阅读说明：本技术 磁力仪以及磁力仪检测方法 (Magnetometer and magnetometer detection method ) 是由 罗文浩 杨仁福 魏小刚 张笑楠 杜艺杰 丛楠 于 2021-07-27 设计创作，主要内容包括：本发明涉及一种磁力仪以及磁力仪检测方法。激光模块用于发射第一激光光束。分束模块设置于第一激光光束的光路上。线偏振模块设置于第二激光光束的光路上。声光调制模块设置于光强可调线偏振光光束的光路上。衍射光选择模块设置于衍射光的光路上。圆偏振模块设置于1级衍射光的光路上。原子气室设置于圆偏振光的光路上。光电探测模块设置于探测光的光路上。信号发生模块的输出端与声光调制模块的控制端连接。锁相放大模块的输入端分别与光电探测模块的输出端与信号发生模块的输出端连接。控制模块的输入端与锁相放大模块的输出端连接,控制模块的输出端与信号发生模块的控制端连接。(The invention relates to a magnetometer and a magnetometer detection method. The laser module is used for emitting a first laser beam. The beam splitting module is arranged on a light path of the first laser beam. The linear polarization module is arranged on the light path of the second laser beam. The acousto-optic modulation module is arranged on a light path of the light intensity adjustable linearly polarized light beam. The diffraction light selection module is arranged on the light path of the diffraction light. The circular polarization module is arranged on the light path of the 1 st-order diffraction light. The atom air chamber is arranged on the light path of the circularly polarized light. The photoelectric detection module is arranged on a light path of the detection light. The output end of the signal generation module is connected with the control end of the acousto-optic modulation module. The input end of the phase-locked amplifying module is respectively connected with the output end of the photoelectric detection module and the output end of the signal generating module. The input end of the control module is connected with the output end of the phase-locking amplification module, and the output end of the control module is connected with the control end of the signal generation module.)

1. A magnetometer, comprising:

a laser module (10) for emitting a first laser beam;

the beam splitting module (120) is arranged on the light path of the first laser beam and is used for splitting the first laser beam to form a second laser beam;

the linear polarization module (210) is arranged on a light path of the second laser beam and is used for converting the second laser beam into a linearly polarized light beam with adjustable light intensity;

the acousto-optic modulation module (230) is arranged on the light path of the light intensity adjustable linearly polarized light beam and is used for modulating the light intensity adjustable linearly polarized light beam to form diffracted light;

a diffraction light selection module (310) which is arranged on the light path of the diffraction light and is used for selecting the diffraction light to form 1 st-order diffraction light;

the circular polarization module (340) is arranged on the light path of the 1 st-order diffraction light and is used for converting the 1 st-order diffraction light into circularly polarized light;

the atom air chamber (40) is arranged on a light path of the circularly polarized light, and the circularly polarized light emits detection light after passing through the atom air chamber (40);

the photoelectric detection module (410) is arranged on the optical path of the detection light and used for converting the detection light into a detection electric signal;

the output end of the signal generation module (530) is connected with the control end of the acousto-optic modulation module (230) and is used for outputting a voltage modulation signal to control the acousto-optic modulation module (230);

the input end of the phase-locked amplification module (510) is respectively connected with the output end of the photoelectric detection module (410) and the output end of the signal generation module (530), and is used for receiving the detection electric signal and the voltage modulation signal and demodulating the detection electric signal according to the voltage modulation signal to obtain a frequency discrimination signal;

the input end of the control module (520) is connected with the output end of the phase-locked amplifying module (510), and the output end of the control module (520) is connected with the control end of the signal generating module (530) and used for controlling the signal generating module (530) to output the voltage modulation signal according to the frequency discrimination signal.

2. The magnetometer of claim 1, wherein the splitting module (120) splits the first laser beam to form a third laser beam, the magnetometer further comprising:

and the wavelength locking module (130) is arranged on a light path of the third laser beam, and the output end of the wavelength locking module (130) is connected with the laser module (10) and is used for locking the wavelength of the laser module (10) according to the third laser beam.

3. The magnetometer of claim 1, wherein the signal generating module (530) comprises:

a first signal generator (531) for generating a sawtooth wave signal;

a second signal generator (532), an input end of the second signal generator (532) is connected with an output end of the first signal generator (531) for generating a square wave signal;

the square wave signal is the voltage modulation signal.

4. The magnetometer of claim 1, wherein the linear polarization module (210) comprises:

a first half-wave plate (211) arranged on the optical path of the second laser beam;

and the first polarization beam splitter prism (212) is arranged on the light path of the second laser beam passing through the first half-wave plate (211) and is used for converting the second laser beam into the linearly polarized light beam with adjustable light intensity.

5. The magnetometer of claim 1, wherein the circular polarization module (340) comprises:

a second half-wave plate (341) provided on the optical path of the 1 st order diffracted light;

and the quarter-wave plate (343) is arranged on the light path of the 1 st-order diffracted light passing through the second half-wave plate (341) and is used for converting the 1 st-order diffracted light into the circularly polarized light.

