A miniaturized triaxial SERF atomic magnetometer device with dual-pumped light semi-transparent and semi-reflective structure

Abstract

This invention relates to a miniaturized triaxial SERF atomic magnetometer device with dual-pump light semi-transparent and semi-reflective beams. A single pump light is guided into the probe by a polarization-maintaining fiber. Then, using a half-wave plate, a polarization beam splitter, a right-angle mirror, and a quarter-wave plate, the pump light is split into two circularly polarized pump lights of equal intensity, which then pass perpendicularly through the same alkali metal gas cell. The pump light passing through the gas cell is then split by a semi-transparent and semi-reflective planar beam splitter; half of the pump light is detected by a photodetector to extract magnetic field information, while the other half returns along the same path and passes through the alkali metal gas cell a second time. This invention achieves high-sensitivity simultaneous measurement of triaxial magnetic fields in a miniaturized triaxial SERF atomic magnetometer, enhances atomic spin polarizability, and improves the uniformity of atomic spin polarizability within the gas cell. It addresses the technical challenge of achieving uniform spin polarizability in miniaturized SERF atomic magnetometer applications, and is beneficial for applications of array-type triaxial SERF atomic magnetometers in fields such as magnetocardiography and magnetoencephalography.

Description

Technical Field

[0001] This invention belongs to the technical field of spin-exchange relaxation-free (SERF) atomic magnetometers, specifically relating to a miniaturized triaxial SERF atomic magnetometer device with dual-pump optical semi-transparent and semi-reflective structure. Background Technology

[0002] A magnetic field measurement device based on the SERF effect has achieved a sensitivity of 0.16 fT / Hz. 1 / 2 The magnetic field measurement using SERF (Spin-exchange Relaxation-Free) technology theoretically reaches the aT level. This ultra-sensitive magnetic field measurement device holds promise for applications in fundamental physics research, biomedicine, and other fields. To promote the development of magnetic field measurement devices in these areas, miniaturized SERF atomic magnetometers need to be developed.

[0003] Classical single-beam SERF atomic magnetometers and dual-beam SERF atomic magnetometers can generally only achieve single-axis or dual-axis magnetic field measurements, making it difficult to measure the magnetic field in the pump light direction. Obtaining complete triaxial magnetic field information has advantages such as improving the accuracy of magnetic source positioning, enhancing the ability to distinguish the measured magnetic field from the environmental interference magnetic field, and suppressing motion artifacts. Currently, the schemes for achieving triaxial magnetic field measurement with SERF atomic magnetometers include the cross low-frequency magnetic field modulation scheme in pump-detection dual-beam SERF atomic magnetometers, the time-division DC bias magnetic field scheme, and the triaxial low-frequency modulation scheme and transverse axis high-frequency modulation scheme in single-beam atomic magnetometers. These schemes have problems such as complex structure which is not conducive to miniaturization, inability to measure the triaxial magnetic field simultaneously, and low magnetic field sensitivity in the pump light direction, which limits the application of triaxial magnetic field measurement with SERF atomic magnetometers.

[0004] SERF atomic magnetometers utilize the interaction between magnetic fields, optical fields, and atoms to measure weak magnetic fields. Atomic spin polarizability, a physical quantity representing the degree of spin polarization of atoms after optical pumping, is a crucial parameter characterizing the performance of atomic magnetometers. To achieve high sensitivity, atomic magnetometers typically operate at 120℃-200℃ to maintain a high alkali metal density in the gas cell. However, this high alkali metal density causes absorption of the pump light, leading to uneven distribution of atomic spin polarizability within the gas cell and affecting the magnetometer's performance.

[0005] Based on the above, this invention proposes a miniaturized triaxial SERF atomic magnetometer device with dual-pumped light semi-transparent and semi-reflective properties. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and propose a miniaturized triaxial SERF atomic magnetometer device with dual-pump light semi-transparent and semi-reflective structure. A single pump light is guided into the probe by a polarization-maintaining fiber. Then, using a half-wave plate, a polarization beam splitter prism, a mirror, and a quarter-wave plate, the pump light is split into two circularly polarized pump lights of equal intensity, which then pass perpendicularly through the same alkali metal gas cell. By detecting the pump light passing through the gas cell, high-sensitivity synchronous and independent measurement of the triaxial magnetic field can be achieved. This overcomes the problem of high-sensitivity measurement of the pump axis magnetic field in classic single-beam and dual-beam SERF atomic magnetometers. Furthermore, the pump light that passes through the gas cell partially returns and passes through the gas cell again, enhancing the uniformity of atomic spin polarization and improving the technical challenge of achieving uniform spin polarization in miniaturized SERF atomic magnetometer applications.

