Double-pump light semi-transparent and semi-reflective miniaturized triaxial SERF atom magnetometer device

Abstract

The invention relates to a double-pump light semi-transparent and semi-reflective miniaturized triaxial SERF atom magnetometer device, which is characterized in that single pump light is guided into a probe by a polarization maintaining optical fiber; and then one beam of pump light is divided into two beams of circular polarization pump light with the same light intensity by using a half-wave plate, a polarization splitting prism, a right-angle reflector and a quarter-wave plate, and then the two beams of circular polarization pump light vertically pass through the same alkali metal gas chamber. After the pump light penetrating through the air chamber passes through the semi-transparent and semi-reflective flat beam splitter, one half of the pump light is detected by the photoelectric detector and used for extracting magnetic field information, and the other half of the pump light returns to the original path and passes through the alkali metal air chamber for the second time. According to the invention, high-sensitivity simultaneous measurement of a three-axis magnetic field of the miniaturized three-axis SERF atom magnetometer is realized, the atomic spin polarizability is enhanced, the uniformity of the atomic spin polarizability in the air chamber is improved, and the technical problem of spin polarizability uniformity in miniaturized application of the SERF atom magnetometer is solved; and the application of the array type triaxial SERF atom magnetometer in the fields of magnetocardiography, brain magnetism and the like is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of spin-exchange relaxation-free (SERF) atomic magnetometers, and in particular relates to a dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device. Background Art

[0002] The SERF effect-based magnetic field measurement device has achieved a sensitivity of 0.16fT / Hz 1 / 2 The SERF atomic magnetometer is a kind of magnetic field measurement device with high sensitivity, which can theoretically achieve aT-level magnetic field measurement. Ultra-high sensitive magnetic field measurement devices are expected to be applied in basic physics research, biomedicine and other fields. In order to promote the development of magnetic field measurement devices in related fields, it is necessary to develop miniaturized SERF atomic magnetometers.

[0003] Classic single-beam SERF atomic magnetometers and dual-beam SERF atomic magnetometers can generally only achieve single-axis or dual-axis magnetic field measurements, and it is difficult to achieve magnetic field measurements in the direction of the pump light. Obtaining complete three-axis magnetic field information has the advantages of improving the accuracy of magnetic source positioning, improving the ability to distinguish the magnetic field to be measured from the environmental interference magnetic field, and suppressing motion artifacts. At present, the schemes for SERF atomic magnetometers to achieve three-axis magnetic field measurement include the cross-low-frequency magnetic field modulation scheme in the pump-detection dual-beam SERF atomic magnetometer, the time-sharing DC bias magnetic field scheme, and the three-axis low-frequency modulation scheme in the single-beam atomic magnetometer, the transverse axis high-frequency modulation scheme, etc. These schemes have complex structures that are not conducive to miniaturization, the three-axis magnetic field cannot be measured simultaneously, and the magnetic field sensitivity in the direction of the pump light is low. This limits the application of SERF atomic magnetometers in three-axis magnetic field measurement.

[0004] SERF atomic magnetometers use the interaction between magnetic fields, light fields and atoms to measure weak magnetic fields. Atomic spin polarization is a physical quantity that indicates the degree of spin polarization of atoms after being optically pumped. It is an important parameter that characterizes the performance of atomic magnetometers. In order to obtain higher sensitivity, atomic magnetometers usually operate at 120℃-200℃ to maintain a higher alkali metal density in the gas chamber. However, a higher alkali metal density in the gas chamber will cause absorption of pump light intensity, resulting in uneven distribution of atomic spin polarization in the gas chamber, affecting the performance of the magnetometer.

[0005] Based on the above, the present invention proposes a dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device. Summary of the invention

[0006] The technical problem to be solved by the present invention is: to overcome the shortcomings of the prior art, and to propose a dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device, wherein a single pump light is introduced into a probe by a polarization-maintaining optical fiber, and then a half-wave plate, a polarization beam splitter, a reflector and a quarter-wave plate are used to realize that a beam of pump light is divided into two beams of circularly polarized pump light with equal light intensity, and then vertically pass through the same alkali metal gas chamber, and by detecting the pump light passing through the gas chamber, high-sensitivity synchronous and independent measurement of the three-axis magnetic field can be realized, thereby overcoming the problem that the classical single-beam and double-beam SERF atomic magnetometers are difficult to realize high-sensitivity measurement of the pump axis magnetic field, and the pump light part that passes through the gas chamber returns and passes through the gas chamber again, thereby enhancing the uniformity of atomic spin polarization, and improving the technical problem of spin polarization rate uniformity in the miniaturized application of SERF atomic magnetometer.

