Single-beam zero-field biaxial vector magnetometer and its use and applications

Abstract

This invention relates to the field of ultrasensitive magnetic measurement technology based on quantum sensing, and in particular to a single-beam zero-magnetic-field dual-axis vector magnetometer and its usage and applications. This invention employs a single probe laser beam to simultaneously perform pumping and detection functions, and innovatively combines the tensor-vector polar moment conversion (AOC) effect, magnetic field modulation, and large-amplitude modulation of the optical frequency. This significantly reduces the resonant linewidth of the magnetometer while suppressing photon shot noise and detector electronic noise, and achieves dual-axis magnetic field measurement in a zero-magnetic environment. In laboratory desktop experiments, a sensitivity of level 10 can be achieved.

Description

Technical Field

[0001] This invention relates to the field of ultrasensitive magnetic measurement technology based on quantum sensing, and in particular to a single-beam zero-magnetic-field dual-axis vector magnetometer and its usage and application. Background Technology

[0002] Zero-field vector magnetometers have significant applications in magnetoencephalography (MEG), magnetocardiography (MEG), biomagnetic fields, and extremely low-field nuclear magnetic resonance (NMR). Superconducting quantum interference devices (SQUIDs), as superconducting instruments, rely on a massive liquid helium cooling system, resulting in enormous size and extremely high operating costs; however, it was once the only option for achieving femtosecond-level ultra-high sensitivity. The new generation of atomic magnetometers, however, operates at room temperature using optical methods, are as small as chips, require no cooling, and significantly reduce costs. Their sensitivity is comparable to, or even surpasses, that of SQUIDs, representing the miniaturization and cost reduction direction of magnetic field measurement technology. Currently, the most sensitive zero-field vector atomic magnetometers all employ a spin-exchange relaxation-free (SERF) configuration with a high-temperature, high-atomic-density gas cell. In a SERF magnetometer, lasers polarize the atoms in the alkali metal atom gas cell, making their spin directions highly consistent. Under near-zero magnetic field conditions, spin exchange relaxation caused by interatomic collisions is suppressed, and the spin coherence time is greatly extended. Extremely weak external magnetic fields can cause atomic spin to deflect. By detecting changes in laser polarization or light power, magnetic fields can be measured with high sensitivity.Although this scheme can achieve vector measurement sensitivity at the femtometer level (SHAH V, DOYLE C, OSBORNE J. Zero field parametric resonance magnetometer with triaxial sensitivity: 10775450[P]. 2020; ALLRED JC, LYMAN RN, KORNACK TW, et al. High-Sensitivity Atomic Magnetometer Unaffected by Spin-Exchange Relaxation[J / OL]. Physical Review Letters, 2002, 89(13): 130801. DOI:10.1103 / PhysRevLett.89.130801; ZHANG J, CHEN T, WEI C, et al. Single-beam three-axis SERFatomic magnetometer based on coordinate system rotation[J / OL]. OpticsExpress, 2024, 32(10): 17165-17172. DOI:10.1364 / OE.524308;SELTZER SJ,ROMALIS M V. Unshielded three-axis vector operation of a spinexchange-relaxation-free atomic magnetometer[J / OL]. Applied Physics Letters, 2004, 85(20): 4804-4806. DOI:10.1063 / 1.1814434), but the following problems exist: at high temperatures above 100 ℃, the atomic gas cell cannot get very close to the analyte that is sensitive to high temperature, and the heating system consumes a lot of power, as does the probe pump light.

[0003] Atomic magnetometer systems that operate at room temperature have low power consumption and are suitable for close-range detection of temperature-sensitive objects. In the atomic gas cell, wall relaxation caused by collisions between alkali metal atoms and the inner wall is a major factor disrupting atomic spin coherence. There are two methods to reduce wall relaxation: one is to inject a high-pressure inert buffer gas into the cell to slow the diffusion of alkali metal atoms to the inner wall; the other is to coat the inner wall with a paraffin or silane-based anti-relaxation coating to directly reduce wall relaxation. Collisions between the buffer gas and alkali metal atoms reduce the intensity of the interaction between light and atoms, weakening the signal. Therefore, atomic gas cells using buffer gases need to operate at higher temperatures to obtain a higher atomic number density to enhance the signal. However, the atomic number density is low at room temperature, making it unsuitable to reduce wall relaxation using inert buffer gases. Therefore, atomic magnetometers operating at room temperature generally employ anti-relaxation coated gas cells. Existing single-beam magnetometers are divided into Mx magnetometers based on the orientation magnetic resonance effect and non-linear magneto-optical rotation (NMOR) magnetometers based on the tensor polarity (BUDKER D, GAWLIK W, KIMBALL DF, et al. Resonant nonlinear magneto-optical effects in atoms[J / OL]. Reviews of Modern Physics, 2002, 74(4): 1153-1201. DOI:10.1103 / RevModPhys.74.1153.). Among them, the Mx magnetometer measures the magnetic field by resonating the oscillation frequency of the applied radio frequency field with the Larmor frequency of the static magnetic field to be measured. It is suitable for scalar magnetic field measurement but not suitable for measuring vector magnetic fields in zero magnetic environment. Therefore, room-temperature magnetometers in zero-magnetic environments generally rely on the NMOR effect. The principle of this method is as follows: When a beam of near-resonant linearly polarized light passes through an alkali metal atom gas cell, the atoms are optically pumped and form a spin tensor alignment along the direction of light polarization. Under the influence of an external magnetic field along the direction of light propagation, this tensor alignment deflects. This deflection causes the two polarization components of the same beam, parallel and perpendicular to the tensor alignment, to be absorbed to different degrees, resulting in a deflection of the polarization plane by an angle (i.e., the "optical rotation angle"). By measuring this optical rotation angle using well-known methods, the magnetic field strength can be deduced.

[0004] Currently, there are NMOR magnetometers that perform uniaxial vector measurements by modulating light frequency (BUDKER D, KIMBALL DF, YASHCHUK VV, et al. Nonlinear magneto-optical rotation with frequency-modulated light[J / OL]. Physical Review A, 2002, 65(5): 055403. DOI:10.1103 / PhysRevA.65.055403). However, NMOR magnetometers still have the following problems: (1) The atomic number density is low and the signal is small at room temperature, so a large atomic gas cell is needed to increase the optical path and amplify the signal (BUDKER D, YASHCHUK V, ZOLOTOREV M. Nonlinear Magneto-optic Effects with Ultranarrow Widths[J / OL].Physical Review Letters, 1998, 81(26): 5788-5791. DOI:10.1103 / PhysRevLett.81.5788; ZIGDON T, WILSON-GORDON AD, GUTTIKONDA S, et al. Nonlinear magneto-optical rotation in the presence of radio-frequency field[J / OL].Optics Express, 2010, 18(25): 25494. (DOI:10.1364 / OE.18.025494), which is extremely detrimental to probe miniaturization and also increases the equivalent distance between the probe and the object being measured. (2) Since this system relies on the absorption of light by atoms to polarize atoms and generate optical rotation under a magnetic field, the absorption of light will cause relaxation of atomic polarization, resulting in spectral broadening and limiting the sensitivity of magnetic measurement. In order to reduce light absorption relaxation, the detection light power often needs to be reduced to a level that makes the absorption relaxation and wall relaxation comparable, usually at the microwatt level.This increases the magnetic noise caused by photon shot noise, limiting the fundamental sensitivity of this type of magnetometer, and also increases the electronic noise of the photodetector (LEDBETTER MP, ACOSTA VM, ROCHESTER SM, et al. Detection of radio-frequency magnetic fields using nonlinear magneto-optical rotation[J / OL]. Physical Review A, 2007, 75(2): 023405. DOI:10.1103 / PhysRevA.75.023405). (3) If a multi-path gas cell is used, the light will undergo multiple reflections within the gas cell to increase the intensity of the interaction between the light and atoms, thereby increasing the signal and solving the above problem (1), but it will make problem (2) more prominent. There are currently no cases of using a multi-reflection anti-relaxation coated gas cell to make a zero-magnetic-field magnetometer.

[0005] In addition, performing multi-axis vector measurements in a zero-magnetic environment using the NMOR effect is also a challenge. Patent CN118033499A discloses a method for measuring the three-axis vector magnetic field of a single-beam NMOR atomic magnetometer. NMOR vector magnetometers often require a large external magnetic field. Although they can achieve some vector magnetic measurement functions, this method is not sensitive to small magnetic fields perpendicular to the direction of the external magnetic field.

