Atomic magnetometer light power regulation system and method based on linewidth scanning

Abstract

The application provides an atomic magnetometer light power adjustment system and method based on line width scanning, and belongs to the field of precision measurement. The atomic magnetometer light power adjustment system comprises: a magnetic field generating coil configured to generate a scanning magnetic field linearly changing over time based on a preset waveform driving current; an atomic gas chamber configured to modulate detection light of an atomic magnetometer based on the scanning magnetic field to obtain a light modulation signal; a photodetector configured to convert the light modulation signal into an initial electric signal; a signal processing module configured to obtain an atomic spectral line width value based on the initial electric signal; and an adjustment module configured to adjust a light attenuator of the atomic magnetometer based on a preset light power-atomic spectral line width calibration relationship, a target light power value and the atomic spectral line width value, so as to update the light power value of the atomic magnetometer.

Description

Technical Field

[0001] This invention relates to the field of precision measurement, and more specifically, to an optical power adjustment system and method for an atomic magnetometer based on linewidth scanning. Background Technology

[0002] In some types of atomic magnetometers, such as those using spin-exchange-relaxation-free (SERF) atomic magnetometers, fluctuations in laser power directly affect the transition characteristics of atomic energy levels, thus impacting the magnetometer's sensitivity and accuracy. Therefore, real-time and accurate monitoring and active locking of the laser output power are crucial for improving the operational stability of atomic magnetometers.

[0003] Laser optical power monitoring includes direct and indirect detection methods. Direct detection uses a beam splitter to extract a portion of the laser beam and a photodetector to directly measure the laser intensity, thus deducing the laser's optical power. However, this introduces additional components, increasing system complexity. Indirect detection monitors parameters such as the laser's drive current or die temperature to indirectly assess the output optical power. However, circuit drift can lead to inaccurate indirectly detected optical power values.

[0004] Therefore, there is an urgent need to propose an atomic magnetometer optical power adjustment system that requires no additional hardware expansion and has long-term stability. Summary of the Invention

[0005] In view of this, the present invention provides an optical power adjustment system and method for an atomic magnetometer based on linewidth scanning.

[0006] One aspect of the present invention provides an atomic magnetometer optical power adjustment system based on linewidth scanning, comprising: a magnetic field generating coil configured to generate a scanning magnetic field that varies linearly with time based on a driving current of a preset waveform; an atomic gas cell configured to modulate the probe light of the atomic magnetometer based on the scanning magnetic field to obtain an optical modulation signal; a photodetector configured to convert the optical modulation signal into an initial electrical signal; a signal processing module configured to obtain an atomic spectral linewidth value based on the initial electrical signal; and an adjustment module configured to adjust the optical attenuator of the atomic magnetometer based on a preset optical power-atomic spectral linewidth calibration relationship, a target optical power value, and an atomic spectral linewidth value to update the optical power value of the atomic magnetometer.

[0007] According to an embodiment of the present invention, the adjustment module is configured to: determine a first optical power value corresponding to the atomic spectral linewidth value based on a preset optical power-atomic spectral linewidth calibration relationship and atomic spectral linewidth value; determine a target attenuation coefficient based on the target optical power value and the first optical power value; and adjust the optical attenuator of the atomic magnetometer based on the target attenuation coefficient to update the optical power value of the atomic magnetometer.

[0008] According to an embodiment of the present invention, the signal processing module is configured to: determine a first time point and a second time point from an initial electrical signal; determine a first magnetic field strength corresponding to the first time point and a second magnetic field strength corresponding to the second time point based on the first time point, the second time point and the scanning magnetic field; and determine the atomic spectral linewidth value based on the first magnetic field strength and the second magnetic field strength.

[0009] According to an embodiment of the present invention, the signal processing module is configured to: perform numerical differentiation on the initial electrical signal to obtain a differential electrical signal; determine the time point corresponding to the maximum value of the differential electrical signal as a first time point, and determine the time point corresponding to the minimum value of the differential electrical signal as a second time point.

[0010] According to an embodiment of the present invention, the signal processing module is configured to: determine the maximum value and minimum value of the initial electrical signal; determine the intermediate value of the electrical signal based on the arithmetic mean of the maximum value and minimum value of the electrical signal; and, based on the initial electrical signal, determine the time point corresponding to the intermediate value of the electrical signal during the rising edge phase of the initial electrical signal as a first time point, and the time point corresponding to the intermediate value of the electrical signal during the falling edge phase of the initial electrical signal as a second time point.

