A dead zone-free measurement method and device for NMOR atomic magnetometer based on dual-axis magnetic pulse control

Abstract

The present invention discloses a dead zone-free measurement method and device of an NMOR atomic magnetometer based on dual-axis magnetic pulse control, which relates to the technical field of atomic magnetometers and includes the following steps: S1: polarizing alkali metal atoms using linearly polarized lasers and detecting optical rotation signals; S2: applying a short-time pulse magnetic field along the light propagation direction to change the atomic polarization direction; S3: collecting data through a data acquisition module after turning off the pulse magnetic field; S4: applying a short-time pulse magnetic field along the direction perpendicular to the vibration plane of light to change the atomic polarization direction; S5: collecting data through a data acquisition module after turning off the pulse magnetic field; S6: using a data processing module to extract the Larmor precession frequency and calculate the magnetic field amplitude. The present invention adopts the above-mentioned dead zone-free measurement method and device of an NMOR atomic magnetometer based on dual-axis magnetic pulse control, and uses dual-axis magnetic pulses to control the atomic polarization direction to achieve dead zone-free measurement of magnetic fields by an NMOR atomic magnetometer, while having the advantages of small size, low cost, and easy integration.

Description

Technical Field

[0001] The invention relates to the technical field of atomic magnetometers, and in particular to a dead-zone-free measurement method and device of a NMOR atomic magnetometer based on dual-axis magnetic pulse control. Background Art

[0002] For a long time, the measurement and application of magnetic fields have played an important role in promoting the development of human science and technology. With the development of modern science and technology, the measurement of magnetic fields has become more and more precise. In recent years, with the development of quantum physics and laser technology, NMOR (Nonlinear Magneto-Optical Rotation) atomic magnetometers have become the focus of research. Compared with superconducting quantum interference devices (SQUID, Superconducting Quantum Interference Device), SERF (Spin-Exchange Relaxation Free, spin exchange relaxation free) atomic magnetometers, etc., NMOR atomic magnetometers have the advantages of wide dynamic range, simple device, low application environment requirements, and can maintain ultra-high sensitivity. It has broad application prospects in the fields of biological health monitoring, mineral exploration, magnetic anomaly detection, etc.

[0003] The traditional NMOR atomic magnetometer based on magneto-optical interaction has a dead zone problem, that is, the response signal of the atomic magnetometer to the magnetic field in certain specific directions is severely attenuated or even zero, resulting in large deviations or measurement errors in the magnetic field amplitude measured by the magnetometer. At present, the single-beam NMOR atomic magnetometer uses linearly polarized laser to polarize atoms and detect optical rotation signals. There is a dead zone along the direction of the linearly polarized laser, and the signal is almost zero in the plane perpendicular to the direction of light transmission.

[0004] Therefore, it is necessary to provide a dead-zone-free measurement method and device for a NMOR atomic magnetometer based on dual-axis magnetic pulse control to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide a method and device for measuring the NMOR atomic magnetometer without dead zone based on dual-axis magnetic pulse control, so as to overcome the problem of "dead zone" in the magnetic field measurement of the existing NMOR atomic magnetometer, and use linearly polarized laser to polarize alkali metal atoms and detect optical rotation signals; in the atomic polarization stage, the polarization direction is changed by alternately applying pulsed magnetic fields in the laser propagation direction and in the direction perpendicular to the linearly polarized laser vibration plane; during the detection stage, the pulsed magnetic field is turned off, and the atoms precess freely, and finally the Larmor precession frequency is extracted by using a data processing module, and the magnetic field amplitude is calculated and output. Using dual-axis magnetic pulses to control the atomic polarization direction can realize the NMOR atomic magnetometer to measure the magnetic field without dead zone, and at the same time has the advantages of small size, low cost and easy integration.

[0006] To achieve the above object, the present invention provides a dead zone-free measurement method of an NMOR atomic magnetometer based on dual-axis magnetic pulse control, comprising the following steps:

[0007] S1: Use linearly polarized laser to polarize alkali metal atoms and detect the optical rotation signal;

[0008] S2: Apply a short-duration pulse magnetic field along the direction of light propagation to change the polarization direction of atoms;

[0009] S3: After the pulse magnetic field is turned off, data is collected through the data acquisition module;

[0010] S4: Apply a short-duration pulse magnetic field perpendicular to the vibration plane of light to change the polarization direction of atoms;

[0011] S5: After the pulse magnetic field is turned off, the data acquisition module collects data;

[0012] S6: Use the data processing module to extract the Larmor precession frequency and calculate the magnetic field amplitude.