[0006] Therefore, it is crucial to provide a zero-magnetic-atom magnetometer solution that can operate at or near room temperature while combining the simplicity, low power consumption, and high-performance vector measurement capabilities of a single-beam system. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide a single-beam zero-magnetic-field dual-axis vector magnetometer and its usage and application.

[0008] The objective of this invention can be achieved through the following technical solutions: The first objective of this invention is to provide a single-beam, zero-magnetic-field, dual-axis vector magnetometer that allows for the simultaneous measurement of the X-axis and Z-axis components of the magnetic field to be measured by a linearly polarized probe laser polarized along the Y-axis through the tensor-vector polar moment conversion effect on alkali metal atoms. The magnetometer comprises: Magnetic shielding components used to counteract external magnetic fields and provide a zero-magnetic environment; An atomic gas chamber filled with alkali metal atoms is set inside the magnetic shielding assembly. A probe laser configured to interact with alkali metal atoms in the atomic gas chamber to simultaneously serve as a pump and a probe. A laser incident component disposed on the inlet side of the atomic gas chamber, used to adjust the power of the probe laser and prepare its polarization state as linearly polarized along the Y-axis, allowing the probe laser to propagate through the atomic gas chamber along the Z-axis direction; A Y-axis symmetric tensor moment was established on the hyperfine energy level of the ground state of the alkali metal atom using a probe laser polarized along the Y-axis and propagating along the Z direction. The magnetic field to be measured generates a vector polar moment parallel to the component of the magnetic field to be measured in the XZ plane through the tensor-vector conversion effect of the probe laser on alkali metal atoms; An optical rotation measurement component is installed on the outlet side of the atomic gas cell to receive the probe laser emitted from the atomic gas cell and measure the Faraday rotation angle generated by the vector polar moment; A lock-in amplifier for receiving and demodulating the output signal of the optical rotation measurement component; A data acquisition and processing system for receiving and recording the demodulated data from the lock-in amplifier to read biaxial magnetic field information; The X-axis, Y-axis, and Z-axis are orthogonal to each other.

[0009] In one embodiment of the present invention, the inner wall of the atomic gas chamber is provided with an anti-relaxation coating; In one embodiment of the invention, the magnetometer includes features for generating a frequency along the Y-axis. The first coil of the modulated magnetic field.

[0010] The first coil is a set of Helmholtz coils; the first coil allows the generation of a modulated magnetic field using a first signal generator or a lock-in amplifier, and allows the delivery of a reference frequency to the lock-in amplifier.

[0011] In one embodiment of the invention, the magnetometer includes a second signal generator for transmitting signals at a frequency... The frequency of the probe laser is significantly modulated, and this frequency is allowed to... The frequency is delivered to the lock-in amplifier as a reference frequency; The second signal generator is configured to modulate the frequency of the probe laser within the range where the lower frequency limit is located at the D1 line of the alkali metal atom. The blue detuned side of the transition resonance center, in order to Tensor polar moments are generated at energy levels; their upper frequency limit lies at the D1 line of alkali metal atoms. Within a range of 3 linewidths from the center of the transition resonance, in order to All atoms in the energy level are pumped to Energy level, and in Tensor polar moments are generated at energy levels; where the lower frequency limit is at The magnitude and rate at which the tensor polar moments of the energy levels are generated are much greater than the upper frequency limit; Under the aforementioned frequency modulation, the probe laser simultaneously performs both pumping and detection functions, eliminating the need for an additional independent probe beam. The lock-in amplifier is also configured to operate at a frequency The Z component of the magnetic field to be measured is obtained by demodulation.

[0012] In one embodiment of the present invention, frequency Much greater than the atomic polar moment relaxation rate The established vector polar moment is not based on Oscillation, while the Faraday rotation angle of the probe light is modulated by frequency. oscillation.

[0013] In one embodiment of the present invention, the magnetic shielding component is a magnetic shielding cover.

[0014] In one embodiment of the present invention, the laser incident assembly includes a first optical power changing device and a first polarizing device arranged sequentially along the laser incident direction. The first optical power changing device is used to adjust the beam power and is selected from one of the following: polarization device (including but not limited to polarizing device, wave plate or Fresnel rhombus prism), Faraday rotator, optical attenuator, optical modulator (including but not limited to acousto-optic modulator, electro-optic modulator, photoelastic modulator or liquid crystal modulator); The first polarizing device is selected from one of the following linear polarizing polarizers: a wire grid polarizer, a thin film polarizer, a birefringent crystal, or a polarizing beam splitter. The birefringent crystal includes, but is not limited to, Glan laser polarizers, Glan-Taylor polarizers, Glan-Thompson polarizers, Wollaston polarizers, or Loch Hung prisms. The polarization beam splitter includes, but is not limited to, a polarization beam splitter cube, a polarization flat beam splitter, a Wollaston polarizing mirror, a Lochte prism, or a polarization beam deflector.

[0015] In one embodiment of the present invention, the optical rotation measurement component includes an optical rotation device, a polarization beam splitter, and a balance detector arranged sequentially along the laser emission direction; The optical rotator is selected from one of the following: a half-wave plate, a Faraday rotator, and a Fresnel rhombus prism. The polarization beam splitter is selected from one of the following: polarization beam splitting cube, polarization flat beam splitter, Wollaston polarizing mirror, Lochte prism, or polarization beam deflector.

[0016] In one embodiment of the invention, the magnetometer allows a uniform static magnetic field to be generated at the location of the atomic gas cell via a second coil, or as a calibration field for calibrating the sensitivity baseline of the magnetometer; the second coil generates the uniform static magnetic field via a current source.

[0017] In one embodiment of the present invention, the alkali metal atoms are selected from... 87 Rb atoms, 85 Rb atoms or 133 One of the Cs atoms.

[0018] In one embodiment of the present invention, the magnetometer further includes an auxiliary light and an auxiliary light incident component, wherein the auxiliary light is configured as a linearly polarized light beam with the same polarization direction as the probe laser and orthogonal to the propagation direction, for enhancing atomic polarization; The auxiliary light incident component includes a second optical power changing device and a second polarizing device arranged sequentially along the auxiliary light incident direction.

[0019] In one embodiment of the invention, the frequency of the auxiliary light is related to the D1 or D2 lines of alkali metal atoms. Transition resonance, in which I It is the spin quantum number of the alkali metal atom nucleus.

[0020] A second objective of this invention is to provide a method for using the aforementioned single-beam zero-magnetic-field dual-axis vector magnetometer, which is based on the tensor-vector conversion effect and includes the following steps: The frequency applied along the Y-axis is The modulated magnetic field; Measuring the Faraday rotation angle of the probe laser at a frequency The X component of the magnetic field to be measured is obtained by demodulation at a frequency of 2. The Z component of the magnetic field to be measured is obtained by demodulation.

[0021] A third objective of this invention is to provide a method for using the aforementioned single-beam zero-magnetic-field dual-axis vector magnetometer, which is based on the tensor-vector conversion effect and includes the following steps: The frequency applied along the Y-axis is The modulated magnetic field; simultaneously with frequency The frequency of the probe laser is modulated, and the modulation range of the probe laser frequency is configured such that the lower frequency limit is located at the D1 line of the alkali metal atom. The blue detuned side of the transition resonance center, in order to Tensor polar moments are generated at energy levels; their upper frequency limit lies at the D1 line of alkali metal atoms. Within three linewidths of the transition resonance center, to... All atoms in the energy level are pumped to Energy level, and in Tensor polar moments are generated at energy levels; Measuring the Faraday rotation angle of the probe laser at a frequency The X component of the magnetic field to be measured is obtained by demodulation at a frequency of [frequency value missing]. The Z component of the magnetic field to be measured is obtained by demodulation.

[0022] The fourth objective of this invention is to provide an application of the above-mentioned single-beam zero-magnetic-field biaxial vector magnetometer in the synchronous measurement of biaxial or single-axis magnetic fields in a zero-magnetic environment.