[0011] According to an embodiment of the present invention, the optical power adjustment system of the atomic magnetometer based on linewidth scanning further includes: an analog-to-digital converter, electrically connected to a photodetector and a signal processing module, configured to perform analog-to-digital conversion processing on the initial electrical signal input to the photodetector based on a preset sampling rate to obtain a first electrical signal in digital encoding form, and output the first electrical signal to the signal processing module; wherein, the signal processing module is configured to obtain the atomic spectral linewidth value based on the first electrical signal.

[0012] According to an embodiment of the present invention, the atomic magnetometer optical power adjustment system based on linewidth scanning further includes: a signal conditioning device electrically connected to a photodetector and a signal processing module, configured to amplify and filter the initial signal input to the photodetector to obtain a second electrical signal, and output the second electrical signal to the signal processing module; wherein the signal processing module is configured to obtain the atomic spectral linewidth value based on the second electrical signal.

[0013] According to an embodiment of the present invention, the optical power adjustment system of the atomic magnetometer based on linewidth scanning further includes: a current generating device electrically connected to the magnetic field generating coil, configured to generate an analog voltage signal through a digital-to-analog converter based on a preset digital scanning sequence, and input the analog voltage signal to a voltage-controlled current source circuit to obtain a driving current of a preset waveform.

[0014] According to an embodiment of the present invention, if the absolute value of the difference between the updated optical power value and the target optical power value of the atomic magnetometer is greater than a first preset value, the atomic spectral linewidth value of the atomic magnetometer after the updated optical power value is obtained, so as to continue to adjust the optical power of the atomic magnetometer.

[0015] Another aspect of the present invention provides a method for adjusting the optical power of an atomic magnetometer based on linewidth scanning, applied to the aforementioned optical power adjustment system for an atomic magnetometer based on linewidth scanning, comprising: generating a scanning magnetic field that varies linearly with time based on a driving current of a preset waveform; modulating the probe light of the atomic magnetometer based on the scanning magnetic field to obtain an optical modulation signal; converting the optical modulation signal into an initial electrical signal; obtaining an atomic spectral linewidth value based on the initial electrical signal; and adjusting the optical attenuator of the atomic magnetometer based on a preset optical power-atomic spectral linewidth calibration relationship, a target optical power value, and an atomic spectral linewidth value to update the optical power value of the atomic magnetometer.

[0016] According to an embodiment of the present invention, the probe light of the atomic magnetometer is modulated by a magnetic field generating coil and an atomic gas cell to obtain an optical modulation signal. The atomic spectral linewidth value is obtained based on the optical modulation signal to determine the optical power value of the atomic magnetometer. This allows for real-time and accurate monitoring and active locking of the laser's optical power, avoiding the effects of circuit drift and the increased system complexity caused by the introduction of additional components, thus improving the long-term stability of the atomic magnetometer. Attached Figure Description

[0017] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0018] Figure 1 A schematic diagram of an atomic magnetometer optical power adjustment system based on linewidth scanning according to an embodiment of the present invention is shown;

[0019] Figure 2 A schematic diagram of the circuit architecture of an atomic magnetometer optical power adjustment system based on linewidth scanning according to an embodiment of the present invention is shown;

[0020] Figure 3 A schematic diagram of the initial electrical signal according to an embodiment of the present invention is shown;

[0021] Figure 4A schematic diagram illustrating the preset optical power-atomic spectral linewidth calibration relationship according to an embodiment of the present invention is shown;

[0022] Figure 5 A flowchart of an atomic magnetometer optical power adjustment method based on linewidth scanning according to an embodiment of the present invention is shown;

[0023] Figure 6 A schematic diagram of an atomic magnetometer optical power adjustment method based on linewidth scanning according to another embodiment of the present invention is shown;

[0024] Figure 7 A schematic diagram of the circuit principle of an atomic magnetometer optical power adjustment system based on linewidth scanning according to an embodiment of the present invention is shown. Detailed Implementation

[0025] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0026] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0027] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0028] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0029] In existing technologies, the direct detection method is commonly used for monitoring laser optical power, and it is also the conventional technical solution adopted by commercially available atomic magnetometers. However, the direct detection method has at least the following problems: it requires the introduction of an additional beam splitter and a separate detector, increasing the system's complexity, size, and weight, thus introducing additional points of failure; long-term drift in the beam splitting ratio can introduce measurement errors; and it cannot monitor optical power without interrupting the normal operation of the atomic magnetometer, limiting further improvements in its performance.

