converts these signals into electrical signals. The light intensity signals include reflected s-polarized light corresponding to rubidium 85 and transmitted p-polarized light corresponding to rubidium 87. A signal processing module receives the electrical signals converted by the photoelectric detection module, extracts the Zeeman resonance signals corresponding to rubidium 85 and rubidium 87 from the electrical signals, performs differential processing on the Zeeman resonance signals, and obtains the corrected magnetic field measurement values. In this application, a laser module is used to combine two laser beams into a coaxial beam and incident it onto a single atomic gas cell. After the two laser beams are incident coaxially into the gas cell, rubidium-85 and rubidium-87 in the single atomic gas cell resonate in the same magnetic field and optical path environment. A photoelectric detection module collects the two light intensity signals emitted from the single atomic gas cell and converts them into electrical signals, which are then sent to a signal processing module. The signal processing module extracts the Zeeman resonance signals corresponding to different rubidium isotopes and performs differential calculations based on the two Zeeman resonance signals to cancel common-mode interference such as laser power drift, environmental electromagnetic interference, and gas cell vibration, thereby obtaining a corrected magnetic field measurement value and improving the accuracy of the magnetic field measurement value.

[0009] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0010] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0011] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This paper shows a structural block diagram of a single-probe rubidium isotope differential detection device for an optically pumped magnetometer according to an embodiment of this application. Figure 2 The diagram shows a flowchart of a rubidium isotope differential detection method for a single probe of an optically pumped magnetometer provided in an embodiment of this application. Detailed Implementation

[0013] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0014] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0015] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0016] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0017] The relevant technologies mainly use rubidium-87 monoisotope pumping and resonance detection for magnetic measurements. The main drawbacks are sensitivity to common-mode interference, limitations in temperature compensation, and uncontrollable pressure drift. For example, for every 1°C change in temperature, the density of rubidium-87 vapor changes by about 5%, introducing an error of ≥0.05nT; a 5% fluctuation in laser power causes a ≥10% change in the amplitude of the resonance signal, further amplifying the error. Passive heat preservation or single-point calibration cannot cover the wide temperature range of -20°C to 60°C, and the drift in industrial / field scenarios is ≥0.1nT; when the pressure changes by 1 kPa due to micro-leakage of the buffer gas, the atomic relaxation time changes by 8%, and the resolution drops to below 0.05nT.

[0018] To address the shortcomings of existing technologies that rely on single isotope-based magnetic measurements, such as sensitivity to common-mode interference, limitations in temperature compensation, and uncontrollable pressure drift, resulting in low accuracy, this application provides a rubidium isotope differential detection device and method for a single probe in an optically pumped magnetometer.

[0019] like Figure 1 As shown, an embodiment of this application provides a rubidium isotope differential detection device 1 for a single probe of an optically pumped magnetometer. The device includes: a laser module 11, a single atomic gas cell 12, a magnetic field modulation module 13, a photoelectric detection module 14, and a signal processing module 15. The laser module 11 outputs a tunable narrow-linewidth laser, which is split into two laser beams by a beam splitter and combined into a coaxial beam incident on the single atomic gas cell 12. The two laser beams are used to match the resonance absorption spectra of rubidium 85 and rubidium 87. The single atomic gas cell 12 contains... The system is filled with a mixture of rubidium 85 and rubidium 87 vapor and a buffer gas. The single atomic gas cell 12 is used to receive the coaxial beam, so that the rubidium 85 and rubidium 87 resonate with the two laser beams respectively. The magnetic field modulation module 13 is used to apply a static bias magnetic field and a high-frequency modulation magnetic field to the single atomic gas cell 12, so that the rubidium 85 and rubidium 87 generate Zeeman level splitting. The photoelectric detection module 14 is used to collect the light intensity signals corresponding to the two laser beams emitted from the single atomic gas cell 12 and convert the light intensity signals into electrical signals. The light intensity signals include the reflected s-polarized light corresponding to rubidium 85 and the transmitted p-polarized light corresponding to rubidium 87. The signal processing module 15 is used to receive the electrical signals converted by the photoelectric detection module 14, extract the Zeeman resonance signals corresponding to rubidium 85 and rubidium 87 respectively from the electrical signals, perform differential processing based on the Zeeman resonance signals, and obtain the corrected magnetic field measurement value.

[0020] In some embodiments, the laser module 11 can output a tunable narrow-linewidth laser, which is split into two laser beams by a beam splitter. The two laser beams include a first laser beam and a second laser beam, and are narrow-linewidth lasers. The first laser beam can be used to match the D1 line of rubidium 85, and the second laser beam can be used to match the D1 line of rubidium 87, such as 794.76nm (rubidium 85) and 795.00nm (rubidium 87). The two laser beams are then adjusted to a coaxial state by a beam combining and collimating element, and are combined into a coaxial beam along a preset optical path and incident on the incident end window of the single atom gas cell 12, so that the paths of the two laser beams completely overlap in the gas cell, ensuring the consistency of interference to rubidium 85 and rubidium 87 atoms. When the laser passes through the single atom gas cell 12, it can resonate with the rubidium 85 and rubidium 87 mixed vapor inside the single atom gas cell 12. The atoms absorb the laser energy of the corresponding frequency, resulting in an attenuation of the emitted laser intensity related to the Zeeman level splitting state.