[0023] This invention employs a single probe laser beam to simultaneously perform pumping and detection functions. It innovatively combines the tensor-vector polar moment conversion (AOC) effect with magnetic field modulation techniques. This reduces system relaxation, narrows the magnetometer's resonant linewidth, significantly suppresses photon shot noise and detector electronic noise, and achieves simultaneous dual-axis magnetic field measurement in a zero-magnetic environment. In laboratory desktop experiments, a value of 10 can be achieved. Level sensitivity.

[0024] An angular momentum quantum number is The spin polarization states of a spin system can be decomposed into states from 0 to 1. Most A linear superposition of polar moments. The first-order polar moment, commonly known as the "vector polar moment" (orientation), is a directional vector, denoted as . The second-order polar moment, commonly known as the "tensor alignment," is a tensor with no directionality but an axis of symmetry, denoted as . .

[0025] The basic principle of using AOC to measure magnetic fields is as follows: Linearly polarized light can produce light along the polarization axis within atoms. 2) An external magnetic field causes atoms to... The axis of symmetry deflects around the direction of the magnetic field by an angle proportional to the magnitude of the magnetic field. θ When the polarization axis of linearly polarized light and the atom When the axes are neither parallel nor perpendicular, the tensor shift effect of light on atoms can cause the atoms to... Convert to simultaneously perpendicular to and the linear polarization axis Its conversion rate is proportional to Therefore, the resulting 3) The projection along the direction of light propagation causes the polarization plane of linearly polarized light to rotate (Faraday rotation effect), with the rotation angle being... Proportional to ; through measurement 4) By applying a modulated magnetic field in the linear polarization direction, the optical rotation angle signal can be modulated to a high-frequency region with less environmental noise, and magnetic field information on two orthogonal axes perpendicular to the linear polarization direction can be obtained simultaneously.

[0026] Furthermore, the AOC effect can cause an oscillatory transition between tensor polar moments and vector polar moments, the frequency of which is denoted as . When the system relaxation rate Γ is less than At this time, the tensor polar moment and the vector polar moment will oscillate under the AOC effect. If the frequency of the magnetic field to be measured is equal to or an odd multiple of the AOC conversion frequency (2... m -1) (in m =1,2,..., F , F If the spin quantum number of the hyperfine level satisfies the near-resonance condition, the amplitude of the vector polar moment will be significantly enhanced compared to when it is far from the resonance condition, thereby greatly improving the measurement sensitivity of the magnetometer. This is the AOC resonance effect.

[0027] This invention utilizes the AOC effect, using a beam of light with D1 lines of alkali metal atoms. or The near-resonance linearly polarized light transition achieves three goals at once: realizing the atomic ground state. or The method utilizes indirect pumping of the tensor polarity at the energy level, AOC driving, and vector polarity detection. Furthermore, it avoids relaxation caused by light absorption and suppresses electronic noise and photon shot noise caused by insufficient light power in traditional NMOR magnetometers, thereby improving the signal-to-noise ratio.

[0028] This invention modulates the magnetic field along the polarization direction of the probe laser, enabling efficient and non-destructive modulation of a DC signal to a high frequency, while simultaneously and independently acquiring the magnitudes of the magnetic fields in two orthogonal directions perpendicular to the polarization direction.

[0029] In addition, the present invention also allows for frequency The probe laser frequency is subjected to large-amplitude frequency modulation, and the magnetic field along the probe laser propagation direction is obtained by demodulating the probe laser frequency independently. The modulation range of the probe laser frequency is configured such that its lower frequency limit lies at the D1 line of alkali metal atoms. The blue detuned side of the transition resonance center, in order to Tensor polar moments are generated at energy levels; their upper frequency limit lies at the D1 line of alkali metal atoms. Within three linewidths of the transition resonance center, to... All atoms in the energy level are pumped to Energy level, and in Tensor polar moments are generated at the energy level.

[0030] Because the lower limit of the modulation frequency is close to the D1 line of alkali metal atoms The transition resonance center, with its appropriately introduced relaxation, increases the system bandwidth. Furthermore, the AOC effect remains effective throughout the entire frequency modulation range, and this is further enhanced by the closer proximity of the probe laser's average frequency. The transition significantly reduces the optical power required to reach the same AOC resonant frequency. Because of this frequency... Much greater than the relaxation rate Γ of the atomic polar moment, the atomic polar moment itself cannot keep up with the rapid changes in light frequency, and therefore the established vector polar moment does not follow the rapid changes in light frequency. Oscillation. For In terms of measurement, the intensity of the light-atomic interaction varies periodically with frequency modulation, causing the Faraday rotation angle of the probe laser after passing through the atomic gas cell to change with frequency. Oscillation, thus through frequency The magnetic field information to be measured is obtained through demodulation. For In terms of measurement, the detuning experienced by the atom in this process is an average detuning, which is about half the value of the hyperfine level splitting of the ground state of the alkali metal atom. This results in a larger Faraday rotation angle compared to not modulating the light.

[0031] Compared with the prior art, the present invention has the following beneficial effects: (1) Simplified system structure: The present invention uses a single light source and a single beam to simultaneously complete the pumping of the tensor polar moment maximization, the conversion of tensor to vector polar moment, the detection of vector polar moment, and the high-frequency modulation of the optical rotation angle signal, which significantly reduces the system's size, cost, assembly and adjustment difficulty and long-term maintenance requirements.

[0032] (2) Narrowing inherent linewidth and improving signal-to-noise ratio: This invention utilizes the AOC effect of detuned linearly polarized light on atoms to convert the atomic tensor polar moment into a vector polar moment, and uses the Faraday rotation effect of the atomic vector polar moment on detuned linearly polarized light to detect the change of the magnetic field on the vector polar moment; moreover, the absorption of far-detuned detection laser by atoms is extremely low, thereby avoiding the broadening of the magnetic field response curve caused by light absorption relaxation, so that a larger detection laser power can be used to suppress photon shot noise and detector electronic noise, laying a physical basis for achieving higher measurement sensitivity at room temperature.

[0033] (3) Dual-axis vector measurement: This invention achieves simultaneous measurement of magnetic field components in two orthogonal directions by modulating the magnetic field along the polarization axis of linearly polarized light. Since the modulated magnetic field and the electric vector of light are coaxial, the angle between the axis of symmetry and the electric vector remains unchanged when the tensor moment swings around the modulated magnetic field. Based on the principle of AOC effect, the magnitude of the vector moment to be measured will not be changed.

[0034] (4) Optimization of power consumption and applicability: By adopting an anti-relaxation coated gas chamber, this invention can achieve ultra-high sensitivity magnetic field measurement at room temperature or near room temperature. This not only significantly reduces the power consumption of the probe, but also makes the probe suitable for close-range measurement of temperature-sensitive objects, such as organisms and chemical substances. Attached Figure Description

[0035] Figure 1 The experimental principle diagram of the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 1 is shown (the three-axis static magnetocoupler is not shown due to space limitations).

[0036] Figure 2 This is a schematic diagram of the measurement principle of the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 2; where, a: the left side is... 87 Rb atom D1 line energy level diagram; where arrows represent light frequencies and solid lines represent light pairs. The pumping effect of the upper atoms, the dashed line represents the light pair AOC interaction of upper atoms and Faraday optical rotation detection; the right side shows the effect after pumping. The atomic population distribution formed on the surface contains tensor polar moments. b: The components; a: the light pumped by the light polarized along the Y-axis Schematic diagram (assuming the external magnetic field is zero); c: Modulating the magnetic field when there is no magnetic field in the XZ plane. Unable to cause With the axis changed, the polarization direction of light remains parallel to the axis. A schematic diagram of the axis without the AOC effect.

[0037] Figure 3 In the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 2 B x Generate vector polar moments And detect its projection along the Z-axis Schematic diagram; where a: has a static magnetic field. B x hour, Deflection occurs in the YZ plane right The AOC effect produces along the X direction. b: for modulating the magnetic field Under the influence of, , Simultaneously, it oscillates around the Y-axis, generating oscillations. And this leads to the detection of the laser electric vector The same frequency oscillation of the optical rotation angle after passing through the atom.

[0038] Figure 4 In the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 2 B z Generate vector polar moments And detect its projection along the Z-axis Schematic diagram; where a: has a static magnetic field. hour, A deflection occurs in the XY plane, and AOC is generated along the Z direction. b: In the modulated magnetic field Under the influence of, , Simultaneously, it oscillates around the Y-axis, generating oscillations. This causes the probe laser rotation angle to oscillate.