[0030] When an atomic magnetometer is operating under normal conditions, the aforementioned problems can be partially resolved through periodic calibration. However, in special operating environments, such as in space, periodic calibration cannot be manually performed, and prolonged space radiation can damage the additional independent detectors introduced by the direct detection method. Furthermore, due to space payload limitations, significant modifications to the atomic magnetometer are not feasible. Therefore, improvements to existing direct detection methods cannot guarantee the long-term stable operation of the atomic magnetometer in a space environment.

[0031] Another approach is to indirectly assess the output optical power by monitoring parameters such as the laser's drive current or die temperature. However, the atomic magnetometer will experience a certain degree of circuit drift during long-term operation in space, resulting in a significant deviation in the indirectly assessed output optical power. Furthermore, the circuit drift cannot be corrected under the conditions of space.

[0032] After attempts to miniaturize the additional components introduced by the direct detection method and to introduce additional calibration modules for periodic automatic calibration of the atomic magnetometer failed, the possibility of using power broadening to monitor the optical power of a laser was considered. In atomic physics, power broadening generally refers to the phenomenon in optical systems where changes in optical power cause an increase in the linewidth of atomic spectra. For example, when a strong light field acts on an atomic system, it alters the energy level transition characteristics of atoms, resulting in spectral line broadening. Furthermore, atomic spectral linewidths can be directly obtained based on the existing architecture of the atomic magnetometer, without the need for additional hardware. Since atomic spectral linewidths are obtained based on the difference in the measurement signal, they can reduce the impact of circuit drift on the measurement results to some extent. Therefore, this characteristic of power broadening can be used to pre-calibrate the atomic spectral linewidths corresponding to different optical power levels. The optical power can then be deduced from these calibration data and the acquired atomic spectral linewidths, thereby achieving optical power locking.

[0033] Figure 1 A schematic diagram of an atomic magnetometer optical power adjustment system based on linewidth scanning according to an embodiment of the present invention is shown.

[0034] like Figure 1As shown, the optical power adjustment system of the atomic magnetometer based on linewidth scanning includes a magnetic field generating coil 101, an atomic gas cell 102, a photodetector 103, a signal processing module 104, and an adjustment module 105.

[0035] The magnetic field generating coil 101 is configured to generate a scanning magnetic field that varies linearly with time based on a driving current of a preset waveform. The atomic gas chamber 102 is configured to modulate the probe light of the atomic magnetometer based on the scanning magnetic field to obtain an optical modulation signal. The photodetector 103 is configured to convert the optical modulation signal into an initial electrical signal. The signal processing module 104 is configured to obtain the atomic spectral linewidth value based on the initial electrical signal. The adjustment module 105 is configured to adjust the optical attenuator of the atomic magnetometer based on a preset optical power-atomic spectral linewidth calibration relationship, a target optical power value, and an atomic spectral linewidth value to update the optical power value of the atomic magnetometer.

[0036] In embodiments of the present invention, the magnetic field generating coil 101, the atomic gas chamber 102, and the photodetector 103 can all be existing functional components in an atomic magnetometer, and the signal processing module 104 and the adjustment module 105 can be implemented based on a field programmable gate array (FPGA).

[0037] In embodiments of the present invention, the atomic magnetometer may include a laser, a thermoelectric cooler, a thermistor, and an atomic magnetometer probe integrating an atomic gas cell 102 and a magnetic field generating coil 101. The thermoelectric cooler and the thermistor form a highly stable temperature control loop, ensuring the long-term stability of the laser's output wavelength and power. The probe light output from the laser acts on the atomic gas cell 102 in the atomic probe, interacting with the working atoms. Based on the digital-to-analog converter, operational amplifier, voltage-controlled current source circuit, and magnetic field generating coil 101, a high-precision controllable magnetic field can be generated. The photodetector 103 can convert the optical signal transmitted through the atomic gas cell 102 into an electrical signal to detect the optical signal reflecting atomic energy level transitions. This optical signal contains atomic absorption or dispersion information caused by magnetic field scanning.