[0007] The technical solution of the present invention is as follows:

[0008] A miniaturized triaxial SERF atomic magnetometer device with dual-pump light semi-transparent and semi-reflective characteristics is characterized by comprising Y-axis circularly polarized pump light passing through an alkali metal gas cell along the y-axis and Z-axis circularly polarized pump light passing through the alkali metal gas cell along the z-axis. The Z-axis and Y-axis circularly polarized pump lights are spatially separated within the alkali metal gas cell. A second planar beam splitter is disposed on the emission side of the Y-axis circularly polarized pump light from the alkali metal gas cell. The second planar beam splitter is a semi-transparent and semi-reflective planar beam splitter, which transmits the Y-axis light through the gas cell. The transmitted light is transmitted to the second photodetector, and the second flat beam splitter reflects the Y-axis reflected light in situ and enters the alkali metal gas cell a second time. A first flat beam splitter is provided on the Z-axis circularly polarized pump light emission side of the alkali metal gas cell. The first flat beam splitter is a semi-transparent and semi-reflective flat beam splitter. The first flat beam splitter transmits the Z-axis transmitted light to the first photodetector, and the first flat beam splitter reflects the Z-axis reflected light in situ and enters the alkali metal gas cell a second time. Both the Z-axis circularly polarized pump light and the Y-axis circularly polarized pump light come from a single light source.

[0009] The first photodetector and the second photodetector are respectively connected to the connecting plate through their respective connecting lines. The surface of the alkali metal gas chamber is provided with a platinum resistance thermometer. The alkali metal gas chamber is located inside the oven. The surface of the oven is provided with a non-magnetic electric heating coil. The oven is located inside a miniature triaxial magnetic coil. The miniature triaxial magnetic coil, the non-magnetic electric heating coil and the platinum resistance thermometer are respectively connected to the connecting plate through their respective connecting lines. The connecting plate is connected to the electronic control system.

[0010] The miniature triaxial magnetic coil is located inside the large triaxial magnetic coil, which is located inside the magnetic shielding barrel. The large triaxial magnetic coil is connected to a signal generator located outside the magnetic shielding barrel.

[0011] The incident side of the Y-axis circularly polarized pump light from the alkali metal gas cell is connected to the transmission side of the polarization beam splitter via a first quarter-wave plate and a first right-angle reflecting prism. The incident side of the Z-axis circularly polarized pump light from the alkali metal gas cell is connected to the reflection side of the polarization beam splitter via a second quarter-wave plate and a second right-angle reflecting prism. The input side of the polarization beam splitter is connected to the laser via a half-wave plate, a collimator, and a polarization-maintaining fiber.

[0012] The magnetic shielding barrel consists of five layers of μ-metal cylinders and is used to shield the ambient magnetic field.

[0013] The laser is a DBR laser or a DFB laser, and the wavelength of the light source generated by the laser is set to the D1 line of the alkali metal atoms in the alkali metal gas cell.

[0014] The alkali metal chamber is filled with one of three alkali metals: potassium, rubidium, and cesium, and is also filled with buffer gas helium and quenching gas nitrogen.

[0015] Based on the response of the atom's spin polarization to the external magnetic field, the x-axis and z-axis magnetic fields are measured using the Y-axis transmitted light, and the x-axis and y-axis magnetic fields are measured using the Z-axis transmitted light, thereby achieving simultaneous measurement of the three-axis magnetic fields through the combination of responses.

[0016] The optical pumping rate R of circularly polarized light in the alkali metal chamber op (l) The expression is as follows:

[0017]

[0018] Where R rel Let w be the relaxation rate other than the optical pump rate, and R be the real part of the Lambert function. op (0) is the initial pump rate, e is the natural constant, n is the number density of alkali metal atoms in the alkali metal chamber, σ(v) is the absorption cross section related to the wavelength v of the circularly polarized light, and l is the propagation distance of the circularly polarized light in the alkali metal chamber.

[0019] The advantages of this invention compared to the prior art are:

[0020] 1. The present invention discloses a miniaturized triaxial SERF atomic magnetometer device with dual-pump light semi-transparent and semi-reflective structure. A single pump light is guided into the probe by a polarization-maintaining fiber. Then, a half-wave plate, a polarizing beam splitter, a right-angle mirror, and a quarter-wave plate are used to split the pump light into two circularly polarized pump lights of equal intensity, which then pass perpendicularly through the same alkali metal gas cell. Based on this rational design, high-sensitivity simultaneous measurement of triaxial magnetic fields is achieved using two circularly polarized beams passing through the same gas cell. Furthermore, the use of a single light source simplifies the structure compared to a dual-beam design, which is beneficial for the miniaturization of the triaxial SERF atomic magnetometer.

[0021] 2. The miniaturized triaxial SERF atomic magnetometer device with dual-pump light semi-transparent and semi-reflective structure described in this invention has an optical path design in which the pump light passing through the gas cell is detected by a photodetector after passing through a semi-transparent and semi-reflective flat beam splitter to extract triaxial magnetic field information. The other half of the pump light returns along the original path and passes through the alkali metal gas cell a second time. This improves the uniformity of spin polarization in the miniaturized application of the triaxial SERF atomic magnetometer, enhances the uniformity of atomic spin polarization, and strengthens the corresponding intensity of the magnetometer. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a miniaturized triaxial SERF atomic magnetometer device with dual-pumped light semi-transparent and semi-reflective properties, which implements the present invention.