[0021] The beam splitter can be used to split a single laser beam into multiple independent laser beams, each with its own frequency adjustable. The output of the laser module 11 can be coupled to the input of the beam splitter via a single-mode polarization-maintaining fiber. The fiber optic connection reduces interference from external vibrations on the optical path, making it suitable for portable or field-use magnetometers. Alternatively, a free-space optical path connection can be used. A collimating lens is installed at the output port of the laser module 11 to calibrate the diverging laser beam into a parallel beam, which is then directly incident on the beam splitter surface of the beam splitter. Correspondingly, the two split laser beams can be adjusted for their optical path direction using independent fine-tuning mirrors. The two laser beams are then incident on a beam combining and collimating element, calibrating their propagation axes to be completely coincident. The calibrated coaxial beam can then be focused into a narrow beam by a focusing lens and incident perpendicularly onto the incident optical window of the single atomic gas cell 12.

[0022] In some embodiments, the coil of the magnetic field modulation module 13 may be mounted around or close to the individual atom gas cell 12 to apply a composite magnetic field. The coupling between the magnetic field modulation module 13 and the individual atom gas cell 12 must ensure that the magnetic field inside the gas cell is uniform to avoid distortion of the resonance signal caused by local magnetic field gradients. Accordingly, the static bias magnetic field can be used to adjust the atomic energy level baseline so that the Zeeman splitting is in an easily detectable range; the high-frequency modulation magnetic field can be used to modulate the energy level splitting spacing so that the resonance signal carries a frequency marker. The external magnetic field to be measured superimposed on the composite magnetic field directly determines the final spacing of the Zeeman energy level splitting of rubidium atoms. Accordingly, the individual atom gas cell 12 may include a gaseous mixture of rubidium 85 and rubidium 87, and the buffer gas may be an inert gas, such as argon or nitrogen, filled in the individual atom gas cell 12 to reduce collisions between rubidium atoms and the gas cell wall and improve the stability of the resonance signal.

[0023] For example, the photoelectric detection module 14 may include two photodetectors aligned with the optical path of the exit window of the single atomic gas cell 12, and the two photodetectors are arranged corresponding to the two laser beams, so that the two laser beams at the exit of the single atomic gas cell 12 are respectively incident on the corresponding photodetectors; the photodetectors can convert the light intensity signal into an electrical signal, which may contain Zeeman resonance characteristic information and environmental interference noise. Specifically, after the two laser beams are combined into a coaxial beam and incident on the single atomic gas cell, the coaxial beam can be split into two light intensity signals by a polarization beam splitter: transmitted p-polarized light (the original second laser beam, the signal light corresponding to rubidium 87) and reflected s-polarized light (the original first laser beam, the signal light corresponding to rubidium 85). The two separated beams are respectively incident on two high-sensitivity photodetectors, converted into two electrical signals, and then the two electrical signals are differentially amplified and demodulated to filter out random noise and improve the sensitivity of magnetic field measurement.

[0024] In some embodiments, the output of the photodetector module 14 is electrically connected to the input of the signal processing module 15 via a shielded cable; the electrical signal from the photodetector is transmitted to the signal processing module 15 via the shielded cable. Accordingly, the signal processing module 15 can extract the Zeeman resonance signals corresponding to the rubidium isotopes from the electrical signal, and then perform differential calculations on the two Zeeman resonance signals to cancel common-mode interference, obtaining the corrected magnetic field measurement value. For example, the signal processing module 15 demodulates the Zeeman resonance signals corresponding to rubidium 85 and rubidium 87, determines the resonance magnetic field values ​​corresponding to the two Zeeman resonance signals, and obtains the corrected magnetic field measurement value by performing differential calculations on the resonance magnetic field values ​​corresponding to rubidium 85 and rubidium 87.

[0025] In this way, this embodiment utilizes the laser module 11 to obtain two laser beams through a beam splitter, one matched to the D1 line of rubidium 85 and the other matched to the D1 line of rubidium 87. The two laser beams are combined into a coaxial beam and incident on a single atomic gas cell 12. The single atomic gas cell 12 is filled with a mixture of rubidium 85 and rubidium 87 vapor. Dual isotope differential detection is achieved through a single probe. Furthermore, the magnetic field modulation module 13 applies a static bias magnetic field and a high-frequency modulated magnetic field to the single atomic gas cell 12, ensuring that after the coaxial beam is incident on the cell, the rubidium isotopes are in a completely identical magnetic field environment. Resonance occurs in the optical path environment. The photoelectric detection module 14 collects the two light intensity signals emitted from the single atomic gas cell 12 by the two laser beams, converts them into electrical signals and sends them to the signal processing module 15. The signal processing module 15 extracts the Zeeman resonance signals corresponding to different rubidium isotopes, and performs differential operation based on the two Zeeman resonance signals to cancel common-mode interference such as laser power drift, environmental electromagnetic interference, and gas cell vibration, and obtains the corrected magnetic field measurement value, thereby improving the accuracy of the magnetic field measurement value. Moreover, no additional probe is required, which effectively reduces the size and cost and makes it suitable for portable devices.

