Pulse laser pumping cesium atom magnetometer and magnetic field measurement method

Abstract

The invention provides a pulse laser pumping cesium atom magnetometer and a measuring method. The magnetometer comprises a physical probe part and a circuit part. The physical probe comprises a VCSEL laser, an optical element, a cesium atom absorption gas chamber, a radio frequency coil and a photoelectric detector; the circuit part comprises a photoelectric conversion circuit, a differential amplification circuit and a radio frequency excitation circuit. The method comprises the following steps: carrying out optical pumping on cesium atoms by adopting pulse laser, inducing magnetic resonance through a radio frequency field, detecting precession signals by utilizing a time division multiplexing mechanism, forming self-oscillation through differential amplification and feedback, and calculating the external magnetic field intensity through oscillation frequency. The invention further provides a scheme for adaptively switching between a high-sensitivity working mode and a wide-bandwidth working mode based on the change degree of a magnetic field measurement value and a scheme for accumulatively detecting a magnetic field for mobile platform application. The invention has the characteristics of high sensitivity, large bandwidth, small volume and low power consumption, and is suitable for geomagnetic field and magnetic field measurement in a wider range.

Description

Technical Field

[0001] This application relates to the field of magnetometer technology, and in particular to a cesium atom magnetometer with high sensitivity and large bandwidth and a method for measuring the magnetic field thereon. Background Technology

[0002] An atomic magnetometer is a highly sensitive magnetic field measurement device based on the Zeeman splitting of atomic energy levels in a magnetic field and the interaction between light and atoms. Optically pumped atomic magnetometers use circularly polarized light to pump atoms to specific energy levels, inducing a macroscopic magnetic moment in the atomic system. By applying a radio frequency field resonating with the Larmor frequency, the atoms can undergo magnetic resonance, causing the macroscopic magnetic moment to precess, thereby modulating the absorptivity of the probe light. The magnetic resonance signal is obtained by detecting changes in the intensity of the transmitted light; the resonance frequency is proportional to the strength of the external magnetic field, thus enabling absolute measurement of the magnetic field.

[0003] To simplify system structure and improve dynamic response speed, self-oscillating atomic magnetometers have been extensively studied. In this type of scheme, the detected magnetic resonance signal is amplified, phase-shifted, and directly fed back to the radio frequency coil, forming a closed-loop oscillation circuit, and the system automatically locks onto the Larmor frequency for oscillation. For example, a classic continuous-wave (CW) optically pumped self-oscillating magnetometer is described in the paper "A high-sensitivity laser-pumped Mx magnetometer" (EB Alexandrov et al., Meas. Sci. Technol., 2004). While this type of scheme avoids the complexity of active frequency scanning, it has two inherent limitations that are interrelated:

[0004] (1) Sensitivity is limited by background noise and interference: In continuous wave operation mode, pump light, probe light (sometimes combined into one beam), and radio frequency field coexist. On the one hand, the optical noise (photon shot noise, laser intensity noise) brought by strong pump light will directly drown out the weak magnetic resonance signal (see the literature "Noise analysis of a single-beamoptically pumped magnetometer" (JC Allred et al., Phys. Rev. A, 2002)). On the other hand, the electromagnetic interference generated by the radio frequency field itself will also couple into the probe circuit, forming an additional noise floor. Although techniques such as lock-in amplification can be used to extract the signal, these coexisting interference sources fundamentally limit further improvement of signal-to-noise ratio and sensitivity.

[0005] (2) There is an inherent contradiction between response bandwidth and sensitivity: The dynamic response bandwidth of an atomic magnetometer is mainly constrained by the transverse relaxation time (T2) of the atomic spin. To obtain high sensitivity, T2 needs to be extended as much as possible (i.e., to maintain the coherence of the atomic spin for a longer time), but this will slow down the system's response to changes in the magnetic field and narrow the bandwidth (BW∼1 / (πT2)). This is an inherent physical trade-off. In order to maintain loop stability, the feedback parameters (gain, phase) of traditional self-excited oscillation circuits are usually set conservatively, which further limits their ability to track rapidly changing magnetic fields, i.e., insufficient effective measurement bandwidth (as discussed in the literature "Bandwidth optimization of an atomic magnetometer operated in the spin-exchange relaxation-free regime" (IM Savukov et al., J. Appl.Phys., 2012)). In practical applications, such as airborne magnetometry and magnetocardiography, both high sensitivity to detect weak signals and wide bandwidth to capture rapid transients or perform high-speed scanning are required, making this contradiction particularly prominent.

