Three-axis vector atomic magnetometer based on hybrid pumping

Abstract

The invention belongs to the field of weak magnetic detection, and particularly provides a three-axis vector atomic magnetometer based on mixed pumping, which is used for solving the problem of low sensitivity in the simultaneous measurement process of three axes of the three-axis vector atomic magnetometer. The triaxial vector atomic magnetometer comprises a light source part, a pump light path part, a detection light path part, an atomic gas chamber part and a signal acquisition part, the atomic gas chamber part adopts a double-gas-chamber structure, and each atomic gas chamber adopts a K-Rb atom mixing pump; the light path part adopts a pumping-detection orthogonal detection structure, and a single atomic gas chamber adopts one beam of pumping light and two beams of detection light; through creative design of a double-air-chamber structure and a mixed pumping and double-optical-path detection structure, the triaxial measurement sensitivity is improved, and the crosstalk problem existing in triaxial measurement of a traditional triaxial atomic magnetometer is avoided. The three-axis vector magnetic field sensor can realize simultaneous measurement of three-axis magnetic fields, has the advantage of ultrahigh sensitivity, and has important significance for realizing high-sensitivity three-axis vector magnetic field measurement.

Description

Technical Field

[0001] The present invention belongs to the field of weak magnetic field detection, and specifically provides a three-axis vector atomic magnetometer based on hybrid pumping, which is suitable for high-precision measurement of weak magnetic fields in a zero magnetic environment and realizes simultaneous measurement of three-axis magnetic fields. Background Art

[0002] Thanks to the development of quantum technology, ultra-high-sensitivity magnetic field measurement technology based on atomic spin effects has been widely studied. It combines many disciplines such as atomic physics, quantum optics, and precision measurement, and has the world's highest magnetic field measurement sensitivity. Compared with other magnetic field measurement equipment, atomic magnetometers have the characteristics of ultra-high sensitivity and small size. They are currently the most sensitive magnetic field measurement equipment and are also the key research direction of weak magnetic detection.

[0003] The basic principle of the atomic magnetometer based on spin-exchange relaxation is to use the sensitive characteristics of atomic spins to magnetic fields to measure magnetic fields. Its sensitivity is mainly limited by the quantum noise caused by spin relaxation. For traditional atomic magnetometers, the polarizability and polarization uniformity of alkali metal atoms are often difficult to balance, which limits the sensitivity of atomic magnetometers. In addition, for applications such as magnetic source positioning, the realization of three-axis vector measurement is crucial, and the existing three-axis vector atomic magnetometer is difficult to achieve high-sensitivity simultaneous measurement. Therefore, it is very important to study a three-axis vector atomic magnetometer with high-sensitivity and simultaneous measurement. Summary of the invention

[0004] The purpose of the present invention is to provide a three-axis vector atomic magnetometer based on hybrid pumping to achieve three-axis magnetic field simultaneous measurement, in order to solve the problem of low sensitivity in the three-axis simultaneous measurement process of a three-axis vector atomic magnetometer. The three-axis vector atomic magnetometer has the advantage of ultra-high sensitivity, which is of great significance for achieving high-sensitivity three-axis vector magnetic field measurement.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A three-axis vector atomic magnetometer based on hybrid pumping comprises: a light source part, a pump optical path part, a detection optical path part, an atomic gas chamber part and a signal acquisition part; the characteristic is that the atomic gas chamber part adopts a double gas chamber structure, and each atomic gas chamber adopts K-Rb atomic hybrid pumping; the light source part emits detection light and pump light, the pump light is incident on two atomic gas chambers respectively after passing through the pump optical path part, and the detection light is incident on two atomic gas chambers respectively after passing through the detection optical path part, each atomic gas chamber has a beam of pump light and two beams of detection light, and the detection optical path and the pump optical path both form an orthogonal detection structure, and the pump optical paths of the two atomic gas chambers have different directions; the signal acquisition part collects the detection light emitted by the atomic gas chamber and outputs an electromagnetic signal after data processing.