[0026] Optionally, the laser module 11 includes a laser, a wavelength tuning unit, and a power stabilization unit; the laser's drive interface is connected to the output of the wavelength tuning unit, and the laser's output port is connected to the input port of the power stabilization unit; the laser is used to output tunable narrow-linewidth laser light, and the laser includes a distributed feedback laser and a vertical cavity surface-emitting laser; the wavelength tuning unit tunes the two laser beams to the resonant wavelengths of the corresponding resonant absorption lines of rubidium 85 and rubidium 87 by adjusting the laser temperature, injection current, or external grating feedback; the power stabilization unit is used to control the laser power of the two laser beams according to a preset stable power.

[0027] The preset stable power can be a target value of laser output power that is determined in advance based on the measurement requirements of the optical pump magnetometer, so as to ensure that the atoms resonate fully without causing atomic saturation due to excessive power, such as 1mW.

[0028] In some embodiments, the laser module 11 may include a distributed feedback (DFB) laser or a vertical-cavity surface-emitting laser (VCSEL), coupled with a wavelength tuning unit (temperature control circuit + current drive circuit / grating feedback) and a power stabilization unit (photoelectric feedback closed-loop circuit). For example, it can output a 780nm tunable narrow-linewidth laser, which is split into at least two paths by a beam splitter, respectively matching the resonant wavelengths of rubidium 85 (D1 / D2 line, e.g., 780.24nm) and rubidium 87 (D1 / D2 line, e.g., 780.02nm), with laser power fluctuation ≤0.5%. The beam splitter may be a polarization beam splitter, fiber beam splitter, or grating beam splitter, used to split the laser into two orthogonally polarized or wavelength-separated beams, which are then combined into a coaxial beam incident on a single atomic gas cell 12, with an optical axis overlap ≥95%.

[0029] Optionally, the individual atomic gas chamber 12 may include, but is not limited to, an uncoated glass gas chamber, a quartz gas chamber, or a micro-machined gas chamber; the individual atomic gas chamber 12 is filled with a mixture of rubidium 85 and rubidium 87 vapors according to a preset molar ratio; the individual atomic gas chamber 12 is filled with a buffer gas according to a preset gas pressure, and the buffer gas may include at least one of neon, argon, and krypton.

[0030] In some embodiments, the incident window of the individual atomic gas chamber 12 may be made of high-transmittance optical glass, such as fused silica, and the surface of the window needs to be treated with an anti-reflection film to reduce laser reflection loss. For example, the material of the individual atomic gas chamber 12 may be uncoated glass, quartz, or a micro-machined chamber, with a volume ranging from 0.2 to 5 cm³, and it is filled with a mixture of rubidium 85 and rubidium 87 vapors and a buffer gas. The preset molar ratio of the rubidium 85 and rubidium 87 vapors can range from 1:1 to 3:1, and the preset pressure of the buffer gas can range from 5 to 20 kPa.

[0031] Optionally, an insulation layer and a temperature sensor are attached to the outside of the individual atomic gas chamber 12; the insulation layer is used to maintain the internal temperature stability of the individual atomic gas chamber 12; the temperature sensor is used to monitor the gas chamber temperature of the individual atomic gas chamber 12 in real time.

[0032] In some embodiments, the insulation layer outside the gas chamber covers the area where the temperature sensor and the individual atomic gas chamber 12 are in contact, reducing the interference of external ambient temperature fluctuations on the gas chamber temperature detection. The temperature sensor's sensing probe can be mounted close to the outer wall surface of the individual atomic gas chamber 12, with thermally conductive silicone grease filling the space between them to reduce thermal resistance and ensure that the temperature sensor can respond quickly and accurately to temperature changes inside the gas chamber. For example, a PT1000 platinum resistance thermometer can be used as the temperature sensor, eliminating measurement errors caused by lead resistance, achieving an accuracy of ±0.1℃ and a temperature control accuracy of ±0.02℃.

[0033] Optionally, the signal processing module 15 includes a calibration unit; the calibration unit is used to dynamically adjust the correction coefficients and system calibration coefficients corresponding to the differential operation of the Zeeman resonance signal according to the gas chamber temperature or a standard magnetic field source.

[0034] In some embodiments, the calibration unit can be dynamically calibrated based on a standard magnetic field source (accuracy ±0.001nT) or a temperature fitting model to output an absolute magnetic field value. The signal output pin of the temperature sensor is connected to the temperature signal acquisition interface of the calibration unit via a shielded three-core cable. The calibration unit can have a built-in signal conditioning circuit to convert the resistance signal output by the temperature sensor into a digital temperature value. Then, based on a temperature-coefficient mapping table calibrated by a standard magnetic field source, or equipped with a temperature fitting model, it dynamically adjusts the differential correction coefficient α and the system calibration coefficient k according to the real-time temperature of a single atomic gas chamber 12 to perform error compensation and absolute value calibration of the Zeeman resonance signal corresponding to the rubidium isotope, and finally outputs a high-precision absolute magnetic field measurement value.