[0006] In addition, in order to maintain the working temperature of the gas chamber, the heating coil of a traditional heating system may introduce additional AC or DC magnetic field noise, which becomes a factor that cannot be ignored in affecting the limiting sensitivity.

[0007] Therefore, there is an urgent need in this field for an innovative atomic magnetometer solution that aims to break the aforementioned trade-off between sensitivity and bandwidth, achieving both high sensitivity and large bandwidth, while effectively suppressing system background noise, in order to meet the urgent needs of modern high-dynamic-precision magnetic field measurement. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a pulsed laser-pumped cesium atom magnetometer and magnetic field measurement method with high sensitivity and large measurement bandwidth.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a pulsed laser-pumped cesium atom magnetometer, comprising a physical probe and a circuit.

[0011] The physical probe component includes:

[0012] VCSEL lasers are used to emit pulsed lasers containing D1 lines of cesium atoms.

[0013] A convex lens, a filter, a polarizer, and a quarter-wave plate arranged sequentially along the optical path are used to shape the laser beam emitted by the laser into collimated left-handed circularly polarized light.

[0014] The cesium atom absorption chamber is filled with alkali metal cesium.

[0015] A radio frequency coil, wound around the cesium atom absorption gas cell, is used to generate a radio frequency magnetic field perpendicular to the optical axis;

[0016] A photodetector is installed on the light-emitting side of the cesium atom absorption gas cell to detect changes in the intensity of transmitted light and convert them into electrical signals.

[0017] The circuit portion includes:

[0018] A timing control system is used to control the pulse operating timing of the VCSEL laser and the radio frequency coil;

[0019] A photoelectric conversion and amplification circuit, connected to the photodetector, is used to initially amplify the electrical signal;

[0020] A differential amplifier circuit, connected to the photoelectric conversion and amplification circuit, is used to extract and amplify specific frequency components in the electrical signal;

[0021] The radio frequency excitation circuit, connected to the differential amplifier circuit and the radio frequency coil, is used to generate a radio frequency signal to drive the radio frequency coil based on the processed signal, thereby forming a closed-loop self-excited oscillation circuit.

[0022] The oscillation frequency of the self-excited oscillation circuit when it is stable is proportional to the strength of the external magnetic field to be measured.

[0023] Secondly, the present invention provides a method for measuring magnetic fields using the above-mentioned magnetometer, comprising the following steps:

[0024] Optical pumping step: The VCSEL laser is driven by a timing control system to emit pulsed left-handed circularly polarized light to optically pump cesium atoms in the cesium atom absorption gas cell and prepare a quantum state;

[0025] Magnetic resonance procedure: A radio frequency magnetic field is applied through a radio frequency coil to induce Larmor precession of the macroscopic magnetic moment of the atoms;

[0026] Optical detection step: Using a time-division multiplexing mechanism, a photodetector detects the periodic changes in absorbed light intensity caused by precession and converts them into an alternating current signal;

[0027] Signal processing and feedback steps: The AC signal is amplified and processed sequentially through a photoelectric conversion and amplification circuit and a differential amplification circuit, and then fed back to the radio frequency coil through a radio frequency excitation circuit to form self-excited oscillation;

[0028] Frequency measurement and magnetic field calculation steps: Measure the oscillation frequency of the self-excited oscillation circuit when it is stable, and calculate the external magnetic field strength based on the linear relationship between frequency and magnetic field.