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

[0008] A dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device, characterized in that it comprises a Y-axis circularly polarized pump light passing through an alkali metal gas chamber along the y-axis direction, and a Z-axis circularly polarized pump light passing through the alkali metal gas chamber along the z-axis direction, wherein the Z-axis circularly polarized pump light and the Y-axis circularly polarized pump light present a spatially separated distribution in the alkali metal gas chamber, and a second flat-plate beam splitter is arranged on the Y-axis circularly polarized pump light exit side of the alkali metal gas chamber, the second flat-plate beam splitter is a semi-transmissive and semi-reflective flat-plate beam splitter, and the second flat-plate beam splitter transmits its Y-axis circularly polarized pump light to the alkali metal gas chamber. The Z-axis circularly polarized pump light is transmitted to the first photodetector, the second flat-plate beam splitter reflects its Y-axis reflected light in situ and enters the alkali metal gas chamber for the second time, a first flat-plate beam splitter is arranged on the Z-axis circularly polarized pump light exit side of the alkali metal gas chamber, the first flat-plate beam splitter is a semi-transparent and semi-reflective flat-plate beam splitter, the first flat-plate beam splitter transmits its Z-axis transmitted light to the first photodetector, the first flat-plate beam splitter reflects its Z-axis reflected light in situ and enters the alkali metal gas chamber for the second time, the Z-axis circularly polarized pump light and the Y-axis circularly polarized pump light both come from a single light source.

[0009] The first photodetector and the second photodetector are respectively connected to the connecting plate through their own connecting wires, a platinum resistor is arranged on the surface of the alkali metal gas chamber, the alkali metal gas chamber 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, the micro-three-axis magnetic coil, the non-magnetic electric heating coil and the platinum resistor are respectively connected to the connecting plate through their own connecting wires, and the connecting plate is connected to an electronic control system.

[0010] The miniature three-axis magnetic coil is located inside the large three-axis magnetic coil, the large three-axis magnetic coil is located inside the magnetic shielding barrel, and the large three-axis magnetic coil is connected to a signal generator located outside the magnetic shielding barrel.

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

[0012] The magnetic shielding barrel is composed of five layers of μ-metal cylinders and is used for shielding the environmental 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 be the D1 line of the alkali metal atoms in the alkali metal gas cell.

[0014] The alkali metal gas 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] According to the response of the atomic spin polarization to the external magnetic field, the Y-axis transmitted light is used to measure the x-axis and z-axis magnetic fields, and the Z-axis transmitted light is used to measure the x-axis and y-axis magnetic fields, thereby realizing the synchronous measurement of the three-axis magnetic field by combining the responses of the three-axis magnetic field.

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

[0017]

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

[0019] The advantages of the present invention compared with the prior art are:

[0020] 1. The dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device described in the present invention uses a single pump light to be introduced into the probe by a polarization-maintaining optical fiber, and then uses a half-wave plate, a polarization beam splitter, a right-angle reflector and a quarter-wave plate to realize a beam of pump light divided into two beams of circularly polarized pump light with equal light intensity and then vertically pass through the same alkali metal gas chamber. Based on the above reasonable design, the high-sensitivity simultaneous measurement of the three-axis magnetic field is realized by using two beams of circularly polarized light passing through the same gas chamber. In addition, the use of a single light source has a simpler structure than a dual-beam light beam, which is conducive to the miniaturization of the three-axis SERF atomic magnetometer.

[0021] 2. The present invention discloses a dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device. In the optical path design, the pump light passing through the gas chamber passes through a semi-transmissive and semi-reflective flat beam splitter, and half of the pump light is detected by a photodetector to extract three-axis magnetic field information. The other half of the pump light returns along the original path and passes through the alkali metal gas chamber for the second time, thereby improving the uniformity of spin polarization rate in the miniaturized application of the three-axis SERF atomic magnetometer, improving the uniformity of atomic spin polarization rate and enhancing the corresponding intensity of the magnetometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a schematic structural diagram of a dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device.

[0023] Figure 2 Two circularly polarized pump beams are Figure 1 Schematic diagram of the spatial distribution structure within the alkali metal gas cell.