[0035] Optionally, the signal processing module 15 further includes a preamplifier unit, a lock-in amplifier unit, and a differential operation unit; the output terminal of the preamplifier unit is connected to the input terminal of the lock-in amplifier unit, and the output terminal of the lock-in amplifier unit is connected to the input terminal of the differential operation unit; the preamplifier unit is used to perform low-noise amplification processing on the electrical signal to obtain a low-noise amplified signal; the lock-in amplifier unit is used to demodulate the Zeeman resonance signal based on the modulation magnetic field frequency output by the magnetic field modulation module 13 and the low-noise amplified signal; the differential operation unit is used to obtain the corrected magnetic field measurement value based on the resonance magnetic field value, correction coefficient, and system calibration coefficient corresponding to the Zeeman resonance signal.

[0036] In some embodiments, each unit in the signal processing module 15 can be integrated using an FPGA chip, and the specific functions of each unit are as follows: Preamplifier unit: configured with a gain of 1000 and a noise figure ≤ The low-noise amplifier circuit is used to amplify the weak electrical signal output by the photoelectric detection module 14 with low noise, increasing the signal amplitude to the effective input threshold of the lock-in amplifier unit, while avoiding the introduction of additional noise that would degrade the signal-to-noise ratio. The preamplifier unit may include a preamplifier; Lock-in amplifier unit: Using the high-frequency modulation magnetic field applied by the magnetic field modulation module 13 as a reference frequency, it performs correlation demodulation operations on the electrical signal amplified by the preamplifier unit, filters out random environmental noise, and accurately extracts the Zeeman resonance signal corresponding to the Zeeman level splitting. The lock-in amplifier unit may include a lock-in amplifier; Differential operation unit: Receives the Zeeman resonance signals corresponding to rubidium 85 and rubidium 87 output from the lock-in amplifier unit. In this way, the two signals are differentially amplified and demodulated to filter out random noise and improve the magnetic field measurement sensitivity. Then, according to the differential algorithm, combined with the correction coefficient and system calibration coefficient, the resonant magnetic field values ​​corresponding to the two signals are differentially processed to offset the measurement errors introduced by common-mode interference such as laser power drift and environmental vibration, and output the corrected magnetic field measurement value.

[0037] Optionally, the magnetic field modulation module 13 includes a static bias magnetic field coil and a high-frequency modulation magnetic field coil; the static bias magnetic field coil and the high-frequency modulation magnetic field coil are coaxially wrapped around the outer wall of the single atomic gas chamber 12, and are used to generate a static bias magnetic field and a high-frequency modulation magnetic field when current passes through, which act on the rubidium 85 and rubidium 87 mixed vapor inside the single atomic gas chamber 12.

[0038] In some embodiments, a static bias magnetic field coil (such as a Helmholtz coil) and a high-frequency modulation magnetic field coil can be coaxially wrapped around the outer wall of a single atomic gas chamber 12, or fixed tightly against the gas chamber shell; a high-permeability gasket can be installed between the coil and the gas chamber to improve the uniformity of the magnetic field inside the gas chamber. Optionally, a DC current can be output through a drive circuit to generate a static bias magnetic field, and a high-frequency alternating current can be used to generate a high-frequency modulation magnetic field. When the current flows through the coil, a composite magnetic field is generated. This magnetic field directly acts on the rubidium 85 and rubidium 87 mixed vapor inside the single atomic gas chamber 12, inducing Zeeman splitting of the atomic energy levels.

[0039] For example, the magnetic field modulation module 13 may include a Helmholtz coil and a high-frequency modulation magnetic field coil, which provide a static bias magnetic field and a high-frequency modulation magnetic field, respectively, and are coaxially wound around the outside of the single atom gas cell 12. The static bias magnetic field can be adjusted from 0 to 200 μT to compensate for the ambient magnetic field; the high-frequency modulation magnetic field can have a frequency range of 1 to 15 kHz and an amplitude of 0.1 to 2 μT to cause Zeeman level splitting in rubidium atoms, and the modulation signal is synchronously output to the signal processing module 15 as a phase-locked reference.

[0040] Optionally, the central axis of the magnetic field coil can be aligned with the optical path axis of the individual atomic gas chamber 12 to ensure that the magnetic field on the laser propagation path inside the gas chamber is uniform. The uniformity of the magnetic field inside the individual atomic gas chamber 12 can be adjusted according to a preset uniformity threshold (such as 0.1%). If the magnetic field uniformity is required to be ≤0.1%, the distortion of the resonance signal caused by the local magnetic field gradient can be avoided, thereby improving the detection accuracy.

[0041] Optionally, the output terminal of the photoelectric detection module 14 is connected to the input terminal of the signal processing module 15; the photoelectric detection module 14 includes two photodetectors, which are used to collect the light intensity signals corresponding to the two laser beams emitted from the single atomic gas chamber 12 respectively.