[0007] Furthermore, the atomic gas chamber part includes: a first atomic gas chamber and a second atomic gas chamber, and both are arranged in a magnetic shielding structure; wherein each atomic gas chamber is filled with K atomic vapor, Rb atomic vapor, quenching gas, and buffer gas, the K atomic vapor and the Rb atomic vapor constitute a mixed pump, the molar ratio of K to Rb is 1:(100~270), the quenching gas is N2, the buffer gas is He, and both N2 and He exceed one atmospheric pressure.

[0008] Furthermore, in the atomic gas chamber part, the pump light path of the first atomic gas chamber is along the y direction, and the detection light path is along the x direction and the z direction, and the pump light path of the second atomic gas chamber is along the z direction, and the detection light path is along the x direction and the y direction.

[0009] Furthermore, the light source part includes: a pump laser and a detection laser, wherein the pump laser is tuned to the D1 line of the K atom with a wavelength of 780nm, and the detection laser is tuned to the D1 line of the Rb atom with a wavelength of 795nm.

[0010] Furthermore, the pump light path includes: a one-to-two fiber beam splitter and a circular polarizer; wherein the pump light is equally divided into two beams by the one-to-two fiber beam splitter, each beam of pump light is incident on the circular polarizer through a collimating head and then converted into left-handed circularly polarized light, and the two beams of pump light are incident on two atomic gas chambers respectively.

[0011] Furthermore, the detection optical path portion includes: a polarizer, a Faraday modulator, a one-to-four fiber beam splitter and an analyzer; wherein the detection light forms linearly polarized light after passing through the polarizer, and is modulated by the Faraday modulator, and then divided into four beams by the one-to-four fiber beam splitter, the four detection lights are divided into two groups and are respectively incident on two atomic gas chambers, two detection lights in each group are incident on the atomic gas chamber in two directions after passing through a collimator head, and the four detection lights are transmitted through the atomic gas chamber and respectively passed through the analyzer to be collected by the signal acquisition portion.

[0012] Furthermore, the signal acquisition part includes: four PD probes, two dual-channel phase-locked amplifiers and a data processing system; wherein, the dual-channel phase-locked amplifiers correspond one-to-one to the atomic gas chambers, and the PD probes collect detection light in four directions, convert the optical signals into electrical signals and transmit them to the dual-channel phase-locked amplifiers accordingly, and then convert them into digital signals after demodulation and amplification and transmit them to the data processing system, and finally the magnetic field signal is extracted by the data processing system.

[0013] Based on the above technical solution, the beneficial effects of the present invention are:

[0014] The present invention provides a three-axis vector atomic magnetometer based on hybrid pumping, creatively proposes an innovative structural design combining a double gas chamber structure, a hybrid pump and a dual optical path detection structure, and realizes high-sensitivity three-axis vector detection of the atomic magnetometer; compared with the prior art, the present invention adopts a hybrid pumping technology to ensure the polarization rate of alkali metal atoms while improving the polarization uniformity, and at the same time, adopts a dual optical path detection structure combined with a Faraday rotation detection technology to replace a single optical path structure magnetic field modulation technology, thereby avoiding the problem of magnetic field crosstalk in a multi-axis measurement process, and has the advantages of three-axis simultaneous measurement, high sensitivity and a small multi-axis sensitivity difference. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the three-axis vector atomic magnetometer based on hybrid pumping in the present invention.

[0016] Figure 2 Schematic diagram of the detection optical path of the three-axis vector atomic magnetometer based on hybrid pumping in the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0018] This embodiment provides a three-axis vector atomic magnetometer based on hybrid pumping, and its structure is as follows: Figure 1 As shown, it includes: a light source part, a pump optical path part, a detection optical path part, an atomic gas chamber part and a signal acquisition part; wherein the atomic gas chamber part adopts a double gas chamber structure, and each atomic gas chamber adopts K-Rb atomic hybrid pumping; the light source part emits detection light and pump light, the pump light is incident on two atomic gas chambers respectively after passing through the pump optical path part, and the detection light is incident on two atomic gas chambers respectively after passing through the detection optical path part, each atomic gas chamber has a beam of pump light and two beams of detection light, and the detection optical path and the pump optical path both form an orthogonal detection structure, and the pump optical paths of the two atomic gas chambers have different directions; the signal acquisition part collects the detection light emitted by the atomic gas chamber and outputs an electromagnetic signal after data processing.