[0029] Specifically, the working process of the magnetometer described in this invention is as follows: The timing control system pulses the circularly polarized light emitted by the VCSEL laser to generate periodic laser pulses for optical pumping of cesium atoms, thereby preparing a highly polarized quantum state; subsequently, a radio frequency magnetic field is applied through the radio frequency coil to induce magnetic resonance, causing Larmor precession of the macroscopic magnetic moment of the atoms. This invention creatively employs time-division multiplexing of the output laser light from the VCSEL laser: when used as pump light, its wavelength is set to 895 nm; when converted to detection light, its wavelength is synchronously and precisely adjusted to 894.98 nm through a frequency shifting circuit. During the detection light's working period, the radio frequency field signal is synchronously turned off, effectively avoiding interference from the pump light and the radio frequency field on the detection signal. At this time, a photodetector detects the periodic changes in the absorption light intensity caused by atomic precession, and the converted electrical signal is fed back to the radio frequency coil after lock-in amplification and phase shifting, ultimately forming a self-excited oscillation synchronized with the Larmor frequency. By measuring this stable oscillation frequency, the external magnetic field strength can be accurately inferred.

[0030] Furthermore, the magnetometer described in this invention can achieve dynamic optimization of measurement sensitivity and bandwidth through extended timing control and signal processing strategies, and can effectively suppress environmental vibration noise by utilizing coherent cumulative detection technology, thereby maintaining excellent performance in both static precision measurement and dynamic fast tracking scenarios.

[0031] The beneficial effects of this invention are as follows:

[0032] High sensitivity and high signal-to-noise ratio: The time-division multiplexing scheme of pulsed laser pumping and detection effectively avoids direct interference between the pump light and the radio frequency field during detection. Combined with a differential amplifier circuit, the background noise is significantly eliminated, resulting in a substantial increase in the signal amplitude of the magnetometer output, achieving a sensitivity of 0.9 pT / √Hz.

[0033] Wide bandwidth and fast response: The pulse operating mode reduces the transient response time of the system. Combined with the optimized feedback circuit, it achieves a wider measurement bandwidth than the traditional continuous wave scheme, enabling rapid tracking of dynamic changes in the magnetic field.

[0034] Compact structure and low power consumption: Using a VCSEL laser as the core light source, combined with highly integrated optical and circuit design, the entire magnetometer is small in size, low in power consumption, and highly reliable, making it very suitable for field and airborne magnetic surveying applications. Attached Figure Description

[0035] 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.

[0036] Figure 1 This is a block diagram of the pulsed laser-pumped cesium atom magnetometer of the present invention; Figure 2 This is a schematic diagram of the control timing and Larmor precession frequency of the pulsed laser-pumped cesium atom magnetometer of the present invention; Figure 3 This is a schematic diagram of the differential amplifier circuit of the present invention; Figure 4 This is a comparison diagram of the magnetic field signals before and after differential amplification in this invention; Figure 5 The graph shows the magnetic field results (a) and sensitivity test indicators (b) measured by the atomic magnetometer used in this invention.

[0037] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] Example 1

[0040] like Figure 1 As shown, the pulsed laser-pumped cesium atom magnetometer of this embodiment consists of a physical probe and a circuit section.

[0041] The physical probe is internally sealed, and its optomechanical structure is as follows: After the VCSEL laser is ignited, the emitted light is parallelized by a convex lens. The parallel light then passes through a filter to select the target wavelength. This beam is then polarized by a polarizer. The linearly polarized light then passes through a quarter-wave plate, whose fast and slow axes are precisely adjusted to make the outgoing light left-handed circularly polarized. This left-handed circularly polarized light is incident on the cesium atom absorption gas cell. The gas cell is maintained at its operating temperature by a non-magnetic heating system. An RF coil wound around the gas cell carries an RF current, generating an oscillating magnetic field perpendicular to the optical axis. The light transmitted through the gas cell is received by a photodetector.

[0042] The circuit's workflow is as follows: The output of the photodetector is pre-amplified by a photoelectric conversion and amplification circuit. The amplified signal is then fed into a differential amplifier circuit to effectively extract and amplify the magnetic resonance signal at a specific frequency while suppressing common-mode noise. The processed signal is then fed into an RF excitation circuit to generate an RF signal that drives the RF coil. From the coil to the detector, then to the circuit, and finally back to the coil, a complete positive feedback closed loop is formed, and the system generates stable self-excited oscillations at the Larmor frequency. The oscillation frequency is measured by a frequency meter, and the processor ultimately calculates and outputs the magnetic field value according to the formula B0 = f / γ (where γ is the gyromagnetic ratio of cesium atoms).