[0023] Figure 2 Two circularly polarized pump lights are in Figure 1 A schematic diagram of the spatial distribution structure within the medium-alkali metal chamber.

[0024] Figure 3 This is a schematic diagram of the overall structure of a miniaturized triaxial SERF atomic magnetometer device with dual-pumped light semi-transparent and semi-reflective properties, which implements the present invention.

[0025] The reference numerals in the attached diagram are explained as follows: 1-Laser; 2-Polarization-maintaining fiber; 3-Collider; 4-Half-wave plate; 5-Polarization beam splitter; 6-First right-angle reflecting prism; 7-First quarter-wave plate; 8-Non-magnetic electric heating coil; 9-Oven; 10-Alkali metal gas chamber; 11-First planar beam splitter; 12-First photodetector; 13-Miniature triaxial magnetic coil; 14-Second planar beam splitter; 15-Second photodetector; 16-Platinum resistance thermometer; 17-Second quadrature magnetic coil; 18-Second right-angle reflecting prism; 19-Connecting line; 20-Connecting plate; 21-Mechanical structural component; 22-Electrical control system; 23-Y-axis circularly polarized pump light; 24-Z-axis circularly polarized pump light; 25-Signal generator; 26-Miniaturized triaxial SERF atomic magnetometer probe; 27-Large triaxial magnetic coil; 28-Magnetic shielding barrel; 101-Gas handle; 102-Gas chamber body; xyz-Cartesian coordinate system three axes (i.e., x-axis, y-axis, and z-axis). Detailed Implementation

[0026] The following is in conjunction with the attached diagram ( Figures 1-3 The invention will be described in the following sections and examples.

[0027] Figure 1 This is a schematic diagram of the structure of a miniaturized triaxial SERF atomic magnetometer device with dual-pumped light semi-transparent and semi-reflective properties, which implements the present invention. Figure 2 Two circularly polarized pump lights are in Figure 1 A schematic diagram of the spatial distribution structure within the medium-alkali metal chamber. Figure 3 This is a schematic diagram of the overall structure of a miniaturized triaxial SERF atomic magnetometer device with dual-pumped optical semi-transparent and semi-reflective structure, implementing the present invention. (Reference) Figures 1 to 3 As shown, a miniaturized triaxial SERF atomic magnetometer device with dual-pump light semi-transparent and semi-reflective polarization includes a Y-axis circularly polarized pump light 23 passing through an alkali metal gas cell 10 along the Y-axis and a Z-axis circularly polarized pump light 24 passing through the alkali metal gas cell 10 along the Z-axis. The Z-axis circularly polarized pump light 24 and the Y-axis circularly polarized pump light 23 are spatially separated in the alkali metal gas cell 10 (this reduces the intersection region of the two circularly polarized pump lights acting on the same atoms and suppresses the coupling between the triaxial magnetic fields). A second planar beam splitter 14 is provided on the emission side of the Y-axis circularly polarized pump light in the alkali metal gas cell 10. The second planar beam splitter 14 is a semi-transparent and semi-reflective planar beam splitter, which transmits its Y-axis transmitted light to a second photodetector 15 (for detection). The second planar beam splitter 14 reflects its Y-axis reflected light in situ and enters the alkali metal gas cell 10 a second time (which can enhance the uniformity of spin polarization and spin polarization rate, and improve the response signal intensity of the magnetometer). A first planar beam splitter 11 is provided on the Z-axis circularly polarized pump light emission side of the alkali metal gas cell 10. The first planar beam splitter 11 is a semi-transparent and semi-reflective planar beam splitter. The first planar beam splitter 11 transmits its Z-axis transmitted light to the first photodetector 12 (for detection). The first planar beam splitter 11 reflects its Z-axis reflected light in situ and enters the alkali metal gas cell 10 a second time (which can enhance the uniformity of spin polarization and spin polarization rate, and improve the response signal intensity of the magnetometer). The Z-axis circularly polarized pump light 24 and the Y-axis circularly polarized pump light 23 both come from a single light source.

[0028] The first photodetector 12 and the second photodetector 15 are respectively connected to the connecting plate 20 via their respective connecting lines 19. A platinum resistance thermometer 16 is disposed on the surface of the alkali metal gas chamber 10, which is located inside the oven 9. A non-magnetic electric heating coil 8 is disposed on the surface of the oven 9, which is located inside a miniature triaxial magnetic coil 13. The miniature triaxial magnetic coil 13, the non-magnetic electric heating coil 8, and the platinum resistance thermometer 16 are respectively connected to the connecting plate 20 via their respective connecting lines 19. The connecting plate 20 is connected to the electronic control system 22. The miniature triaxial magnetic coil 13 is located inside a large triaxial magnetic coil 27, which is located inside a magnetic shielding barrel 28. The large triaxial magnetic coil 27 is connected to a signal generator 25 located outside the magnetic shielding barrel 28.