[0038] In embodiments of this invention, the FPGA can integrate a logic control unit, signal processing algorithms, and a servo feedback control loop. The logic control unit can send precise scan signal sequences to control the entire linewidth scanning process, while simultaneously controlling the analog-to-digital converter (ADC) for synchronous data acquisition. The logic control unit can also process the digital signals acquired by the ADC in real time, for example, by accurately calculating the linewidth value of the atomic spectrum using a differential algorithm. The FPGA can also control the optical attenuator inside the atomic magnetometer via the servo feedback control loop to update the optical power value of the atomic magnetometer.

[0039] Through the embodiments of the present invention, the probe light of the atomic magnetometer is modulated by the magnetic field generating coil and the atomic gas cell to obtain the optical modulation signal, and the atomic spectral linewidth value is obtained based on the optical modulation signal to determine the optical power value of the atomic magnetometer. This allows for real-time and accurate monitoring and active locking of the laser's optical power, avoiding the effects of circuit drift and the increased system complexity caused by the introduction of additional components, and improving the long-term stability of the atomic magnetometer.

[0040] According to an embodiment of the present invention, the optical power adjustment system of the atomic magnetometer based on linewidth scanning further includes: a current generating device electrically connected to the magnetic field generating coil, configured to generate an analog voltage signal through a digital-to-analog converter based on a preset digital scanning sequence, and input the analog voltage signal to a voltage-controlled current source circuit to obtain a driving current of a preset waveform.

[0041] In embodiments of this invention, a digital scanning sequence can be generated based on a control algorithm within the FPGA. This digital scanning sequence can then be converted into a high-precision analog voltage signal using a digital-to-analog converter (DAC). The analog voltage signal is used as a setpoint and input to a voltage-controlled current source circuit composed of a high-precision operational amplifier to generate a drive current. The generated drive current is then supplied to the magnetic field generating coil of the atomic magnetometer. The voltage-controlled current source circuit can employ a Howland current source structure. The Howland current source structure ensures the linearity and stability of the voltage-to-current conversion through a precision resistor network. The resistors in the voltage-controlled current source circuit can be precision alloy foil resistors to ensure good consistency in resistance values.

[0042] In an embodiment of the present invention, the digital-to-analog converter has a 16-bit resolution, a power supply voltage of ±4.5 V, a reference voltage of 3.3 V, an output refresh rate of 256 Hz, a digital control value range from 0x0000 to 0xFFFF, a minimum step of 0x100, a scanning range of -140 nT to +140 nT for the scanning magnetic field, and a scanning interval accuracy of 1.09 nT.

[0043] According to an embodiment of the present invention, the atomic magnetometer optical power adjustment system based on linewidth scanning further includes: a signal conditioning device electrically connected to a photodetector and a signal processing module, configured to amplify and filter the initial signal input to the photodetector to obtain a second electrical signal, and output the second electrical signal to the signal processing module; wherein the signal processing module is configured to obtain the atomic spectral linewidth value based on the second electrical signal.

[0044] Photodetectors can convert optically modulated signals into initial electrical signals. However, these initial electrical signals are relatively weak current signals, requiring signal amplification and filtering. The initial electrical signal is first input into a transimpedance amplifier, which includes a feedback resistor and a feedback capacitor. The feedback resistor provides gain to the initial electrical signal, while the feedback capacitor compensates for frequency fluctuations to suppress high-frequency oscillations. The transimpedance amplifier linearly converts the current signal into a voltage signal, completing signal conversion, primary amplification, and improved driving capability. The voltage signal output from the transimpedance amplifier can then be fed into a low-pass filter circuit. The low-pass filter's filtering characteristics further remove high-frequency noise, ultimately smoothly extracting the DC component signal that reflects the atomic absorption spectral profile.

[0045] According to an embodiment of the present invention, the optical power adjustment system of the atomic magnetometer based on linewidth scanning further includes: an analog-to-digital converter, electrically connected to a photodetector and a signal processing module, configured to perform analog-to-digital conversion processing on the initial electrical signal input to the photodetector based on a preset sampling rate to obtain a first electrical signal in digital encoding form, and output the first electrical signal to the signal processing module; wherein, the signal processing module is configured to obtain the atomic spectral linewidth value based on the first electrical signal.