6. The magnetometer of claim 1, further comprising:

and the magnetic shielding module (420) surrounds to form a first accommodating space, and the atomic gas chamber (40) is arranged in the first accommodating space and used for shielding the ambient magnetic field noise.

7. The magnetometer of claim 6, further comprising:

the three-dimensional magnetic field coil (430) is arranged in the first accommodating space, the three-dimensional magnetic field coil (430) surrounds to form a second accommodating space, and the atom air chamber (40) is arranged in the second accommodating space and used for generating a bias magnetic field and compensating a residual magnetic field in the first accommodating space.

8. The magnetometer of claim 1, further comprising:

and the heating device (440) is arranged on the outer surface of the atom gas chamber (40) and is used for heating the atom gas chamber (40) and generating magnetic fields with equal magnitude and opposite directions.

9. The magnetometer of claim 1, further comprising:

a first fiber coupler (110), wherein the input end of the first fiber coupler (110) is connected with the output end of the laser module (10);

the beam splitting module (120) is disposed on a light path of the first laser beam passing through the first fiber coupler (110).

10. A magnetometer detection method characterized by using the magnetometer of any one of claims 1 to 9 for detection.

Technical Field

The application relates to the technical field of quantum precision measurement, in particular to a magnetometer and a magnetometer detection method.

Background

The detection of the weak magnetic field signal can be applied to many important fields, such as nondestructive testing, geological exploration, underwater long wave communication, geomagnetic navigation and the like. The magnetic field measured by the traditional fluxgate is generally in nT magnitude, and weaker magnetic field measurement cannot be realized. The magnetometers and gradiometers developed based on the quantum effect mainly have two categories, one is a magnetometer or gradiometer developed based on a superconducting quantum interferometer, and the other is an atomic magnetometer or a magnetic gradiometer. The atomic magnetometer does not need a huge refrigerating device, the miniaturization of the device is easier to realize, meanwhile, the sensitivity can also reach the sub-fT magnitude, and the atomic magnetometer is widely applied to many fields.

However, a plurality of radio frequency coils are provided in the conventional magnetometer. The introduction of radio frequency coils has serious drawbacks in many applications. Crosstalk between the rf coils can introduce errors that can result in a low sensitivity of the magnetometer. In addition, the included angle between the radio frequency coil and the pump light in the conventional magnetometer needs to be accurately maintained at 45 degrees, and the deviation of the angle also causes the deviation of the measurement magnetic field. The traditional magnetometer has two dead zones, and magnetic field detection cannot be carried out on a polar zone parallel to an optical path and an equatorial zone perpendicular to the optical path. Therefore, the traditional magnetometer has inaccurate magnetic field measurement and low measurement precision.

Disclosure of Invention

In view of the above, it is desirable to provide a magnetometer and a magnetometer detecting method.

The present application provides a magnetometer. The magnetometer comprises a laser module, a beam splitting module, a linear polarization module, an acousto-optic modulation module, a diffraction light selection module, a circular polarization module, an atom air chamber, a photoelectric detection module, a signal generation module, a phase-locked amplification module and a control module. The laser module is used for emitting a first laser beam. The beam splitting module is arranged on a light path of the first laser beam and is used for splitting the first laser beam to form a second laser beam. And the linear polarization module is arranged on a light path of the second laser beam and is used for converting the second laser beam into a linearly polarized light beam with adjustable light intensity. The acousto-optic modulation module is arranged on a light path of the light intensity adjustable linearly polarized light beam and is used for modulating the light intensity adjustable linearly polarized light beam to form diffracted light. The diffraction light selection module is arranged on the light path of the diffraction light and is used for selecting the diffraction light to form 1 st-order diffraction light. The circular polarization module is arranged on a light path of the 1 st-order diffraction light and is used for converting the 1 st-order diffraction light into circularly polarized light. The atom air chamber is arranged on a light path of the circularly polarized light, and the circularly polarized light is emitted out of the atom air chamber after passing through the atom air chamber. The photoelectric detection module is arranged on a light path of the detection light and used for converting the detection light into a detection electric signal. The output end of the signal generation module is connected with the control end of the acousto-optic modulation module and is used for outputting a voltage modulation signal to control the acousto-optic modulation module. The input end of the phase-locked amplifying module is respectively connected with the output end of the photoelectric detection module and the output end of the signal generating module, and is used for receiving the detection electric signal and the voltage modulation signal and demodulating the detection electric signal according to the voltage modulation signal to obtain a frequency discrimination signal. The input end of the control module is connected with the output end of the phase-locked amplifying module, and the output end of the control module is connected with the control end of the signal generating module and used for controlling the signal generating module to output the voltage modulation signal according to the frequency discrimination signal.

