Miniaturized omni-directional wide temperature range geomagnetic field atomic magnetometer device

Abstract

The present application relates to the technical field of geomagnetic field measurement, and provides a miniaturized omnidirectional wide temperature range geomagnetic field atomic magnetometer device. The present application mainly solves the limitations of the magnetometer in sensitivity, range, working temperature range, omnidirectionality and the like in the prior art. The main scheme comprises the following steps: precise temperature control is realized by using a VCSEL laser and a TEC controller to ensure stable operation of the laser; the atomic gas chamber is heated to a predetermined temperature by a DIP controller to create ideal conditions for magnetic field measurement; the wavelength of the VCSEL laser is controlled by a laser frequency modulation phase-locked amplifier to track the fine structure transition of the alkali metal atom D1 line, thereby improving the measurement precision; the drift of the microwave generator is reduced by using a digital phase-locked loop and microwave modulation technology, thereby improving the long-term stability; and the magnetic field strength is measured by a Zeeman frequency generator and phase modulation technology, thereby realizing high sensitivity and precision. The present application is suitable for accurate measurement of the geomagnetic field and can be widely applied in the fields of geological exploration, space exploration and the like.

Description

Technical Field

[0001] This invention relates to the field of quantum precision sensing and measurement, and provides a miniaturized omnidirectional wide-temperature-range geomagnetic field atomic magnetometer device. Background Technology

[0002] In the field of quantum sensing and precision measurement technology, frequency measurement is one of the most accurate and extensively studied measurement methods. The measurement principle of a quantum magnetic field meter is based on the determination of the difference frequency between two atoms or molecules. Therefore, by using precisely known quantum mechanical relationships, the measured frequency can be correlated with the external magnetic field acting on the quantum system.

[0003] The CDSM (Coupled Dark State Magnetometer) is an absolute scalar magnetometer based on the two-photon spectrum of free alkali atoms. In an external magnetic field, multiple coherent dark resonance peaks related to the magnetic field are generated. Each resonance peak reaches its maximum intensity at different angles between the magnetic field direction and the sensor reference axis defined by the laser excitation optical path. The strongest usable resonance is selected according to this angle, which enables omnidirectional measurement without dead zones, without the need for complex sensor design or additional moving parts or radio frequency coils.

[0004] Single CPT (coherent population trapping) atomic magnetometers based on the two-photon spectrum of free base atoms can be chip-based and achieve high sensitivity. However, measurement errors are limited by factors such as the type and pressure of the buffer gas in the atomic chamber and the ambient temperature, requiring high temperature control accuracy and a narrow operating temperature range. Widely used optically pumped magnetometers suffer from dead zones, have complex sensor designs with RF coils, and some applications require multiple optically pumped sensor probes to compensate for the measurement dead zone. They also have narrow temperature adaptability, making them unsuitable for applications such as UAVs and space magnetic field detection. Quantum system design is crucial, determining the main performance indicators and wide temperature adaptability of the magnetometer. Innovative quantum system design also necessitates the miniaturization of sensor probes. In optical design, the use of embedded coupling mirrors instead of commercial coupling mirrors further reduces the size and weight of sensor probes. UAV airborne applications also require miniaturization of the electronic systems; this device can reduce the size and power consumption of the electronic systems. In conclusion, the realization of a miniaturized, omnidirectional, and wide-temperature-range atomic magnetometer is of great significance for geophysical exploration applications, accelerating domestic production and independent control.

[0005] This invention aims to propose a miniaturized atomic magnetometer device and sensor probe design for measuring the Earth's magnetic field and magnetic anomalies (10). -4(Within T). The method is based on the Zeeman effect and utilizes multiple dark resonances to measure the magnetic field. In this method, the quantum system of the working atoms of the sensor is irradiated with electromagnetic radiation of different frequencies in an atomic gas cell and frequency-tuned, causing frequency splitting and frequency shifts due to the Zeeman effect. This frequency splitting leads to a decrease in fluorescence radiation, a decrease in absorption, or an increase in transmission at a certain resonance frequency (i.e., dark resonance). This resonance frequency depends on the magnetic field and is determined by frequency tuning in order to measure the magnetic field. The key feature of this method is that it uses multicolor electromagnetic radiation coupled to multiple dark resonances, and thus performs frequency detection that depends solely on the frequency shift caused by the magnetic field to measure the magnetic field.