[0043] The core of this invention is the pulse operation and time-division multiplexing process, combined with Figure 2 The control timing shown is as follows:

[0044] Optical pumping stage: The timing control system first controls the VCSEL laser to emit pulsed left-handed circularly polarized light with a wavelength of 895nm to fully optically pump the atoms in the cesium atom absorption gas cell, preparing them to a specific highly polarized quantum state (such as a certain Zeeman sublevel).

[0045] Magnetic Resonance Excitation and Detection Stage: After the pump light pulse ends, the timing control system performs two synchronous operations: First, it controls the VCSEL laser to rapidly and precisely adjust its output laser wavelength to 894.98 nm via a built-in or external frequency-shifting circuit, converting it into detection light; second, it shuts off the drive signal of the RF coil. At this time, the macroscopic magnetic moments of the atoms, under the established polarization, are only affected by the external magnetic field to be measured, and precess freely at the Larmor frequency. This precession modulates the absorption rate of the detection light as it passes through the gas cell, causing periodic variations in the intensity of the transmitted light.

[0046] Signal feedback and self-oscillation establishment: The photodetector converts the aforementioned periodic light intensity changes into corresponding alternating current signals. After initial amplification by the photoelectric conversion and amplification circuit, this signal is further amplified by the differential amplifier circuit (such as...). Figure 3 Further extracting and enhancing its Larmor frequency components, and suppressing noise, the magnetic field signals before and after differential amplification are compared, for example... Figure 4 As shown. Subsequently, the signal undergoes phase-locked amplification and phase adjustment in the radio frequency excitation circuit to generate a radio frequency signal with the same frequency and phase as the atomic precession, which is then fed back to drive the radio frequency coil. This feedback signal precisely and continuously excites the atomic precession, thus forming a self-excited oscillating closed loop that satisfies both phase and amplitude conditions. The system quickly locks in and stabilizes at this Larmor frequency.

[0047] Frequency Measurement and Output: The oscillation frequency is captured in real time by a high-precision frequency measurement and processing unit (such as an FPGA or a high-speed frequency meter). Finally, the microprocessor calculates and outputs in real time the absolute strength B0 of the magnetic field to be measured according to the formula B0=f / γ (where, for cesium atoms, the gyromagnetic ratio γ is 3.5Hz / nT). (The sensitivity of this embodiment is as follows:) Figure 5 (As shown).

[0048] Example 2

[0049] The magnetic field measurement using the magnetometer described in Example 1 includes the following steps: The system is started, and the non-magnetic heating system is preheated to its operating temperature. A timing control system issues a command, and the VCSEL laser emits pulsed laser light during the pumping phase to optically pump cesium atoms, preparing atomic polarization. After the pumping phase, the detection phase begins. An RF coil applies an RF field to induce Larmor precession of the atomic macroscopic magnetic moment. At this time, a photodetector detects the periodically changing intensity of transmitted light due to precession and converts it into an AC signal. This AC signal is amplified and noise-suppressed by a photoelectric conversion and amplification circuit and a differential amplification circuit, and then fed back to the RF coil by the RF excitation circuit, forming a self-excited oscillation. A frequency meter accurately measures the oscillation frequency f at this time, and the microprocessor calculates and outputs the magnetic field strength B0 in real time according to the formula B0 = f / 3.5 (nT / Hz). When the external magnetic field changes, the self-excited oscillation frequency automatically tracks the change, achieving continuous and high-precision measurement of the magnetic field.

[0050] Example 3

[0051] Based on Example 1, this embodiment expands the functionality of the timing control system and feedback loop, enabling it to dynamically adjust the relaxation time of the atomic spin system according to measurement requirements. This allows for optimized switching between two modes: high-sensitivity static measurement and wide-bandwidth dynamic tracking, thus resolving the inherent contradiction between "sensitivity and bandwidth" mentioned in the background art.