In one embodiment, the beam splitting module splits the first laser beam to form a third laser beam, and the magnetometer further comprises a wavelength locking module. The wavelength locking module is arranged on a light path of the third laser beam. And the output end of the wavelength locking module is connected with the laser module and used for locking the wavelength of the laser module according to the third laser beam.

In one embodiment, the signal generation module includes a first signal generator and a second signal generator. The first signal generator is used for generating a sawtooth wave signal. The input end of the second signal generator is connected with the output end of the first signal generator and used for generating square wave signals. The square wave signal is the voltage modulation signal.

In one embodiment, the linear polarization module includes a first half-wave plate and a first polarization splitting prism. The first half-wave plate is arranged on a light path of the second laser beam. The first polarization beam splitter prism is arranged on a light path of the second laser beam passing through the first half-wave plate and used for converting the second laser beam into the light-intensity-adjustable linearly polarized light beam.

In one embodiment, the circular polarization module includes a second half-wave plate and a quarter-wave plate. The second half-wave plate is arranged on the light path of the 1 st-order diffraction light. The quarter wave plate is arranged on a light path of the 1 st-order diffracted light passing through the second half wave plate and used for converting the 1 st-order diffracted light into the circularly polarized light.

In one embodiment, the magnetometer further comprises a magnetic shielding module. The magnetic shield module surrounds and forms a first accommodation space. The atomic gas chamber is arranged in the first accommodating space and used for shielding environmental magnetic field noise.

In one embodiment, the magnetometer further comprises a three-dimensional magnetic field coil. The three-dimensional magnetic field coil is disposed in the first accommodating space. The three-dimensional magnetic field coil surrounds to form a second accommodating space. The atomic gas chamber is arranged in the second accommodating space and used for generating a bias magnetic field and compensating a residual magnetic field in the first accommodating space.

In one embodiment, the magnetometer further comprises a heating device. The heating device is arranged on the outer surface of the atom gas chamber and used for heating the atom gas chamber and generating magnetic fields with equal size and opposite directions.

In one embodiment, the magnetometer further comprises a first fiber optic coupler. And the input end of the first optical fiber coupler is connected with the output end of the laser module. The beam splitting module is arranged on a light path of the first laser beam passing through the first optical fiber coupler.

In one embodiment, the present application provides a magnetometer detection method, which uses the magnetometer described in any of the above embodiments for detection.

In the above magnetometer, the acousto-optic modulation module is modulated by the voltage modulation signal output by the signal generation module, and can convert the second laser beam into a square wave with a specific frequency. The second laser beam is pump light. The waveform of the second laser beam is determined by the waveform of the voltage modulation signal output by the signal generation module. The diffracted light includes 0 th order diffracted light and 1 st order diffracted light. The diffraction light selection module is used for selecting the diffraction light so that the 1 st order diffraction light is incident to the circular polarization module.

The atomic gas chamber can be used as a magnetic probe to sense the change of an external magnetic field. The detection light passing through the atomic gas chamber enters the photoelectric detection module. The detection light is detected by the photoelectric detection module, and an optical signal is converted into an electric signal to form the detection electric signal. And the detection electric signal and the voltage modulation signal enter the phase-locking amplification module. The phase-locked amplification module demodulates the detection electric signal by taking the voltage modulation signal as a reference signal to obtain a formant curve. And obtaining the frequency discrimination signal by differentiating the formant curve. The frequency discrimination signal is a frequency discrimination curve. And the frequency discrimination signal is output to the control module. The control module sets a locking point of the frequency discrimination signal. And the locking point of the frequency discrimination signal is output to the signal generation module to form a closed-loop system. It can also be understood that when the magnetic field at the position of the atomic gas cell changes, the peak value of the formant curve shifts, and the voltage of the frequency discrimination signal (which may also be understood as a frequency discrimination curve) corresponding to the peak value of the formant changes and deviates from the voltage value of 0. The control module obtains a voltage compensation value to perform self-adaptive compensation, the voltage compensation value is output to the signal generation module, and the voltage modulation signal is modulated, so that the modulation frequency of the pump light modulated by the acousto-optic modulation module is locked at the Larmor precession frequency of the magnetic field at the position of the atomic gas chamber.

The control module is connected with the signal generating module, so that the modulation frequency of the acousto-optic modulation module can be further adjusted, and the magnetic sensitivity of the magnetometer is improved. The magnetometer does not include a radio frequency coil, and therefore the problem of crosstalk caused by the radio frequency coil is avoided.

Through the system structure of the magnetometer, the magnetometer only has a dead zone of the direction of the pump light, and the magnetometer cannot detect the magnetic field. The magnetometer reduces the number of measurement dead zones. In addition, the magnetometer adopts a Frequency (FM) modulation Bell-Bloom type structure, so that not only is the magnetic sensitivity improved, but also the magnetometer can be miniaturized.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a magnetometer provided in an embodiment.