[0006] This design can eliminate the ground state frequency ν. HFS The systematic errors in (p,T) make magnetic field measurements unaffected by factors such as the buffer gas in the atomic chamber, temperature, and pressure. A significant advantage of optical dark resonance compared to radio frequency excitation is the ability to transmit excitation radiation into the sample using optical fibers. This is particularly beneficial for sensitive magnetometers, as all magnetic and electronic components can be located away from the measurement volume. Furthermore, in principle, spatial resolution in the micrometer range is possible with optical excitation, rather than the centimeter-sized excitation region in radio frequency experiments. Therefore, such designs enable the miniaturization and microscale reduction of sensors, and even the development of chip-based atomic magnetometers.

[0007] Employing multiple coherent population trapped atom resonance peak detection schemes and triple frequency modulation spectroscopy, the sensor features an all-optical design with no radio frequency coils or motor drive mechanisms. It possesses omnidirectional measurement capabilities without dead zones within a wide temperature range (2060℃), meeting the needs of various geomagnetic range scalar magnetic field detection applications, including spaceborne magnetic field, UAV magnetic surveying, and near-shore magnetic field detection.

[0008] 133 Cs coherent dark resonance excited by a D1-line laser has a narrower linewidth and thus better sensitivity than the D2-line laser, achieving the same saturated vapor pressure in an atomic cell. 133 Cs has a lower heating temperature, which helps reduce overall power consumption. At room temperature, the vapor pressure of a cesium atom is approximately... Experiments and tests can be conducted at room temperature without the need for temperature control. 133 Cs is purified by reduction from natural cesium salts, compared to isotopes. 87 Rb is dozens of times cheaper, based on 133 Cs atomic magnetometers are advantageous for reducing costs and are more suitable for productization and industrialization. Summary of the Invention

[0009] This invention proposes a miniaturized, omnidirectional, and wide-temperature-range geomagnetic field atomic magnetometer device and sensor probe design, mainly addressing the limitations of existing magnetometers in terms of sensitivity, measurement range, operating temperature range, and omnidirectionality. This device is based on... 133 The Cs-based D1-line excited coupled dark-state magnetic field measurement scheme employs all-optical triple-frequency modulation spectroscopy, enabling dead-zone-free omnidirectional measurements over a wide temperature range of 2060℃. The sensor probe utilizes a non-magnetic housing material and fiber optic coupling, achieving a miniaturized design. Furthermore, the electronics system has been miniaturized and designed for low power consumption, comprehensively meeting the requirements of applications such as UAV aeromagnetic surveys, satellite-borne space magnetic field measurements, and unmanned vehicle magnetic navigation.

[0010] To achieve the above objectives, the following technical solutions cannot be invented: This invention provides a miniaturized omnidirectional wide-temperature-range geomagnetic field atomic magnetometer device, comprising: Sensor probe: Connects to multimode optical fiber for receiving and transmitting optical signals; Multimode fiber: Connected to sensor probes, coupling mirrors, and photodetectors to transmit optical signals; Coupler and photodetector: Connected to multimode fiber for detecting optical signals; Preamplifier: Connected to the coupling mirror and photodetector, used to amplify optical signals; Laser frequency modulation lock-in amplifier: connected to the preamplifier, used to demodulate the laser frequency modulation signal; Microwave frequency modulation lock-in amplifier: connected to the preamplifier, used to demodulate microwave frequency modulation signals; Zeeman frequency modulation lock-in amplifier: connected to a preamplifier, used to demodulate Zeeman frequency modulation signals; Controller: Connected to laser frequency modulation lock-in amplifier, microwave frequency modulation lock-in amplifier, and Zeeman frequency modulation lock-in amplifier, used for controlling signal processing and equipment operation; Zeeman frequency generator: Connected to the controller, used to generate Zeeman frequency signals; Microwave modulation frequency generator: connected to the controller, used to generate microwave modulation frequency signals; Coupler and gradient refractive index fiber: VCSEL laser (14) and sensor probe (1) are connected; TEC temperature controller: Connected to the VCSEL laser to control the laser temperature; Static constant current source: connected to the VCSEL laser to provide the laser's operating current; VCSEL laser: Connected to a static constant current source, TEC temperature controller, coupling mirror and gradient refractive index fiber, it is used to generate laser signals; DC biaser: Connected to the VCSEL laser to provide the laser bias voltage; First signal adder: Connected to the laser current modulation frequency generator and the static constant current source, used for signal addition processing between the laser current modulation frequency generator and the static constant current source; 50-ohm impedance matching: Connected to DC bias (15) for impedance matching; Electrically adjustable attenuator: connected to a dielectric oscillator, used to adjust the amplitude of microwave signals; Medium oscillator (VCO): Connected to an electrically adjustable attenuator and a digital phase-locked loop, it is used to generate microwave signals; Second signal adder: connected to digital phase-locked loop, used for signal addition processing of Zeeman frequency generator (9) and microwave modulation frequency (10); Digital phase-locked loop: connected to a second signal adder, a dielectric oscillator, and a temperature-controlled crystal oscillator (OCXO) to lock the frequency of a microwave signal; Temperature-controlled voltage crystal oscillator: connected to a digital phase-locked loop to provide a stable reference frequency; Laser current modulation frequency generator: connected to the controller, used to generate laser current modulation signals; Host computer: Connected to the controller, used for data processing and equipment control; Sensor probe PID temperature controller: connected to the sensor probe, used to control the temperature of the sensor probe; Zeeman tracking modulation frequency generator: Connected to the controller, it is used to generate Zeeman tracking modulation frequency signals.