[0042] For example, both photodetectors can be high-sensitivity photodetectors, such as InGaAs photodiodes with a response wavelength of 700~1100nm and a dark current ≤1nA. These are used to collect the two laser intensity signals corresponding to rubidium 85 and rubidium 87, respectively, convert them into low-noise electrical signals, and transmit them to the signal processing module 15. Specifically, a polarization beam splitter can be used to split the coaxial beam penetrating the gas chamber into two paths: the reflected s-polarized light corresponding to the first laser beam and the transmitted p-polarized light corresponding to the second laser beam. These two separated beams are then incident on two high-sensitivity photodetectors to obtain the corresponding laser intensity signals.

[0043] Compared with related technologies, this embodiment provides a solution for differential detection of rubidium 85 and rubidium 87 within a single probe. While maintaining a compact structure and controllable cost, it can offset common-mode interferences such as temperature, laser power, and air pressure drift, improve measurement accuracy and stability, and adapt to the needs of multiple scenarios. This embodiment uses a single atomic gas chamber 12 filled with a mixture of rubidium 85 and rubidium 87 vapor. A single probe enables differential detection of two isotopes. The calibration unit in the signal processing module 15 dynamically adjusts the correction coefficients and system calibration coefficients corresponding to the differential operation of the Zeeman resonance signal based on the temperature of the single atomic gas chamber 12 or a standard magnetic field source. A preamplifier unit performs low-noise amplification of the electrical signal, and a lock-in amplifier unit demodulates the Zeeman resonance signal based on the modulation magnetic field frequency and the low-noise amplified signal. Finally, a differential operation unit performs differential operations based on the correction coefficients and system calibration coefficients to obtain the corrected magnetic field measurement value. Based on the common-mode response of rubidium 85 and rubidium 87 to temperature, light, and pressure, the measurement accuracy is improved to ±0.01 nT after differential operation, and the stability is improved by more than 50%; the temperature drift is reduced from 0.1 nT. The error is reduced to 0.005nT when the laser power fluctuates by 5%, decreasing from 0.06nT to 0.005nT, effectively improving anti-interference capability. A single probe achieves dual isotope differential, eliminating the need for additional probes. The size is reduced by 40%, and the cost by 30%. The compact structure and low cost allow the overall probe size to be reduced to 8cm×5cm×3cm, making it suitable for portable devices. It has high adaptability to multiple scenarios. By adjusting the gas chamber parameters, modulating the magnetic field, and signal algorithms, it can adapt to various needs such as static geomagnetic measurement (resolution 0.005nT), dynamic UAV detection (error ≤0.02nT), and wide temperature range industrial scenarios (drift ≤0.02nT from -20℃ to 60℃). Long-term stability is optimized. The dynamic calibration model compensates for long-term errors such as air pressure leakage and temperature drift, with a 24-hour stability ≤0.01nT, meeting the requirements of high-precision scenarios such as geomagnetic reference stations.

[0044] like Figure 2 As shown, embodiments of this application provide a method for differential detection of rubidium isotopes in a single probe of an optically pumped magnetometer. This method can be applied to the aforementioned differential detection device for rubidium isotopes in a single probe of an optically pumped magnetometer. The method for differential detection of rubidium isotopes in a single probe of an optically pumped magnetometer may include: Step 101: Combine the two laser beams into a coaxial beam and direct it into a single atom gas cell.

[0045] The two laser beams are used to match the resonant absorption spectral lines of rubidium 85 and rubidium 87. The single atomic gas chamber is filled with a mixture of rubidium 85 and rubidium 87 vapor and a buffer gas. The single atomic gas chamber is used to receive the coaxial beam, so that rubidium 85 and rubidium 87 resonate with the two laser beams respectively.

[0046] In some embodiments, the two laser beams can be narrow-linewidth lasers, one matched to the D1 line of rubidium-85 and the other matched to the D1 line of rubidium-87, such as 794.76nm (rubidium-85) and 795.00nm (rubidium-87). The combined beam is a coaxial beam incident on a single atom gas cell, so that the different rubidium isotopes filled inside the single atom gas cell resonate with the two laser beams respectively, and the paths of the two laser beams completely overlap in the gas cell, ensuring the consistency of the interference of rubidium-85 and rubidium-87 atoms.

[0047] Step 102: Apply a static bias magnetic field and a high-frequency modulated magnetic field to a single atom gas cell to cause Zeeman level splitting in rubidium 85 and rubidium 87.

[0048] In some embodiments, the static bias magnetic field coil and the high-frequency modulation magnetic field coil of the magnetic field modulation module apply a static bias magnetic field and a high-frequency modulation magnetic field to a single atom gas cell, causing rubidium atoms to split into Zeeman levels. The coupling between the magnetic field modulation module and the single atom gas cell must ensure that the magnetic field inside the gas cell is uniform, and avoid local magnetic field gradients that cause resonance signal distortion.

[0049] Step 103: Collect the light intensity signals corresponding to the two laser beams emitted from a single atomic gas cell, and convert the light intensity signals into electrical signals.

[0050] The light intensity signal can be the light intensity signal corresponding to the two laser beams emitted from a single atomic gas cell, collected by two photodetectors. It can include the reflected s-polarized light corresponding to rubidium-85 and the transmitted p-polarized light corresponding to rubidium-87. Specifically, a polarization beam splitter splits the coaxial beam emitted from a single atomic gas cell into two light signals: the transmitted p-polarized light corresponding to rubidium-87 and the reflected s-polarized light corresponding to rubidium-85. These signals are then converted into electrical signals and sent to the signal processing model to obtain the corresponding magnetic field measurement value.