Fig. 2 is a schematic structural diagram of a wavelength locking module provided in an embodiment.

Fig. 3 is a schematic structural diagram of a heating device provided in an embodiment.

Fig. 4 is a schematic diagram of a detection electrical signal received by the photodetection module provided in an embodiment.

Fig. 5 is a schematic diagram of a resonance curve and a frequency discrimination curve provided in an embodiment.

FIG. 6 is a diagram of a magnetic field test curve provided in an embodiment.

FIG. 7 is a diagram of a noise spectrum curve provided in an embodiment.

Description of reference numerals:

the magnetometer 100, the laser module 10, the first fiber coupler 110, the beam splitting module 120, the linear polarization module 210, the acousto-optic modulation module 230, the diffraction light selection module 310, the circular polarization module 340, the atom gas cell 40, the photodetection module 410, the signal generation module 530, the lock-in amplification module 510, the control module 520, the wavelength locking module 130, the first signal generator 531, the second signal generator 532, the first half-wave plate 211, the first polarization splitting prism 212, the second half-wave plate 341, the second fiber coupler 3421, the third fiber coupler 3422, the quarter-wave plate 343, the magnetic shielding module 420, the three-dimensional magnetic field coil 430, the heating device 440, the heating wire 441, the wavelength locking module 130, the third half-wave plate 131, the second polarization splitting prism 132, the fourth half-wave plate 133, the third polarization splitting prism 134, the wavelength-locked atom gas cell 135, the total reflection mirror 1311, the first dielectric reflection mirror 138, the acousto-optic modulation module 230, the atomic cell 40, the photoelectric detection module 410, and the wavelength locking module, A fifth half-wave plate 137, a second dielectric reflector 136, a wavelength locking photodetector 139, a first diffraction light total reflection mirror 320, a second diffraction light total reflection mirror 330, a control power supply 610, a fluxgate display 620 and a computer 630.

Detailed Description

To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Embodiments of the present application are set forth in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

It will be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it can be directly on, adjacent to, connected or coupled to the other elements or layers or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to" or "directly coupled to" other elements or layers, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, doping types and/or sections, these elements, components, regions, layers, doping types and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type or section from another element, component, region, layer, doping type or section.

Spatial relational terms, such as "under," "below," "under," "over," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements or features described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "under" can encompass both an orientation of above and below. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations) and the spatial descriptors used herein interpreted accordingly.

As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, in this specification, the term "and/or" includes any and all combinations of the associated listed items.

Referring to fig. 1, the present application provides a magnetometer 100. The magnetometer 100 comprises a laser module 10, a beam splitting module 120, a linear polarization module 210, an acousto-optic modulation module 230, a diffraction light selection module 310, a circular polarization module 340, an atom gas cell 40, a photodetection module 410, a signal generation module 530, a lock-in amplification module 510, and a control module 520. The laser module 10 is configured to emit a first laser beam.

The beam splitting module 120 is disposed on a light path of the first laser beam, and configured to split the first laser beam to form a second laser beam. The linear polarization module 210 is disposed on a light path of the second laser beam, and is configured to convert the second laser beam into a linearly polarized light beam with adjustable light intensity. The acousto-optic modulation module 230 is disposed on the light path of the light-intensity-adjustable linearly polarized light beam, and is configured to modulate the light-intensity-adjustable linearly polarized light beam to form diffracted light. The diffraction light selection module 310 is disposed on the light path of the diffraction light, and is configured to select the diffraction light to form 1 st-order diffraction light.

The circular polarization module 340 is disposed on the light path of the 1 st order diffracted light, and is configured to convert the 1 st order diffracted light into circularly polarized light. The atom air chamber 40 is arranged on a light path of the circularly polarized light, and the circularly polarized light is emitted out of the atom air chamber 40. The photo-detection module 410 is disposed on a light path of the detection light, and is configured to convert the detection light into a detection electrical signal.

The output end of the signal generating module 530 is connected to the control end of the acousto-optic modulation module 230, and is configured to output a voltage modulation signal to control the acousto-optic modulation module 230. The input end of the phase-locked amplifying module 510 is connected to the output end of the photodetection module 410 and the output end of the signal generating module 530, respectively, and is configured to receive the detection electrical signal and the voltage modulation signal, and demodulate the detection electrical signal according to the voltage modulation signal to obtain a frequency discrimination signal. The input end of the control module 520 is connected to the output end of the phase-locked amplifying module 510, and the output end of the control module 520 is connected to the control end of the signal generating module 530, and is configured to control the signal generating module 530 to output the voltage modulation signal according to the frequency discrimination signal.

The acousto-optic modulation module 230 can convert the second laser beam into a square wave with a specific frequency by being modulated by the voltage modulation signal output by the signal generation module 530. The second laser beam is pump light. The waveform of the second laser beam is determined by the waveform of the voltage modulation signal output by the signal generation module 530. The diffracted light includes 0 th order diffracted light and 1 st order diffracted light. The diffraction light selection module 310 is configured to select the diffraction light, so that the 1 st order diffraction light is incident to the circular polarization module 340.