[0011] In the above scheme, the sensor probe includes: The non-magnetic housing has a thin-film heater at its bottom. Inside the non-magnetic housing, in the order of the optical path, are an embedded micro-coupler, a neutral density filter, a polarizer, a quarter-glass slide, an alkali metal atom gas cell, and the embedded micro-coupler.

[0012] In the above scheme, the sensor probe includes an embedded miniature coupling mirror that is set inside a non-magnetic housing via a coupling mirror adjustment bracket.

[0013] In the above scheme, the VCSEL laser adopts 133 Cs D1 line laser.

[0014] The present invention also provides a control method for a miniaturized omnidirectional wide-temperature-range geomagnetic field atomic magnetometer device, comprising the following steps: Step 1: The VCSEL laser is temperature controlled by a PID controller with a set temperature control point, and the static constant current source is used to set the static operating current of the VCSEL laser. The first signal adder is connected to the laser current modulation frequency generator and the static constant current source, and is used for signal addition processing of the laser current modulation frequency generator and the static constant current source. Step 2: Based on the given set temperature, start the sensor probe PID temperature controller to heat the atomic gas chamber to the predetermined temperature range; Step 3: The controller controls the laser current modulation frequency generator to generate the laser frequency modulation signal f. refL The first frequency-modulated spectrum is generated. The frequency-modulated absorption spectrum is obtained through a coupling mirror and a photodetector. After being amplified by a preamplifier and demodulated by a laser frequency-modulated lock-in amplifier, the demodulated value is collected by a controller and the output of the static constant current source is adjusted to control the wavelength of the VCSEL laser. This enables the wavelength of the VCSEL laser to track the fine structure transition of the D1 line of alkali metal atoms and suppress frequency-modulated spectrum drift. Step 4: The controller controls the digital phase-locked loop (PLL) to lock the dielectric oscillator, which uses a temperature-controlled voltage-controlled crystal oscillator as a reference source, to generate a microwave signal f. HFS The controller controls the microwave modulation frequency generator to generate the microwave modulation frequency f. refM The signal is input to the digital phase-locked loop through the second signal adder, which generates a modulation sideband in the output microwave signal of the dielectric oscillator. The microwave signal is then input to the DC bias after being adjusted by the electrically tunable attenuator, thereby driving the VCSEL laser to generate a second frequency-modulated spectrum. The transmitted light coherent layout trapping signal is obtained through the coupling mirror and photodetector, amplified by the preamplifier, demodulated by the microwave frequency-modulated phase-locked amplifier, and locked to the temperature-controlled voltage-controlled crystal oscillator. This reduces the drift of the microwave generator and improves the long-term stability of the atomic magnetometer. Step 5: The controller drives the Zeeman frequency generator to synthesize the scanning frequency, and generates the Zeeman tracking modulation frequency f through the Zeeman tracking modulation frequency generator. refZ The Zeeman scanning frequency signal is modulated and fed into the phase modulation input of the digital phase-locked loop through the second signal adder. The frequency value corresponding to the zero-crossing point of the quadrature phase output of the Zeeman frequency modulation phase-locked amplifier is measured to track the change of Zeeman energy level induced by the magnetic field. The controller sends the obtained frequency data to the host computer and calculates the magnetic field B value using the Briet-Rabi formula.

[0015] In the above scheme, the VCSEL laser converts the projected light into linearly polarized light through an embedded micro-coupler. Then, the linearly polarized light is converted into σ+ circularly polarized light through a 1 / 4 glass plate at a 45° angle to the optical axis. The circularly polarized light is projected into a cylindrical alkali metal atom gas cell, and the transmitted light is coupled to the coupler and photodetector through a multimode fiber.

[0016] The formula for calculating the magnetic field B value in the above scheme is as follows: in, Let B be the Zeeman frequency of the magnetic field. for 133 Bohr magneton of Cs For fine-structure Landé factors, The Landé factor of the atomic nucleus, and the numbering of the CPT dark resonance. , , express 133 Cs atomic nucleus spin quantum number express 133 The magnetic quantum number of the Cs ground state with F=3 express 133 The magnetic quantum number of the Cs ground state with F=4 It is Planck's constant.

