A Bell-Bloom type Cs- 4 He atomic magnetometer

Abstract

The present invention discloses a Bell-Bloom type Cs- 4 The He atomic magnetometer includes a Doppler-eliminating frequency stabilization optical path; the Doppler-eliminating frequency stabilization optical path divides a light beam into two beams, the first beam is used for frequency stabilization, and the second beam is used for power stabilization through an acousto-optic modulator power stabilization optical path; the stabilized light of the acousto-optic modulator power stabilization optical path enters an electro-optic modulator pump modulation optical path for pump modulation, and the modulated light enters a sensor probe cross-shaped double-beam detection optical path to polarize Cs atoms and cause He atoms to undergo Larmor precession, and the second laser beam of the sensor probe cross-shaped double-beam detection optical path enters an atomic gas chamber perpendicular to the first modulated laser beam to detect He atoms. The present invention performs a multiple folding design on the optical path, thereby ensuring that the pump laser has stable frequency and power and uniform energy distribution, and ensuring the stable output of the pump modulation optical path.

Description

Technical Field

[0001] The present invention belongs to the technical field of atomic magnetometers, and in particular relates to a Bell-Bloom type atomic magnetometer with a diatomic gas chamber. 4 He atomic magnetometer has the advantages of reasonable optical path layout, compact structure, convenient installation and adjustment, simple experimental operation, etc. 4 It provides a basis for the development of He magnetometer. Background Art

[0002] Atomic magnetometers play an important role in cutting-edge fields such as military, medicine, aerospace, brain magnetic detection, and geophysical exploration. The cesium helium atomic magnetometer is used in the geomagnetic field environment and is one of the atomic magnetometers with the highest accuracy record in the world. It is mostly used in national metrology benchmark construction, geomagnetic observation and other fields that require high accuracy measurement. In 2000, the Russian Institute of Metrology (VNIIM) built a metrology benchmark device based on the cesium helium atomic resonance principle. It is the highest level benchmark device in the world today, and its accuracy has surpassed the NMR quantum benchmark for the first time. The research on the cesium helium magnetometer has important scientific significance and practical value for the improvement and perfection of my country's metrology benchmark devices.

[0003] The cesium helium atomic magnetometer is mainly used to eliminate the optical frequency shift error that is common in optical pumping magnetometers, and is of great significance to improving the accuracy and sensitivity of the magnetometer. The cesium helium magnetometer uses an indirect pumping technology. The cesium atoms in the cesium helium atomic gas chamber are first polarized by the pumping light, and then the polarized spin magnetic moment of the cesium atoms is transferred to the metastable helium atoms through the Penning ionization process and the self-selected exchange collision process between the cesium atoms and the helium atoms, so that the metastable helium atoms also produce macroscopically measurable polarized spin magnetic moments. The cesium helium magnetometer is less affected by parameters such as temperature, light intensity, and magnetic field, and therefore has good metrological characteristics. The Bell-Bloom type cesium helium atomic magnetometer can reduce atomic broadening to further improve the accuracy and sensitivity of the cesium helium magnetometer.

[0004] Although the accuracy of the current cesium helium magnetometer is high enough, it is still limited by the excessive atomic broadening and low sensitivity, and cannot simultaneously meet the requirements of miniaturization, fast response speed, high sensitivity and high accuracy of the cesium helium magnetometer. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention proposes a Bell-Bloom type Cs-He atomic magnetometer for geomagnetic detection, which adopts Doppler frequency stabilization technology, acousto-optic modulation power stabilization technology, electro-optic modulation technology and dual-beam detection technology, and has the advantages of reasonable layout, compact structure, convenient installation and adjustment, simple experimental operation, etc., which provides a basis for the development of high-accuracy cesium helium magnetometer. The circuit control system adopts digital circuit, which has the advantages of convenient parameter adjustment and fast response speed.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0007] A Bell-Bloom type Cs- 4 The He atomic magnetometer comprises a Doppler frequency stabilization optical path (1), an acousto-optic modulator power stabilization optical path (2), an electro-optic modulator pump modulation optical path (3) and a sensor probe cross-shaped double-beam detection optical path (4); the Doppler frequency stabilization optical path (1) divides a light beam into two beams, the first beam is used for frequency stabilization, and the second beam is used for power stabilization through the acousto-optic modulator power stabilization optical path (2); the stabilized light of the acousto-optic modulator power stabilization optical path (2) enters the electro-optic modulator pump modulation optical path (3) for pump modulation, and the modulated light enters the sensor probe cross-shaped double-beam detection optical path (4) to polarize Cs atoms and cause He atoms to undergo Larmor precession, and the second laser beam of the sensor probe cross-shaped double-beam detection optical path (4) enters the atomic gas chamber perpendicular to the first modulated laser beam to detect He atoms.