The atomic gas cell 40 may be used as a magnetic probe to sense changes in an external magnetic field. The detection light passing through the atomic gas cell 40 enters the photo-detection module 410. The detection light is detected by the photo detection module 410 and converts the optical signal into an electrical signal, forming the detection electrical signal. The detection electrical signal and the voltage modulation signal enter the phase-locked amplification module 510. The phase-locked amplification module 510 demodulates the detection electrical signal by using the voltage modulation signal as a reference signal to obtain a formant curve. And obtaining the frequency discrimination signal by differentiating the formant curve. The frequency discrimination signal is a frequency discrimination curve. The frequency discrimination signal is output to the control module 520. The control module 520 sets the lock point of the frequency discrimination signal. The lock point of the frequency discrimination signal is output to the signal generation module 530 to form a closed loop system.

It can be understood that when the magnetic field at the position of the atomic gas cell 40 changes, the peak value of the formant curve shifts, and the voltage of the discrimination signal (which may be also understood as a discrimination curve) corresponding to the peak value of the formant changes and deviates from the voltage value of 0. The voltage compensation value obtained by the control module 520 is adaptively compensated, and the voltage compensation value is output to the signal generation module 530 to modulate the voltage modulation signal, so that the modulation frequency of the pump light modulated by the acousto-optic modulation module 230 is locked to the larmor precession frequency of the magnetic field at the position of the atomic gas cell 40.

The magnetometer 100 implements the modulation of the pump light by the acousto-optic modulation module 230. When the modulation frequency of the pump light is equal to the larmor precession frequency, resonance is generated. The alkali metal Rb atoms in the atomic gas cell 40 absorb the angular momentum of the photons and transition from the ground state to the excited state, thereby achieving polarization of the atoms. When a magnetic field exists in the non-pumping light direction, polarized atoms precess around the external magnetic field under the action of the spin magnetic moment, and the precession frequency is Larmor precession frequency. When the modulation frequency of the pump light and the larmor precession frequency are in a certain relationship, a resonance phenomenon occurs. The satisfied relationship is:

ω_L＝mω_mod

wherein m is 0,1,2 …, ω_LIs the Larmor precession frequency, omega_modThe modulation frequency of the pump light. When the modulation frequency is 1/2 omega_L、1/3ω_L、1/4ω_LAt this time, a formant still appears. The magnitude of the magnetic field can be calculated by acquiring the resonance frequency. The control module 520 is connected to the signal generating module 530, so as to further adjust the modulation frequency of the acousto-optic modulation module 230, thereby improving the magnetic sensitivity of the magnetometer 100. The magnetometer 100 does not include a radio frequency coil and thus does not introduce cross talk problems caused by the radio frequency coil.

With the system structure of the magnetometer 100, the magnetometer 100 has only one dead zone in the direction of the pump light, and cannot detect the magnetic field. The magnetometer 100 reduces the number of measurement dead zones. Further, the magnetometer 100 has a Frequency (FM) modulated Bell-Bloom type structure, and not only improves magnetic sensitivity but also can be miniaturized.

In one embodiment, the laser module 10 is a 795nm distributed feedback (DBF) laser for generating laser light around 795nm, i.e., the first laser beam. The wavelength of the first laser beam is located at the D1 line of Rb, which can be used to achieve polarization of Rb atoms. The first laser beam may be used as both pump light and detection light. The pump light and the detection light are the same beam of light. The magnetometer 100 is formed in a single beam configuration.

In one embodiment, the magnetometer 100 further comprises a first fiber coupler 110. The input end of the first optical fiber coupler 110 is connected with the output end of the laser module 10. The beam splitting module 120 is disposed on the light path of the first laser beam passing through the first fiber coupler 110. The first fiber coupler 110 is used to convert an optical fiber into spatial light.

In one embodiment, the beam splitting module 120 may include a glass plate for splitting the spatial light into two beams, i.e., the second laser beam and the third laser beam. The second laser beam is 90% of the first laser beam for AOM modulation. The third laser beam is 5% of the first laser beam and is used for building the wavelength locking module 130.

In one embodiment, the linear polarization module 210 includes a first half-wave plate 211 and a first polarization splitting prism 212. The first half-wave plate 211 is disposed on an optical path of the second laser beam. The first polarization splitting prism 212 is disposed on the light path of the second laser beam passing through the first half-wave plate 211, and is configured to convert the second laser beam into the linearly polarized light beam with adjustable light intensity.

The first half wave plate 211 is an 1/2 wave plate. The first polarization splitting prism 212 and the first half-wave plate 211 form a light intensity matching device, which can change the light intensity entering the acousto-optic modulation module 230. By adjusting the first half wave plate 211, the linear polarization state of light can be changed, and the light intensity can also be changed.