[0024] Figure 3 The present invention is a schematic diagram of the overall structure of a dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device.

[0025] The reference numerals are as follows: 1-laser; 2-polarization-maintaining optical fiber; 3-collimator; 4-half-wave plate; 5-polarization beam splitter; 6-first right-angle reflection prism; 7-first quarter-wave plate; 8-non-magnetic electric heating coil; 9-oven; 10-alkali metal gas chamber; 11-first flat beam splitter; 12-first photodetector; 13-micro three-axis magnetic coil; 14-second flat beam splitter; 15-second photodetector; 16-platinum resistor; 17-second fourth One-fifth wave plate; 18-second right-angle reflecting prism; 19-connecting wire; 20-connecting plate; 21-mechanical structure; 22-electric control system; 23-Y-axis circularly polarized pump light; 24-Z-axis circularly polarized pump light; 25-signal generator; 26-miniaturized three-axis SERF atomic magnetometer probe; 27-large three-axis magnetic coil; 28-magnetic shielding barrel; 101-air handle; 102-air chamber body; xyz-three axes of the rectangular coordinate system (i.e., x-axis, y-axis, and z-axis). DETAILED DESCRIPTION

[0026] Below is the attached figure ( Figure 1-Figure 3 ) and Examples illustrate the present invention.

[0027] Figure 1 The present invention is a schematic structural diagram of a dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device. Figure 2 Two circularly polarized pump beams are Figure 1 Schematic diagram of the spatial distribution structure within the alkali metal gas cell. Figure 3 This is a schematic diagram of the overall structure of a dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device according to the present invention. Figures 1 to 3 As shown, a dual pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device includes a Y-axis circularly polarized pump light 23 passing through an alkali metal gas chamber 10 along the y-axis direction, and a Z-axis circularly polarized pump light 24 passing through the alkali metal gas chamber 10 along the z-axis direction, wherein 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 chamber 10 (this can reduce the crossover region where the two circularly polarized pump lights act on the same atom and suppress the mutual coupling of the three-axis magnetic fields), and a second flat beam splitter 14 is arranged on the Y-axis circularly polarized pump light exit side of the alkali metal gas chamber 10, the second flat beam splitter 14 is a semi-transmissive and semi-reflective flat beam splitter, and the second flat beam splitter 14 transmits its Y-axis transmitted light to a second photodetector 15 (for detection) The second flat beam splitter 14 reflects its Y-axis reflected light in situ for a second time into the alkali metal gas chamber 10 (which can enhance the uniformity of spin polarization and spin polarization rate and improve the response signal strength of the magnetometer). A first flat beam splitter 11 is arranged on the Z-axis circularly polarized pump light exit side of the alkali metal gas chamber 10. The first flat beam splitter 11 is a semi-transparent and semi-reflective flat beam splitter. The first flat beam splitter 11 transmits its Z-axis transmitted light to the first photodetector 12 (for detection). The first flat beam splitter 11 reflects its Z-axis reflected light in situ for a second time into the alkali metal gas chamber 10 (which can enhance the uniformity of spin polarization and spin polarization rate and improve the response signal strength 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 connected to the connecting plate 20 through their respective connecting wires 19, a platinum resistor 16 is provided on the surface of the alkali metal gas chamber 10, the alkali metal gas chamber 10 is located in the oven 9, a non-magnetic electric heating coil 8 is provided on the surface of the oven 9, the oven 9 is located in the micro-miniature three-axis magnetic coil 13, the micro-miniature three-axis magnetic coil 13, the non-magnetic electric heating coil 8 and the platinum resistor 16 are connected to the connecting plate 20 through their respective connecting wires 19, and the connecting plate 20 is connected to the electric control system 22. The micro-miniature three-axis magnetic coil 13 is located in the large three-axis magnetic coil 27, the large three-axis magnetic coil 27 is located in the magnetic shielding barrel 28, and the large three-axis magnetic coil 27 is connected to the signal generator 25 located outside the magnetic shielding barrel 28.