[0029] The incident side of the Y-axis circularly polarized pump light of the alkali metal gas chamber 10 is connected to the transmission side of the polarization beam splitter prism 5 via a first quarter-wave plate 7 and a first right-angle reflecting prism 6. The incident side of the Z-axis circularly polarized pump light of the alkali metal gas chamber 10 is connected to the reflection side of the polarization beam splitter prism 5 via a second quarter-wave plate 17 and a second right-angle reflecting prism 18. The input side of the polarization beam splitter prism 5 is connected to the laser 1 via a half-wave plate 4, a collimator 3, and a polarization-maintaining fiber 2. The magnetic shielding barrel 28 is composed of five layers of μ-metal cylinders and is used to shield the ambient magnetic field. The laser 1 is a DBR laser or a DFB laser, and the wavelength of the light source generated by the laser 1 is set to the D1 line of the alkali metal atoms in the alkali metal gas chamber 10. The alkali metal gas chamber 10 is filled with one of the three alkali metals potassium, rubidium, and cesium, and is also filled with buffer gas helium and quenching gas nitrogen. Based on the response of the atom's spin polarization to the external magnetic field, the x-axis and z-axis magnetic fields are measured using the Y-axis transmitted light, and the x-axis and y-axis magnetic fields are measured using the Z-axis transmitted light, thereby achieving simultaneous measurement of the three-axis magnetic fields through the combination of responses.

[0030] The optical pumping rate R of circularly polarized light in the alkali metal chamber op (l) The expression is as follows:

[0031]

[0032] Where R rel Let w be the relaxation rate other than the optical pump rate, and R be the real part of the Lambert function. op (0) is the initial pump rate, e is the natural constant, n is the number density of alkali metal atoms in the alkali metal chamber, σ(v) is the absorption cross section related to the wavelength v of the circularly polarized light, and l is the propagation distance of the circularly polarized light in the alkali metal chamber.

[0033] This invention relates to a miniaturized triaxial SERF atomic magnetometer device with dual-pump light semi-transparent and semi-reflective beams. A single pump light is guided into the probe by a polarization-maintaining fiber. Then, using a half-wave plate, a polarization beam splitter, a right-angle mirror, and a quarter-wave plate, the pump light is split into two circularly polarized pump lights of equal intensity, which then pass perpendicularly through the same alkali metal gas cell. The pump light passing through the gas cell is then split by a semi-transparent and semi-reflective planar beam splitter; half of the pump light is detected by a photodetector to extract magnetic field information, while the other half returns along the same path and passes through the alkali metal gas cell a second time. This invention achieves high-sensitivity simultaneous measurement of triaxial magnetic fields in a miniaturized triaxial SERF atomic magnetometer, enhances atomic spin polarizability, and improves the uniformity of atomic spin polarizability within the gas cell. It addresses the technical challenge of achieving uniform spin polarizability in miniaturized SERF atomic magnetometer applications, and is beneficial for applications of array-type triaxial SERF atomic magnetometers in fields such as magnetocardiography and magnetoencephalography.

[0034] A miniaturized triaxial SERF atomic magnetometer device with dual-pumped light semi-transmissive and semi-reflective characteristics includes a miniaturized triaxial SERF atomic magnetometer probe, a large triaxial magnetic coil, a magnetic shielding barrel, a laser, and an electronic control system. The miniaturized triaxial SERF atomic magnetometer probe includes an alkali metal gas chamber, an oven, mechanical structural components, optical components, and electronic component assemblies.

[0035] The alkali metal chamber includes a chamber body and a handle. The chamber body is a cube with four sides serving as light-transmitting surfaces and is made of high borosilicate glass. The alkali metal chamber is filled with one of three alkali metals: potassium, rubidium, and cesium, and also with buffer gas helium and quenching gas nitrogen.

[0036] The oven is made of a highly thermally conductive boron nitride material and is used to heat the alkali metal gas chamber.

[0037] The mechanical structural components are all made of non-magnetic polyetheretherketone polymer material and are used to fix the alkali metal gas chamber, the optical components and the electronic components.

[0038] The optical assembly includes a polarization-maintaining fiber with a collimating head, a half-wave plate, a polarizing beam splitter, a quarter-wave plate, a right-angle mirror, and a flat beam splitter. The polarization-maintaining fiber with the collimating head guides a linearly polarized beam into the miniaturized triaxial SERF atomic magnetometer probe via a coupling head connected to the laser. This beam is split into two beams of equal intensity, orthogonal along the y-axis and z-axis, by the half-wave plate and the beam splitter. After passing through the right-angle mirror, the two beams deflect their propagation direction by 90°; that is, the beam propagating along the y-axis passes through the gas cell along the z-axis after the right-angle mirror, and the beam propagating along the z-axis passes through the gas cell along the y-axis after the right-angle mirror. Then, after passing through the quarter-wave plate, the two beams are converted into circularly polarized light and pass perpendicularly through the alkali metal gas cell. The circularly polarized light passing through the gas cell is then reflected in situ by the flat beam splitter, resulting in half of the light being reflected a second time through the alkali metal gas cell. This enhances the uniformity of spin polarization and spin polarizability, increasing the response signal intensity of the magnetometer. The other half of the light is detected by the photodetector. Based on the response of atomic spin polarization to external magnetic fields, the Y-axis light can measure the x-axis and z-axis magnetic fields with high sensitivity, and the Z-axis light can measure the x-axis and y-axis magnetic fields with high sensitivity. By combining the responses of the Y-axis and Z-axis light to the three-axis magnetic fields, highly sensitive synchronous measurement of the three-axis magnetic fields can be achieved.