In one embodiment, the acousto-optic modulation module 230 may be an AOM acousto-optic modulator.

In one embodiment, the beam splitting module 120 splits the first laser beam to form a third laser beam, and the magnetometer 100 further comprises a wavelength locking module 130. The wavelength locking module 130 is disposed on an optical path of the third laser beam. And the output end of the wavelength locking module 130 is connected to the laser module 10, and is configured to lock the wavelength of the laser module 10 according to the third laser beam.

The wavelength locking module 130 is used to lock the wavelength of the laser module 10, and can accurately lock the laser module 10 at about 795nm, that is, at the D1 line of Rb, which can be used to realize polarization of Rb atoms.

Referring to fig. 2, in an embodiment, the wavelength locking module 130 includes a third half-wave plate 131, a second polarization splitting prism 132, a fourth half-wave plate 133, a third polarization splitting prism 134, a wavelength locking atom gas cell 135, a total reflection mirror 1311, a first dielectric mirror 138, a fifth half-wave plate 137, a second dielectric mirror 136, and a wavelength locking photodetector 139. The first dielectric mirror 138 and the second dielectric mirror 136 are 45 ° dielectric mirrors.

The wavelength locking module 130 is disposed on an optical path of the third laser beam. The third laser beam is incident on the third half-wave plate 131. The third half-wave plate 131 and the second polarization splitting prism 132 constitute a light intensity matching device. The fourth half-wave plate 133 is used for adjusting the linear polarization state of the third laser beam after passing through the second polarization beam splitter prism 132. The third laser beam after passing through the fourth half-wave plate 133 enters the third polarization beam splitter prism 134, and is split into two beams by the third polarization beam splitter prism 134. One beam sequentially passes through the second dielectric reflector 136, the fifth half-wave plate 137, the first dielectric reflector 138 and the total reflection mirror 1311 to be reflected and then enters the wavelength locking atom gas chamber 135 as pumping light. The second dielectric mirror 136, the first dielectric mirror 138 and the total reflection mirror 1311 function to change the direction of light. The fifth half-wave plate 137 is used to adjust the linear polarization state of the light beam. The other beam passes through the wavelength-locked atomic gas cell 135 in turn as detection light to enter the wavelength-locked photodetector 139. Photoelectric conversion is performed by the wavelength locking photodetector 139, and an electric signal is fed back to the laser for locking the wavelength of the laser.

In one embodiment, the signal generating module 530 includes a first signal generator 531 and a second signal generator 532. The first signal generator 531 is used to generate a sawtooth wave signal. An input terminal of the second signal generator 532 is connected to an output terminal of the first signal generator 531 for generating a square wave signal. The square wave signal is the voltage modulation signal.

The first signal generator 531 is for generating a sawtooth wave signal having a peak value of 5V and a time required for scanning from 0 to 5V of 10 s. The sawtooth wave signal is transmitted to the input end of the second signal generator 532, and the second signal generator 532 is controlled to generate a square wave signal which is scanned in a certain frequency range. The duty ratio of the square wave signal is 50%, the scanning range is 5KHz to 135KHz, the low level is 0V, the high level is 5V, and the scanning time is 10 s. The square wave signal is input to the acousto-optic modulation module 230 as the voltage modulation signal. Under the control of the acousto-optic modulation module 230, the pump light is modulated to form the diffracted light. Screened by the diffraction light selection module 310 and converted into the 1 st order diffraction light.

In one embodiment, the diffractive light selection module 310 is a 0 th order diffractive light absorption element, which is used to absorb and shield the 0 th order diffractive light to screen out the 1 st order diffractive light.

In one embodiment, the circular polarization module 340 includes a second half-wave plate 341 and a quarter-wave plate 343. The second half-wave plate 341 is disposed on the optical path of the 1 st order diffracted light. The quarter wave plate 343 is disposed on the light path of the 1 st order diffracted light passing through the second half wave plate 341, and is configured to convert the 1 st order diffracted light into the circularly polarized light.

The second half-wave plate 341 is an 1/2-wave plate for adjusting the 1 st order diffracted light to linearly polarized light. A second fiber coupler 3421 and a third fiber coupler 3422 are disposed between the second half-wave plate 341 and the quarter-wave plate 343. The spatial light is switched to the optical fiber through the second optical fiber coupler 3421. The third optical fiber coupler 3422 and the second optical fiber coupler 3421 are connected by an optical fiber for converting the light in the optical fiber into space light. The spatial light is changed into the circularly polarized light through the quarter-wave plate 343. The circularly polarized light enters the atomic gas cell 40.

The coupling efficiency of the second fiber coupler 3421 and the third fiber coupler 3422 is 80%. The light intensity of the linearly polarized light after coupling is about 200 muW.