[0029] The Y-axis circularly polarized pump light incident side of the alkali metal gas chamber 10 is connected to the transmission side of the polarization beam splitter prism 5 through the first quarter wave plate 7 and the first right-angle reflection prism 6 in sequence, the Z-axis circularly polarized pump light incident side of the alkali metal gas chamber 10 is connected to the reflection side of the polarization beam splitter prism 5 through the second quarter wave plate 17 and the second right-angle reflection prism 18 in sequence, and the input side of the polarization beam splitter prism 5 is connected to the laser 1 through the half wave plate 4, the collimator 3 and the polarization-maintaining optical fiber 2 in sequence. The magnetic shielding barrel 28 is composed of five layers of μ-metal cylinders and is used to shield the environmental 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. According to the response of the atomic spin polarization to the external magnetic field, the Y-axis transmitted light is used to measure the x-axis and z-axis magnetic fields, and the Z-axis transmitted light is used to measure the x-axis and y-axis magnetic fields, thereby realizing the synchronous measurement of the three-axis magnetic field by combining the responses of the three-axis magnetic field.

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

[0031]

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

[0033] The present invention relates to a dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device, which uses a single pump light to be introduced into a probe by a polarization-maintaining optical fiber, and then uses a half-wave plate, a polarization beam splitter, a right-angle reflector and a quarter-wave plate to realize that a beam of pump light is divided into two beams of circularly polarized pump light with equal light intensity and then vertically passes through the same alkali metal gas chamber. After the pump light passing through the gas chamber passes through the semi-transmissive and semi-reflective flat beam splitter, half of the pump light is detected by a photodetector to extract magnetic field information, and the other half of the pump light returns to the original path and passes through the alkali metal gas chamber for the second time. The present invention not only realizes the high-sensitivity simultaneous measurement of the three-axis magnetic field of the miniaturized three-axis SERF atomic magnetometer, but also enhances the atomic spin polarization rate and improves the uniformity of the atomic spin polarization rate in the gas chamber, improves the technical difficulty of the uniformity of the spin polarization rate in the miniaturized application of the SERF atomic magnetometer, and is conducive to the application of the array-type three-axis SERF atomic magnetometer in the fields of heart magnetism, brain magnetism, etc.

[0034] A dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device includes a miniaturized three-axis SERF atomic magnetometer probe, a large three-axis magnetic coil, a magnetic shielding barrel, a laser, and an electric control system. The miniaturized three-axis SERF atomic magnetometer probe includes an alkali metal gas chamber, an oven, a mechanical structure, an optical component, and an electronic component component.

[0035] The alkali metal gas chamber comprises a gas chamber body and a gas handle. The gas chamber body is a cube, four faces of which are light-transmitting faces and are made of borosilicate glass. The alkali metal gas 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.

[0036] The oven is made of a high thermal conductivity boron nitride material and is used for heating the alkali metal gas chamber.

[0037] The mechanical structural parts 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 optical fiber with a collimating head, a half-wave plate, a polarization beam splitter, a quarter-wave plate, a right-angle reflector, and a flat beam splitter. The polarization-maintaining optical fiber with a collimating head introduces a beam of linearly polarized light into the miniaturized three-axis SERF atomic magnetometer probe by connecting the coupling head in the laser; the light beam is split into two beams of equal light intensity orthogonal along the y-axis and the z-axis by the half-wave plate and the beam splitter; the two beams of light deflect 90° in their propagation direction after passing through the right-angle reflector, that is, the light beam propagating along the y-axis passes through the air chamber along the z-axis after passing through the right-angle reflector, and the light beam propagating along the z-axis passes through the air chamber along the y-axis after passing through the right-angle reflector; then the two beams of light are converted into circularly polarized light after passing through the quarter-wave plate, and pass vertically through the alkali metal air chamber. The circularly polarized light passing through the gas chamber passes through the flat beam splitter, and half of the light is reflected in situ and passes through the alkali metal gas chamber for the second time, thereby enhancing the uniformity of spin polarization and spin polarization rate and improving the response signal intensity of the magnetometer. The other half of the light is detected by the photodetector. According to the response of the spin polarization of the atoms to the external magnetic field, 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. The combination of the response of the Y-axis light and the Z-axis light to the three-axis magnetic field can realize the synchronous measurement of the three-axis magnetic field with high sensitivity.