[0039] Figure 5 In the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 2 and A schematic diagram showing the projected oscillation frequency generated along the Z-axis; where... for The swing angle under the action of the Y-axis modulated magnetic field The oscillation frequency is ,and The oscillation frequency is .

[0040] Figure 6 This is a diagram of Zeeman level splitting caused by tensor optical shift in a single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 2; wherein, for a quantum number of... F In this system, the AOC resonant frequency will be at 1, 3, 5, ..., 2. F - 1x It appears in the location.

[0041] Figure 7 The single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 2 was scanned respectively. B x (Above image) and B z (See the image below) Output diagram of the magnetometer.

[0042] Figure 8 This is a schematic diagram illustrating the response capabilities of the X and Z channels to magnetic fields of different frequencies in the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 2.

[0043] Figure 9 The diagram shows the sensitivity of the X and Z channels in the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 2. The solid line and dashed line represent the noise spectrum of the magnetometer when the external calibration field is applied. To avoid introducing additional noise from the calibration field, the sensitivity results after turning off the calibration field are shown as dotted lines and dashed lines.

[0044] Figure 10 The experimental principle diagram of the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 3 is shown (the three-axis static magnetocoupler is not shown due to space limitations).

[0045] Figure 11 The single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 4 was scanned respectively. B x (Above image) andB z (See the image below) Output diagram of the magnetometer.

[0046] Figure 12 This is a schematic diagram illustrating the response capabilities of the X and Z channels to magnetic fields of different frequencies in the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 4.

[0047] Figure 13 This is a schematic diagram of the X and Z channel sensitivity of the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 4; where the blue and green lines represent the noise spectrum of the magnetometer when the external calibration field is applied; to avoid the introduction of additional noise by the calibration field, the sensitivity results after the calibration field is turned off are shown by the black and red lines.

[0048] Figure 14 The experimental principle diagram of the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 5 is shown (the three-axis static magnetocoupler is not shown due to space limitations).

[0049] Figure 15 The single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 6 was scanned respectively. B x (Above image) and B z (See the image below) Output diagram of the magnetometer.

[0050] Figure 16 This is a schematic diagram illustrating the response capabilities of the X and Z channels of the magnetometer to magnetic fields of different frequencies in the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 6.

[0051] Figure 17 This is a schematic diagram of the X and Z channels sensitivity of the magnetometer in the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 6; where the blue and green lines represent the noise spectrum when the external calibration field is applied; to avoid introducing additional noise from the calibration field, the sensitivity results after turning off the calibration field are shown in black and red.

[0052] Figure 18 The experimental principle diagram of the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 7 is shown (the three-axis static magnetocoupler is not shown due to space limitations).

[0053] Figure 19 The single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 8 was scanned respectively. B x (Above image) and B z (See the image below) Output diagram of the magnetometer.

[0054] Figure 20 This is a schematic diagram illustrating the response capabilities of the X and Z channels to magnetic fields of different frequencies in the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 8.

[0055] Figure 21 This is a schematic diagram of the X and Z channel sensitivity of the single-beam zero-magnetic-field dual-axis vector magnetometer provided in Example 8; where the blue and green lines represent the noise spectrum of the magnetometer when an external calibration field is applied; to avoid introducing additional noise from the calibration field, the sensitivity results after turning off the calibration field are shown as the black and red lines.

[0056] The diagram is labeled as follows: 1. Detector laser; 2. First half-wave plate; 3. First Glan-Thompson prism; 4. Atomic gas cell; 5. First coil; 6. Magnetic shield; 7. Second half-wave plate; 8. Polarization beam splitter cube; 9. Balance detector; 10. Lock-in amplifier; 11. Data acquisition and processing system; 12. Current source; 13. Signal generator; 14. Auxiliary light; 15. Third half-wave plate; 16. Third Glan-Thompson prism. Detailed Implementation

[0057] An angular momentum quantum number is The spin polarization states of a spin system can be decomposed into states from 0 to 1. Most A linear superposition of polar moments. The first-order polar moment, commonly known as the "vector polar moment" (orientation), is a directional vector, denoted as . The second-order polar moment, commonly known as the "tensor alignment," is a tensor with no directionality but an axis of symmetry, denoted as . .

[0058] The basic principle of using AOC to measure magnetic fields is as follows: 1) Linearly polarized light can produce polarized light along the polarization axis within atoms. 2) An external magnetic field causes atoms to... The axis of symmetry deflects around the direction of the magnetic field by an angle proportional to the magnitude of the magnetic field. θ When the polarization axis of linearly polarized light and the atom When the axes are neither parallel nor perpendicular, the tensor shift effect of light on atoms can cause the atoms to... Convert to simultaneously perpendicular to and the linear polarization axis Its conversion rate is proportional to Therefore, the resulting 3) The projection along the direction of light propagation causes the polarization plane of linearly polarized light to rotate (Faraday rotation effect), with the rotation angle being... Proportional to ; through measurement 4) By applying a modulated magnetic field in the linear polarization direction, the optical rotation angle signal can be modulated to a high-frequency region with less environmental noise, and magnetic field information on two orthogonal axes perpendicular to the linear polarization direction can be obtained simultaneously.

[0059] Based on the above principles, this invention provides the following method for synchronous measurement of biaxial magnetic fields in a zero-magnetic environment: The first method utilizes a single-beam probe laser polarized along the Y-axis and propagating along the Z-direction to simultaneously perform pumping and probing functions, establishing a tensor polar moment in the atomic ground state. By applying a modulation magnetic field along the Y-axis, combined with the AOC effect, the projection of the vector polar moment in the Z-direction is generated... and 2 Oscillations with frequency characteristics, respectively at frequencies and 2 The Faraday rotation angle is demodulated to obtain the X and Z components of the magnetic field to be measured.

[0060] The second method involves simultaneously applying a Y-axis modulation magnetic field and significantly modulating the frequency of the probe laser; the optical frequency modulation frequency... Much greater than the Y-axis magnetic field modulation frequency ; through frequency The X component of the magnetic field to be measured is obtained by demodulation at a frequency of [frequency value missing]. The Z component of the magnetic field to be measured is obtained by demodulation, realizing dual-axis synchronous measurement.

[0061] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0062] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0063] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0064] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0065] In the following embodiments, unless otherwise specified, the structures or components used are conventional structures or components in the art, as long as they can achieve the corresponding functions.

[0066] Example 1 This embodiment provides a single-beam zero-magnetic-field dual-axis vector magnetometer, which allows the tensor-vector polar moment conversion effect of a linearly polarized probe laser 1 polarized along the Y-axis to measure the X-axis and Z-axis components of the magnetic field to be measured through the test of the tensor-vector polar moment conversion effect of alkali metal atoms. Figure 1 As shown, the magnetometer includes: A magnetic shielding component (magnetic shield 6 in this embodiment) is used to counteract external magnetic fields and provide a zero magnetic environment. An atomic gas chamber 4 filled with alkali metal atoms is set inside the magnetic shielding cover 6; The detection laser 1 is configured to interact with alkali metal atoms in the atomic gas chamber 4 to simultaneously serve as a pump and a detector. A laser incident component located at the inlet side of the atomic gas chamber 4, used to adjust the power of the probe laser 1 and prepare its polarization state as linearly polarized along the Y-axis, allowing the probe laser to propagate through the atomic gas chamber 4 along the Z-axis direction; A probe laser 1 polarized along the Y-axis and propagating along the Z-direction is used to establish a Y-axis symmetric tensor polar moment on the ground state hyperfine energy level of the alkali metal atom; The magnetic field to be measured generates a vector polar moment parallel to the magnetic field to be measured through the tensor-vector conversion effect of light on atoms; An optical rotation measurement component is installed on the outlet side of the atomic gas cell 4 to receive the probe laser 1 emitted from the atomic gas cell 4 and to measure the Faraday rotation angle generated by the vector polar moment. A lock-in amplifier 10 is used to receive and demodulate the output signal of the optical rotation measurement component; A data acquisition and processing system 11 is used to receive and record the demodulated data of the lock-in amplifier 10 to read the dual-axis magnetic field information; The X-axis, Y-axis, and Z-axis are orthogonal to each other.

