A high-sensitivity all-optical atomic magnetometer device based on amplitude modulation

Abstract

A high-sensitivity all-optical atomic magnetometer device based on amplitude modulation, based on light source amplitude modulation technology, can avoid the bandwidth loss and magnetic field crosstalk caused by magnetic field modulation of the magnetic field modulated SERF atomic magnetometer. At the same time, by switching the all-optical SERF atomic magnetometer to perform DC output and first harmonic demodulation output, it is beneficial to maintain high sensitivity performance within the bandwidth range of the kHz level under high-frequency modulation, so as to play a promoting role in related applications requiring high-bandwidth magnetic field measurement.

Description

Technical Field

[0001] The present invention relates to the technical field of high-sensitivity all-optical atomic magnetometers, and in particular to a high-sensitivity all-optical atomic magnetometer device based on amplitude modulation. Based on light source amplitude modulation technology, the device can avoid bandwidth loss and magnetic field crosstalk caused by magnetic field modulation of a SERF atomic magnetometer. At the same time, by switching the all-optical SERF atomic magnetometer to perform DC output and first harmonic demodulation output, the device is advantageously able to maintain high sensitivity within a kHz-level bandwidth under high-frequency modulation, thereby promoting related applications requiring high-bandwidth magnetic field measurement. Background Art

[0002] With the technological innovation and emergence of new instruments in the fields of optics, materials science, micro-nano processing, etc., the atomic magnetometer integrated on this basis has both high sensitivity and small size, and is an important development direction of the new generation of ultra-high sensitivity magnetometers. Among them, the magnetic field measurement sensitivity based on the spin-exchange relaxation-free (SERF) effect has entered the sub-femtoliter / Hz range. 1 / 2 It is of the highest level of human weak magnetic field detection at present, and has very broad prospects in biomedical and basic physics detection fields such as biomagnetic imaging, geological exploration, and dark matter discovery.

[0003] The bandwidth of traditional magnetic field modulated SERF atomic magnetometers is in the hundreds of Hz range. Although it is possible to expand its bandwidth by closing the magnetic field loop, this method requires complex equipment, and the achievable bandwidth range depends on the specific parameters of the compensation coil. In some studies, although the bandwidth has been expanded, the sensitivity has been reduced to pT / Hz. 1 / 2 Based on this, the present invention proposes a high-sensitivity all-optical atomic magnetometer device based on amplitude modulation. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: to overcome the shortcomings of the existing technology and propose a high-sensitivity all-optical atomic magnetometer device based on amplitude modulation. Based on the light source amplitude modulation technology, it can avoid the bandwidth loss and magnetic field crosstalk caused by the magnetic field modulation of the magnetic field modulation type SERF atomic magnetometer. At the same time, by switching the all-optical SERF atomic magnetometer to perform DC output and first harmonic demodulation output, it is beneficial to maintain high sensitivity performance within a bandwidth range of the kHz level under high-frequency modulation, so as to play a promoting role in related applications requiring high-bandwidth magnetic field measurement.

[0005] The technical solutions of the present invention are as follows:

[0006] A high-sensitivity all-optical atomic magnetometer device based on amplitude modulation is characterized by including a pumping system and a detection system. The pumping system includes a pumping laser and an acousto-optic modulator. The pumping light emitted by the pumping laser is amplitude-modulated by the acousto-optic modulator and then enters the alkali metal gas chamber along the positive z-axis to complete the polarization of the alkali metal atoms. The detection system includes a detection laser, a differential detection device, a transimpedance amplifier, and a lock-in amplifier. The detection light emitted by the detection laser passes through the alkali metal gas chamber along the negative y-axis and outputs a differential detection signal through the differential detection device. The differential detection signal is amplified by the transimpedance amplifier and then enters the lock-in amplifier to complete DC demodulation and first harmonic demodulation. By switching the DC demodulation output and the first harmonic demodulation output, the all-optical atomic magnetometer can maintain fT / Hz within a bandwidth range of the order of kHz under high-frequency modulation. 1 / 2 High sensitivity performance of the order of magnitude.