[0013] Preferably, in step S1, the following steps are specifically included: turning on the semiconductor laser, tuning the frequency of the laser to the resonance frequency of the alkali metal atoms, allowing the laser to pass through the gas chamber, the alkali metal atoms in the gas chamber reach an average polarization state under the combined action of the external magnetic field and the linearly polarized laser, and adjusting the half-wave plate so that the initial signal is 0.

[0014] Preferably, in step S2, the specific operations are as follows: the CH1 channel of the signal generator is turned on, so that the coil in the light propagation direction generates a short-time pulse magnetic field, and under the action of the pulse magnetic field, the polarization direction of the alkali metal atoms deflects a certain angle and reaches a steady state.

[0015] Preferably, in step S3, the specific operations are as follows: the CH1 channel of the signal generator is disconnected, the pulse magnetic field generated in the direction of light propagation is turned off, the polarized atoms precess freely around the magnetic field to be measured at the Larmor frequency, the precessing atoms act on the linearly polarized laser, causing the polarization plane of the linearly polarized laser to rotate, and a periodic optical rotation signal that changes at the Larmor frequency is generated, the optical rotation detection module detects the optical rotation signal, and outputs a voltage signal, and the data is collected through the data acquisition module.

[0016] Preferably, in step S4, the specific operations are as follows: the CH2 channel of the signal generator is turned on, and the coil perpendicular to the direction of the light vibration plane generates a short-time pulse magnetic field. Under the action of the pulse magnetic field, the polarization direction of the alkali metal atoms deflects a certain angle and reaches a steady state.

[0017] Preferably, in step S5, the following steps are specifically included: disconnecting the CH2 channel of the signal generator, turning off the pulse magnetic field generated by the coil perpendicular to the direction of the light vibration plane, allowing the polarized atoms to precess freely at the Larmor frequency around the magnetic field to be measured, and the precessing atoms act on the linearly polarized laser to rotate the polarization plane of the linearly polarized laser, thereby generating a periodic optical rotation signal that changes at the Larmor frequency, and the optical rotation detection module detects the optical rotation signal and outputs a voltage signal, and collects data through the data acquisition module.

[0018] Preferably, in step S6, the data processing module processes the data collected in step S3 and step S5 and outputs the magnetic field amplitude; the specific steps are as follows:

[0019] S61: The data processing module filters the data to remove the DC component and the low-frequency drift part;

[0020] S62: The data processing module extracts the frequency of the precession signal, and obtains the magnetic field amplitude and outputs it according to the formula: B=ω / γ, where ω is the frequency of the free precession signal and γ is the gyromagnetic ratio;

[0021] Step S2 to step S6 constitute a cycle, and steps S2 to S6 are repeated to achieve real-time measurement of the magnetic field without dead zones.

[0022] A dead-zone-free measuring device for an NMOR atomic magnetometer based on dual-axis magnetic pulse regulation, wherein a semiconductor laser is connected to a collimator through an optical fiber, a Glan prism is arranged between the collimator and an alkali metal gas chamber, a non-magnetic heater is arranged outside the alkali metal gas chamber, a coil is arranged outside the non-magnetic heater, a signal generator is connected to the coil, an optical rotation detection module is arranged on the other side of the coil, the optical rotation detection module comprises a half-wave plate, a polarization beam splitter, a first photodetector, a second photodetector and a differential amplifier, a half-wave plate is arranged between the coil and the polarization beam splitter, a transmission output end of the polarization beam splitter is connected to the first photodetector, a reflection output end of the polarization beam splitter is connected to the second photodetector, the other ends of the first photodetector and the second photodetector are connected to the input end of the differential amplifier, and the output end of the differential amplifier is connected to a computer. The above structure realizes the steps of a dead-zone-free measuring method for an NMOR atomic magnetometer based on dual-axis magnetic pulse regulation.

[0023] Preferably, the coil includes an x-axis coil and a y-axis coil, the signal generator includes two channels, CH1 and CH2, the output end of the CH1 channel is connected to the x-axis coil, and the output end of the CH2 channel is connected to the y-axis coil to generate a short-time pulse magnetic field.

[0024] Preferably, the computer includes a data acquisition module and a data processing module.

[0025] Therefore, the present invention adopts the above-mentioned NMOR atomic magnetometer dead zone-free measurement method and device based on dual-axis magnetic pulse control, which has the following beneficial effects:

[0026] (1) The present invention starts from the mechanism of interaction between atoms and magneto-optics in the NMOR atomic magnetometer, applies a pulsed magnetic field to polarized atoms, controls the deflection of the polarization direction of the atoms, turns off the pulsed magnetic field to allow the atoms to freely precess around the magnetic field to be measured, extracts the free precession frequency and thus obtains the magnetic field amplitude, thereby achieving dead-zone-free magnetic field measurement.