In one embodiment, the magnetometer 100 further comprises a first diffractive light holomirror 320 and a second diffractive light holomirror 330. The first diffractive light holomirror 320 is disposed on the optical path of the 1 st order diffractive light, and is used for changing the transmission direction of the optical path. The second diffractive light holomirror 330 is disposed on the light path of the 1 st order diffractive light passing through the first diffractive light holomirror 320, and is used for changing the light path transmission direction. The 1 st order diffracted light after passing through the second diffracted light holomirror 330 is incident to the second half-wave plate 341. The transmission direction of the light path can be changed by the first diffraction light holomirror 320 and the second diffraction light holomirror 330, which is beneficial to miniaturizing the magnetometer 100.

In one embodiment, the magnetometer 100 further comprises a magnetic shielding module 420. The magnetic shield module 420 surrounds to form a first receiving space. The atomic gas chamber 40 is disposed in the first accommodating space, and is used for shielding ambient magnetic field noise. The magnetic shielding module 420 is used for shielding environmental magnetic field noise and ensuring that the magnetic field in the shielding barrel is below 1 nT. The magnetic shield module 420 includes a 5-layer permalloy cylinder, and it is possible to ensure that the residual magnetic field inside the magnetic shield module 420 is below 1 nT.

In one embodiment, the magnetometer 100 further comprises a three-dimensional magnetic field coil 430. The three-dimensional magnetic field coil 430 is disposed in the first accommodating space. The three-dimensional magnetic field coil 430 surrounds to form a second accommodation space. The atomic gas chamber 40 is disposed in the second accommodating space, and is configured to generate a bias magnetic field and compensate for a residual magnetic field in the first accommodating space. The three-dimensional magnetic field coil 430 is used to generate a bias magnetic field while compensating for a residual magnetic field within the magnetic shield module 420. The three-dimensional magnetic field coil 430 is a three-dimensional Helmholtz compensation coil, and the compensation precision is 1 nT. The three-dimensional magnetic field coil 430 may not only compensate for a residual magnetic field inside the magnetic shielding module 420, but also generate an externally applied bias magnetic field to simulate an external geomagnetic environment.

In one embodiment, the magnetometer 100 further comprises a control power source 610, a fluxgate display 620 and a computer 630. The three-dimensional magnetic field coil 430, the control power supply 610 and the fluxgate display 620 form a closed loop, and can realize functions of setting and scanning a magnetic field. The computer 630 is used to receive magnetic field data.

Referring to fig. 3, in one embodiment, the magnetometer 100 further comprises a heating device 440. The heating device 440 is disposed on an outer surface of the atom gas cell 40, and is configured to heat the atom gas cell 40 and generate magnetic fields with equal magnitude and opposite directions.

The circularly polarized light enters the atomic gas cell 40 as pump light. The heating device 440 is made of polyimide and nonmagnetic nickel-chromium materials, and the heating frequency is 500 KHz. The heating device 440 heats the atomic gas cell 40 to 100 ℃. The pump light passing through the atomic gas cell 40 is detected by the photodetection module 410. The photo-detection module 410 may be a photo-detector.

The heating device 440 comprises two oppositely wound heating wires 441. After the two heating wires 441 are energized, a driving current is formed to and fro, and magnetic fields with equal magnitude and opposite directions are generated. Thus, a mutual cancellation of the magnetic fields can be achieved by the two oppositely wound heating wires 441.

In one embodiment, the distance between the two counter-wound heating wires 441 is in the order of μm, which allows better magnetic field cancellation. During preparation, a flexible circuit board process is adopted, and the heating wires 441 are placed on the flexible substrate and are uniformly wound. The flexible substrate is made of polyimide materials. The heating wire 441 is made of non-magnetic nickel-chromium material.

In one embodiment, the resistance of the two oppositely wound heating wires 441 is set to be large, so that the current passing through the heating wires 441 is small, and the residual magnetic field generated is also small.

In one embodiment, the heating device 440 heats by high frequency heating. During high-frequency heating, the frequency of the driving current is set to be 500KHz, so that residual magnetism caused by direct-current heating can be avoided.

In one embodiment, the magnetic field simulating the external geomagnetic environment is in a direction perpendicular to the pump light, that is, perpendicular to the circularly polarized light. Simulating an external partThe magnitude of the magnetic field of the geomagnetic environment is 10000 nT. According to the expression omega_Lγ B, wherein ω_LAt Larmor precession frequency, gamma being R_bThe value of the gyromagnetic ratio is 7, and B is the magnitude of the magnetic field sensed by the gas chamber. When the external magnetic field is set to 10000nT, the corresponding larmor precession frequency is 70KHz, i.e., a distinct resonance signal occurs when the modulation frequency of the pump light is around 70 KHz. The resonance signal received by the photodetection module 410 under the condition of containing the voltage modulation signal is observed as shown in fig. 4.