[0052] The specific implementation method is as follows:

[0053] Dynamic parameter control module: The timing control system integrates or connects to a dynamic parameter control module. This module can dynamically adjust the following key parameters according to external commands or preset programs:

[0054] Pump laser parameters include the pump pulse width (T_pump), power (P_pump), and duty cycle. For example, when high sensitivity is required to measure static or slowly varying magnetic fields, a longer T_pump (e.g., 1 ms) and a higher P_pump are set to establish higher atomic polarization (long T_2). When rapid tracking of dynamic magnetic fields is required, T_pump is shortened (e.g., 0.1 ms) and P_pump may be appropriately reduced to sacrifice some polarization for a faster system response (effectively shortening T_2).

[0055] RF excitation parameters: The automatic gain control (AGC) module in the RF excitation circuit dynamically sets the gain threshold and response speed of the feedback loop. In high-sensitivity mode, a higher gain and fine phase locking are used to maintain stable oscillation of extremely low amplitude signals; in wide-bandwidth mode, the gain is appropriately reduced and the AGC response speed is accelerated to enhance the loop's ability to track rapid frequency changes and prevent loss of lock.

[0056] Workflow (taking mode switching as an example):

[0057] After the system is powered on, it enters adaptive mode by default. The frequency measurement and processing unit continuously monitors the rate of change (df / dt) of the self-excited oscillation frequency.

[0058] When df / dt is lower than a preset low-speed threshold (e.g., 10 nT / s), the system determines that the magnetic field change is slow and automatically switches to "high-sensitivity mode." At this time, the timing control system controls the VCSEL laser to emit a pump light pulse with a longer pulse width and higher power, and the AGC of the RF excitation circuit is set to high gain and slow response. Figure 5 As shown, in this mode, the system sensitivity can reach 0.9 pT / √Hz.

[0059] When df / dt exceeds a preset high-speed threshold (e.g., 100 nT / s), the system determines that the magnetic field is changing rapidly and automatically switches to "wide bandwidth mode." The timing control system then shortens the pump pulse width and may fine-tune the pump optical power; simultaneously, the AGC of the RF excitation circuit is adjusted to a moderate gain and fast response state. In this mode, such as Figure 4 As shown, although the absolute amplitude of the signal may be slightly lower than that of the high-sensitivity mode, the differential amplifier circuit can still effectively extract the signal, and the system bandwidth can be increased to several times that of the traditional continuous wave scheme, thus achieving fast tracking.

[0060] The mode switching process is smooth and continuous, the self-excited oscillation loop remains locked, and the magnetic field measurement data is output continuously.

[0061] Beneficial effects: This embodiment, by introducing dynamic relaxation control, enables the same magnetometer to intelligently adapt to different measurement scenarios, substantially breaking the static trade-off between sensitivity and bandwidth. It is not a simple compromise, but rather achieves optimal adaptive operation by actively and in real-time manipulating the dynamic parameters of the quantum system (atomic spin) and the characteristics of the electronic feedback loop—a non-obvious advancement.

[0062] Example 4

[0063] This embodiment targets high-vibration environments such as airborne magnetic surveys and vehicle-mounted mobile platforms. Under the pulse operation and time-division multiplexing framework of Embodiment 1, coherent accumulation detection technology is introduced to suppress signal phase noise and amplitude fluctuations caused by vibration, thereby further improving the effective signal-to-noise ratio and measurement robustness in harsh environments.

[0064] The specific implementation method is as follows:

[0065] Synchronous Accumulation Processing Unit: A synchronous accumulation processing module is added to the frequency measurement and processing unit (such as an FPGA). This module is strictly synchronized with the timing control system and can coherently accumulate the AC signals output by the photodetector and processed by the differential amplifier circuit within multiple consecutive detection cycles.

[0066] Workflow:

[0067] The system operates at a fixed pulse repetition frequency (PRF, e.g., 1 kHz), with each cycle including pumping, excitation, and detection phases (timing sequence as follows). Figure 2 (As shown).

[0068] During each detection period (T_detect), the sinusoidal signal output by the photodetector, which characterizes the Larmor precession of atoms, is sampled by a high-speed ADC and sent to the FPGA.