[0046] The initial electrical signal converted by the photodetector is an analog signal. This analog signal is susceptible to noise and electromagnetic interference during transmission and processing. Interference can directly superimpose on the analog signal, causing irreversible distortion. Therefore, an analog-to-digital converter (ADC) can be used to convert the initial electrical signal to digital form, obtaining a first electrical signal in digital encoding. In this embodiment, the ADC resolution can be 18 bits, the sampling rate can be 320 kHz, the supply voltage is ±4.5V, and the reference voltage is 3.3V. During signal acquisition by the ADC, 1024 consecutive sampling data points can be selected as a processing unit. The data is accumulated, summed, and then averaged. This digital filtering method of averaging effectively cancels out random noise interference in the sampled data, ultimately outputting a digital sequence with a high signal-to-noise ratio, providing a reliable data foundation for subsequent signal processing.

[0047] Figure 2 A schematic diagram of the circuit architecture of an atomic magnetometer optical power adjustment system based on linewidth scanning according to an embodiment of the present invention is shown.

[0048] like Figure 2As shown, the optical signal inside the atomic magnetometer probe 201 is first converted into an electrical signal by a photodetector. Then, the transimpedance amplifier circuit 202 and the low-pass filter circuit 203 amplify and filter the electrical signal. The optical signal is converted from analog to digital by an analog-to-digital converter 204. The FGPA 205 processes the digital electrical signal to generate a digital scanning sequence. The digital scanning sequence is converted into an analog voltage signal by a digital-to-analog converter 206. The analog voltage signal is sent to the voltage-controlled current source circuit 207 to generate a driving current signal, which is then applied to the magnetic field generating coil.

[0049] According to an embodiment of the present invention, the signal processing module is configured to: determine a first time point and a second time point from an initial electrical signal; determine a first magnetic field strength corresponding to the first time point and a second magnetic field strength corresponding to the second time point based on the first time point, the second time point and the scanning magnetic field; and determine the atomic spectral linewidth value based on the first magnetic field strength and the second magnetic field strength.

[0050] In scenarios where spectral line broadening is dominated by a magnetic field gradient, the Zeeman effect causes varying degrees of energy level splitting in atoms due to differences in magnetic field strength at their spatial locations, ultimately leading to spectral line broadening. The extent of broadening is proportional to the difference between the maximum and minimum magnetic fields experienced by the atom, with the proportionality coefficient determined by atomic physical constants such as electron charge, mass, and Planck's constant. Therefore, by determining the difference in magnetic field strength corresponding to specific characteristic points, the atomic spectral linewidth under the current scanning magnetic field can be accurately calculated. This involves calculating the difference between the first and second magnetic field strengths and then multiplying it by a fixed proportionality coefficient to obtain the atomic spectral linewidth.

[0051] According to an embodiment of the present invention, the signal processing module is configured to: perform numerical differentiation on the initial electrical signal to obtain a differential electrical signal; determine the time point corresponding to the maximum value of the differential electrical signal as a first time point, and determine the time point corresponding to the minimum value of the differential electrical signal as a second time point.

[0052] Under the condition that the broadening mechanism is dominated by the magnetic field gradient, the initial electrical signal can be fitted using a Gaussian curve model. In a Gaussian curve, the maximum value of the first derivative is located to the left of the center point of the curve, and the minimum value is located to the right of the center point. Therefore, the maximum and minimum values ​​of the first derivative of the initial electrical signal can be used as feature points. That is, the time point corresponding to the maximum value of the differential signal is determined as the first time point, and the time point corresponding to the minimum value of the differential signal is determined as the second time point.

[0053] According to an embodiment of the present invention, the signal processing module is configured to: determine the maximum value and minimum value of the initial electrical signal; determine the intermediate value of the electrical signal based on the arithmetic mean of the maximum value and minimum value of the electrical signal; and determine, based on the initial electrical signal, a first time point corresponding to the intermediate value of the electrical signal during the rising edge phase of the initial electrical signal and a second time point corresponding to the intermediate value of the electrical signal during the falling edge phase of the initial electrical signal.

[0054] Figure 3 A schematic diagram of the initial electrical signal according to an embodiment of the present invention is shown.

[0055] like Figure 3 As shown, the amplitude of the initial electrical signal changes with time according to a Gaussian curve model. The maximum and minimum values ​​of the initial electrical signal can be obtained through signal processing, and the intermediate value of the electrical signal can be determined based on the arithmetic mean of the maximum and minimum values. Figure 3 In the diagram, when the vertical axis represents the midpoint of the electrical signal, the amplitude curve of the initial electrical signal has a corresponding coordinate point in both the rising and falling edge phases. The horizontal coordinate corresponding to the point where the vertical axis represents the midpoint of the electrical signal in the rising edge phase is taken as the first time point, and the horizontal coordinate corresponding to the point where the vertical axis represents the midpoint of the electrical signal in the falling edge phase is taken as the second time point.