[0067] In this embodiment, the magnetometer is also equipped with a modulated magnetic field for generating a Y-axis. The first coil 5 and the second coil used to generate a zero magnetic field environment at the position of the atomic gas chamber 4; The inner wall of the atomic gas chamber 4 is provided with an anti-relaxation coating; The first coil 5 is a set of Helmholtz coils; The second coil is a triaxial static magnetic coil (allowing the generation of a uniform static magnetic field through current source 12). The laser incident assembly includes a first half-wave plate 2 and a first Gran-Thompson prism 3 arranged sequentially along the laser incident direction; The optical rotation measurement component includes a second half-wave plate 7, a polarization beam splitter cube 8, and a balance detector 9 arranged sequentially along the laser emission direction. The first coil 5 allows the generation of a modulated magnetic field using the signal generator 13 and allows the delivery of a reference frequency to the lock-in amplifier 10.

[0068] Example 2 This embodiment provides an application of a single-beam zero-magnetic-field biaxial vector magnetometer (Example 1) in the synchronous measurement of biaxial magnetic fields in a zero-magnetic environment (single-beam single-optical-path). During use, the temperature of the atomic gas cell is room temperature, and the alkali metal atoms are... 87 Rb, as detailed below: A single-beam probe laser enters the atomic gas cell through the laser incident component and is then sent to the optical rotation measurement component. At the atomic gas chamber, a signal generator is used to generate a modulated magnetic field and synchronously feed back the reference frequency to the lock-in amplifier, and a current source is used to generate a uniform static magnetic field. The output signal of the optical rotation measurement component is sent to the lock-in amplifier, which demodulates the signal according to the magnetic field modulation frequency and records it by the data acquisition and processing system.

[0069] Specifically, a beam propagating along the Z-direction and polarized along the Y-axis, with a power of 1 mW and a frequency of... 87 Rb atom D1 line The near-resonance probe laser (which serves as both pump and probe, and will be referred to as "probe" hereafter) passes through a device equipped with 87 The atomic gas chamber of Rb atoms (internal dimensions 9 mm × 9 mm × 20 mm); due to the sufficiently strong light intensity and the anti-relaxation coating on the inner wall of the atomic gas chamber, The atoms on it will be almost completely emptied, and the vast majority of atoms will be in Above, and forming a shape symmetrical along the Y-axis. ( Figure 2 (b) The light passing through the atomic gas cell is split into two paths by a polarization beam splitter cube and enters a balanced detector to measure the optical rotation angle of the probe light; the output signal of the balanced detector is sent to a lock-in amplifier, and after demodulation, the signal of the magnetic field to be measured is output.

[0070] The entire process can be understood in the following three steps: (1) Pumping preparation of tensor polar moments: The spin quantum numbers of the two hyperfine levels of the alkali metal ground state are defined as follows: and (in I (The quantum number of the nuclear spin of an alkali metal atom). For example... Figure 2 As shown, a beam of light is used to strike the ground state of the D1 or D2 line of alkali metal atoms. When light polarized along the Y-axis illuminates an atom at a hyperfine level transition resonance, this light can... The atomic pump on the transfer Up, and in Generate along the Y-axis Because the frequency of light and The initial jump is far out of tune, therefore it will not be affected. Atomic absorption at energy levels leads to polarization relaxation.

[0071] Similarly, if a beam of light with a frequency located at the D1 line of alkali metal atoms is used... and The light between energy level transitions (in) 87 Taking Rb atoms as an example, this frequency can be selected from relatively... The transition to red detuning at 300 MHz can eliminate the dark state, which can... Atoms on the transfer Up, and in Generate along the Y-axis Due to light and The initial jump is far out of tune, therefore it will not be affected. Atomic absorption at energy levels induces polarization relaxation.

[0072] Specifically, both of the above pumping methods can be used in this invention. For the sake of simplicity, this embodiment uses... Preparation at energy level For example, in the case of [the situation described above].

[0073] In the absence of an external magnetic field in the XZ direction, the Y-axis modulated magnetic field and Its symmetry axis is parallel and has no effect on atomic polarization.

[0074] (2) AOC generates vector polar moment: If there is a magnetic field to be measured in the XZ plane, the magnetic field will cause... The axis deflects around the magnetic field, causing... and Angle The tensor shift of light on atoms produces a force that is simultaneously perpendicular to... and of Its conversion rate is denoted as This is the light field. The AOC effect on atoms will Transformed into a force that is in the same direction as the magnetic field and whose magnitude is proportional to the magnetic field. . Figure 3 , Figure 4 The X-axis magnetic field was shown respectively. and Z-axis magnetic field Caused and .

[0075] Magnetic field to be measured produce See the process Figure 3 : Will go around Larmor precession occurs, deviating from the Y-axis; when the magnetic field is extremely weak, the deviation angle is... light field and The AOC effect will produce a wave along X. Its size is: Equation (1) in, for 87 gyromagnetic ratio of Rb atoms, The atomic polarization relaxation rate (to simplify the formula, we assume different orders of polar moments). (They are all equal) For a specific light intensity and detuning, the AOC conversion rate; when When they were very young, that is , .

[0076] Magnetic field to be measured produce See the process Figure 4 :and produce The process is similar. This will cause a direction along Z. Its size is: Equation (2) Similarly, when When I was very young, .

[0077] The field to be measured In the Y-direction modulation field Under the influence of [the force], it oscillates around the Y-axis; The projection along the Z-axis will be detected by linearly polarized light propagating along the Z-axis. For example... Figure 5 As shown, Projection along the Z-axis The oscillation frequency is The amplitude is proportional to The size. And Projection along the Z-axis The oscillation frequency is The amplitude is proportional to Size. The amplitude of the swing angle about the Y-axis is ,but and The change of the Z-axis projection over time can be expressed as: Equation (3) Equation (4) Expanding the above two equations, we can obtain: Equation (5) Equation (6) in, This represents an nth-order Bessel function. The modulation amplitude is adjusted... It can determine whether the system is More sensitive, or more sensitive? More sensitive, or equally sensitive. It's worth noting that because the modulation field and the electric vector direction coincide, the modulation process remains unchanged. and The angle between them, based on the principle of the AOC effect, will not change. .

[0078] (3) Faraday rotation measurement of vector polar moment: The same beam of light can also be used as a detector Energy level The long-range detuning detection light. and This will cause the polarization plane of the probe light propagating along the Z-axis to rotate, i.e., the paramagnetic Faraday rotation effect, and this rotation angle... φ Also known as the rotation angle, specifically: ( Equation (7) in, l To detect the path of light through an Rb atom medium, n For Rb atomic number density, For the classical radius of the electron, At the speed of light, For the oscillating line intensity of the D1 line of rubidium atoms, Indicates the detection light and Detuning of the D1 line transition of the upper atom Indicating in disharmony The imaginary part of the complex Voigt line.

[0079] The optical rotation angle can be measured using well-known methods for detecting optical rotation angle. φ According to equations (5) to (7), the signal is processed by a lock-in amplifier. Place and Demodulating the signal at the point of output yields the following results: and (These are named the X channel and Z channel, respectively). Then, according to equations (1) to (2), the values ​​can be measured respectively. and Under small magnetic field conditions, the outputs of the X channel and Z channel are respectively proportional to... and .

[0080] In this method, because the frequency of the probe light is relative to... The transitions of the upper atoms are far detuned, at which point the atoms absorb light very weakly, avoiding linewidth broadening caused by light absorption. This enhances the sensitivity of the optical rotation angle signal to the magnetic field being measured.

[0081] Furthermore, the AOC effect can cause not only... Turn to , can also Turn to When the system relaxation rate Less than hour, and Oscillations will occur under the AOC effect. If this oscillation frequency is the same as the oscillation frequency of the magnetic field being measured, AOC resonance will occur, greatly enhancing the magnetic measurement signal. Figure 6 As shown, for a quantum number of F The ultra-fine energy levels will have a total of common A Zeeman sublevel m Let be the quantum number of the Zeeman sublevels. These sublevels are normally degenerate under near-zero magnetic fields. However, the tensor optical shift caused by the AOC will result in different energy level shifts for each Zeeman sublevel: An alternating magnetic field with the same frequency as the energy difference between a pair of adjacent Zeeman sublevels can induce transitions between adjacent Zeeman sublevels in atoms, i.e., a transition with a frequency of... An alternating magnetic field will cause atoms to... and Inter-transition, with a frequency of An alternating magnetic field will cause atoms to... and as well as and Inter-transition. Therefore, for a spin quantum number of...F The energy level system will be in times There exists a common place. F AOC resonant frequencies. If the system quantum number Then the system has only one resonant frequency. AOC oscillation frequency It is directly proportional to the probe light power and inversely proportional to the square of the probe light detuning. For the system described, due to the large detuning, for light ranging from tens of microwatts to a few milliwatts, The range is approximately 1 to 100 Hz, so by changing the power of the probe light, weak low-frequency alternating magnetic fields at different frequencies can be measured.