[0007] The lock-in amplifier is respectively connected to a host computer, the acousto-optic modulator, and a signal generator. The acousto-optic modulator is connected to a first collimator via a polarization-maintaining optical fiber. The first collimator is connected to a second photodetector via a first 1 / 2 wave plate, a first polarization beam splitter, a first 1 / 4 wave plate, and the alkali metal gas chamber. The signal generator is respectively connected to a first three-axis magnetic field coil and a second three-axis magnetic field coil. The first three-axis magnetic field coil and the second three-axis magnetic field coil both surround a ceramic oven. A non-magnetic electric heating coil surrounding the alkali metal gas chamber is provided in the ceramic oven. The host computer calculates and processes data of the DC demodulation output and the first harmonic demodulation output of the lock-in amplifier.

[0008] The signal generator generates a high-frequency square wave signal to drive the acousto-optic modulator to modulate the amplitude of the pumping light.

[0009] The detection laser is connected to the second collimator through a polarization-maintaining optical fiber. The second collimator is connected to the incident end of the third polarization beam splitter prism through a second 1 / 2 wave plate, a second polarization beam splitter prism, a first reflector, a second reflector and a third 1 / 2 wave plate in sequence. The transmission end of the third polarization beam splitter prism is connected to the first input end of the subtractor through a fifth photodetector. The reflection end of the third polarization beam splitter prism is connected to the second input end of the subtractor through a third reflector and a fourth photodetector in sequence. The output end of the subtractor is connected to the lock-in amplifier via a transimpedance amplifier.

[0010] When the frequency of the magnetic field to be measured meets the bandwidth of the DC output, the lock-in amplifier is used to demodulate the DC signal output; when the frequency of the magnetic field to be measured exceeds the bandwidth of the DC output, the lock-in amplifier is used to demodulate the first harmonic signal output.

[0011] The second three-axis magnetic field coil is used to compensate for the three-axis residual magnetic field, and the first three-axis magnetic field coil is used to apply a calibration magnetic field in the sensitive axis direction.

[0012] The alkali metal atoms in the alkali metal gas chamber include one of potassium atoms, rubidium atoms, and cesium atoms, and nitrogen gas serving as a buffer gas and a quenching gas.

[0013] The pumping light frequency emitted by the pumping laser is at the center of the alkali metal atom D1 line used; the detection light frequency emitted by the detection laser is detuned by more than 100 GHz near the alkali metal atom D1 line used.

[0014] The DC component P of the output signal of the all-optical atomic magnetometer DC and the first harmonic component P ω The expression is as follows:

[0015]

[0016]

[0017] Where R0 is the maximum pumping rate, γ e is the classical electron radius, B x is the residual magnetic field in the x-axis direction, Γ is the magnetic resonance linewidth, ω is the modulation frequency, q is the nuclear slowing factor, and t is time.

[0018] The advantages of the present invention compared with the prior art are:

[0019] (1) The all-optical modulation scheme is adopted to reduce the crosstalk and noise caused by magnetic field modulation and improve the measurement sensitivity of the magnetometer.

[0020] (2) High-sensitivity signals are obtained by switching the output mode at different frequencies. The operation is simple and is especially suitable for high-frequency modulation. It can achieve high bandwidth while maintaining high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a schematic structural diagram of a high-sensitivity all-optical atomic magnetometer device based on amplitude modulation.

[0022] The accompanying drawings are marked as follows: 1-pumping laser; 2-acousto-optic modulator; 3-first collimator (the first collimator is connected to the acousto-optic modulator via a polarization-maintaining fiber); 4-first 1 / 2 wave plate; 5-first polarization beam splitter; 6-first photodetector; 7-first 1 / 4 wave plate; 8-first three-axis magnetic field coil; 9-second three-axis magnetic field coil; 10-ceramic oven; 11-non-magnetic electric heating coil; 12-alkali metal gas chamber; 13-second photodetector; 14-detection laser (the detection laser is connected to the second collimator via a polarization-maintaining fiber); 1 5-second collimator; 16-second 1 / 2 wave plate; 17-second polarization beam splitter; 18-third photodetector; 19-first reflector; 20-second reflector; 21-third 1 / 2 wave plate; 22-third polarization beam splitter; 23-third reflector; 24-fourth photodetector; 25-fifth photodetector; 26-subtractor; 27-transimpedance amplifier; 28-phase-locked amplifier; 29-host computer; 30-signal generator; 31-magnetic shielding barrel; xyz-Cartesian coordinate three axes (x-axis, y-axis, z-axis). DETAILED DESCRIPTION

[0023] Below is the attached figure ( Figure 1 ) and Examples illustrate the present invention.