[0008] Preferably, the frequency stabilization module of the Doppler elimination dual-color frequency stabilization technology adopts the Doppler elimination frequency stabilization technology, and after obtaining the frequency information through the Cs atomic gas chamber, the frequency of the laser is locked through the electronic control unit. The specific optical path process is as follows: the laser emitted by the first pump laser (1-1) is converted into linear polarized light through the first pump laser optoelectronic isolator (ISO) (1-2), and the linear polarized light is divided into two laser beams by the first beam splitter (1-3). The first laser beam enters the acousto-optic modulator power stabilization optical path (2), and the second laser beam is reflected to the Cs atomic gas chamber (1-5) by the first reflector (1-4), and then passes through the attenuation plate (1-6), the polarizer (1-7), and the second reflector (1-8) in sequence. The light reflected by the second reflector (1-8) passes through the polarizer (1-7), the attenuation plate (1-6), and the Cs atomic gas chamber (1-5) in sequence and then enters the first reflector (1-5). The light beam is reflected by the first reflector (1-4) to the first beam splitter (1-3), and the first beam splitter (1-3) will split the light beam into two beams again, one beam is blocked by the first pump laser optoelectronic isolator (ISO) (1-2), and the other beam is reflected to the third reflector (1-9), and the reflected light is sequentially incident on the polarization beam splitter (PBS) (1-12) through the half wave plate (λ / 2) (1-10) and the quarter wave plate (λ / 4) (1-11), and the outgoing light is respectively received by the first photodetector (PD) (1-13) and the second photodetector (PD) (1-14), and the laser frequency stabilization is completed through the NI chassis (National Instruments) programming control system (1-15). The NI chassis is a host developed by National Instruments (abbreviated as NI) of the United States.

[0009] Preferably, the first beam splitter lens (1-3) is a 1:9 beam splitter lens.

[0010] Preferably, the first laser beam separated by the first beam splitter (1-3) in the Doppler frequency stabilization optical path 1 enters the acousto-optic modulator (AOM) (2-2) through the fourth reflector (2-1) of the acousto-optic modulator power stabilization optical path (2) to be diffracted, and the diffracted zero-order light enters the second laser photoelectric isolator (2-3), and then passes through the fifth reflector (2-4) and the sixth reflector (2-5) in sequence, and is then split into two beams by the second beam splitter (2-6), the first laser beam enters the electro-optic modulator pump modulation optical path (3) for modulation, and the second laser beam The third photodetector (PD) (2-7) receives the output power of the laser and samples it in real time. The light intensity obtained by the third photodetector (PD) (2-7) is converted into an electrical signal and connected to the noise reduction control system (NoiseEater) (2-8), and then fed back to the acousto-optic modulator (AOM) (2-2) for real-time modulation to form a closed-loop feedback system to achieve the stability of the laser power. Thus, the first laser beam output through the second beam splitter (2-6) can obtain a laser spot with stable frequency, stable power, uniform distribution, and steep boundaries. The noise reduction control system Noise Eater is a prior art, which is a laser power stabilization system for suppressing noise.

[0011] Preferably, the second beam splitter lens (2-6) is a 5:5 beam splitter lens.

[0012] Preferably, the first laser beam output by the second beam splitter (2-6) in the power stabilization optical path of the acousto-optic modulator enters the electro-optic modulator (EOM) (3-1) of the electro-optic modulator pump modulation optical path (3), and the electro-optic control system (3-2) (which belongs to the prior art, i.e., uses an electro-optic modulator and a controller) gives the electro-optic modulator (EOM) (3-1) a control signal, so that the electro-optic modulator (EOM) (3-1) pumps and modulates the light with stable frequency and power, and then outputs it through the seventh reflector (3-3).