[0056] According to an embodiment of the present invention, the adjustment module is configured to: determine a first optical power value corresponding to the atomic spectral linewidth value based on a preset optical power-atomic spectral linewidth calibration relationship and atomic spectral linewidth value; determine a target attenuation coefficient based on the target optical power value and the first optical power value; and adjust the optical attenuator of the atomic magnetometer based on the target attenuation coefficient to update the optical power value of the atomic magnetometer.

[0057] The target optical power value is the optical power value that the atomic magnetometer needs to maintain during normal operation. However, after the atomic magnetometer has been working for a long time, the actual optical power of the laser will change, causing a mismatch between the current optical power value and the target optical power value. Therefore, it is necessary to detect the current optical power value and readjust the optical power value of the atomic magnetometer to the target optical power value through an optical attenuator. In the embodiments of the present invention, the preset optical power-atomic spectral linewidth calibration relationship can be obtained based on calibration experiments. For example, at 100°C, the calibration optical power of the probe light after passing through the atomic gas cell is measured by an optical power meter. At this optical power, a triangular wave magnetic field with a peak value of 200 nT and a frequency of 1 Hz is applied to the atomic gas cell, and the modulated optical signal data after passing through the atomic gas cell is collected by a photodetector. The modulated optical signal data is processed to obtain the atomic spectral linewidth value corresponding to the current calibration optical power. By changing the calibration optical power and repeating the above steps, a series of atomic spectral linewidth values ​​under different optical power conditions can be obtained, i.e., the optical power-atomic spectral linewidth calibration relationship.

[0058] Figure 4 A schematic diagram illustrating a preset optical power-atomic spectral linewidth calibration relationship according to an embodiment of the present invention is shown. Figure 4 As shown, the optical power value and atomic spectral linewidth value of the atomic magnetometer are positively correlated.

[0059] According to an embodiment of the present invention, if the absolute value of the difference between the updated optical power value and the target optical power value of the atomic magnetometer is greater than a first preset value, the atomic spectral linewidth value of the atomic magnetometer after the updated optical power value is obtained, so as to continue to adjust the optical power of the atomic magnetometer.

[0060] In embodiments of the present invention, the actual optical power acting on the atomic magnetometer can be inverted by using the atomic spectral linewidth value calculated in real time based on a preset optical power-atomic spectral linewidth calibration relationship. By setting a first preset value, the actual optical power value acting on the atomic magnetometer can be made to approach the target optical power value one by one, and finally the optical power can be accurately locked.

[0061] Figure 5 A flowchart of an atomic magnetometer optical power adjustment method based on linewidth scanning according to an embodiment of the present invention is shown.

[0062] like Figure 5 As shown, the method for adjusting the optical power of an atomic magnetometer based on linewidth scanning includes operations S510 to S550.

[0063] In operation S510, a scanning magnetic field that changes linearly with time is generated based on the drive current of a preset waveform.

[0064] In operation S520, the probe light of the atomic magnetometer is modulated based on the scanning magnetic field to obtain an optical modulation signal.

[0065] In operation S530, the optical modulation signal is converted into an initial electrical signal.

[0066] In operation S540, the atomic spectral linewidth values ​​are obtained based on the initial electrical signal.

[0067] In operation S550, the optical attenuator of the atomic magnetometer is adjusted based on the preset optical power-atomic spectral linewidth calibration relationship, the target optical power value, and the atomic spectral linewidth value, so as to update the optical power value of the atomic magnetometer.

[0068] Figure 6 A schematic diagram of an atomic magnetometer optical power adjustment method based on linewidth scanning according to another embodiment of the present invention is shown.

[0069] like Figure 6 As shown, a linewidth scan is first performed based on the scanning magnetic field, followed by the acquisition of an initial electrical signal via a photodetector. Next, a numerical differentiation operation is performed on the initial electrical signal to obtain a differential electrical signal. Then, the magnetic field value B1 corresponding to the maximum value and the magnetic field value B2 corresponding to the minimum value of the differential electrical signal are determined, and the current atomic spectral linewidth and current optical power value are obtained based on |B2-B1|. It is then determined whether the current optical power value is the target optical power value. If the current optical power value is not the target optical power value, the optical attenuator of the atomic magnetometer is adjusted, and linewidth scanning continues based on the scanning magnetic field; if the current optical power value is the target optical power value, the linewidth scanning is stopped, and the scanning data is retained.