[0039] When the circularly polarized light propagates within the alkali metal chamber, it is continuously absorbed by the alkali metal atoms until saturation occurs due to the pumping action of the atoms. This process leads to a spin polarization gradient within the alkali metal chamber, resulting in an uneven spin polarization distribution. The attenuation equation corresponding to the propagation of the circularly polarized light within the alkali metal chamber can be described as follows:

[0040]

[0041] The solution to the differential equation is:

[0042]

[0043] Where R op σ is the optical pump rate; l is the propagation distance of the circularly polarized light in the alkali metal gas cell; n is the alkali metal atom number density in the alkali metal gas cell; σ(v) is the absorption cross section related to the wavelength v of the circularly polarized light; R rel R is the relaxation rate excluding the optical pump rate; w is the real part of the Lambert function; op (0) represents the initial pump rate.

[0044] The electronic component assembly includes a platinum resistance thermometer (Pt1000), a non-magnetic electric heating coil, a miniature triaxial magnetic coil, and a photodetector. The Pt1000 platinum resistance thermometer, attached to the surface of the alkali metal gas chamber, is used to monitor the temperature of the alkali metal gas chamber in real time. The non-magnetic electric heating coil, attached to the surface of the oven, is driven by the electronic control system, thereby enabling the alkali metal gas chamber to reach the temperature required to achieve the SERF state of atomic spin. The miniature triaxial magnetic coil, driven by the electronic control system, is used to generate the DC magnetic field (compensating for the residual magnetic field) and AC magnetic field (modulating and calibrating the magnetic field) required for the miniaturized triaxial SERF atomic magnetometer probe. The photodetector is used to detect the circularly polarized pump light passing through the gas chamber, converting the optical signal into a photocurrent that can be processed by the electronic control system.

[0045] The laser provides a light source for the probe and can be a DBR laser or a DFB laser. The wavelength of the light source generated by the laser is set to the D1 line of the alkali metal atom.

[0046] The electronic control system includes a heating film driving signal circuit, a miniaturized triaxial magnetic coil driving signal circuit, a platinum resistance thermometer acquisition signal circuit, a transimpedance amplifier circuit, and a lock-in amplifier circuit. The transimpedance amplifier, connected to the photodetector, converts the photocurrent into a voltage signal. This voltage signal is demodulated by the lock-in amplifier to obtain the response signal corresponding to the triaxial magnetic field to be measured.

[0047] The magnetic shielding barrel consists of five layers of μ-metal cylinders and is used to shield the ambient magnetic field. A large triaxial magnetic coil is placed at the center of the magnetic shielding barrel and is used to calibrate the coil constant of the miniaturized triaxial magnetic coil inside the miniaturized triaxial SERF atomic magnetometer. The miniaturized triaxial SERF atomic magnetometer is positioned at the center of the large triaxial magnetic coil.

[0048] Example 1

[0049] The structure of the dual-pumped light semi-transparent and semi-reflective miniaturized triaxial SERF atomic magnetometer probe in this embodiment is as follows: Figure 1 As shown, the probe includes an oven, an alkali metal gas chamber, mechanical structural components, optical devices, and electronic components.

[0050] The alkali metal gas chamber 10 is the sensitive element of the probe, reference... Figure 2 It includes a gas chamber body 102 and a gas handle 101. The gas chamber body 102 is a cube, with four faces serving as light-transmitting surfaces, and is made of high borosilicate glass. (Reference) Figure 1 The alkali metal chamber 10 is filled with one of three alkali metals: potassium, rubidium, and cesium, and also with buffer gas helium and quenching gas nitrogen. The buffer gas increases the distance between polarized atoms and the inner wall of the alkali metal chamber, and the quenching gas absorbs photons emitted by excited-state atoms decaying to the ground state. These processes suppress atomic spin depolarization. The oven 9, made of highly thermally conductive boron nitride, is used to heat the alkali metal chamber 10 and maintain a uniform temperature within it. The mechanical structural components 21 are all made of non-magnetic polyetheretherketone polymer and are used to fix the alkali metal chamber 10, the oven 9, the optical components, and the electronic components. Another important function is that, through mechanical structural design, the two circularly polarized pump beams are spatially separated within the alkali metal chamber 10 (see reference). Figure 2 The Z-axis circularly polarized light 24 and the Y-axis circularly polarized light 23 reduce the interaction of the two circularly polarized pump lights on the intersection region of the same atom, and suppress the coupling between the three-axis magnetic fields.