[0069] The synchronous accumulation processing module within the FPGA uses the periodic synchronization signal provided by the timing control system as the trigger reference to align and accumulate a segment of sine wave data acquired in the current cycle with the data acquired in the corresponding time periods of the previous N cycles (e.g., 64 cycles). Since the Larmor precession frequency of the atom (i.e., the magnetic field under test) is basically constant in a short time (within N cycles), the signal representing the magnetic field is coherent, and the signal amplitude increases approximately linearly (~N times) after accumulation.

[0070] Noise caused by environmental disturbances such as vibration is random in time. Unlike asynchronous accumulation, coherent accumulation has a suppression effect of √N times on these incoherent noises.

[0071] Therefore, after N cycles of coherent accumulation, the signal-to-noise ratio (SNR) is improved by √N times (for example, when N=64, the SNR is improved by 8 times). The accumulated signal is then used to drive the feedback loop (which can first be processed by digital phase-locked loop amplification) and frequency calculation to obtain a more stable and accurate magnetic field value.

[0072] Phase compensation (optional enhancement): To address minor magnetic field drift or frequency changes that may occur over a longer accumulation period, the accumulation module can integrate a simple digital phase-locked loop (DPLL) or frequency tracking algorithm to perform slight phase or frequency correction on the continuous period signal before accumulation to maintain optimal coherence.

[0073] Beneficial Effects: This embodiment creatively combines the timing determinism of pulse time-division multiplexing with the coherent accumulation technique of digital signal processing. It utilizes the clear, periodic time window provided by pulse operation to achieve synchronous sampling and accumulation of magnetic resonance signals. This method is particularly suitable for suppressing random noise independent of the measurement period (such as broadband noise caused by vibration), significantly improving its practical performance on dynamic, high-noise platforms, and solving a key technical challenge in the application of atomic magnetometers on mobile platforms.

[0074] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A pulsed laser-pumped cesium atom magnetometer, characterized in that, include: The device comprises a physical probe and a circuit. The physical probe includes: a VCSEL laser for emitting pulsed laser light containing cesium atom D1 lines; a convex lens, a filter, a polarizer, and a quarter-wave plate arranged sequentially along the optical path for converting the beam emitted by the VCSEL laser into left-handed circularly polarized light; a cesium atom absorption cell filled with alkali metal cesium for generating atomic polarization through optical pumping under pulsed irradiation of the left-handed circularly polarized light; a radio frequency coil wound around the cesium atom absorption cell for generating a radio frequency magnetic field perpendicular to the optical axis, causing the polarized cesium atoms to undergo magnetic resonance; and a photodetector located on the light-emitting side of the cesium atom absorption cell for detecting changes in transmitted light intensity and... The signal is converted into an electrical signal. The circuit includes: a timing control system for controlling the pulse timing of the VCSEL laser and the RF coil to achieve time-division multiplexing of the optical pumping and detection process; a photoelectric conversion and amplification circuit connected to the photodetector for preliminary amplification of the electrical signal; a differential amplification circuit connected to the photoelectric conversion and amplification circuit for extracting and amplifying specific frequency components in the electrical signal; and an RF excitation circuit connected to the differential amplification circuit and the RF coil for generating an RF signal to drive the RF coil based on the processed signal, thereby forming a closed-loop self-excited oscillation circuit. The oscillation frequency of the self-excited oscillation circuit when it is stable is proportional to the strength of the external magnetic field to be measured.

2. The pulsed laser-pumped cesium atom magnetometer according to claim 1, characterized in that, The timing control system is configured to control the VCSEL laser to operate in the following time-division multiplexing mode: in the first time period, left-handed circularly polarized light with a wavelength of 895nm is emitted as pump light; in the second time period, the laser wavelength is synchronously adjusted to 894.98nm through a frequency shifting circuit, and the drive signal of the radio frequency coil is turned off, at which time the laser is used as detection light.

3. The pulsed laser-pumped cesium atom magnetometer according to claim 1, characterized in that, The cesium atom absorption chamber is equipped with a non-magnetic heating system, which includes a heating coil wound in a twisted pair manner outside the chamber, as well as a temperature sensor and temperature control circuit for monitoring and controlling the temperature of the chamber.