[0070] Figure 7 A schematic diagram of the circuit principle of an atomic magnetometer optical power adjustment system based on linewidth scanning according to an embodiment of the present invention is shown.

[0071] like Figure 7 As shown in (a), the analog voltage signal is converted into a drive current through a voltage-controlled current source circuit. The voltage-controlled current source circuit includes a first operational amplifier U1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a reference resistor Rref. Figure 7 As shown in (b), the initial electrical signal is converted into a second electrical signal through a transimpedance amplifier circuit and a low-pass filter circuit. The transimpedance amplifier circuit includes a second operational amplifier U2, a fifth resistor R5, and a first capacitor C1. The low-pass filter circuit includes a third operational amplifier U3, a sixth resistor R6, a seventh resistor R7, a second capacitor C2, and a third capacitor C3.

[0072] In an embodiment of the present invention, the optical power adjustment system of the atomic magnetometer based on linewidth scanning can achieve fully automatic scanning and calculation based on FPGA. First, the system is calibrated in the laboratory using a voltage-controlled current source and a gaussmeter to establish the relationship between the DAC output code value (CODE) and the magnetic field strength (B) inside the atomic chamber. This relationship can be expressed as:

[0073] (1)

[0074] in, This is the calibration factor for the triaxial coil, approximately 74 nT / mA; and The feedback signal amplitudes are 2 V and -2 V, respectively. The reference resistor for the voltage-controlled current source circuit is 2 kΩ, which controls the drive current between -2.048 mA and 2.048 mA.

[0075] During actual scanning, the FPGA controls the DAC to linearly increase from the code value 0x0000 (corresponding to a magnetic field of -140 nT) to the code value 0xffff, with a step size of 0x100 (corresponding to a magnetic field of 1.09 nT), to achieve a magnetic field scanning interval of 1.09 nT. During the scanning process, the photodetector signal is conditioned by a transimpedance amplifier and a low-pass filter, and then averaged by an analog-to-digital converter at a sampling rate of 320 kHz to obtain a set of discrete data points S[m] of the atomic absorption signal that vary with the DAC output code value (i.e., magnetic field strength), where m is a positive integer representing the m-th discrete data point of the atomic absorption signal. The signal processing unit within the FPGA first performs numerical differentiation on the absorption curve corresponding to the atomic absorption signal, and uses the central difference method to approximate the first derivative, obtaining:

[0076] (2)

[0077] in, The magnetic field scanning interval is 1.09 nT.

[0078] Subsequently, the differential curve was precisely searched based on the algorithm. Record the maximum value (corresponding to the left inflection point of the absorption curve) and the minimum value (corresponding to the right inflection point of the absorption curve), and record the DAC code values ​​corresponding to these two points. and Linewidth of atomic spectra It can be calculated using the following formula:

[0079] (3)

[0080] Where k is a fixed constant.

[0081] Finally, the FPGA uses a pre-calibrated "optical power-atomic spectral linewidth" lookup table to invert the current true optical power from the calculated atomic spectrum linewidth value, thus enabling the adjustment of optical power based on the target optical power value.

[0082] Those skilled in the art will understand that the features described in the various embodiments of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments of the present invention can be combined and / or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

[0083] The embodiments of the present invention have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

Claims

1. A power adjustment system for an atomic magnetometer based on linewidth scanning, characterized in that, include: A magnetic field generating coil is configured to generate a scanning magnetic field that changes linearly with time based on a driving current of a preset waveform; An atomic gas cell is configured to modulate the probe light of an atomic magnetometer based on the scanning magnetic field to obtain an optical modulation signal; A photodetector configured to convert the optical modulation signal into an initial electrical signal; The signal processing module is configured to obtain atomic spectral linewidth values ​​based on the initial electrical signal; The adjustment module is configured to adjust the optical attenuator of the atomic magnetometer based on a preset optical power-atomic spectral linewidth calibration relationship, the target optical power value, and the atomic spectral linewidth value, so as to update the optical power value of the atomic magnetometer.