[0039] When the circularly polarized light propagates in the alkali metal gas chamber, it will be continuously absorbed by the alkali metal atoms until saturation due to the need to pump the alkali metal atoms. This process will cause a spin polarization gradient to be generated in the alkali metal gas chamber, and the spin polarization distribution is uneven. The attenuation equation corresponding to the circularly polarized light propagating in the alkali metal gas chamber can be described as:

[0040]

[0041] The solution to the differential equation is:

[0042]

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

[0044] The electronic component assembly includes a platinum resistor, a non-magnetic electric heating coil, a micro-three-axis magnetic coil, and a photodetector. The platinum resistor Pt1000 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 electric control system, so that the alkali metal gas chamber reaches the temperature required for realizing the SERF state of atomic spin; the micro-three-axis magnetic coil is driven by the electric control system, which is used to generate the DC magnetic field (compensation residual magnetic field) and AC magnetic field (modulation magnetic field and calibration magnetic field) required by the miniaturized three-axis SERF atomic magnetometer probe; the photodetector is used to detect the circularly polarized pump light passing through the gas chamber, and convert the optical signal into a photocurrent that can be processed by the electric control system.

[0045] The laser provides a light source for the probe, which 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 atoms.

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

[0047] The magnetic shielding barrel is composed of five layers of μ-metal cylinders and is used to shield the environmental magnetic field. The large three-axis magnetic coil is placed in the center of the magnetic shielding barrel and is used to calibrate the coil constant of the micro three-axis magnetic coil in the miniaturized three-axis SERF atomic magnetometer. The miniaturized three-axis SERF atomic magnetometer is placed in the center of the large three-axis magnetic coil.

[0048] Embodiment 1

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

[0050] The alkali metal gas chamber 10 is a sensitive unit of the probe, refer to Figure 2 , including an air chamber body 102 and an air handle 101, wherein the air chamber body 102 is a cube, wherein four faces are light-transmitting faces, and is made of borosilicate glass material. Figure 1 The alkali metal gas chamber 10 is filled with one of the three alkali metals potassium, rubidium, and cesium, and is also filled with a buffer gas helium and a quenching gas nitrogen. The buffer gas is used to increase the distance between the polarized atoms and the inner wall of the alkali metal gas chamber, and the quenching gas is used to absorb the photons of excited state atoms decaying to the ground state radiation. These processes can suppress the depolarization of atomic spins. The oven 9 is made of a high thermal conductivity boron nitride material, and is used to heat the alkali metal gas chamber 10 and maintain a uniform temperature in the alkali metal gas chamber 10. The mechanical structural parts 21 are all made of non-magnetic polyetheretherketone polymer material, and are used to fix the alkali metal gas chamber 10, the oven 9, the optical components and the electronic components. Another important function is to make the two beams of circularly polarized pump light present a spatially separated distribution in the alkali metal gas chamber 10 through mechanical structure design (reference Figure 2 The Z-axis circularly polarized light 24 and the Y-axis circularly polarized light 23) are used to reduce the intersection area where the two circularly polarized pump lights act on the same atom, thereby suppressing the mutual coupling of the three-axis magnetic field.

[0051] refer to Figure 1 The optical device includes a polarization-maintaining fiber 2 with a collimating head 3, a half-wave plate 4, a polarization beam splitter prism 5, right-angle reflectors 6 and 18, quarter-wave plates 7 and 17, and flat beam splitters 11 and 14. The laser 1 provides a light source for the miniaturized three-axis SERF atomic magnetometer 26; then the polarization-maintaining fiber 2 with a collimating head 3 guides a linearly polarized light beam into the miniaturized three-axis SERF atomic magnetometer probe 26 by connecting to a coupling head in the laser 1 (refer to Figure 3 ); the light beam is divided into two light beams with equal light intensity along the y-axis and the z-axis orthogonal to each other by the half-wave plate 4 and the beam splitter prism 5; the two light beams deflect the propagation direction of the light by 90° after passing through the right-angle reflectors 6 and 18, that is, the light beam propagating along the y-axis passes through the right-angle reflector 18 and then passes through the alkali metal gas chamber 10 along the z-axis, and the light beam propagating along the z-axis passes through the right-angle reflector 6 and then passes through the alkali metal gas chamber 10 along the y-axis; then the two light beams pass through the quarter-wave plates 7 and 17 and are converted into Z-axis circularly polarized light 24 and Y-axis circularly polarized light 23 respectively (reference Figure 2), and vertically passes through the alkali metal gas chamber 10. The Z-axis circularly polarized light 24 and the Y-axis circularly polarized light 23 that pass through the alkali metal gas chamber 10 pass through the flat beam splitters 11 and 14, so that half of the light is reflected in situ and passes through the gas chamber for the second time, thereby enhancing the uniformity of spin polarization and spin polarization rate and improving the response signal strength of the magnetometer, and the other half of the light is detected by the photodetectors 12 and 15 for realizing simultaneous measurement of the three-axis magnetic field.