[0027] (2) The dead zone-free measurement method of the NMOR atomic magnetometer in the present invention directly extracts the atomic precession frequency, avoiding the noise generated by the phase-locked loop, and has a high measurement accuracy.

[0028] (3) The present invention is easy to operate and can achieve dead-zone-free magnetic field measurement without increasing system volume and cost, and has certain reference value for atomic magnetometers under other linear polarization effects.

[0029] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of a dead zone-free measurement method of an NMOR atomic magnetometer based on dual-axis magnetic pulse control of the present invention;

[0031] Figure 2 It is a schematic diagram of a dead zone-free measurement device of an NMOR atomic magnetometer based on dual-axis magnetic pulse control according to the present invention;

[0032] Figure 3 This is a timing diagram of a dead-zone-free measurement method of an NMOR atomic magnetometer based on dual-axis magnetic pulse control in an embodiment of the present invention;

[0033] 1. Semiconductor laser; 2. Optical fiber; 3. Collimator; 4. Glan prism; 5. Alkali metal gas chamber; 6. Non-magnetic heater; 7. Y-axis coil; 8. X-axis coil; 9. Half-wave plate; 10. Polarization beam splitter; 11. First photodetector; 12. Second photodetector; 13. Differential amplifier; 14. Computer; 15. Signal generator; 16. X-axis magnetic pulse timing (16.1, 16.2, ...); 17. Y-axis magnetic field pulse timing (17.1, 17.2, ...); 18. Signal acquisition timing; 19. Atomic free precession acquisition signal. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0035] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0036] The words "include" or "comprises" and the like used in the present invention mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of also including other elements. The orientation or position relationship indicated by the terms "inside", "outside", "upper", "lower", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation of the present invention. When the absolute position of the described object changes, the relative position relationship may also change accordingly. In the present invention, unless otherwise clearly specified and limited, the terms "attachment" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] like Figure 1 As shown, the present invention provides a method and device for measuring the dead zone of an NMOR atomic magnetometer based on dual-axis magnetic pulse control, comprising the following steps:

[0038] S1: Use linearly polarized laser to polarize alkali metal atoms and detect optical rotation signals; in step S1, the following steps are specifically included: turn on the semiconductor laser, tune the frequency of the laser to the resonance frequency of the alkali metal atoms, let the laser pass through the air chamber, the alkali metal atoms in the air chamber reach an average polarization state under the combined action of the external magnetic field and the linearly polarized laser, and adjust the half wave plate so that the initial signal is 0.

[0039] S2: Apply a short-time pulse magnetic field along the direction of light propagation to change the polarization direction of the atoms; in step S2, the specific operations are as follows: turn on the CH1 channel of the signal generator to make the coil in the direction of light propagation generate a short-time pulse magnetic field. Under the action of the pulse magnetic field, the polarization direction of the alkali metal atoms is deflected by a certain angle and reaches a steady state.

[0040] S3: After turning off the pulsed magnetic field, data is collected through the data acquisition module; in step S3, the specific operations are as follows: the CH1 channel of the signal generator is disconnected, the pulsed magnetic field generated in the direction of light propagation is turned off, the polarized atoms freely precess at the Larmor frequency around the magnetic field to be measured, the precessing atoms act on the linearly polarized laser, causing the polarization plane of the linearly polarized laser to rotate, and a periodic optical rotation signal that changes at the Larmor frequency is generated, the optical rotation detection module detects the optical rotation signal, and outputs a voltage signal, and the data is collected through the data acquisition module.

[0041] S4: Apply a short-time pulse magnetic field along the direction perpendicular to the vibration plane of light to change the polarization direction of atoms; in step S4, the specific operations are as follows: turn on the CH2 channel of the signal generator, and the coil perpendicular to the direction of the vibration plane of light generates a short-time pulse magnetic field. Under the action of the pulse magnetic field, the polarization direction of alkali metal atoms is deflected by a certain angle and reaches a steady state.

[0042] S5: the data acquisition module acquires data after the pulsed magnetic field is turned off; in step S5, the following steps are specifically included: the CH2 channel of the signal generator is disconnected, the pulsed magnetic field generated by the coil perpendicular to the direction of the light vibration plane is turned off, the polarized atoms freely precess at the Larmor frequency around the magnetic field to be measured, the precessing atoms act on the linearly polarized laser, causing the polarization plane of the linearly polarized laser to rotate, thereby generating a periodic optical rotation signal that changes at the Larmor frequency, the optical rotation detection module detects the optical rotation signal, and outputs a voltage signal, and the data is acquired through the data acquisition module.