[0051] Step 104: Extract the Zeeman resonance signals corresponding to rubidium 85 and rubidium 87 from the electrical signal, perform differential processing on the Zeeman resonance signals, and obtain the corrected magnetic field measurement values.

[0052] In some embodiments, the electrical signal can be amplified by the preamplifier unit in the signal processing module to obtain a low-noise amplified signal. Then, the lock-in amplifier unit in the signal processing module demodulates the Zeeman resonance signals corresponding to the rubidium isotopes based on the modulation magnetic field frequency output by the magnetic field modulation module and the low-noise amplified signal. The differential operation unit in the signal processing module performs differential operation based on the resonance magnetic field value corresponding to the Zeeman resonance signal to obtain the corrected magnetic field measurement value.

[0053] In this way, this embodiment combines two laser beams into a coaxial beam and directs it into a single atomic gas cell. The single atomic gas cell is filled with a rubidium isotope mixture vapor. A single probe enables differential detection of two isotopes. A static bias magnetic field and a high-frequency modulated magnetic field are applied to the single atomic gas cell, so that after the two laser beams are coaxially incident into the gas cell, the rubidium isotopes resonate in the same magnetic field and optical path environment. Then, the intensity signals of the two laser beams emitted from the single atomic gas cell are collected and converted into electrical signals. The Zeeman resonance signals corresponding to different rubidium isotopes are extracted from these signals. Differential calculations are then performed based on the two Zeeman resonance signals to cancel common-mode interference such as laser power drift, environmental electromagnetic interference, and gas cell vibration, and to obtain the corrected magnetic field measurement value. This improves the accuracy of the magnetic field measurement value. Moreover, no additional probe is required, which effectively reduces the size and cost, and makes it suitable for portable devices.

[0054] Optionally, differential processing is performed on the Zeeman resonance signal to obtain the corrected magnetic field measurement value. Specifically, this may include: adjusting the correction coefficient and system calibration coefficient corresponding to the differential operation of the Zeeman resonance signal based on the chamber temperature of a single atomic gas cell or a standard magnetic field source; and obtaining the corrected magnetic field measurement value based on the resonance magnetic field value, correction coefficient, and system calibration coefficient corresponding to the Zeeman resonance signal.

[0055] Optionally, the wavelength tuning unit in the laser module can be used to tune the two laser beams to the resonant wavelengths corresponding to rubidium 85 and rubidium 87 by adjusting the laser temperature, injection current, or external grating feedback. The power stabilization unit in the laser module can then be used to control the laser power of the two laser beams according to a preset stable power.

[0056] The preset stable power can be determined in advance based on the rubidium isotope resonance efficiency experiment (e.g., 1mW) and written into the control program of the power stabilization unit. After entering the power stabilization unit, the actual power of the two laser beams output by the laser can be monitored in real time through a photodetector. If the actual power is higher than 1mW, the power stabilization unit can output a compensation signal to reduce the driving current of the laser. If the actual power is lower than 1mW, the driving current is increased. This ensures that the laser power of each of the two laser beams after beam splitting is stable within the error range of the preset stable power, ensuring that the resonance efficiency of rubidium 85, rubidium 87 and the laser is consistent, and avoiding measurement errors caused by power fluctuations.

[0057] In some embodiments, the method of this embodiment may specifically include the following steps: Laser calibration: Start the laser module, and use the wavelength tuning unit to tune the two lasers to the resonant wavelengths of rubidium 85 and rubidium 87 respectively. The power stabilization unit stabilizes the laser power at about 1mW with fluctuations ≤0.5%. Magnetic field application: A static bias magnetic field is applied through a Helmholtz coil to compensate for the ambient magnetic field, so that the individual atom gas cell is in a zero-field bias state; a high-frequency modulated magnetic field (such as 8kHz, 0.5μT) is applied through a high-frequency modulation coil to cause the rubidium atom to split into Zeeman levels; Signal acquisition: The photodetector acquires the light intensity signals of the two emitted lasers, converts them into electrical signals, and transmits them to the signal processing module; Signal demodulation: The preamplifier amplifies the electrical signal by 1000 times, and the lock-in amplifier demodulates the signal with the modulation frequency as a reference to obtain the Zeeman resonance curves of rubidium 85 and rubidium 87, and extracts the resonance magnetic field values ​​B85 and B87 corresponding to the resonance peaks. Differential calculation: Calculated using the formula B = k × (B85 - α × B87), where α is the signal sensitivity ratio of rubidium 85 to rubidium 87 (1.0~1.5), and k is the system calibration coefficient (1.0~1.2). The final magnetic field measurement value B is output. α is determined by fitting sensitivity measurements under different temperature and pressure conditions in a standard magnetic field environment, forming a correlation model. Dynamic calibration: The temperature sensor collects the temperature of the individual atomic gas chamber in real time. Combined with parameters such as ambient air pressure and laser power, the correlation model between α and environmental parameters is called to dynamically adjust α and k to compensate for environmental drift error.