[0082] In this embodiment, , Unless otherwise specified, this data will continue to be used.

[0083] Figure 7 This demonstrates the biaxial magnetometer's response capability to DC magnetic fields. Figure 7 (a) and Figure 7 (b) Represents slow scan (single scan time 39 s) and The output signal of the magnetometer. The theoretical formulas corresponding to this experimental curve are equations (1) to (2). From Figure 7 It can be seen that the magnetometer's response to the magnetic field is approximately linear within the range of ±2 nT, and the crosstalk is very small (mainly caused by the non-parallelism between the probe light and the magnetic field in the Z direction). Figure 8 This demonstrates the magnetometer's response to magnetic fields of different frequencies. This was achieved by applying an amplitude of 24.5 pT in both the X and Z directions. rms With 35 pT rms By calibrating the oscillating magnetic field and slowly scanning (single scan period 76 s) the frequency of the oscillating magnetic field (0.5~38 Hz), the relationship between the magnetometer output amplitude and the calibrated magnetic field frequency can be obtained. The magnetometer has two resonance peaks at 3 Hz and 10 Hz, which are generated by AOC resonance.

[0084] By applying an external frequency of 10 Hz and an amplitude of 7 pT in both the X and Z directions... rms With 10 pT rms The oscillating calibration magnetic field was used, and the spectral signals of the X and Z channels were measured with and without the calibration magnetic field. Then, the magnetometer's sensitivity spectrum was obtained by normalizing the previously obtained frequency response curve. The results are as follows: Figure 9 As shown, at the 10 Hz resonance peak, the X and Z channels of the magnetometer can reach 25 Hz respectively. With 60 Sensitivity. Due to Proportional to the detection light power, the resonant frequency can be changed by altering the detection light power, thereby enabling sensitive detection of alternating weak magnetic fields with frequencies ranging from a few to tens of Hz.

[0085] Example 3 This embodiment provides a single-beam zero-magnetic-field dual-axis vector magnetometer, which allows the tensor-vector polar moment conversion effect of a linearly polarized probe laser 1 polarized along the Y-axis to measure the X-axis and Z-axis components of the magnetic field to be measured through the test of the tensor-vector polar moment conversion effect of alkali metal atoms. Figure 10 As shown, the magnetometer includes: A magnetic shielding component (magnetic shield 6 in this embodiment) is used to counteract external magnetic fields and provide a zero magnetic environment. An atomic gas chamber 4 filled with alkali metal atoms is set inside the magnetic shielding cover 6; The detection laser 1 is configured to interact with alkali metal atoms in the atomic gas chamber 4 to simultaneously serve as a pump and a detector. A laser incident component located at the inlet side of the atomic gas chamber 4, used to adjust the power of the probe laser 1 and prepare its polarization state as linearly polarized along the Y-axis, allowing the probe laser to propagate through the atomic gas chamber 4 along the Z-axis direction; A probe laser 1 polarized along the Y-axis and propagating along the Z-direction is used to establish a Y-axis symmetric tensor polar moment on the ground state hyperfine energy level of the alkali metal atom; The magnetic field to be measured generates a vector polar moment parallel to the magnetic field to be measured through the tensor-vector conversion effect of light on atoms; An optical rotation measurement component is installed on the outlet side of the atomic gas cell 4 to receive the probe laser 1 emitted from the atomic gas cell 4 and to measure the Faraday rotation angle generated by the vector polar moment. A lock-in amplifier 10 is used to receive and demodulate the output signal of the optical rotation measurement component; A data acquisition and processing system 11 is used to receive and record the demodulated data of the lock-in amplifier 10 to read the dual-axis magnetic field information; The X-axis, Y-axis, and Z-axis are orthogonal to each other.

[0086] In this embodiment, the magnetometer further includes an auxiliary light 14 and an auxiliary light incident component. The auxiliary light 14 is configured as a linearly polarized light beam with the same polarization direction as the detection laser 1 and orthogonal to the propagation direction, which is used to enhance atomic polarization. The frequency of the auxiliary light 14 is related to the D1 or D2 lines of alkali metal atoms. Leap resonance.

[0087] In this embodiment, the magnetometer is also equipped with a modulated magnetic field for generating a Y-axis. The first coil 5 and the second coil used to generate a zero magnetic field environment at the position of the atomic gas chamber 4; The inner wall of the atomic gas chamber 4 is provided with an anti-relaxation coating; The first coil 5 is a set of Helmholtz coils; The second coil is a triaxial static magnetic coil (allowing the generation of a uniform static magnetic field through current source 12). The laser incident assembly includes a first half-wave plate 2 and a first Gran-Thompson prism 3 arranged sequentially along the laser incident direction; The optical rotation measurement component includes a second half-wave plate 7, a polarization beam splitter cube 8, and a balance detector 9 arranged sequentially along the laser emission direction. The auxiliary light incident assembly includes a third half-wave plate 15 and a third Gran-Thompson prism 16 arranged sequentially along the auxiliary light incident direction; The first coil 5 allows the generation of a modulated magnetic field using the signal generator 13 and allows the delivery of a reference frequency to the lock-in amplifier 10.

[0088] Example 4 This embodiment provides an application of a single-beam zero-magnetic-field dual-axis vector magnetometer (Example 3) in the synchronous measurement of dual-axis magnetic fields in a zero-magnetic environment (dual-beam single optical path). During use, the temperature of the atomic gas cell is room temperature, and the alkali metal atoms are... 87 Rb, as detailed below: , The generation and detection process are the same as those described in Example 2.

[0089] In this embodiment, the alkali metal atom is 87 Rb, the size of the air chamber is the same as in Example 2.

[0090] In this embodiment, the detection laser 1 is a beam propagating along the Z direction, polarized along the Y axis, with a power of 9.6 mW, and a frequency similar to that of the alkali metal atom D1 line. Probe light near resonance during transition; The auxiliary light is a beam propagating along the X direction, polarized along the Y direction, with a power of 25 μW and a frequency corresponding to the D1 line of alkali metal atoms. Linearly polarized light from transition resonance; used to increase On It also increases the relaxation rate of atomic polarization, thereby increasing the bandwidth.

[0091] Scan separately and The response of the magnetometer is as follows Figure 11 (a) and Figure 11 As shown in (b), when the magnetic field magnitude is within ±2 nT, the magnetometer's response to the magnetic field is approximately linear, and the crosstalk is very small; subsequently, an amplitude of 24.5 pT is applied in both the X and Z directions. rmsWith 35 pT rms By changing the frequency of the oscillating magnetic field (0.5~76 Hz), the frequency response curve of the magnetometer can be obtained, such as... Figure 12 As shown, it can be seen that the magnetometer has a resonance peak around 58 Hz in this configuration, but the linewidth becomes very large.

[0092] Next, an amplitude of 24.5 pT with a frequency of 60 Hz was applied in both the X and Z directions. rms With 35 pT rms The oscillating calibration magnetic field is used, and the spectral signals of the X and Z channels are measured with and without the calibration magnetic field. Then, the magnetometer's sensitivity spectrum is obtained by normalizing the previously obtained frequency response curve. For example... Figure 13 As shown, at 1 Hz, the X and Z channels of the magnetometer can reach 30 Hz respectively. With 40 Sensitivity; at 60 Hz, the X and Z channels of the magnetometer can reach 12 respectively. With 17 Sensitivity.

[0093] Compared to Example 1, the auxiliary light not only improved sensitivity but also increased bandwidth. A sensitivity of less than 40 Hz was achieved across the entire 80 Hz range. The sensitivity is high. In this embodiment, the auxiliary light can propagate in the same direction as the probe light and be combined; and since its optical power is much weaker than that of the probe light, the auxiliary light does not disrupt the detection process. Therefore, it does not affect the "single beam" characteristic of this invention; the frequency of the auxiliary light can also be changed to resonate with the D2 line, that is, with... 87 Rb Leap resonance.