[0043] S6: Using the data processing module to extract the Larmor precession frequency and calculate the magnetic field amplitude. In step S6, the data processing module processes the data collected in step S3 and step S5 and outputs the magnetic field amplitude; the specific steps are as follows:

[0044] S61: The data processing module filters the data to remove the DC component and the low-frequency drift part;

[0045] S62: The data processing module extracts the frequency of the precession signal, and obtains the magnetic field amplitude and outputs it according to the formula: B=ω / γ, where ω is the frequency of the free precession signal and γ is the gyromagnetic ratio;

[0046] Step S2 to step S6 constitute a cycle, and steps S2 to S6 are repeated to achieve real-time measurement of the magnetic field without dead zones.

[0047] like Figure 2As shown, a dead-zone-free measurement device of an NMOR atomic magnetometer based on dual-axis magnetic pulse control, a semiconductor laser 1 is connected to a collimator 3 through an optical fiber 2, a Glan prism 4 is arranged between the collimator 3 and an alkali metal gas chamber 5, a non-magnetic heater 6 is arranged on the outside of the alkali metal gas chamber 5, a coil is arranged on the outside of the non-magnetic heater 6, a signal generator 15 is connected to the coil, an optical rotation detection module is arranged on the other side of the coil, the coil includes an x-axis coil 7 and a y-axis coil 8, the signal generator 15 includes two channels, CH1 and CH2, the output end of the CH1 channel is connected to the x-axis coil 7, and the output end of the CH2 channel is connected to the y-axis coil 8, to generate a short-time pulse magnetic field. The optical rotation detection module includes a half wave plate 9, a polarization beam splitter 10, a first photodetector 11, a second photodetector 12 and a differential amplifier 13. The half wave plate 9 is arranged between the coil and the polarization beam splitter 10. The transmission output end of the polarization beam splitter 10 is connected to the first photodetector 11, the reflection output end of the polarization beam splitter 10 is connected to the second photodetector 12, the other ends of the first photodetector 11 and the second photodetector 12 are connected to the input end of the differential amplifier 13, and the output end of the differential amplifier 13 is connected to a computer 14. The computer 14 includes a data acquisition module and a data processing module. The above structure realizes a method and steps of a dead zone-free measurement of an NMOR atomic magnetometer based on dual-axis magnetic pulse control.

[0048] Example

[0049] like Figure 3 As shown, Figure 3 It includes a magnetic field pulse excitation timing diagram, a signal acquisition timing diagram and an acquisition signal diagram, wherein 16 (16.1, 16.2, ...) is an x-axis magnetic field pulse sequence, 17 (17.1, 17.2, ...) is a y-axis magnetic field pulse sequence, and the x-axis magnetic field pulse and the y-axis magnetic field pulse are alternately turned on and off. At the moment when the magnetic field pulse is turned off, the signal acquisition module collects signals regularly, 18 is the signal acquisition timing, and the collection of free precession signals is shown in the diagram 19. In the atomic polarization stage, the x-axis pulse magnetic field 16.1 is first turned on to flip the atomic polarization direction, and then the x-axis pulse magnetic field is turned off, the atoms precess freely, and the data acquisition module collects signals, and the collection timing is 18; the y-axis pulse magnetic field 17.1 is turned on to flip the atomic polarization direction, and then the y-axis pulse magnetic field is turned off, the atoms precess freely, and the data acquisition module collects signals. Finally, the data processing module processes the collected signal 19 and outputs the magnetic field amplitude. Repeating the above steps can achieve continuous measurement of the magnetic field without dead zone.