[0013] Preferably, the light reflected by the seventh reflector (3-3) in the pump modulation optical path of the electro-optic modulator is reflected into the Cs-He atomic gas chamber (4-2) through the eighth reflector (4-1) of the cross-shaped double-beam detection optical path (4) of the sensor probe, and the Cs-He atomic gas chamber (4-2) excites the He atoms to a metastable state by the Cs-He excitation circuit (Pulse discharge) (4-4), so that the light entering the Cs-He atomic gas chamber (4-2) realizes polarization of the Cs atoms and Larmor precession modulation of the He atoms, the temperature control module (4-5) realizes temperature control and monitoring of the Cs-He atomic gas chamber (4-2), the light entering the Cs-He atomic gas chamber (4-2) through the eighth reflector (4-1) is received by the fourth photodetector (4-3), and after the optical signal is converted into an electrical signal, it is connected to the NI chassis (National The optical path is monitored by a National Instruments programming control system; the laser emitted by the second laser (4-6) enters the Cs-He atomic gas chamber (4-2) to detect the He atoms, and the detected light is split by a polarization beam splitter (PBS) (4-7) and then enters a fifth photodetector (PD) (4-8) and a sixth photodetector (PD) (4-9) to detect the frequency of the He atoms, and the detection data is converted by a NI chassis (National Instruments) programming control system (4-10) to detect the magnetic field.

[0014] The Bell-Bloom atomic magnetometer is an all-optical atomic magnetometer developed by Bell and Bloom. It is a type of atomic magnetometer structure and can also be called an all-optical Cs- 4 He atomic magnetometer.

[0015] The advantages of the present invention compared with the prior art are:

[0016] (1) The present invention performs a multiple folding design on the optical path, thereby ensuring stable frequency and power of the pump laser and uniform energy distribution, thereby ensuring stable output of the pump modulation optical path.

[0017] (2) The present invention performs dual-beam detection on the Cs-He gas chamber, which not only eliminates the optical frequency shift error commonly present in optically pumped magnetometers, but also avoids the low sensitivity caused by excessive atomic line width and improves the accuracy of cesium helium atomic magnetometers.

[0018] (3) The optical path layout of the present invention is reasonable, the structure is compact, the installation and adjustment are convenient, the experimental operation is simple, the parameter adjustment is convenient, and the response speed is fast, which provides a basis for the development of a high-precision Cs-He magnetometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1The Bell-Bloom type Cs- 4 Diagram of the structure of the He atomic magnetometer.

[0020] In the figure: 1 is the Doppler elimination frequency stabilization optical path, 2 is the acousto-optic modulator power stabilization optical path, 3 is the electro-optic modulator pump modulation optical path, 4 is the sensor probe cross double beam detection optical path, 1-1 is the first pump laser, 1-2 is the pump light optoelectronic isolator (ISO), 1-3 is the first beam splitter (1:9), 1-1 is the first reflector, 1-5 is the Cs atomic gas chamber, 1-6 is the attenuation plate, 1-7 is the polarizer, 1-8 is the second reflector, 1-9 is the third reflector, 1-10 is the half wave plate (λ / 2), 1-11 is the quarter wave plate (λ / 4), 1-12 is the polarization beam splitter (PBS), 1-13 is the first photodetector (PD), 1-14 is the second photodetector (PD), 1-15 is the NI chassis (National Instruments) programming control system, 2-1 is the fourth reflector, 2-2 is an acousto-optic modulator (AOM), 2-3 is the second laser optoelectronic isolator (ISO), 2-4 is the fifth reflector, 2-5 is the sixth reflector, 2-6 is the second beam splitter (5:5), 2-7 is the third photodetector (PD), 2-8 is a noise reduction control system (Noise Eater), 3-1 is an electro-optic modulator (EOM), 3-2 is an electro-optic control system, 3-3 is the seventh reflector, 4-1 is the eighth reflector, 4-2 is a Cs-He atomic gas chamber, 4-3 is the fourth photodetector, 4-4 is a Cs-He excitation circuit (Pulsedischarge), 4-5 is a temperature control module, 4-6 is the second detection laser, 4-7 is a polarization beam splitter (PBS), 4-8 is the fifth photodetector (PD), 4-9 is the sixth photodetector (PD), and 4-10 is a NI chassis (National Instruments) programming control system. DETAILED DESCRIPTION