[0058] In summary, the rubidium isotope differential detection method for a single probe of the optically pumped magnetometer provided in this application, compared with the existing technology, uses a single atomic gas cell filled with rubidium isotope mixed vapor to achieve dual isotope differential detection through a single probe. Furthermore, based on the temperature of the single atomic gas cell or a standard magnetic field source, the correction coefficients and system calibration coefficients corresponding to the Zeeman resonance signal differential operation are dynamically adjusted. Then, differential operation is performed based on the Zeeman resonance signal to obtain the corrected magnetic field measurement value. This achieves common-mode response to temperature, light, and pressure based on rubidium-85 and rubidium-87, improving the measurement accuracy and stability after differential operation, reducing temperature drift and laser power fluctuations, effectively improving anti-interference capability. Dual isotope differential detection is achieved with a single probe, eliminating the need for additional probes. The structure is compact and cost-effective. While maintaining a compact structure and controllable cost, it offsets common-mode interference such as temperature, laser power, and gas pressure drift, improving measurement accuracy and stability, and adapting to various scenario requirements.

[0059] Based on the above, Figure 2 Accordingly, this embodiment also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described method. Figure 2 The method shown.

[0060] Based on this understanding, the technical solution of this application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (such as CD-ROM, USB flash drive, mobile hard drive, etc.) and includes several instructions to cause a computer device (such as personal computer, server, or network device, etc.) to execute the methods of various implementation scenarios of this application.

[0061] Based on the above, Figure 2 To achieve the above objectives, embodiments of this application also provide an electronic device, which includes a storage medium and a processor; the storage medium is used to store a computer program; the processor is used to execute the computer program to implement the above-described... Figure 2 The method shown.

[0062] Optionally, the aforementioned physical devices may also include a user interface, a network interface, a camera, radio frequency (RF) circuitry, sensors, audio circuitry, a Wi-Fi module, etc. The user interface may include a display screen, input units such as a keyboard, etc., and optional user interfaces may also include USB interfaces, card reader interfaces, etc. The network interface may optionally include standard wired interfaces, wireless interfaces (such as Wi-Fi interfaces), etc.

[0063] Those skilled in the art will understand that the physical device structure provided in this embodiment does not constitute a limitation on the physical device, and may include more or fewer components, or combine certain components, or have different component arrangements.

[0064] The storage medium may also include an operating system and a network communication module. The operating system is a program that manages the hardware and software resources of the aforementioned physical device, supporting the operation of information processing programs and other software and / or programs. The network communication module is used to enable communication between the various components within the storage medium, as well as communication with other hardware and software in the information processing physical device.

[0065] Through the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms, or it can be implemented by hardware. By applying the solution of this embodiment, compared with the existing technology, this application uses a single atomic gas cell filled with rubidium isotope mixed vapor, realizes dual isotope differential detection through a single probe, and dynamically adjusts the correction coefficient and system calibration coefficient corresponding to the Zeeman resonance signal differential operation according to the gas cell temperature or standard magnetic field source. Then, differential operation is performed according to the Zeeman resonance signal to obtain the corrected magnetic field measurement value, realizing common-mode response of rubidium-85 and rubidium-87 to temperature, light, and pressure, improving the measurement accuracy and stability after differential operation, reducing temperature drift and laser power fluctuation, effectively improving anti-interference ability, realizing dual isotope differential detection with a single probe without the need for additional probes, with a compact structure and low cost. While maintaining a compact structure and controllable cost, it cancels common-mode interference such as temperature, laser power, and gas pressure drift, improves measurement accuracy and stability, and adapts to multiple scenario requirements.

[0066] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the term "comprising" or any other variations thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0067] The above are merely specific embodiments of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to these embodiments, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A rubidium isotope differential detection device for a single probe of an optically pumped magnetometer, characterized in that, The device includes: a laser module, a single atom gas cell, a magnetic field modulation module, a photoelectric detection module, and a signal processing module; The laser module is used to output a tunable narrow linewidth laser. The tunable narrow linewidth laser is split into two laser beams by a beam splitter, and the two laser beams are combined into a coaxial beam and incident on the single atom gas cell. The two laser beams are used to match the resonance absorption spectra of rubidium 85 and rubidium 87, respectively. The individual atomic gas chamber is filled with a mixture of rubidium 85 and rubidium 87 vapors and a buffer gas. The individual atomic gas chamber is used to receive the coaxial beam, so that the rubidium 85 and rubidium 87 resonate with the two laser beams respectively. The magnetic field modulation module is used to apply a static bias magnetic field and a high-frequency modulation magnetic field to the individual atom gas cell, so that the rubidium 85 and rubidium 87 generate Zeeman level splitting. The photoelectric detection module is used to collect the light intensity signals corresponding to the two laser beams emitted from the single atomic gas cell, and convert the light intensity signals into electrical signals. The light intensity signals include reflected s-polarized light corresponding to rubidium 85 and transmitted p-polarized light corresponding to rubidium 87. The signal processing module is used to receive the electrical signal converted by the photoelectric detection module, extract the Zeeman resonance signals corresponding to rubidium 85 and rubidium 87 from the electrical signal, perform differential processing on the Zeeman resonance signals, and obtain the corrected magnetic field measurement value.