[0050] Therefore, the present invention adopts the above-mentioned NMOR atomic magnetometer dead-zone-free measurement method and device based on dual-axis magnetic pulse control, and can realize NMOR atomic magnetometer dead-zone-free magnetic field measurement by controlling the atomic polarization direction through dual-axis magnetic pulses.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A dead zone-free measurement method of NMOR atomic magnetometer based on dual-axis magnetic pulse control, characterized in that: The following steps are involved: S1: Use linearly polarized laser to polarize alkali metal atoms and detect the optical rotation signal; S2: Apply a short-duration pulse magnetic field along the direction of light propagation to change the polarization direction of atoms; In step S2, the specific operations are as follows: the CH1 channel of the signal generator is turned on, so that the coil in the light propagation direction generates a short-time pulse magnetic field. Under the action of the pulse magnetic field, the polarization direction of the alkali metal atoms deflects a certain angle and reaches a steady state; S3: After the pulse magnetic field is turned off, data is collected through the data acquisition module; In step S3, the specific operations are as follows: the CH1 channel of the signal generator is disconnected, the pulse magnetic field generated in the light propagation direction is turned off, the polarized atoms freely precess around the magnetic field to be measured at the Larmor frequency, the precessing atoms act on the linearly polarized laser, so that the polarization plane of the linearly polarized laser rotates, and a periodic optical rotation signal that changes at the Larmor frequency is generated, the optical rotation detection module detects the optical rotation signal, and outputs a voltage signal, and the data is collected through the data acquisition module; S4: Apply a short-duration pulse magnetic field perpendicular to the vibration plane of light to change the polarization direction of atoms; In step S4, the specific operations are as follows: the CH2 channel of the signal generator is turned on, and the coil perpendicular to the direction of the light vibration plane generates a short-time pulse magnetic field. Under the action of the pulse magnetic field, the polarization direction of the alkali metal atoms deflects a certain angle and reaches a steady state; S5: After the pulse magnetic field is turned off, the data acquisition module collects data; In step S5, the following steps are specifically included: disconnecting the CH2 channel of the signal generator, turning off the pulse magnetic field generated by the coil perpendicular to the light vibration plane, allowing the polarized atoms to freely precess around the magnetic field to be measured at the Larmor frequency, and the precessing atoms act on the linearly polarized laser to rotate the polarization plane of the linearly polarized laser, thereby generating a periodic optical rotation signal that changes at the Larmor frequency, and the optical rotation detection module detects the optical rotation signal and outputs a voltage signal, and collects data through the data acquisition module; S6: Utilize the data processing module to extract the Larmor precession frequency and calculate the magnetic field amplitude; In step S6, the data processing module processes the data collected in step S3 and step S5 and outputs the magnetic field amplitude; the specific steps are as follows: S61: The data processing module filters the data to remove the DC component and the low-frequency drift part; S62: The data processing module extracts the frequency of the precession signal according to the formula: ; The magnetic field amplitude is obtained and output, where is the frequency of the free precession signal, is the gyromagnetic ratio; Step S2 to step S6 constitute a cycle, and steps S2 to S6 are repeated to achieve real-time measurement of the magnetic field without dead zones.

2. The method for measuring the NMOR atomic magnetometer without dead zone based on dual-axis magnetic pulse control according to claim 1 is characterized in that: In step S1, the following steps are specifically included: turning on the semiconductor laser, tuning the frequency of the laser to the resonance frequency of the alkali metal atoms, allowing the laser to pass through the gas chamber, the alkali metal atoms in the gas chamber reach an average polarization state under the combined action of the external magnetic field and the linearly polarized laser, and adjusting the half-wave plate so that the initial signal is 0.

3. A NMOR atomic magnetometer dead zone measurement device based on dual-axis magnetic pulse control, characterized in that: A semiconductor laser is connected to a collimator through an optical fiber, a Glan prism is arranged between the collimator and the alkali metal gas chamber, a non-magnetic heater is arranged outside the alkali metal gas chamber, a coil is arranged outside the non-magnetic heater, a signal generator is connected to the coil, and an optical rotation detection module is arranged on the other side of the coil. The optical rotation detection module includes a half wave plate, a polarization beam splitter, a first photodetector, a second photodetector and a differential amplifier. A half wave plate is arranged between the coil and the polarization beam splitter, a transmission output end of the polarization beam splitter is connected to the first photodetector, a reflection output end of the polarization beam splitter is connected to the second photodetector, the other ends of the first photodetector and the second photodetector are connected to the input end of the differential amplifier, and the output end of the differential amplifier is connected to a computer. The above device is used to implement the steps of a dead-zone-free measurement method of an NMOR atomic magnetometer based on dual-axis magnetic pulse control as described in any one of claims 1 to 2.

4. The NMOR atomic magnetometer dead zone-free measurement device based on dual-axis magnetic pulse control according to claim 3 is characterized in that: The coils include the x-axis coil and The signal generator includes two channels, CH1 and CH2. The output end of the CH1 channel is connected to the x-axis coil, and the output end of the CH2 channel is connected to the The shaft coil is connected to generate a short-time pulse magnetic field.

5. The NMOR atomic magnetometer dead zone-free measurement device based on dual-axis magnetic pulse control according to claim 3 is characterized in that: The computer includes a data acquisition module and a data processing module.

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