[0052] When the Z-axis circularly polarized light 24 and the Y-axis circularly polarized light 23 propagate in the alkali metal gas chamber 10, they will be continuously absorbed by the alkali metal atoms until saturation due to the need to pump the alkali metal atoms. This process will lead to uneven distribution of atomic spin polarization in the alkali metal gas chamber 10. The attenuation equation corresponding to the Z-axis circularly polarized light 24 and the Y-axis circularly polarized light 23 propagating in the alkali metal gas chamber 10 can be described as:

[0053]

[0054] The solution to the differential equation is:

[0055]

[0056] Where R op is the optical pumping 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 is the relaxation rate other than the optical pumping rate; the w function is the real part of the Lambert w function; R op (0) is the initial pump rate. Atomic polarizability = optical pump rate / (optical pump rate + relaxation rate other than optical pump rate). By passing the pump light through the alkali metal gas chamber 10 twice, the uniformity of the optical pump rate in the alkali metal gas chamber 10 can be improved, thereby enhancing the atomic spin polarization and the uniformity of the atomic spin polarization rate, and improving the response signal strength and sensitivity of the magnetometer.

[0057] The electronic components include a platinum resistor 16, a non-magnetic electric heating coil 8, a miniature three-axis magnetic coil 13, and photodetectors 12 and 15. The platinum resistor 16 attached to the surface of the alkali metal gas chamber 10 is used to monitor the temperature of the gas chamber in real time, and the PI closed-loop control system of the Labview program is used to keep the gas chamber temperature stable at the set temperature ±0.03°C (PI, proportional integral control) in real time; the non-magnetic electric heating coil 8 attached to the surface of the oven 9 is driven by the electric control system 22, so that the alkali metal gas chamber 10 reaches the temperature required by the atomic magnetometer to realize the SERF state of atomic spin; the miniature three-axis magnetic coil 13 is driven by the electric control system 22, and is used to generate the DC magnetic field (compensation residual magnetic field) and AC magnetic field (modulation magnetic field and calibration magnetic field) required by the miniaturized three-axis SERF atomic magnetometer probe 26; the photodetectors 12 and 15 are used to detect the Z-axis circularly polarized light 24 and the Y-axis circularly polarized light 23 passing through the alkali metal gas chamber, respectively, and convert the optical signal into a photocurrent that can be processed by the electric control system 22.

[0058] Embodiment 2

[0059] Figure 2 The spatial distribution structure of two circularly polarized pump lights in the alkali metal chamber of the dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device is shown. Through mechanical structure design, the Z-axis circularly polarized light 24 and the Y-axis circularly polarized light 23 are spatially separated in the alkali metal chamber 10, reducing the cross-region where the Z-axis circularly polarized light 24 and the Y-axis circularly polarized light 23 act on the same atom, and suppressing the three-axis magnetic field measurement coupling caused by crosstalk of adjacent channels. The spatial separation distance of the Z-axis circularly polarized light 24 and the Y-axis circularly polarized light 23 in the alkali metal chamber can be designed by the diffusion distance of atoms in 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 pumping rate R op Add the relaxation rate R in addition to the optical pumping rate rel .

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

[0063]

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

[0065] Embodiment 3

[0066] Figure 3 The structure of the dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device is shown. The laser 1 provides a light source for the miniaturized three-axis SERF atomic magnetometer probe 26, which 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 is composed of five layers of μ-metal cylinders and is used to shield the environmental magnetic field. The large three-axis magnetic coil 27 is placed in the center of the magnetic shielding barrel 28 and is used to calibrate the coil constant of the micro three-axis magnetic coil 13 in the miniaturized three-axis SERF atomic magnetometer probe 26. The miniaturized three-axis SERF atomic magnetometer probe 26 is placed in the center of the large three-axis magnetic coil 27.