[0024] Figure 1 This is a schematic diagram of the structure of a high-sensitivity all-optical atomic magnetometer device based on amplitude modulation for implementing the present invention. Figure 1 As shown, a high-sensitivity all-optical atomic magnetometer device based on amplitude modulation includes a pumping system and a detection system. The pumping system includes a pumping laser 1 and an acousto-optic modulator 2. The pumping light emitted by the pumping laser 1 is amplitude-modulated by the acousto-optic modulator 2 and then enters the alkali metal gas chamber 12 along the positive direction of the z-axis to complete the polarization of the alkali metal atoms. The detection system includes a detection laser 14, a differential detection device, a transimpedance amplifier 27, and a lock-in amplifier 28. The detection light emitted by the detection laser 14 passes through the alkali metal gas chamber 12 along the negative direction of the y-axis and outputs a differential detection signal through the differential detection device. The differential detection signal is amplified by the transimpedance amplifier 27 and then enters the lock-in amplifier 28 to complete DC demodulation and first harmonic demodulation. By switching the DC demodulation output and the first harmonic demodulation output, the all-optical atomic magnetometer can maintain fT / Hz within a bandwidth range of the order of kHz under high-frequency modulation. 1 / 2 High sensitivity performance of the order of magnitude.

[0025] The lock-in amplifier 28 is connected to a host computer 29, the acousto-optic modulator 2, and a signal generator 30. The acousto-optic modulator 2 is connected to a first collimator 3 via a polarization-maintaining fiber. The first collimator 3 is connected to a second photodetector 13 via a first half-wave plate 4, a first polarization beam splitter 5, a first quarter-wave plate 7, and the alkali metal gas chamber 12. The signal generator 30 is connected to a first three-axis magnetic field coil 8 and a second three-axis magnetic field coil 9, both of which surround a ceramic oven 10. The ceramic oven 10 is provided with a non-magnetic electric heating coil 11 surrounding the alkali metal gas chamber 12. The host computer 29 calculates and processes the DC demodulation output and the first harmonic demodulation output of the lock-in amplifier 28. The signal generator 30 generates a high-frequency square wave signal to drive the acousto-optic modulator 2 to modulate the amplitude of the pump light.

[0026] The detection laser 14 is connected to the second collimator 15 through a polarization-maintaining optical fiber. The second collimator 15 is connected to the incident end of the third polarization beam splitter prism 22 through a second 1 / 2 wave plate 16, a second polarization beam splitter prism 17, a first reflector 19, a second reflector 20 and a third 1 / 2 wave plate 21 in sequence. The transmission end of the third polarization beam splitter prism 22 is connected to the first input end of the subtractor 26 through a fifth photodetector 25. The reflection end of the third polarization beam splitter prism 22 is connected to the second input end of the subtractor 26 through a third reflector 23 and a fourth photodetector 24 in sequence. The output end of the subtractor 26 is connected to the lock-in amplifier 28 via a transimpedance amplifier 27.

[0027] When the frequency of the magnetic field to be measured meets the bandwidth of the DC output, the phase-locked amplifier 28 is used to demodulate the DC signal output; when the frequency of the magnetic field to be measured exceeds the bandwidth of the DC output, the phase-locked amplifier 28 is used to demodulate the first harmonic signal output. The second three-axis magnetic field coil 9 is used to compensate for the three-axis residual magnetic field, and the first three-axis magnetic field coil 8 is used to apply a calibration magnetic field in the sensitive axis direction. The alkali metal atoms in the alkali metal gas chamber 12 include one of potassium atoms, rubidium atoms, and cesium atoms, as well as nitrogen as a buffer gas and quenching gas. The pumping light frequency emitted by the pump laser 1 is at the center of the alkali metal atom D1 line used; the detection light frequency emitted by the detection laser 14 is detuned by more than 100 GHz near the alkali metal atom D1 line used.