[0019] The atomic gas chamber part includes: a first atomic gas chamber 3-1 and a second atomic gas chamber 3-2, the first atomic gas chamber and the second atomic gas chamber are both arranged in a magnetic shielding structure 12, and each atomic gas chamber is respectively equipped with a non-magnetic electric heating module 10; wherein each atomic gas chamber is filled with K atomic vapor, Rb atomic vapor, quenching gas, and buffer gas, the K atomic vapor and the Rb atomic vapor form a mixed pumping structure, the molar ratio of K to Rb is 1:(100-270), the quenching gas is N2, the buffer gas is He, and both N2 and He exceed one atmospheric pressure ; The non-magnetic electric heating module 10 includes: a heating film, a thermal insulation structure and a temperature control system. The heating film is printed on a ceramic substrate and affixed to the air chamber wall. The thermal insulation structure includes: thermal insulation cotton and a boron nitride cube. The temperature control system is implemented based on the STM32 development board; the magnetic shielding structure 12 includes: a magnetic shielding barrel composed of 5 layers of Permalloy and an active magnetic compensation system composed of a three-axis coil. The active magnetic compensation system is regulated by a separate precision current source; it should be noted that the specific structure of the non-magnetic electric heating module and the magnetic shielding structure is a conventional technology in the field and will not be further described in detail here.

[0020] The light source part includes: a pump laser 2 and a detection laser 1, wherein the pump laser 2 is tuned to the D1 line of K atoms with a wavelength of 780nm, and the detection laser 1 is tuned to the D1 line of Rb atoms with a wavelength of 795nm.

[0021] The pump optical path portion includes: a one-to-two optical fiber beam splitter 8 and a circular polarizer 6; wherein, the pump laser output pump light is equally divided into two beams of spatial linear polarized light with a diameter of 3 mm by the one-to-two optical fiber beam splitter, and each beam of spatial linear polarized light is incident on the circular polarizer 6 by a collimating head to form left-handed circularly polarized light, and the two beams of left-handed circularly polarized light are respectively incident on the first atomic gas chamber 3-1 and the second atomic gas chamber 3-2 to realize the polarization of alkali metal atoms, and the pump optical path of the first atomic gas chamber is along the y direction, and the pump optical path of the second atomic gas chamber is along the z direction.

[0022] The detection optical path part is as follows Figure 2 As shown, it includes: a polarizer 5, a Faraday modulator 4, a one-to-four fiber beam splitter 9 and an analyzer 7; wherein, the detection laser 1 emits detection light to form a linearly polarized light with a determined direction after passing through the polarizer 5, and the linearly polarized light is modulated by the Faraday modulator 4 and then equally divided into four spatial linearly polarized lights with a diameter of 2 mm through the one-to-four fiber beam splitter 9, and the four spatial linearly polarized lights are divided into two groups, and the two groups of spatial linearly polarized lights are respectively incident on the first atomic gas chamber 3-1 and the second atomic gas chamber 3-2 to realize atomic polarization detection; the two spatial linearly polarized lights in each group are incident on the atomic gas chamber along two directions after passing through the collimator head, the detection light path of the first atomic gas chamber is along the x direction and the z direction, and the detection light path of the second atomic gas chamber is along the x direction and the y direction; the four detection lights are transmitted through the atomic gas chamber and then passed through the analyzer 7 to be collected by the signal acquisition part.

[0023] The signal acquisition part includes: four photodiode PD probes 11, two phase-locked amplifiers 13 and a data processing system 14; wherein the PD probe 11 collects detection light in four directions, converts the optical signal into an electrical signal and transmits it to two dual-channel phase-locked amplifiers 13 accordingly, the electrical signal is converted into a digital signal after demodulation and amplification in the phase-locked amplifier, the modulation mode is set to internal modulation, and finally the magnetic field signal is extracted by the data processing system 14.