[0068] The electric control system 22 includes a heating film drive signal circuit, a miniaturized three-axis magnetic coil drive signal circuit, a platinum resistance acquisition signal circuit, a transimpedance amplifier circuit and a phase-locked amplifier circuit. After the transimpedance amplifier is connected to the photodetectors 12 and 15, the photocurrent is converted into a voltage signal, and the voltage signal is demodulated by the phase-locked amplifier to obtain a response signal corresponding to the three-axis magnetic field to be measured. Specifically, according to the response of the atomic spin polarization to the 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 response combination of the Y-axis circularly polarized pump light 23 and the Z-axis circularly polarized pump light 24 to the three-axis magnetic field realizes the synchronous measurement of the three-axis magnetic field with high sensitivity. When the pumping 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 as follows:

[0069]

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

[0071] When a high-frequency modulated magnetic field is applied simultaneously on the x-axis, y-axis, and z-axis, that is, B is the modulated magnetic field, B i0 is the initial magnetic field, i is the intermediate quantity, is the magnetic field amplitude, ω i is the magnetic field frequency, t is the time, 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 24 direction can be expressed as:

[0073]

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

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

[0076]

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

[0078] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. It is pointed out here that the above description helps those skilled in the art to understand the invention, but does not limit the protection scope of the invention. Any equivalent replacement, modification and / or simplification of the above description without departing from the essence of the invention falls within the protection scope of the invention.

Claims

1. A dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device, characterized in that: The invention comprises a Y-axis circularly polarized pump light passing through the alkali metal gas chamber along the y-axis direction, and a Z-axis circularly polarized pump light passing through the alkali metal gas chamber along the z-axis direction, wherein the Z-axis circularly polarized pump light and the Y-axis circularly polarized pump light are spatially separated in the alkali metal gas chamber, a second flat plate beam splitter is arranged on the Y-axis circularly polarized pump light exiting side of the alkali metal gas chamber, the second flat plate beam splitter is a semi-transparent and semi-reflective flat plate beam splitter, the second flat plate beam splitter transmits its Y-axis transmitted light to a second photodetector, the second flat plate beam splitter reflects its Y-axis reflected light in situ for a second time to enter the alkali metal gas chamber, a first flat plate beam splitter is arranged on the Z-axis circularly polarized pump light exiting side of the alkali metal gas chamber, the first flat plate beam splitter is a semi-transparent and semi-reflective flat plate beam splitter, the first flat plate beam splitter transmits its Z-axis transmitted light to a first photodetector, the first flat plate beam splitter reflects its Z-axis reflected light in situ for a second time to enter the alkali metal gas chamber, and the Z-axis circularly polarized pump light and the Y-axis circularly polarized pump light both come from a single light source.

2. The dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device according to claim 1, characterized in that: The first photodetector and the second photodetector are respectively connected to the connecting plate through their own connecting wires, a platinum resistor is arranged on the surface of the alkali metal gas chamber, the alkali metal gas chamber 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, the micro-three-axis magnetic coil, the non-magnetic electric heating coil and the platinum resistor are respectively connected to the connecting plate through their own connecting wires, and the connecting plate is connected to an electronic control system.

3. The dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device according to claim 1, characterized in that: The miniature three-axis magnetic coil is located inside the large three-axis magnetic coil, the large three-axis magnetic coil is located inside the 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-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device according to claim 1, characterized in that: The Y-axis circularly polarized pump light incident side of the alkali metal gas cell is connected to the transmission side of the polarization beam splitter prism through the first quarter wave plate and the first right-angle reflection prism in sequence, the Z-axis circularly polarized pump light incident side of the alkali metal gas cell is connected to the reflection side of the polarization beam splitter prism through the second quarter wave plate and the second right-angle reflection prism in sequence, and the input side of the polarization beam splitter prism is connected to the laser through the half wave plate, the collimator and the polarization-maintaining optical fiber in sequence.

5. The dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device according to claim 3, characterized in that: The magnetic shielding barrel is composed of five layers of μ-metal cylinders and is used for shielding the environmental magnetic field.

6. The dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device according to claim 4, characterized in that: The laser is a DBR laser or a DFB laser, and the wavelength of the light source generated by the laser is set to be the D1 line of the alkali metal atoms in the alkali metal gas cell.

7. The dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device according to claim 1, characterized in that: The alkali metal gas 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.

8. The dual-pump light semi-transmissive and semi-reflective miniaturized three-axis SERF atomic magnetometer device according to claim 1, characterized in that: According to the response of the atomic spin polarization to the external magnetic field, the Y-axis transmitted light is used to measure the x-axis and z-axis magnetic fields, and the Z-axis transmitted light is used to measure the x-axis and y-axis magnetic fields, thereby realizing the synchronous measurement of the three-axis magnetic field by combining the responses of the three-axis magnetic field.

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

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