[0017] Because the present invention employs the above-mentioned technical means, it has the following beneficial effects: 1. High-sensitivity measurement scheme: adopting a method based on... 133 The Cs D1 line-excited coupled dark-state magnetic field measurement scheme, compared to 87 Rb has a narrower dark resonance linewidth, thus achieving higher sensitivity. Meanwhile, due to... 133 Cs has a lower heating temperature, which helps to reduce the overall power consumption of the machine.

[0018] 2. Wide-temperature-range dead-zone-free omnidirectional measurement: Utilizing all-optical triple-frequency modulation spectroscopy, dead-zone-free omnidirectional measurement capability is achieved within a wide temperature range of 20-60℃. This design can handle multiple dark resonance signals generated by magnetic fields at different angles and select the strongest usable resonance peak based on the direction of the magnetic field and optical axis, enabling omnidirectional dead-zone-free measurement without the need for additional motor adjustment or RF coils.

[0019] 3. Miniaturized design of the sensor probe: An embedded micro-coupler was designed using a non-magnetic housing material and fiber optic coupling, further reducing the size and weight of the sensor probe. Simultaneously, optical path collimation was adjusted by using an optical platform to adjust the height and lateral position of the support for the coupler, thus optimizing the dark resonance spectral linewidth.

[0020] 4. Miniaturized and Low-Power Electronics System: The mixing of two modulation frequencies is achieved using the phase control terminal of a digital phase-locked loop, thus miniaturizing the mixing circuit. The lock-in amplifier employs synchronous integration based on integrated operational amplifiers and phase-sensitive detection circuits based on electronic switches, achieving miniaturization of the lock-in amplifier and reducing its size, weight, and power consumption.

[0021] These innovations collectively address the shortcomings of individual CPT resonant atomic magnetometers and optically pumped magnetometers in terms of performance, sensor probes, and electronic systems, making the device particularly suitable for applications such as UAV aeromagnetic measurement, satellite-borne space magnetic field measurement, and unmanned vehicle magnetic navigation. It has significant practical value and broad application prospects. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of a miniaturized, omnidirectional, wide-temperature-range geomagnetic field atomic magnetometer device. Figure 2 This is a schematic diagram of the sensor probe structure.

[0023] Figure 1 This is a schematic diagram of the overall structure of a miniaturized omnidirectional wide-temperature-range geomagnetic field atomic magnetometer device for implementing the present invention. Figure 2 yes Figure 1 A schematic diagram of the sensor probe structure involved.

[0024] Attached Figure ( Figure 1 The labels are listed below: 1-Sensor probe; 2-Multimode fiber; 3-Coupled mirror and photodetector; 4-Preamplifier; 5-Laser frequency-modulated phase-locked amplifier; 6-Microwave frequency-modulated phase-locked amplifier; 7-Zeeman frequency-modulated phase-locked amplifier; 8-Controller; 9-Zeeman frequency generator; 10-Microwave modulation frequency generator; 11-Coupled mirror and gradient refractive index fiber; 12-TEC temperature controller; 13-Static constant current source; 14-VCSEL laser; 15-DC biaser; 16-First signal adder; 17-50 ohm impedance matching; 18-Electrically adjustable attenuator; 19-Dielectric oscillator; 20-Second signal adder; 21-Digital phase-locked loop; 22-Temperature-controlled voltage-controlled crystal oscillator; 23-Laser current modulation frequency generator; 24-Host computer; 25-Sensor probe PID temperature controller; 26-Zeeman tracking modulation frequency generator.

[0025] Attached Figure ( Figure 2 The markings are listed below: 27-Embedded miniature coupler; 28-Neutral light shield; 29-Polarizer; 30-1 / 4 glass slide; 31-Alkali metal atom gas cell; 32-Thin film heater; 33-Coupler adjustment support; 34-Non-magnetic housing. Detailed Implementation

[0026] The embodiments of the present invention will be described in detail below. Although the present invention will be described and illustrated in conjunction with some specific embodiments, it should be noted that the present invention is not limited to these embodiments. On the contrary, any modifications or equivalent substitutions made to the present invention should be covered within the scope of the claims of the present invention.

[0027] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art will understand that the present invention can be practiced without these specific details.