[0094] Example 5 This embodiment provides a single-beam zero-magnetic-field dual-axis vector magnetometer, which allows the tensor-vector polar moment conversion effect of a linearly polarized probe laser 1 polarized along the Y-axis to measure the X-axis and Z-axis components of the magnetic field to be measured through the test of the tensor-vector polar moment conversion effect of alkali metal atoms. Figure 14 As shown, the magnetometer includes: A magnetic shielding component (magnetic shield 6 in this embodiment) is used to counteract external magnetic fields and provide a zero magnetic environment. An atomic gas chamber 4 filled with alkali metal atoms is set inside the magnetic shielding cover 6; The detection laser 1 is configured to interact with alkali metal atoms in the atomic gas chamber 4 to simultaneously serve as a pump and a detector. A laser incident component located at the inlet side of the atomic gas chamber 4, used to adjust the power of the probe laser 1 and prepare its polarization state as linearly polarized along the Y-axis, allowing the probe laser to propagate through the atomic gas chamber 4 along the Z-axis direction; A probe laser 1 polarized along the Y-axis and propagating along the Z-direction is used to establish a Y-axis symmetric tensor polar moment on the ground state hyperfine energy level of the alkali metal atom; The magnetic field to be measured generates a vector polar moment parallel to the magnetic field to be measured through the tensor-vector conversion effect of light on atoms; An optical rotation measurement component is installed on the outlet side of the atomic gas cell 4 to receive the probe laser 1 emitted from the atomic gas cell 4 and to measure the Faraday rotation angle generated by the vector polar moment. A lock-in amplifier 10 is used to receive and demodulate the output signal of the optical rotation measurement component; A data acquisition and processing system 11 is used to receive and record the demodulated data of the lock-in amplifier 10 to read the dual-axis magnetic field information; The X-axis, Y-axis, and Z-axis are orthogonal to each other.

[0095] In this embodiment, the magnetometer is also equipped with a modulated magnetic field for generating a Y-axis. The first coil 5 and the second coil used to generate a zero magnetic field environment at the position of the atomic gas chamber 4; The inner wall of the atomic gas chamber 4 is provided with an anti-relaxation coating; The first coil 5 is a set of Helmholtz coils; The second coil is a triaxial static magnetic coil (allowing the generation of a uniform static magnetic field through current source 12). The laser incident assembly includes a first half-wave plate 2 and a first Gran-Thompson prism 3 arranged sequentially along the laser incident direction; The optical rotation measurement component includes a second half-wave plate 7, a polarization beam splitter cube 8, and a balance detector 9 arranged sequentially along the laser emission direction. The first coil 5 allows the generation of a modulated magnetic field using the signal generator 13 and allows the delivery of a reference frequency to the lock-in amplifier 10.

[0096] The signal generator 13 allows modulation of the laser: it detects the frequency of the laser 1 and allows a reference frequency to be delivered to the lock-in amplifier 10; the lower limit of the modulation range of the detected light frequency is located at the D1 line of the alkali metal atom. The blue detuned side of the transition resonance center, in order to Tensor polar moments are generated at energy levels; their upper frequency limit lies at the D1 line of alkali metal atoms. The blue detuned side of the transition resonance center is used to pump atoms back. energy level.

[0097] Example 6 This embodiment provides an application of a single-beam zero-magnetic-field dual-axis vector magnetometer (Embodiment 5) (frequency-modulated single-beam single-path). During use, the temperature of the atomic gas cell is room temperature, as detailed below: In this embodiment, the alkali metal atom is 87 Rb, the probe laser is a probe beam that propagates along the Z direction, is polarized along the Y axis, and has a modulated frequency.

[0098] Based on Examples 1 and 2, the probe light is frequency Optical frequency modulation is performed, with the modulation range being: the lower frequency limit relative to the D1 line of alkali metal atoms. The blue detuning at the transition resonance center is approximately 0.5 times the absorption linewidth (full width), in order to... Tensor polar moments are generated at energy levels; their upper frequency limit is relative to the D1 line of alkali metal atoms. The blue detuning at the resonance center of the transition is approximately one times the absorption linewidth (full width) to pump all atoms back. Energy level, and in Tensor polar moments are generated at energy levels. This approach can simultaneously achieve the following effects: 1) Increase On 2) Introduce a small amount of relaxation to increase bandwidth; 3) The average frequency of the probe light is close to the signal. Leap, Disharmony Decrease, thereby increase The resulting optical rotation angle; 4) The signal can be frequency-controlled. Demodulation is performed to obtain Therefore, the Y-axis modulation field can be optimized separately. modulation amplitude To obtain a larger Response; 5) The AOC effect remains active throughout the modulation process, and because the average frequency of the probe laser is closer to... The transition, therefore, greatly reduces the optical power required to achieve the same resonant frequency.

[0099] Optical path diagram as follows Figure 14 As shown, the probe light in 87 Rb D1 line Leap and The transition is sinusoidally modulated, with an output optical power of 640 microwatts, a modulation frequency of 20×2π kHz, and a Y-axis modulation magnetic field frequency of 2×2π kHz.

[0100] In this embodiment, , The generation process is the same as in Examples 2 and 4. The detection process is the same as in Examples 1 and 2. The detection process differs, specifically as follows: produce Subsequently, under different detuning conditions of the probe light, The different optical rotation angles of the probe light, i.e., in equation (7) Will by frequency Oscillation. Therefore, modulation of the optical frequency will cause... Caused optical rotation angle With frequency Oscillation. Therefore, by making the Z channel of the lock-in amplifier oscillate. By demodulating the output voltage signal of the balanced detector, one can obtain... Thus obtain .

[0101] Scan separately and The response of the magnetometer is as follows Figure 15 (a) and Figure 15 As shown in (b), when the magnetic field strength is within ±2 nT, the magnetometer's response to the magnetic field is approximately linear, with very little crosstalk. Subsequently, an amplitude of 24.5 pT is applied in both the X and Z directions. rms With 35 pT rms By oscillating the calibration magnetic field and changing its frequency (0.5~76 Hz), the magnetometer's response curves to magnetic fields at different frequencies can be obtained, such as... Figure 16 As shown.

[0102] Next, an amplitude of 24.5 pT with a frequency of 60 Hz was applied in both the X and Z directions. rms With 35 pT rms The oscillating calibration magnetic field is used, and the spectral signals of the X and Z channels are measured with and without the calibration magnetic field. Then, the magnetometer's sensitivity spectrum is obtained by normalizing the previously obtained frequency response curve. For example... Figure 17 As shown, the X-channel sensitivity of the magnetometer is better than 20 Hz in the range of 0–76 Hz. The Z-channel sensitivity is better than 30. The X-channel sensitivity is approximately 10 in the 40–60 Hz range. The Z-channel sensitivity is better than 20 in the 30~76 Hz range. .

[0103] Compared to Examples 2 and 4, this example achieves excellent sensitivity and bandwidth performance in a single-beam configuration by modulating the frequency of the probe light, and can detect both DC and alternating magnetic fields with great sensitivity; at the same time, the required light intensity is greatly reduced, which is beneficial for integrating the laser head into the probe.

[0104] Example 7 This embodiment provides a single-beam zero-magnetic-field dual-axis vector magnetometer, which allows the tensor-vector polar moment conversion effect of a linearly polarized probe laser 1 polarized along the Y-axis to measure the X-axis and Z-axis components of the magnetic field to be measured through the test of the tensor-vector polar moment conversion effect of alkali metal atoms. Figure 18 As shown, the magnetometer includes: A magnetic shielding component (magnetic shield 6 in this embodiment) is used to counteract external magnetic fields and provide a zero magnetic environment. An atomic gas chamber 4 filled with alkali metal atoms is set inside the magnetic shielding cover 6; The detection laser 1 is configured to interact with alkali metal atoms in the atomic gas chamber 4 to simultaneously serve as a pump and a detector. A laser incident component located at the inlet side of the atomic gas chamber 4, used to adjust the power of the probe laser 1 and prepare its polarization state as linearly polarized along the Y-axis, allowing the probe laser to propagate through the atomic gas chamber 4 along the Z-axis direction; A probe laser 1 polarized along the Y-axis and propagating along the Z-direction is used to establish a Y-axis symmetric tensor polar moment on the ground state hyperfine energy level of the alkali metal atom; The magnetic field to be measured generates a vector polar moment parallel to the magnetic field to be measured through the tensor-vector conversion effect of light on atoms; An optical rotation measurement component is installed on the outlet side of the atomic gas cell 4 to receive the probe laser 1 emitted from the atomic gas cell 4 and to measure the Faraday rotation angle generated by the vector polar moment. A lock-in amplifier 10 is used to receive and demodulate the output signal of the optical rotation measurement component; A data acquisition and processing system 11 is used to receive and record the demodulated data of the lock-in amplifier 10 to read the dual-axis magnetic field information; The X-axis, Y-axis, and Z-axis are orthogonal to each other.