[0021] The present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, the preferred embodiment of the present invention relates to a Bell-Bloom type Cs- 4The He atomic magnetometer includes a Doppler frequency stabilization optical path 1, an acousto-optic modulator power stabilization optical path 2, an electro-optic modulator pump modulation optical path 3, and a sensor probe cross double-beam detection optical path 4. The Doppler frequency stabilization optical path 1 divides the light beam into two beams, the first beam is used for frequency stabilization, and the second beam is power-stabilized through the acousto-optic modulator power stabilization optical path 2; the stabilized light of the acousto-optic modulator power stabilization optical path 2 is pump-modulated through the electro-optic modulator pump modulation optical path 3, and the modulated light enters the sensor probe cross double-beam detection optical path 4 to polarize the Cs atoms and cause the He atoms to undergo Larmor precession. The second laser beam of the sensor probe cross double-beam detection optical path 4 enters the atomic gas chamber perpendicular to the first modulated laser beam to detect the He atoms. The specific structure and principle are described as follows.

[0023] In this embodiment, the Doppler-eliminating frequency stabilization optical path 1 adopts the Doppler-eliminating frequency stabilization technology, and after obtaining the frequency information through the Cs atomic gas chamber, the frequency of the laser is locked through the electronic control unit. The specific optical path process is as follows: the laser emitted by the first pump laser 1-1 is converted into linear polarized light through the first pump laser optoelectronic isolator (ISO) 1-2, and the linear polarized light is divided into two laser beams by the first beam splitter (1:9) 1-3. The first laser beam enters the acousto-optic modulator power stabilization optical path 2, and the second laser beam is reflected by the first reflector 1-4 to the Cs atomic gas chamber 1-5, and then passes through the attenuation plate 1-6, the polarizer 1-7, and the second reflector 1-8 in turn. The light reflected by the second reflector 1-8 passes through the polarizer 1-7, the attenuation plate 1-6, and the Cs atomic gas chamber 1-5 in turn and enters the first reflector 1-4 , reflected by the first reflector 1-4 to the first beam splitter (1:9) 1-3, the first beam splitter (1:9) 1-3 will split the light beam into two beams again, one beam is blocked by the first pump laser optoelectronic isolator (ISO) 1-2, and the other beam is reflected to the third reflector 1-9, the reflected light is sequentially incident on the polarization beam splitter (PBS) 1-12 through the half wave plate (λ / 2) 1-10 and the quarter wave plate (λ / 4) 1-11, the emitted light is respectively received by the first photodetector (PD) 1-13 and the second photodetector (PD) 1-14, and the laser frequency stabilization is completed through the NI chassis (National Instruments) programming control system 1-15.

[0024] The first laser beam separated by the first beam splitter (1:9) 1-3 in the Doppler frequency stabilization optical path 1 enters the acousto-optic modulator (AOM) 2-2 through the fourth reflector 2-1 of the acousto-optic modulator power stabilization optical path 2 for diffraction. The diffracted zero-order light enters the second laser photoelectric isolator 2-3, and then passes through the fifth reflector 2-4 and the sixth reflector 2-5 in sequence, and is split into two beams by the second beam splitter (5:5) 2-6. The first laser beam enters the electro-optic modulator pump modulation optical path 3 for modulation, and the second laser beam is received by the third photodetector (PD) 2-7, and the output power of the laser is sampled in real time. The light intensity obtained by the third photodetector (PD) 2-7 is converted into an electrical signal and connected to the noise reduction control system (Noise Reduction Control System). Eater) 2-8, and then fed back to the acousto-optic modulator (AOM) 2-2 for real-time modulation, forming a closed-loop feedback system to achieve laser power stability, thereby the first laser beam output through the second beam splitter (5:5) 2-6 can obtain a laser spot with stable frequency, stable power, uniform distribution and steep boundaries.