[0028] Figure 1 This is a schematic diagram of the overall structure of a miniaturized omnidirectional wide-temperature-range geomagnetic field atomic magnetometer device for implementing the present invention. Figure 2 yes Figure 1 A schematic diagram of the sensor probe structure is shown in the attached figure. A specific implementation method for a miniaturized omnidirectional wide-temperature-range geomagnetic field atomic magnetometer device and its sensor probe design includes the following steps: Step 1, the VCSEL laser 14 is temperature-controlled using a PID method by setting a temperature control point via a TEC temperature controller 12, and the static constant current source 13 sets the static operating current of the VCSEL laser 14; Step 2, according to the given set temperature, the sensor probe PID temperature controller 25 is activated to heat the atomic gas chamber to the predetermined temperature range; Step 3, the controller 8 controls the laser current modulation frequency generator 23 to generate a laser frequency modulation signal f. refL The first frequency-modulated spectrum is generated. The absorption spectrum of the frequency-modulated spectrum is obtained by photodetector 3, amplified by preamplifier 4, demodulated by laser frequency-modulated lock-in amplifier 5, and the demodulated value is collected by controller 8 and the output of static constant current source is adjusted to control the wavelength of VCSEL laser 14, so that the wavelength of VCSEL laser 14 tracks the fine structure transition of alkali metal atom D1 line and suppresses frequency-modulated spectrum drift; in step 4, controller 8 controls digital phase-locked loop 21 with temperature-controlled voltage-controlled crystal oscillator 22 as reference source to lock dielectric oscillator 19 and generate microwave signal f. HFS Controller 8 controls microwave modulation frequency generator 10 to generate microwave modulation frequency f. refM The signal is input to the digital phase-locked loop 21 via the second signal adder 20, which generates a modulation sideband in the output microwave signal of the dielectric oscillator 19. This microwave signal is then adjusted by the electrically adjustable attenuator 18 and input to the DC bias 15, thereby driving the VCSEL laser 14 to generate a second frequency-modulated spectrum. The transmitted light coherent layout trapping (CPT) signal is obtained by the photodetector 3, amplified by the preamplifier 4, demodulated by the microwave lock-in amplifier 6, and locked to the OCXO, reducing the drift of the microwave generator and thus improving the long-term stability of the atomic magnetometer. In step 5, the controller 8 drives the Zeeman frequency generator 9 to synthesize the scanning frequency, and the Zeeman tracking modulation frequency f is generated by the Zeeman tracking modulation frequency generator 26. refZThe Zeeman scanning frequency signal is modulated and sent to the phase modulation input terminal of the digital phase-locked loop 21 through the second signal adder 20. The frequency value corresponding to the zero crossing point of the quadrature phase output of the Zeeman frequency modulation phase-locked amplifier 7 is measured to track the change of Zeeman energy level induced by the magnetic field. The controller MCU8 sends the obtained frequency data to the host computer 24 and calculates the B value using the Briet-Rabi formula.

[0029] exist Figure 2 In the process, the optical path collimation is adjusted by using an optical platform to adjust the height and lateral position of the coupling mirror and the support 33; the polarizer 29 will... Figure 1 The light projected by the VCSEL laser 14 through the embedded coupler is converted into linearly polarized light. Then, it passes through a quarter-glass plate at a 45° angle to the optical axis, converting the linearly polarized light into σ+ circularly polarized light. This circularly polarized light is projected into the cylindrical alkali metal atom gas cell 31. The transmitted light passes through… Figure 1 Multimode fiber 2 is coupled to a coupling mirror and photodetector 3.