[0051] refer to Figure 1 The optical components include a polarization-maintaining fiber 2 with a collimator 3, a half-wave plate 4, a polarizing beam splitter 5, right-angle mirrors 6 and 18, quarter-wave plates 7 and 17, and planar beam splitters 11 and 14. The laser 1 provides a light source for the miniaturized triaxial SERF atomic magnetometer 26; then, the polarization-maintaining fiber 2 with the collimator 3 guides a linearly polarized beam into the miniaturized triaxial SERF atomic magnetometer probe 26 via a coupling head connected to the laser 1 (see reference). Figure 3 The beam is split into two beams of equal intensity orthogonal along the y-axis and z-axis by the half-wave plate 4 and the beam splitter 5. After passing through the right-angle mirrors 6 and 18, the propagation direction of the two beams is deflected by 90° respectively. That is, the beam propagating along the y-axis passes through the alkali metal gas chamber 10 along the z-axis after passing through the right-angle mirror 18, and the beam propagating along the z-axis passes through the alkali metal gas chamber 10 along the y-axis after passing through the right-angle mirror 6. Then, after passing through the quarter-wave plates 7 and 17, the two beams are converted into Z-axis circularly polarized light 24 and Y-axis circularly polarized light 23 respectively (see reference). Figure 2The light passes perpendicularly through the alkali metal gas chamber 10. The Z-axis circularly polarized light 24 and Y-axis circularly polarized light 23 passing through the alkali metal gas chamber 10 are then reflected by the flat beam splitters 11 and 14, achieving a second in-situ reflection of half of the light through the gas chamber. This enhances the uniformity of spin polarization and spin polarization rate, and improves the response signal intensity of the magnetometer. The other half of the light is detected by the photodetectors 12 and 15 to achieve simultaneous triaxial magnetic field measurement.

[0052] When the Z-axis circularly polarized light 24 and the Y-axis circularly polarized light 23 propagate within the alkali metal gas chamber 10, they are continuously absorbed by the alkali metal atoms until saturation due to the need to pump them. This process leads to uneven spin polarization distribution of the atoms within the alkali metal gas chamber 10. The attenuation equations corresponding to the propagation of the Z-axis circularly polarized light 24 and the Y-axis circularly polarized light 23 within the alkali metal gas chamber 10 can be described as follows:

[0053]

[0054] The solution to the differential equation is:

[0055]

[0056] Where R op σ is the optical pump rate; l is the propagation distance of the Z-axis circularly polarized light 24 and the Y-axis circularly polarized light 23 in the alkali metal gas chamber 10; n is the number density of alkali metal atoms in the alkali metal gas chamber 10; σ(v) is the absorption cross-section related to the wavelength v of the Z-axis circularly polarized light 24 and the Y-axis circularly polarized light; R rel R is the relaxation rate excluding the optical pump rate; w is the real part of the Lambert w function; op (0) represents the initial pump rate. The polarizability of an atom = optical pump rate / (optical pump rate + relaxation rate other than optical pump rate). By having the pump light pass through the alkali metal gas cell 10 twice, the uniformity of the optical pump rate within the alkali metal gas cell 10 can be improved, thereby enhancing the uniformity of atomic spin polarization and atomic spin polarizability, and improving the response signal intensity and sensitivity of the magnetometer.

[0057] The electronic components include a platinum resistance thermometer 16, a non-magnetic electric heating coil 8, a miniature triaxial magnetic coil 13, and photodetectors 12 and 15. The platinum resistance thermometer 16, attached to the surface of the alkali metal gas chamber 10, is used to monitor the temperature of the chamber in real time and maintain the temperature stable within ±0.03℃ (PI, proportional-integral control) using a LabVIEW program's PI closed-loop control system. The non-magnetic electric heating coil 8, attached to the surface of the oven 9, is driven by the electronic control system 22, thereby enabling the alkali metal gas chamber 10 to reach the temperature required for the atomic magnetometer to achieve the SERF state of atomic spin. The miniature triaxial magnetic coil 13, driven by the electronic control system 22, is used to generate the DC magnetic field (compensating for the residual magnetic field) and AC magnetic field (modulating and calibrating magnetic field) required by the miniaturized triaxial SERF atomic magnetometer probe 26. The photodetectors 12 and 15 are used to detect the Z-axis circularly polarized light 24 and Y-axis circularly polarized light 23 transmitted through the alkali metal gas chamber, respectively, converting the optical signals into photocurrents that can be processed by the electronic control system 22.