2. The optical power adjustment system for an atomic magnetometer based on linewidth scanning according to claim 1, characterized in that, The adjustment module is configured as follows: Based on the preset optical power-atomic spectral linewidth calibration relationship and the atomic spectral linewidth value, a first optical power value corresponding to the atomic spectral linewidth value is determined; The target attenuation coefficient is determined based on the target optical power value and the first optical power value; The optical attenuator of the atomic magnetometer is adjusted based on the target attenuation coefficient to update the optical power value of the atomic magnetometer.

3. The optical power adjustment system for an atomic magnetometer based on linewidth scanning according to claim 1, characterized in that, The signal processing module is configured as follows: Determine the first time point and the second time point from the initial electrical signal; Based on the first time point, the second time point, and the scanning magnetic field, determine the first magnetic field strength corresponding to the first time point and the second magnetic field strength corresponding to the second time point; The atomic spectral linewidth is determined based on the first magnetic field strength and the second magnetic field strength.

4. The optical power adjustment system for an atomic magnetometer based on linewidth scanning according to claim 3, characterized in that, The signal processing module is configured as follows: The initial electrical signal is numerically differentiated to obtain the differential electrical signal; The time point corresponding to the maximum value of the differential electrical signal is determined as the first time point, and the time point corresponding to the minimum value of the differential electrical signal is determined as the second time point.

5. The optical power adjustment system for an atomic magnetometer based on linewidth scanning according to claim 3, characterized in that, The signal processing module is configured as follows: Determine the maximum and minimum values ​​of the initial electrical signal; The intermediate value of the electrical signal is determined based on the arithmetic mean of the maximum and minimum values ​​of the electrical signal. Based on the initial electrical signal, the time point corresponding to the intermediate value of the electrical signal during the rising edge phase of the initial electrical signal is determined as the first time point, and the time point corresponding to the intermediate value of the electrical signal during the falling edge phase of the initial electrical signal is determined as the second time point.

6. The optical power adjustment system for an atomic magnetometer based on linewidth scanning according to claim 1, characterized in that, The atomic magnetometer optical power adjustment system based on linewidth scanning also includes: An analog-to-digital converter is electrically connected to the photodetector and the signal processing module, and is configured to perform analog-to-digital conversion processing on the initial electrical signal input to the photodetector based on a preset sampling rate to obtain a first electrical signal in digital encoding form, and output the first electrical signal to the signal processing module; The signal processing module is configured to obtain atomic spectral linewidth values ​​based on the first electrical signal.

7. The optical power adjustment system for an atomic magnetometer based on linewidth scanning according to claim 1, characterized in that, The atomic magnetometer optical power adjustment system based on linewidth scanning also includes: A signal conditioning device is electrically connected to the photodetector and the signal processing module, and is configured to amplify and filter the initial electrical signal input to the photodetector to obtain a second electrical signal, and output the second electrical signal to the signal processing module. The signal processing module is configured to obtain atomic spectral linewidth values ​​based on the second electrical signal.

8. The optical power adjustment system for an atomic magnetometer based on linewidth scanning according to claim 1, characterized in that, The atomic magnetometer optical power adjustment system based on linewidth scanning also includes: The current generating device is electrically connected to the magnetic field generating coil and is configured to generate an analog voltage signal through a digital-to-analog converter based on a preset digital scanning sequence. The analog voltage signal is then input to a voltage-controlled current source circuit to obtain a driving current with a preset waveform.

9. The optical power adjustment system for an atomic magnetometer based on linewidth scanning according to claim 1, characterized in that, If the absolute value of the difference between the updated optical power value of the atomic magnetometer and the target optical power value is greater than a first preset value, the atomic spectral linewidth value of the atomic magnetometer after the updated optical power value is obtained, so as to continue to adjust the optical power of the atomic magnetometer.

10. A method for adjusting the optical power of an atomic magnetometer based on linewidth scanning, characterized in that, The optical power adjustment system for an atomic magnetometer based on linewidth scanning as described in any one of claims 1-9 includes: A scanning magnetic field that varies linearly with time is generated based on a driving current with a preset waveform. The detection light of the atomic magnetometer is modulated based on the scanning magnetic field to obtain an optical modulation signal; The optical modulation signal is converted into an initial electrical signal; Atomic spectral linewidth values ​​are obtained based on the initial electrical signal; Based on the preset optical power-atomic spectral linewidth calibration relationship, the target optical power value, and the atomic spectral linewidth value, the optical attenuator of the atomic magnetometer is adjusted to update the optical power value of the atomic magnetometer.

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