2. The apparatus according to claim 1, characterized in that, The laser module includes a laser, a wavelength tuning unit, and a power stabilization unit; The laser's drive interface is connected to the output of the wavelength tuning unit, and the laser's output port is connected to the input port of the power stabilization unit. The laser is used to output tunable narrow linewidth laser light, and the laser includes a distributed feedback laser and a vertical cavity surface emitter laser. The wavelength tuning unit tunes the two laser beams to the resonant wavelengths of the resonant absorption lines corresponding to rubidium 85 and rubidium 87 by adjusting the laser temperature, injection current, or external grating feedback. The power stabilization unit is used to control the laser power of the two laser beams according to a preset stable power.

3. The apparatus according to claim 1, characterized in that, The individual atomic gas chambers include uncoated glass gas chambers, quartz gas chambers, and micro-fabricated gas chambers; The individual atomic gas chamber is filled with a mixture of rubidium 85 and rubidium 87 vapors at a preset molar ratio, and the individual atomic gas chamber is filled with buffer gas at a preset pressure. The buffer gas includes neon, argon, and krypton.

4. The apparatus according to claim 1, characterized in that, The single atomic gas chamber is equipped with an insulation layer and a temperature sensor on its outer side. The insulation layer is used to maintain the internal temperature stability of each atomic gas chamber; The temperature sensor is used to monitor the temperature of the individual atomic gas chamber in real time.

5. The apparatus according to claim 4, characterized in that, The signal processing module includes a calibration unit; The calibration unit is used to dynamically adjust the correction coefficients and system calibration coefficients corresponding to the differential operation of the Zeeman resonance signal based on the temperature of the gas chamber or a standard magnetic field source.

6. The apparatus according to claim 5, characterized in that, The signal processing module also includes a preamplifier unit, a lock-in amplifier unit, and a differential operation unit; The output terminal of the preamplifier unit is connected to the input terminal of the lock-in amplifier unit, and the output terminal of the lock-in amplifier unit is connected to the input terminal of the differential operation unit. The preamplifier unit is used to perform low-noise amplification processing on the electrical signal to obtain a low-noise amplified signal. The lock-in amplifier unit is used to demodulate the Zeeman resonance signal based on the modulation magnetic field frequency output by the magnetic field modulation module and the low-noise amplified signal. The differential operation unit is used to obtain the corrected magnetic field measurement value based on the resonant magnetic field value corresponding to the Zeeman resonance signal, the correction coefficient, and the system calibration coefficient.

7. The apparatus according to claim 1, characterized in that, The magnetic field modulation module includes a static bias magnetic field coil and a high-frequency modulation magnetic field coil; The static bias magnetic field coil and the high-frequency modulation magnetic field coil are coaxially wrapped around the outer wall of the single atomic gas chamber, and are used to generate a static bias magnetic field and a high-frequency modulation magnetic field when an electric current passes through, which act on the rubidium 85 and rubidium 87 mixed vapor inside the single atomic gas chamber.

8. The apparatus according to claim 1, characterized in that, The output terminal of the photoelectric detection module is connected to the input terminal of the signal processing module; The photoelectric detection module includes two photodetectors, which are used to collect the light intensity signals corresponding to the two laser beams emitted from the single atomic gas cell.

9. A method for differential detection of rubidium isotopes using a single probe in an optically pumped magnetometer, characterized in that, The method is applied to the optically pumped magnetometer single-probe rubidium isotope differential detection device as described in any one of claims 1-8, and the method includes: Two laser beams are combined into a coaxial beam and incident into a single atomic gas chamber. The two laser beams are used to match the resonant absorption lines of rubidium 85 and rubidium 87. The single atomic gas chamber is filled with a mixture of rubidium 85 and rubidium 87 vapor and a buffer gas. The single atomic gas chamber is used to receive the coaxial beam, so that rubidium 85 and rubidium 87 resonate with the two laser beams respectively. A static bias magnetic field and a high-frequency modulated magnetic field are applied to the individual atomic gas cell, causing the Zeeman level splitting of the rubidium 85 and rubidium 87. The light intensity signals corresponding to the two laser beams emitted from the single atomic gas cell are collected and converted into electrical signals. The light intensity signals include reflected s-polarized light corresponding to rubidium 85 and transmitted p-polarized light corresponding to rubidium 87. The Zeeman resonance signals corresponding to rubidium 85 and rubidium 87 are extracted from the electrical signal, and differential processing is performed on the Zeeman resonance signals to obtain the corrected magnetic field measurement values.

10. The method according to claim 9, characterized in that, The step of performing differential processing on the Zeeman resonance signal to obtain the corrected magnetic field measurement value includes: Adjust the correction coefficients and system calibration coefficients corresponding to the differential operation of the Zeeman resonance signal based on the chamber temperature of the individual atomic gas chamber or a standard magnetic field source. The corrected magnetic field measurement value is obtained based on the resonant magnetic field value corresponding to the Zeeman resonance signal, the correction coefficient, and the system calibration coefficient.

Images