[0025] The first laser beam output by the second beam splitter (5:5) 2-6 in the power stabilization optical path 2 of the acousto-optic modulator enters the electro-optic modulator (EOM) 3-1 of the electro-optic modulator pump modulation optical path 3, and the electro-optic control system 3-2 gives the electro-optic modulator (EOM) 3-1 a control signal to make the electro-optic modulator (EOM) 3-1 pump modulate the light with stable frequency and power, and then output it through the seventh reflector 3-3.

[0026] The light reflected by the seventh reflector 3-3 in the electro-optic modulator pump modulation optical path 3 is reflected into the Cs-He atomic gas chamber 4-2 through the eighth reflector 4-1 of the sensor probe cross double beam detection optical path 4. The Cs-He atomic gas chamber 4-2 excites the He atoms to a metastable state by the Cs-He excitation circuit (Pulse discharge) 4-4, so that the light entering the Cs-He atomic gas chamber 4-2 realizes polarization of the Cs atoms and Larmor precession modulation of the He atoms. The temperature control module 4-5 realizes temperature control and monitoring of the Cs-He atomic gas chamber 4-2. The light entering the Cs-He atomic gas chamber 4-2 through the seventh reflector 4-1 is received by the fourth photodetector 4-3. After the optical signal is converted into an electrical signal, it is connected to the NI chassis (National The optical path is monitored by a National Instruments (NI) programming control system; the laser emitted by the second laser 4-6 enters the Cs-He atomic gas chamber 4-2 to detect the He atoms, and the detected light is split by a polarization beam splitter (PBS) 4-7 and then enters a fifth photodetector (PD) 4-8 and a sixth photodetector (PD) 4-9 to detect the frequency of the He atoms, and the detection data is converted by a NI chassis (National Instruments) programming control system 4-10 to detect the magnetic field.

[0027] The contents not described in detail in the specification of the present invention may adopt the existing technologies known to those skilled in the art.

[0028] The invention discloses a Bell-Bloom type Cs- 4 He atomic magnetometer, which is used for Mz type Cs- 4 The accuracy of the He magnetometer is limited by the technical problems of excessive line width and low sensitivity, so improvements are made. The present invention includes a frequency stabilization module using Doppler frequency stabilization technology, a power stabilization module using an acousto-optic modulator for laser modulation, a pump module using an electro-optic modulator for laser modulation, and a sensor probe module for cross-shaped dual-beam laser detection. The frequency stabilization module stabilizes the pump light of the atomic magnetometer; the power stabilization module stabilizes the frequency of the pump light of the atomic magnetometer; the pump module electro-optically modulates the stabilized pump light; the sensor module uses the modulated light to polarize Cs atoms and to cause He atoms to perform Larmor precession. The light emitted by another laser is perpendicular to the modulated light and hits the Cs-He gas chamber, which is connected to the NI host after PBS, and the magnetic field value is obtained after signal processing. The present invention has a perfect structural layout, simple experimental operation, and high integration, and is a high-accuracy Cs- 4 He provided technical support for the development of magnetometer.