4. The pulsed laser-pumped cesium atom magnetometer according to claim 1, characterized in that, The differential amplifier circuit includes a high common-mode rejection ratio circuit composed of an instrumentation amplifier or a precision operational amplifier. It is configured to perform differential processing on the signal output by the photoelectric conversion and amplification circuit and the background reference signal to suppress common-mode noise and amplify the amplitude of the AC signal characterizing magnetic resonance by more than 10 times.

5. The pulsed laser-pumped cesium atom magnetometer according to claim 1, characterized in that, The radio frequency excitation circuit includes an automatic gain control module and a phase shifting module, which are used to automatically adjust the gain and phase of the feedback signal according to the signal amplitude output by the differential amplifier circuit, so as to maintain the stable oscillation of the self-excited oscillation circuit.

6. The pulsed laser-pumped cesium atom magnetometer according to claim 1, characterized in that, It also includes a frequency measurement and processing unit, which is connected to the self-excited oscillation circuit for real-time measurement of the oscillation frequency and, based on the preset cesium atom gyromagnetic ratio γ, calculates and outputs the magnetic field strength B0 to be measured using the formula B0 = f / γ.

7. The pulsed laser-pumped cesium atom magnetometer according to claim 6, characterized in that, The frequency measurement and processing unit is implemented using a digital frequency meter based on FPGA or high-speed microprocessor, and integrates real-time filtering, calibration and data output functions for the measurement results.

8. The pulsed laser-pumped cesium atom magnetometer according to any one of claims 1 to 7, characterized in that, The timing control system further includes a dynamic parameter adjustment module, which is used to dynamically adjust the pump pulse parameters of the VCSEL laser and / or the feedback loop parameters of the radio frequency excitation circuit according to a preset mode or the real-time measured magnetic field change rate, so as to achieve adaptive optimization of measurement sensitivity and tracking bandwidth.

9. The pulsed laser-pumped cesium atom magnetometer according to claim 8, characterized in that, The dynamic parameter control module is configured to: when the detected magnetic field change rate is lower than a first threshold, control the VCSEL laser to emit pump light with a first pulse width and a first power, and control the radio frequency excitation circuit to operate with a first gain setting, entering a high-sensitivity mode; when the detected magnetic field change rate is higher than a second threshold, control the VCSEL laser to emit pump light with a second pulse width less than the first pulse width, and control the radio frequency excitation circuit to operate with a second gain setting different from the first gain setting, entering a wide-bandwidth tracking mode.

10. The pulsed laser-pumped cesium atom magnetometer according to claim 6 or 7, characterized in that, The frequency measurement and processing unit also includes a synchronous accumulation processing module, which is synchronized with the timing control system and is used to perform coherent accumulation processing on the signals output by the differential amplifier circuit within multiple consecutive detection cycles, so as to improve the signal-to-noise ratio of the output signal.

11. A method for measuring the magnetic field based on the pulsed laser-pumped cesium atom magnetometer according to any one of claims 1 to 10, characterized in that, Includes the following steps: S1. Optical Pumping Step: The VCSEL laser is driven by a timing control system to emit pulsed, left-handed circularly polarized light to optically pump cesium atoms in the cesium atom absorption chamber, thus preparing a quantum state; S2. Magnetic Resonance Excitation Step: A radio frequency magnetic field is applied through a radio frequency coil to induce Larmor precession of the macroscopic magnetic moment of the atoms around the direction of the external magnetic field; S3. Signal Detection and Extraction Step: During the detection period when the radio frequency magnetic field is turned off, a photodetector is used to detect the periodic changes in the intensity of transmitted light caused by atomic precession and convert them into an alternating current signal; S4. Signal processing and feedback steps: The AC signal is amplified and noise suppressed by the photoelectric conversion and amplification circuit and the differential amplification circuit in sequence, and then processed by the radio frequency excitation circuit and fed back to drive the radio frequency coil to form a closed-loop self-excited oscillation; S5. Frequency measurement and magnetic field calculation steps: Measure the stable frequency f of the self-excited oscillation in real time, and calculate the intensity B0 of the external magnetic field to be measured according to the formula B0 = f / γ, where γ is the gyromagnetic ratio of cesium atoms.

12. The magnetic field measurement method according to claim 8, characterized in that, The gyromagnetic ratio γ is 3.5 Hz / nT.

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