[0030] Specifically, this invention is used to implement... 133 The design and implementation steps of the coupled dark-state atomic magnetometer device and sensor probe excited by the Cs D1 line laser are as follows: Step 1, the VCSEL laser 14 is set to a temperature control point of 75℃ by the TEC controller 12 and the temperature is controlled by PID. The static constant current source 13 sets the static operating current of the VCSEL laser 14 to 1-1.2mA, and the wavelength of the VCSEL laser 14 is measured to be approximately 894.59nm; Step 2, the temperature of the sensor probe 1 is set to 50℃, and the PID temperature controller 25 of the sensor probe is started to heat the atomic gas chamber to the predetermined temperature range. The heating temperature is monitored by the negative coefficient thermistor (NTC) attached to the outside of the sensor probe 1; Step 3, the controller 8 controls the laser current modulation frequency generator 23 to generate the laser frequency modulation signal f. refL A 5kHz square wave can be used for frequency modulation to generate the first frequency-modulated spectrum. The Doppler absorption spectrum after frequency modulation is obtained by photodetector 3 and amplified by preamplifier 4. The preamplifier is a transimpedance amplifier that outputs an AC signal with a certain amplification factor and signal-to-noise ratio. This signal is demodulated by laser frequency modulation lock-in amplifier 5, and the demodulated value is acquired by controller 8, which adjusts the output of static constant current source to control the wavelength of VCSEL laser 14, so that VCSEL laser 14 wavelength tracking... 133 Cs atom D1 line fine structure transition suppresses frequency modulation spectrum drift; Step 4, controller 8 controls the ∑-Δ digital phase-locked loop 21, with a 10MHz isothermal voltage-controlled crystal oscillator (OCXO) 22 as the reference source, to lock the 4596MHz dielectric oscillator 19, generating microwave signal f. HFS 9192.63MHz, controller 8 controls microwave modulation frequency generator 10 to generate microwave modulation frequency f refMThe signal, 300 kHz, is input to the digital phase-locked loop 21 via the second signal adder 20, thereby generating a modulation sideband in the output microwave signal of the dielectric oscillator 19. The frequency difference between the two first-order sidebands is 9192.63 MHz. This microwave signal is then input to the DC bias 15 after being adjusted by the electrically tunable attenuator 18, thereby driving the VCSEL laser 14 to generate a second frequency-modulated spectrum. The transmitted light coherent layout trapping (CPT) signal is obtained by the photodetector 3, amplified by the preamplifier 4, demodulated by the microwave lock-in amplifier 6, and locked to the 10 MHz temperature-controlled crystal oscillator (OCXO) 22 to reduce the drift of the microwave generator and thus improve the long-term stability of the atomic magnetometer. In step 5, the controller 8 drives the Zeeman frequency generator 9 to synthesize the scanning frequency (<1.2 MHz, step 0.3 mHz), and generates the Zeeman tracking modulation frequency f through the Zeeman tracking modulation frequency generator 26. refZ (3kHz) Modulated Zeeman scan frequency signal, which is sent to the phase modulation input terminal of digital phase-locked loop 21 through second signal adder 20, to measure the frequency value corresponding to the zero-crossing point of the quadrature phase output of Zeeman frequency modulation phase-locked amplifier 7. By tracking the Zeeman level changes induced by the magnetic field, the controller MCU8 sends the obtained frequency data to the host computer 24, which calculates the value of B using the Briet-Rabi formula. The Briet-Rabi formula is shown below: in, Let B be the Zeeman frequency of the magnetic field. for 133 Bohr magneton of Cs For fine-structure Landé factors, The Landé factor of the atomic nucleus, and the numbering of the CPT dark resonance. , , express 133 Cs atomic nucleus spin quantum number express 133 The magnetic quantum number of the Cs ground state with F=3 express 133 The magnetic quantum number of the Cs ground state with F=4 It is Planck's constant.

[0031] The mixing of two modulation frequencies is achieved by using the phase control terminal of a digital phase-locked loop 21, instead of a ring mixer or circulator, thus enabling miniaturization of the mixing circuit. The laser frequency modulation phase-locked amplifier 5, microwave frequency modulation phase-locked amplifier 6, and Zeeman frequency modulation phase-locked amplifier 7 employ synchronous integration based on integrated operational amplifiers and phase-sensitive detection circuits based on electronic switches. Miniaturization of these amplifiers is achieved using surface-mount integrated operational amplifier ICs.

[0032] exist Figure 2 In the process, the optical path collimation is adjusted by using an optical platform to adjust the height and lateral position of the coupling mirror and the support 33; the polarizer 29 will... Figure 1 The light projected by the VCSEL laser 14 through the embedded coupler is converted into linearly polarized light. The polarization angle of the quarter-glass slide is obtained by polarization measurement. The light is then placed in the non-magnetic housing 34 of the sensor probe and converted into σ+ circularly polarized light by passing through the quarter-glass slide at a 45° angle to the optical axis. The circularly polarized light is projected onto the cylindrical alkali metal atom gas cell 31, and the transmitted light passes through... Figure 1 The multimode fiber 2 is coupled to the coupling mirror and photodetector 3. The neutral density filter 28 is adjusted and replaced in the device, and the short-term stability change of the 10MHz output is optimized by measuring the change.

[0033] Apart from the sensor probe and coupler, the rest of the device can be designed as a miniaturized, low-power mixed-signal electronics system implemented on a single circuit board. In particular, multiple lock-in amplifiers are implemented using synchronous integration based on integrated operational amplifiers and switching phase-sensitive detector circuits, which reduces size, weight and power consumption and eliminates the risk of lack of independent control.