[0058] Example 2

[0059] Figure 2 This describes the spatial distribution structure of the two circularly polarized pump beams within the alkali metal chamber of the aforementioned dual-pump light semi-transparent and semi-reflective miniaturized triaxial SERF atomic magnetometer device. Through mechanical structure design, the Z-axis circularly polarized light 24 and the Y-axis circularly polarized light 23 are spatially separated within the alkali metal chamber 10, reducing the interaction between the Z-axis and Y-axis circularly polarized light 24 and the cross-region of the same atoms, and suppressing triaxial magnetic field measurement coupling caused by crosstalk between adjacent channels. The spatial separation distance between the Z-axis and Y-axis circularly polarized light 24 and 23 within the alkali metal chamber can be designed based on the diffusion distance of the atoms within the alkali metal chamber 10. The diffusion distance can be expressed as:

[0060]

[0061] Where D is the diffusion coefficient; Γ is the total relaxation rate, which is equal to the optical pump rate R. op Add the relaxation rate R other than the light pump rate rel .

[0062] The diffusion coefficient D of alkali metal atoms in high-pressure buffer and quenching gases can be expressed as:

[0063]

[0064] Where D0 is the initial diffusion coefficient under standard atmospheric pressure; T is the temperature inside the alkali metal chamber; T0 equals 273.15K; P0 is standard atmospheric pressure; and P is the pressure inside the alkali metal chamber.

[0065] Example 3

[0066] Figure 3 This describes the structure of a miniaturized triaxial SERF atomic magnetometer device with dual-pumped light semi-transparent and semi-reflective characteristics. The laser 1 provides a light source for the miniaturized triaxial SERF atomic magnetometer probe 26, and can be a DBR laser or a DFB laser. The wavelength of the light source generated by the laser 1 is set to the D1 line of the alkali metal atoms.

[0067] The magnetic shielding barrel 28 consists of five layers of μ-metal cylinders and is used to shield the ambient magnetic field. The large triaxial magnetic coil 27 is placed at the center of the magnetic shielding barrel 28 and is used to calibrate the coil constant of the miniature triaxial magnetic coil 13 inside the miniaturized triaxial SERF atomic magnetometer probe 26. The miniaturized triaxial SERF atomic magnetometer probe 26 is placed at the center of the large triaxial magnetic coil 27.

[0068] The electronic control system 22 includes a heating film driving signal circuit, a miniaturized triaxial magnetic coil driving signal circuit, a platinum resistance acquisition signal circuit, a transimpedance amplifier circuit, and a lock-in amplifier circuit. The transimpedance amplifier, connected to the photodetectors 12 and 15, converts the photocurrent into a voltage signal. This voltage signal is demodulated by the lock-in amplifier to obtain the response signal corresponding to the triaxial magnetic field to be measured. Specifically, based on the response of atomic spin polarization to an external magnetic field, the Y-axis circularly polarized pump light 23 can measure the x-axis and z-axis magnetic fields with high sensitivity, and the Z-axis circularly polarized pump light 24 can measure the x-axis and y-axis magnetic fields with high sensitivity. The combined response of the Y-axis circularly polarized pump light 23 and the Z-axis circularly polarized pump light 24 to the triaxial magnetic field achieves high-sensitivity synchronous measurement of the triaxial magnetic field. When the pump direction is on the Z-axis, according to the principle of the SERF atomic magnetometer, the atomic spin dynamics evolution process can be expressed by the Bloch equation:

[0069]

[0070] Where P is the electron spin polarizability, t is time; q(P) is the nuclear slowing factor; γ e = 2π × 28 Hz / nT, γ e B is the gyromagnetic ratio of a single electron; B is the vector magnetic field; R op s is the optical pump rate; s is the circular polarization vector of the photon; R is a unit quantity along the z-axis. rel For relaxation rates other than pump rate.

[0071] When a high-frequency modulated magnetic field is applied simultaneously along the x-axis, y-axis, and z-axis, i.e. B is the modulation magnetic field, B i0 is the initial magnetic field, and i is an intermediate quantity. It is the magnetic field amplitude, ω i Where t is the magnetic field frequency, and t is time. It is a unit vector.

[0072] Based on the perturbation iteration method, the projection of the first harmonic term of the atomic spin polarization component along the Z-axis circularly polarized pump light direction 24 can be approximately expressed as:

[0073]

[0074] in It is the first harmonic term ω of the atomic spin polarization component. x Projected along the Z-axis circularly polarized pump light direction, where It is the first harmonic term ω of the atomic spin polarization component. y Projecting along the Z-axis circularly polarized pump light direction, It is the z-axis optical pump rate, γ e It is the electron gyromagnetic ratio, J0 is the 0th-order Bessel function, J1 is the 1st-order Bessel function, R rel It is the relaxation rate, B x0 It is the initial magnetic field along the x-axis, B y0 It is the initial magnetic field along the y-axis. It is the x-axis magnetic field reference frequency. t is the reference frequency of the y-axis magnetic field, and t is time.