[0024] In terms of working principle:

[0025] When the atomic magnetometer works in a state without spin exchange relaxation, the atomic polarization evolution can be described by the Bloch equation, which is specifically expressed as:

[0026]

[0027] Where P represents the atomic polarization vector, q represents the nuclear slowing factor related to the polarization of the nucleus and alkali electrons, and γ e represents the gyromagnetic ratio of the electron, R op represents the optical pumping rate of circularly polarized light, B represents the external magnetic field, s represents the optical pumping vector, and R tol represents the spin relaxation rate;

[0028] When the magnetometer works in a state without spin exchange relaxation, its atomic polarization can be regarded as a slow variable. If dP / dt=0, the quasi-static solution of the Bloch equation can be obtained:

[0029]

[0030] Where P0 represents the electron equilibrium spin polarization, B x , B y , B z Represents the three-axis components of the magnetic field to be measured, represents a simplified expression for the relaxation term;

[0031] From the steady-state solution, it can be seen that when pumping along the z direction, in order to ensure a zero magnetic environment, the x-direction polarization P x During detection, the magnetic field in the y and z directions will be compensated to 0. At this time, the polarization in the x direction is proportional to the magnetic field in the y direction. x B can be measured x , magnetic field B in the y direction y can be measured by the same method; however, the z-direction magnetic field cannot be directly extracted, which means that the pump direction is an insensitive axis in the magnetic field measurement process.

[0032] Based on the basic measurement principle of the atomic magnetometer mentioned above, the traditional three-axis scheme usually uses a single-beam detection technology, which applies two pumping lights to a gas chamber and measures the intensity of the pumping lights to measure the dual-axis magnetic field; therefore, the three-axis magnetic field can be measured by combining the dual-chamber structure with the single-beam detection principle; however, the single-beam detection technology usually requires the introduction of a modulated magnetic field, demodulating and extracting the corresponding magnetic field signal to be measured from the first-order harmonic component of the modulated signal. When measuring the three-axis magnetic field to be measured, the crosstalk between the three-axis modulated magnetic fields will greatly reduce the three-axis sensitivity, making it difficult for the structure to achieve high-sensitivity three-axis simultaneous measurement. In contrast, the dual-beam detection technology that extracts the magnetic field signal to be measured by detecting the optical rotation angle of linearly polarized light does not require the application of a modulated magnetic field to the atomic gas chamber, which can effectively solve the influence of the crosstalk coupling of the modulated magnetic field. However, the dual-beam detection based on the single-chamber structure can only measure the dual-axis magnetic field, and cannot perform three-axis vector detection. In addition, the traditional single alkali metal atomic gas chamber is affected by atomic relaxation, so that its optimal polarizability can only reach 50%, which shows the sensitivity of magnetic field detection.

[0033] In summary, in view of some defects existing in the traditional structure, the present invention provides a three-axis vector atomic magnetometer based on hybrid pumping. The hybrid pumping technology removes the limitation of atomic relaxation on polarizability and can achieve higher sensitivity magnetic field measurement. The dual optical path detection technology combined with the dual gas chamber structure avoids the introduction of the modulated magnetic field, making it possible to achieve high-sensitivity three-axis simultaneous magnetic field measurement, ultimately achieving high-sensitivity three-axis simultaneous magnetic field measurement.

[0034] Specifically, the measurement process of the three-axis vector atomic magnetometer based on hybrid pumping is as follows:

[0035] Step 1: Lock the pump laser 2 to the D1 line of the K atom with a wavelength of 780 nm, and lock the probe laser 1 to the D1 line of the Rb atom with a wavelength of 795 nm;

[0036] Step 2: Turn on the atomic gas chamber heating module 10 to raise the gas chamber temperature to 210° C. Turn on the active magnetic compensation coil of the magnetic shielding module 12 to compensate the magnetic field around the atomic gas chamber to a zero magnetic condition;

[0037] Step 3: Turn on the lock-in amplifier 13, set the modulation frequency of the Faraday modulator, adjust the angles of the polarizer and the analyzer to be 90° vertical, and adjust the amplification factor of the lock-in amplifier to ensure a suitable signal-to-noise ratio;

[0038] Step 4: Measure the three-axis magnetic field. For the first atomic gas chamber 3-1, the detection light along the z and x directions can measure the magnetic field in the x and z directions; for the second atomic gas chamber 3-2, the detection light along the y and x directions can measure the magnetic field in the x and y directions; at this time, the four-way detection light signal is collected by the PD probe and transmitted to the phase-locked amplifier for demodulation;

[0039] Step 5: In the data processing system, the digital signals demodulated by the two lock-in amplifiers are processed to extract two magnetic field signals in the x direction, one magnetic field signal in the y direction, and one magnetic field signal in the z direction;

[0040] Therefore, this embodiment provides a three-axis vector atomic magnetometer based on hybrid pumping, which realizes the simultaneous measurement of three-axis magnetic fields, and the signal crosstalk between the axes is extremely small, and extremely high sensitivity can be obtained.