[0034] The miniaturized atomic magnetometer developed using the method of this patent has high sensitivity, wide measurement range, wide operating temperature range, and omnidirectional properties without dead zones. It can be used for UAV aeromagnetic measurement or satellite-borne space magnetic field measurement. It can be used in various fields such as geophysical surveying and mapping, port or near-shore salvage exploration, seismic station geomagnetic monitoring, military unexploded ordnance detection, and concealed tactical target detection within the Earth's magnetic field range. Its miniaturization and wide temperature range are particularly suitable for UAV-mounted applications and can also be used for portable field magnetic detection.

Claims

1. A miniaturized omnidirectional wide-temperature-range geomagnetic field atomic magnetometer device, characterized in that, include: Sensor probe (1): connected to multimode optical fiber (2) for receiving and transmitting optical signals; Multimode fiber (2): connected to sensor probe (1) and coupling mirror and photodetector (3) for transmitting optical signals; Coupler and photodetector (3): connected to multimode fiber (2) for detecting optical signals; Preamplifier (4): Connected to the coupling mirror and photodetector (3), used to amplify the optical signal; Laser frequency modulation lock-in amplifier (5): connected to preamplifier (4) for demodulating laser frequency modulation signal; Microwave frequency modulation lock-in amplifier (6): connected to preamplifier (4) for demodulating microwave frequency modulation signals; Zeeman frequency modulation lock-in amplifier (7): connected to the preamplifier (4) for demodulating Zeeman frequency modulation signals; Controller (8): Connected to laser frequency modulation lock-in amplifier (5), microwave frequency modulation lock-in amplifier (6), and Zeeman frequency modulation lock-in amplifier (7), used for controlling signal processing and equipment operation; Zeeman frequency generator (9): One end is connected to the controller (8), and the other end is connected to the second signal adder (20). It is used to generate Zeeman scanning frequency signals and send them to the phase modulation input terminal of the digital phase-locked loop (21) through the second signal adder (20). Microwave modulation frequency generator (10): One end is connected to the controller (8), and the other end is connected to the second signal adder (20). It is used to generate microwave modulation frequency signals and input them to the digital phase-locked loop (21) through the second signal adder (20). Coupler and gradient refractive index fiber (11): connected to VCSEL laser (14) and sensor probe (1); TEC temperature controller (12): connected to VCSEL laser (14) for controlling laser temperature; Static constant current source (13): connected to DC bias (15) through first signal adder (16), DC bias (15) is connected to VCSEL laser (14), and static constant current source (13) is also connected to controller (8) to provide laser operating current; VCSEL laser (14): connected to TEC temperature controller (12), coupling mirror and gradient refractive index fiber (11) to generate laser signal; DC bias unit (15): connected to VCSEL laser (14) to provide laser bias voltage; First signal adder (16): connected to laser current modulation frequency generator, static constant current source and DC bias (15), used to add the signals from laser current modulation frequency generator and static constant current source to DC bias (15). 50-ohm impedance matching (17): Set on the microwave signal transmission path between the DC bias (15) and the electrically adjustable attenuator (18) to achieve impedance matching for microwave signal transmission; Electrically adjustable attenuator (18): connects the 50-ohm impedance matching (17) and the dielectric oscillator (19) to adjust the amplitude of the microwave signal; Dielectric oscillator (19): connected to electrically adjustable attenuator (18) and digital phase-locked loop (21) to generate microwave signals; Second signal adder (20): connected to digital phase-locked loop (21), used for signal addition processing of Zeeman frequency generator (9) and microwave modulation frequency generator (10); Digital phase-locked loop (21): Connected to the second signal adder (20), dielectric oscillator (19), and temperature-controlled crystal oscillator (22), it is used to lock the microwave signal frequency and lock the dielectric oscillator (19) to generate the microwave signal f using the temperature-controlled crystal oscillator (22) as a reference source. HFS Thermostatic voltage-controlled crystal oscillator (22): connected to digital phase-locked loop (21) and controller (8) to provide a stable reference frequency; Laser current modulation frequency generator (23): connected to controller (8), used to generate laser current modulation signal; Host computer (24): connected to controller (8) for data processing and equipment control; Sensor probe PID temperature controller (25): connected to sensor probe (1) and used to control the temperature of sensor probe; Zeeman tracking modulation frequency generator (26): connected to controller (8) for generating Zeeman tracking modulation frequency signal; The sensor probe (1) includes: A non-magnetic housing (34) is provided with a thin film heater (32) at the bottom of the non-magnetic housing (34). Inside the non-magnetic housing (34), in the order of the optical path direction, there are embedded micro-coupler (27), neutral light blocker (28), polarizer (29), 1 / 4 glass slide (30), alkali metal atom gas cell (31), and embedded micro-coupler (27). The polarizer (29) is used to convert the incident light into linearly polarized light, and the optical axis of the 1 / 4 glass plate (30) is at a 45° angle to the polarization direction, which is used to convert the linearly polarized light into σ+ circularly polarized light to be projected into the alkali metal atom gas cell (31).