Claims

1. A Bell-Bloom type Cs- 4 He atomic magnetometer, characterized in that: The invention comprises a Doppler frequency stabilization optical path (1), an acousto-optic modulator power stabilization optical path (2), an electro-optic modulator pump modulation optical path (3) and a sensor probe cross-shaped double-beam detection optical path (4); the Doppler frequency stabilization optical path (1) divides a light beam into two beams, the first beam is used for frequency stabilization, and the second beam is used for power stabilization through the acousto-optic modulator power stabilization optical path (2); the stabilized light of the acousto-optic modulator power stabilization optical path (2) enters the electro-optic modulator pump modulation optical path (3) for pump modulation, and the modulated light enters the sensor probe cross-shaped double-beam detection optical path (4) to polarize Cs atoms and cause He atoms to undergo Larmor precession, and the second laser beam of the sensor probe cross-shaped double-beam detection optical path (4) enters the atomic gas chamber perpendicular to the first modulated laser beam to detect He atoms; The specific structure of the Doppler-eliminating frequency stabilization optical path (1) is as follows: the laser light emitted by the first pump laser (1-1) is converted into linear polarization light by the first pump laser photoelectric isolator (1-2), and the linear polarization light is divided into two laser beams by the first beam splitter (1-3). The first laser beam enters the acousto-optic modulator power stabilization optical path (2), and the second laser beam is reflected by the first reflector (1-4) to the Cs atomic gas chamber (1-5), and then passes through the attenuation plate (1-6), the polarization plate (1-7), and the second reflector (1-8) in sequence. The light reflected by the second reflector (1-8) passes through the polarization plate (1-7), the attenuation plate (1-6), the Cs atomic gas chamber (1-5), and the second reflector (1-8) in sequence. The light beam enters the first reflector (1-4) after passing through the sub-gas chamber (1-5), and is reflected by the first reflector (1-4) to the first beam splitter (1-3). The first beam splitter (1-3) splits the light beam into two beams, one of which is blocked by the first pump laser photoelectric isolator (1-2), and the other is reflected to the third reflector (1-9). The reflected light is sequentially incident on the polarization beam splitter (1-12) through the half-wave plate (1-10) and the quarter-wave plate (1-11). The emitted light is respectively received by the first photodetector (1-13) and the second photodetector (1-14), and the laser frequency stabilization is completed through the NI chassis programming control system (1-15). The first laser beam split by the first beam splitter (1-3) in the Doppler frequency stabilization optical path (1) enters the acousto-optic modulator (2-2) through the fourth reflector (2-1) of the acousto-optic modulator power stabilization optical path (2) to be diffracted, the diffracted zero-order light enters the second laser photoelectric isolator (2-3), and then passes through the fifth reflector (2-4) and the sixth reflector (2-5) in sequence, and is then split into two beams by the second beam splitter (2-6), the first laser beam enters the electro-optic modulator pump modulation optical path (3) for modulation, the second laser beam is received by the third photodetector (2-7), the output power of the laser is sampled in real time, the light intensity obtained by the third photodetector (2-7) is converted into an electrical signal and connected to the noise reduction control system (2-8), and then fed back to the acousto-optic modulator (2-2) for real-time modulation, forming a closed-loop feedback system; The first laser beam outputted by the second beam splitter (2-6) in the power stabilization optical path (2) of the acousto-optic modulator enters the electro-optic modulator (3-1) of the electro-optic modulator pump modulation optical path (3), and the electro-optic control system (3-2) outputs a control signal to the electro-optic modulator (3-1), so that the electro-optic modulator (3-1) performs pump modulation on the light with stable frequency and power, and then outputs the light through the seventh reflector (3-3); Light reflected by the seventh reflector (3-3) in the electro-optic modulator pump modulation optical path (3) is reflected into the Cs-He atomic gas chamber (4-2) via the eighth reflector (4-1) of the sensor probe cross double-beam detection optical path (4). The Cs-He atomic gas chamber (4-2) excites He atoms to a metastable state by a Cs-He excitation circuit (4-4), so that the light entering the Cs-He atomic gas chamber (4-2) realizes polarization of the Cs atoms and Larmor precession modulation of the He atoms. The temperature control module (4-5) realizes temperature control and monitoring of the Cs-He atomic gas chamber (4-2). The light entering the Cs-He atomic gas chamber (4-2) is received by the fourth photodetector (4-3), and after the optical signal is converted into an electrical signal, it is connected to the second NI chassis programming control system (4-10) to monitor the optical path; the laser light emitted by the second laser (4-6) enters the Cs-He atomic gas chamber (4-2) to detect the He atoms, and the detected light is split by the polarization beam splitter (4-7) and enters the fifth photodetector (4-8) and the sixth photodetector (4-9) respectively to detect the frequency of the He atoms, and the detection data is converted by the second NI chassis programming control system (4-10) to detect the magnetic field.

2. A Bell-Bloom type Cs- 4 He atomic magnetometer, characterized in that: The first beam splitter (1-3) is a 1:9 beam splitter.

3. A Bell-Bloom type Cs- 4 He atomic magnetometer, characterized in that: The second beam splitter (2-6) is a 5:5 beam splitter.

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