[0105] In this embodiment, the magnetometer is also equipped with a modulated magnetic field for generating a Y-axis. The first coil 5 and the second coil used to generate a zero magnetic field environment at the position of the atomic gas chamber 4; The front and rear surfaces of the inner wall of the atomic gas chamber 4 are provided with a high-reflectivity film, and an anti-relaxation coating is deposited on the surface of the high-reflectivity film and other surfaces of the inner wall of the atomic gas chamber 4, allowing the detection laser 1 to be reflected multiple times between the front and rear inner surfaces of the atomic gas chamber 4. The first coil 5 is a set of Helmholtz coils; The second coil is a triaxial static magnetic coil (allowing the generation of a uniform static magnetic field through current source 12). The laser incident assembly includes a first half-wave plate 2 and a first Gran-Thompson prism 3 arranged sequentially along the laser incident direction; The optical rotation measurement component includes a second half-wave plate 7, a polarization beam splitter cube 8, and a balance detector 9 arranged sequentially along the laser emission direction. The first coil 5 allows the generation of a modulated magnetic field using the signal generator 13 and allows the delivery of a reference frequency to the lock-in amplifier 10.

[0106] Example 8 This embodiment provides an application of a single-beam zero-magnetic-field dual-axis vector magnetometer (Example 7) (single-beam multi-path). During use, the temperature of the atomic gas cell is room temperature, as detailed below: The atomic gas chamber has internal dimensions of 8 mm × 8 mm × 12 mm; The alkali metal atoms are 87 Rb atoms; The frequency of the detection laser 1 and 87 Rb atom D1 line Leap resonance.

[0107] , The generation and detection process are the same as those described in Example 2.

[0108] Scan separately and The response of the magnetometer is as follows Figure 19 (a) and Figure 19 As shown in (b), when the magnetic field strength is within ±2 nT, the magnetometer's response to the magnetic field is approximately linear, with very little crosstalk. Subsequently, an amplitude of 24.5 pT is applied in both the X and Z directions. rms With 35 pT rms By changing the frequency of the oscillating magnetic field (0.5~76 Hz), the response curves of the magnetometer to magnetic fields at different frequencies can be obtained, such as... Figure 20 As shown, the magnetometer exhibits two resonance peaks at 3 Hz and 10 Hz under the experimental conditions (mainly determined by the power of the probe light).

[0109] Next, an amplitude of 24.5 pT with a frequency of 10 Hz was applied in both the X and Z directions. rms With 35 pT rms The known amplitude oscillating calibration magnetic field was used, and the spectral signals of the X and Z channels were measured with and without the calibration magnetic field. Then, the magnetometer's sensitivity spectrum was obtained by normalizing the previously obtained frequency response curve. The results are as follows: Figure 21 As shown, at 10 Hz, the X and Z channels of the magnetometer can reach 20 Hz respectively. With 30 Sensitivity.

[0110] In summary, compared to Example 2, using a multi-path gas cell can significantly reduce the optical power required for the experiment, which is beneficial for integrating the laser inside the probe. Furthermore, the techniques used in Examples 4 and 6 can also be applied in this example to further improve sensitivity.

[0111] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the interpretation of the present invention, without departing from the scope of the invention, should be within the protection scope of the present invention.

Claims

1. A single-beam zero-field bi-axial vector magnetometer, characterized in that, A magnetometer that allows for simultaneous measurement of the X-axis and Z-axis components of the magnetic field under test using a linearly polarized probe laser polarized along the Y-axis through the tensor-vector polar moment conversion effect on alkali metal atoms includes: Magnetic shielding components used to counteract external magnetic fields and provide a zero-magnetic environment; An atomic gas chamber filled with alkali metal atoms is set inside the magnetic shielding assembly. A probe laser configured to interact with alkali metal atoms in the atomic gas chamber to simultaneously serve as a pump and a probe. A laser incident component disposed on the inlet side of the atomic gas chamber, used to adjust the power of the probe laser and prepare its polarization state as linearly polarized along the Y-axis, allowing the probe laser to propagate through the atomic gas chamber along the Z-axis direction; A Y-axis symmetric tensor moment was established on the hyperfine energy level of the ground state of alkali metal atoms using a probe laser polarized along the Y-axis and propagating along the Z-direction. The magnetic field to be measured generates a vector polar moment parallel to the component of the magnetic field to be measured in the XZ plane through the tensor-vector conversion effect of the probe laser on alkali metal atoms; An optical rotation measurement component is installed on the outlet side of the atomic gas cell to receive the probe laser emitted from the atomic gas cell and measure the Faraday rotation angle generated by the vector polar moment; A lock-in amplifier for receiving and demodulating the output signal of the optical rotation measurement component; A data acquisition and processing system for receiving and recording the demodulated data from the lock-in amplifier to read biaxial magnetic field information; The X-axis, Y-axis, and Z-axis are orthogonal to each other.

2. A single-beam zero-field dual-axis vector magnetometer according to claim 1, characterized in that The inner wall of the atomic gas chamber is coated with an anti-relaxation film.

3. The single-beam zero-magnetic-field dual-axis vector magnetometer according to claim 1, characterized in that, The magnetometer includes features for generating a frequency along the Y-axis. The first coil of the modulated magnetic field.

4. The single-beam zero-magnetic-field dual-axis vector magnetometer according to claim 1, characterized in that, The magnetometer uses frequency Modulate the frequency of the detection laser; The modulation range of the frequency of the probe laser is configured such that the lower frequency limit is located at the D1 line of the alkali metal atom. The blue detuned side of the transition resonance center, in order to Tensor polar moments are generated at energy levels; Its upper frequency limit is located at the D1 line of alkali metal atoms. Within a range of 3 linewidths from the center of the transition resonance, in order to All atoms in the energy level are pumped to Energy level, and in Tensor polar moments are generated at the energy level.

5. A method of using a single-beam zero-magnetic-field dual-axis vector magnetometer as described in any one of claims 1 to 4, wherein the magnetometer is based on the tensor-vector conversion effect, characterized in that... Includes the following steps: The frequency applied along the Y-axis is The modulated magnetic field; Measuring the Faraday rotation angle of the probe laser at a frequency The X component of the magnetic field to be measured is obtained by demodulation at a frequency of 2. The Z component of the magnetic field to be measured is obtained by demodulation.

6. A method of using a single-beam zero-magnetic-field dual-axis vector magnetometer as described in any one of claims 1 to 4, wherein the magnetometer is based on the tensor-vector conversion effect, characterized in that... Includes the following steps: The frequency applied along the Y-axis is The modulated magnetic field; at the same time, with a much larger frequency The frequency of the probe laser is modulated, and the modulation range of the probe laser frequency is configured such that the lower frequency limit is located at the D1 line of the alkali metal atom. The blue detuned side of the transition resonance center, in order to Tensor polar moments are generated at energy levels; Its upper frequency limit is located at the D1 line of alkali metal atoms. Within three linewidths of the transition resonance center, to... All atoms in the energy level are pumped to Energy level, and in Tensor polar moments are generated at energy levels; Measuring the Faraday rotation angle of the probe laser at a frequency The X component of the magnetic field to be measured is obtained by demodulation at a frequency of [frequency value missing]. The Z component of the magnetic field to be measured is obtained by demodulation.

7. The application of a single-beam zero-magnetic-field biaxial vector magnetometer as described in any one of claims 1 to 4 in the synchronous measurement of biaxial or uniaxial magnetic fields in a zero-magnetic environment.

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