[0075] Similarly, the first harmonic term ω of the atomic spin polarization component x and ω z Projection along the Y-axis circularly polarized pump light in direction 23 and It can be represented as:

[0076]

[0077] in It is the y-axis optical pump rate, B z0 It is the initial magnetic field along the z-axis, J i The modulation index is The first kind of i-th order Bessel function, It is the magnetic field amplitude, ω x,y,z It is a first harmonic term, and q(P) is a slowing factor; P z (0) and P y (0) is the equilibrium electron spin polarization when the magnetic field is zero. Using the lock-in amplifier in the aforementioned electronic control system, at the reference frequency... By demodulating the probe response signal corresponding to the Z-axis circularly polarized pump light 24, the magnetic field information to be measured along the x and y axes can be obtained; using the lock-in amplifier in the electronic control system at the reference frequency... By demodulating the probe response signal corresponding to the Y-axis circularly polarized pump light 23, the magnetic field information to be measured on the x-axis and z-axis can be obtained. Using the above combination, the three-axis magnetic field synchronous measurement can be realized.

[0078] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, and / or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. A dual-pumped optically semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device, characterized in that, The Y-axis circularly polarized pump light passes through the alkali metal cell along the Y-axis direction, and the Z-axis circularly polarized pump light passes through the alkali metal cell along the Z-axis direction, the Z-axis circularly polarized pump light and the Y-axis circularly polarized pump light present a spatially separated distribution in the alkali metal cell, a second flat beam splitter is arranged on the Y-axis circularly polarized pump light exit side of the alkali metal cell, the second flat beam splitter is a semi-transparent and semi-reflective flat beam splitter, the second flat beam splitter transmits Y-axis transmitted light to a second photodetector, and the second flat beam splitter reflects Y-axis reflected light in situ for the second time into the alkali metal cell, a first flat beam splitter is arranged on the Z-axis circularly polarized pump light exit side of the alkali metal cell, the first flat beam splitter is a semi-transparent and semi-reflective flat beam splitter, the first flat beam splitter transmits Z-axis transmitted light to a first photodetector, and the first flat beam splitter reflects Z-axis reflected light in situ for the second time into the alkali metal cell, the Z-axis circularly polarized pump light and the Y-axis circularly polarized pump light are from a single light source; The Y-axis circularly polarized pump light incident side of the alkali metal cell sequentially passes through a first quarter-wave plate and a first right-angle reflective prism connected to the transmission side of a polarization beam splitter prism, and the Z-axis circularly polarized pump light incident side of the alkali metal cell sequentially passes through a second quarter-wave plate and a second right-angle reflective prism connected to the reflection side of the polarization beam splitter prism, and the input side of the polarization beam splitter prism sequentially passes through a half-wave plate, a collimator and a polarization maintaining optical fiber connected to a laser. According to the response of the atomic spin polarization to the external magnetic field, the x-axis and z-axis magnetic fields are measured by using the Y-axis transmitted light, and the x-axis and y-axis magnetic fields are measured by using the Z-axis transmitted light, so that the response combination of the three-axis magnetic field is realized to achieve synchronous measurement of the three-axis magnetic field.

2. The dual-pumped optically semi-transparent semi-reflective miniaturized three- axis SERF atomic magnetometer device of claim 1, wherein, The first photodetector and the second photodetector are connected to a connection plate through respective connection lines, a platinum resistance is arranged on the surface of the alkali metal cell, the alkali metal cell is located in an oven, a non-magnetic electric heating coil is arranged on the surface of the oven, the oven is located in a micro three-axis magnetic coil, and the micro three-axis magnetic coil, the non-magnetic electric heating coil and the platinum resistance are connected to the connection plate through respective connection lines.

3. The dual-pumped optically semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device of claim 1, wherein, The micro three-axis magnetic coil is located in a large three-axis magnetic coil, the large three-axis magnetic coil is located in a magnetic shielding barrel, and the large three-axis magnetic coil is connected to a signal generator located outside the magnetic shielding barrel.

4. The dual-pumped optically semi-transparent semi-reflective miniaturized three- axis SERF atomic magnetometer device of claim 3, wherein, The magnetic shielding barrel is composed of five layers of μ-metal cylinders for shielding the environmental magnetic field.

5. The dual-pumped optically semi-transparent semi-reflective miniaturized three- axis SERF atomic magnetometer device of claim 1, wherein, The laser is a DBR laser or a DFB laser, and the wavelength of the light source generated by the laser is set as the D1 line of the alkali metal atoms in the alkali metal cell.

6. The dual-pumped optically semi-transparent semi-reflective miniaturized three- axis SERF atomic magnetometer device of claim 1, wherein, The alkali metal cell is filled with one of three alkali metals, i.e., potassium, rubidium and cesium, and is also filled with buffer gas helium and quenching gas nitrogen.

7. The dual-pumped optically semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device of claim 1, wherein The optical pumping rate R of circularly polarized light in the alkali metal cell op (l) is expressed as follows: wherein R rel is a relaxation rate other than the optical pumping rate, w is the real part of the Lamber function, R op (0) is the initial pumping rate, e is the natural constant, n is the number density of alkali metal atoms in the alkali metal cell, σ(v) is the absorption cross section related to the wavelength v of the circularly polarized light, and l is the propagation distance of the circularly polarized light in the alkali metal cell.

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