[0041] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A three-axis vector atomic magnetometer based on hybrid pumping, comprising: The invention comprises a light source part, a pump optical path part, a detection optical path part, an atomic gas chamber part and a signal collection part; the characteristics are that the atomic gas chamber part adopts a double gas chamber structure, and each atomic gas chamber adopts K-Rb atomic mixed pumping; the light source part emits detection light and pump light, the pump light is incident on two atomic gas chambers respectively after passing through the pump optical path part, and the detection light is incident on two atomic gas chambers respectively after passing through the detection optical path part, each atomic gas chamber has a beam of pump light and two beams of detection light, and the detection optical path and the pump optical path both form an orthogonal detection structure, and the pump optical paths of the two atomic gas chambers have different directions; the signal collection part collects the detection light emitted by the atomic gas chamber and outputs an electromagnetic signal after data processing.

2. The three-axis vector atomic magnetometer based on hybrid pumping according to claim 1, characterized in that: The atomic gas chamber part includes: a first atomic gas chamber and a second atomic gas chamber, and both are arranged in a magnetic shielding structure; wherein each atomic gas chamber is filled with K atomic vapor, Rb atomic vapor, quenching gas and buffer gas, K atomic vapor and Rb atomic vapor form a mixed pump, the molar ratio of K to Rb is 1:(100-270), the quenching gas is N2, the buffer gas is He, and both N2 and He exceed one atmospheric pressure.

3. The three-axis vector atomic magnetometer based on hybrid pumping according to claim 1, characterized in that: In the atomic gas chamber part, the pump light path of the first atomic gas chamber is along the y direction, and the detection light path is along the x direction and the z direction, and the pump light path of the second atomic gas chamber is along the z direction, and the detection light path is along the x direction and the y direction.

4. The three-axis vector atomic magnetometer based on hybrid pumping according to claim 1, characterized in that: The light source part includes: a pump laser and a detection laser, wherein the pump laser is tuned to the D1 line of K atoms with a wavelength of 780nm, and the detection laser is tuned to the D1 line of Rb atoms with a wavelength of 795nm.

5. The three-axis vector atomic magnetometer based on hybrid pumping according to claim 1, characterized in that: The pump light path includes: a one-to-two optical fiber beam splitter and a circular polarizer; wherein the pump light is equally divided into two beams by the one-to-two optical fiber beam splitter, each beam of pump light is incident on the circular polarizer through a collimator head and then converted into left-handed circularly polarized light, and the two beams of pump light are incident on two atomic gas chambers respectively.

6. The three-axis vector atomic magnetometer based on hybrid pumping according to claim 1, characterized in that: The detection optical path part includes: a polarizer, a Faraday modulator, a one-to-four fiber beam splitter and an analyzer; wherein the detection light forms linearly polarized light after passing through the polarizer, and is modulated by the Faraday modulator, and then is equally divided into four beams by the one-to-four fiber beam splitter, the four detection lights are divided into two groups, and are respectively incident on two atomic gas chambers, two detection lights in each group are incident on the atomic gas chamber in two directions after passing through a collimator, and the four detection lights are respectively collected by the signal collection part through the analyzer after being transmitted through the atomic gas chamber.

7. The three-axis vector atomic magnetometer based on hybrid pumping according to claim 1, characterized in that: The signal acquisition part includes: four PD probes, two dual-channel phase-locked amplifiers and a data processing system; wherein the dual-channel phase-locked amplifiers correspond to the atomic gas chambers one by one, the PD probes collect detection light in four directions, convert the optical signal into an electrical signal and transmit it to the dual-channel phase-locked amplifier accordingly, and then convert it into a digital signal after demodulation and amplification and transmit it to the data processing system, and finally the magnetic field signal is extracted by the data processing system.

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