2. The miniaturized omnidirectional wide-temperature-range geomagnetic field atomic magnetometer device according to claim 1, characterized in that: The embedded micro-coupler (27) is set inside the non-magnetic housing (34) via the coupler adjustment support (33).

3. The miniaturized omnidirectional wide-temperature-range geomagnetic field atomic magnetometer device according to claim 1, characterized in that, VCSEL lasers use 133 Cs D1 line laser.

4. The control method for a miniaturized omnidirectional wide-temperature-range geomagnetic field atomic magnetometer device according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: The VCSEL laser (14) is temperature controlled by PID mode by setting the temperature control point through the TEC temperature controller (12), and the static constant current source (13) sets the static operating current of the VCSEL laser (14); the first signal adder (16) is connected to the laser current modulation frequency generator and the static constant current source for signal addition processing of the laser current modulation frequency generator and the static constant current source. Step 2: Based on the given set temperature, start the sensor probe PID temperature controller (25) to heat the atomic gas chamber to the predetermined temperature range; Step 3, the controller (8) controls the laser current modulation frequency generator (23) to generate the laser frequency modulation signal f. refL This generates the first frequency-modulated spectrum; The frequency-modulated absorption spectrum is obtained by a coupling mirror and a photodetector (3), amplified by a preamplifier (4), demodulated by a laser frequency-modulated lock-in amplifier (5), and the demodulated value is collected by a controller (8) and the output of a static constant current source is adjusted to control the wavelength of the VCSEL laser (14), so that the wavelength of the VCSEL laser (14) tracks the fine structure transition of the D1 line of alkali metal atoms and suppresses the frequency-modulated spectrum drift. Step 4: The controller (8) controls the digital phase-locked loop (21) with the isothermal voltage-controlled crystal oscillator (22) as the reference source to lock the dielectric oscillator (19) and generate a microwave signal f. HFS The controller (8) controls the microwave modulation frequency generator (10) to generate the microwave modulation frequency f. refM The signal is input to the digital phase-locked loop (21) through the second signal adder (20), and then a modulation sideband is generated in the output microwave signal of the dielectric oscillator (19). The microwave signal is input to the DC bias (15) after being adjusted by the electrically tunable attenuator (18), thereby driving the VCSEL laser (14) to generate the second frequency-modulated spectrum. The transmitted light coherent layout trapping signal is obtained through the coupling mirror and photodetector (3), amplified by the preamplifier (4), demodulated by the microwave frequency-modulated phase-locked amplifier (6), and locked to the temperature-controlled voltage-controlled crystal oscillator (22), reducing the drift of the microwave generator and thus improving the long-term stability of the atomic magnetometer. Step 5: The controller (8) drives the Zeeman frequency generator (9) to synthesize the Zeeman scanning frequency, and generates the Zeeman tracking modulation frequency f through the Zeeman tracking modulation frequency generator (26). refZ The Zeeman scanning frequency signal is modulated and sent to the phase input terminal of the digital phase-locked loop (21) through the second signal adder (20). The frequency value corresponding to the zero-crossing point of the quadrature phase output of the Zeeman frequency modulation phase-locked amplifier (7) is measured to track the Zeeman energy level change induced by the magnetic field. The controller (8) sends the obtained frequency data to the host computer (24) and calculates the magnetic field B value using the Breit-Rabi formula.

5. The control method for a miniaturized omnidirectional wide-temperature-range geomagnetic field atomic magnetometer device according to claim 4, characterized in that: The light projected by the VCSEL laser (14) through the embedded micro-coupler (27) is converted into linearly polarized light by the polarizer (29), and then converted into σ+ circularly polarized light by a 1 / 4 glass plate (30) at a 45° angle to the optical axis. The circularly polarized light is projected into a cylindrical alkali metal atom gas cell (31), and the transmitted light is coupled to the coupler and photodetector (3) through a multimode fiber (2).

6. The control method for a miniaturized omnidirectional wide-temperature-range geomagnetic field atomic magnetometer device according to claim 5, characterized in that: The formula for calculating the value of the magnetic field B is as follows: in, Let B be the Zeeman frequency of the magnetic field. for 133 Bohr magneton of Cs For fine-structure Landé factors, The Landé factor of the atomic nucleus, and the numbering of the CPT dark resonance. , , express 133 Cs atomic nucleus spin quantum number express 133 The magnetic quantum number of the Cs ground state with F=3 express 133 The magnetic quantum number of the Cs ground state with F=4 It is Planck's constant.

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