In one embodiment, the magnetometer 100 comprises a nonmagnetic pt1000 temperature sensor for measuring the temperature of the atomic gas cell 40. The voltage modulation signal output by the signal generating module 530 is attenuated by a certain value and then input to the input end of the phase-locked amplifying module 510, so as to demodulate the detection electrical signal, thereby obtaining a formant curve.

When the magnetic temperature sensor is used for measuring the temperature of the atomic gas chamber 40, the temperature sensor has certain residual magnetism, so that the position of a resonance peak after demodulation has certain offset compared with 70 KHz. When the non-magnetic pt1000 temperature sensor is used for replacing a magnetic temperature sensor, the residual magnetic field can be eliminated, the line width of a main resonance peak is 6.88KHz, and the line width of a corresponding magnetic field is 983 nT.

In addition to the main formants, there are also formants due to harmonic components, corresponding to 1/2 ω respectively_L、1/3ω_L、1/4ω_LAnd the like.

In one embodiment, the input terminals of the phase-locked amplifying module 510 are respectively connected to the output terminals of the photo-detection module 410 and the signal generation module 530, and are configured to receive the detection electrical signal and the voltage modulation signal. The voltage modulation signal is used as a reference signal and transmitted to the phase-locked amplification module 510, and the detection electrical signal is also transmitted to the phase-locked amplification module 510. The phase-locked amplifier module 510 may be a phase-locked amplifier, which adjusts the phases of the detecting electrical signal and the voltage modulating signal to demodulate a corresponding frequency discrimination curve, as shown in fig. 5.

In fig. 5, the solid line represents the demodulated frequency discrimination signal (which may also be understood as a frequency discrimination curve), and the dotted line represents the resonance curve. The frequency discrimination signal comprises a linear segment at the middle position. In the linear region, the center point of the linear segment corresponds to the 0 voltage value of the discriminator curve voltage. Meanwhile, the center point of the linear line segment also corresponds to the resonance peak of the resonance curve. Therefore, the center point (corresponding to a voltage value of 0) of the linear segment of the frequency discrimination curve is the peak value of the resonance peak of the resonance curve. And detecting the frequency value corresponding to the peak value of the resonance peak of the resonance curve to obtain the corresponding magnetic field value.

In one embodiment, the frequency discrimination curve is output to the control module 520. The control module 520 may be a PID control circuit. The parameters of the PID control circuit are set and the first signal generator 531 is switched off. The operating point of the second signal generator 532 is set by a PID control circuit. The output signal of the PID control circuit is connected to the control end of the second signal generator 532, and is used to control the modulation frequency of the voltage modulation signal and lock the frequency value corresponding to the voltage value of 0 corresponding to the frequency discrimination curve.

It can be understood that when the magnetic field at the position of the atomic gas cell 40 changes, the peak value of the formant curve shifts, and the voltage of the discrimination signal (which may be also understood as a discrimination curve) corresponding to the peak value of the formant changes and deviates from the voltage value of 0. The voltage compensation value obtained by the control module 520 is adaptively compensated, and the voltage compensation value is output to the second signal generator 532, so as to modulate the voltage modulation signal, thereby locking the modulation frequency of the pump light modulated by the acousto-optic modulation module 230 to the larmor precession frequency of the magnetic field at the position of the atomic gas cell 40.

The magnetometer 100 forms a closed loop with the second signal generator 532, the lock-in amplification module 510, and the control module 520. The frequency can be locked to the formants by a closed loop. When the external magnetic field changes, the magnetometer 100 synchronously detects the frequency value corresponding to the formant, and achieves the purpose of detecting the magnetic field according to the frequency value.

When the second signal generator 532, the phase-locked amplifying module 510 and the control module 520 form a closed loop. The frequency change is observed by changing the magnitude of the magnetic field applied by the three-dimensional magnetic field coil 430. Referring to fig. 6, fig. 6 is a magnetic field test curve. The corresponding output situation after changing the magnetic field of 1nT can be known from fig. 6. It can be seen that the magnetometer 100 is significantly sensitive to magnetic fields of 1nT or even less than 1 nT.

The noise spectrum of the magnetometer 100 can be further calculated from the frequency versus time curve of fig. 6, which is shown in fig. 7. The noise spectrum shown in FIG. 7 shows that the magnetometer 100 has a noise of 8.54pT/Hz around 1Hz^1/2。

In one embodiment, the magnetometer 100 can be used to measure magnetocardiogram signals of a human body.

In one embodiment, the present application provides a magnetometer detection method, which uses the magnetometer 100 described in any of the above embodiments for detection. When the magnetometer 100 is used for detection, the magnetometer can be applied to the fields of mineral exploration, petroleum and natural gas exploration, pipeline exploration, volcano observation and the like.

In the description herein, references to the description of "some embodiments," "other embodiments," "desired embodiments," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, a schematic description of the above terminology may not necessarily refer to the same embodiment or example.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features of the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.