[0028] The reflective end of the first polarization beam splitter prism 5 is connected to the first photodetector 6. The reflective end of the second polarization beam splitter prism 17 is connected to the third photodetector 18. The DC component P of the output signal of the all-optical atomic magnetometer DC and the first harmonic component P ω The expression is as follows:

[0029]

[0030]

[0031] Where R0 is the maximum pumping rate, γ e is the classical electron radius, B x is the residual magnetic field in the x-axis direction, Γ is the magnetic resonance linewidth, ω is the modulation frequency, q is the nuclear slowing factor, and t is time.

[0032] The present invention relates to a high-sensitivity all-optical atomic magnetometer based on amplitude modulation. By employing light source amplitude modulation, this method avoids the bandwidth loss and magnetic field crosstalk associated with magnetic field modulation in SERF atomic magnetometers. Furthermore, by switching between DC output and first harmonic demodulation output, the all-optical SERF atomic magnetometer maintains high sensitivity within a kHz-scale bandwidth under high-frequency modulation. This significantly advances the use of atomic magnetometers in applications requiring high-bandwidth magnetic field measurements.

[0033] Figure 1 A high-sensitivity all-optical atomic magnetometer device based on amplitude modulation is shown, comprising a pumping system and a detection system. In the pumping system, the pumping light emitted by the pumping laser 1 is amplitude-modulated by the acousto-optic modulator 2 and then enters the alkali metal gas chamber 12 to complete the polarization of the alkali metal atoms. In the detection system, the detection light emitted by the detection laser 14 enters the alkali metal gas chamber 12 orthogonally to the pumping light and performs differential detection. The all-optical atomic magnetometer operates in the SERF state, that is, it meets the working conditions of high atomic density and zero field. By switching the DC output and the first harmonic demodulation output, the all-optical atomic magnetometer can maintain fT / Hz within a bandwidth range of the order of kHz under high-frequency modulation. 1 / 2 High sensitivity performance of the order of magnitude.

[0034] The DC component P of the output signal of the all-optical SERF atomic magnetometer DC and the first harmonic component P ω It can be expressed as:

[0035]

[0036]

[0037] Where R0 is the maximum pumping rate, γ e is the classical electron radius, B x is the residual magnetic field in the x-axis direction, Γ is the magnetic resonance linewidth, ω is the modulation frequency, and q is the nuclear slowing factor.

[0038] The light emitted by the pump laser 1 is modulated by the acousto-optic modulator 2 and transmitted by the polarization-maintaining optical fiber to the first collimator 3. It is then split by the first 1 / 2 wave plate 4 and the first polarization beam splitter prism 5. The transmitted light passes through the 1 / 4 wave plate 7 and enters the alkali metal gas chamber 12 to polarize the alkali metal atoms. The light is then collected by the second photodetector 13, and the reflected light is collected by the first photodetector 6.

[0039] The light emitted by the detection laser 14 is transmitted via a polarization-maintaining fiber to a second collimator 15, and then split by a second half-wave plate 16 and a second polarization beam splitter prism 17. The transmitted light is reflected by a first reflector 19 and enters the alkali metal gas chamber 12 to detect atomic precession caused by the magnetic field. The light is then reflected by a second reflector 20 and passes through a third half-wave plate 21 to enter a third polarization beam splitter prism 22 and is split. The reflected light from the second polarization beam splitter prism 17 is collected by a third photodetector 18. The transmitted light from the third polarization beam splitter prism 22 is collected by a fifth photodetector 25 and enters a subtractor 26. The reflected light from the third polarization beam splitter prism 22 is reflected by a third reflector 23 and collected by a fourth photodetector 24 before entering a subtractor 26.

[0040] The alkali metal gas chamber 12 is surrounded by a non-magnetic electric heating coil 11, a ceramic oven 10, a first three-axis magnetic field coil 8, a second three-axis magnetic field coil 9, and a magnetic shielding barrel 31, arranged in order from the inside out. The first three-axis magnetic field coil 8 and the second three-axis magnetic field coil 9 are both connected to a signal generator 30. The second three-axis magnetic field coil 9 is used to compensate for the three-axis residual magnetic field, and the first three-axis magnetic field coil 8 is used to apply a calibration magnetic field in the sensitive axis direction.

[0041] The pumping light frequency emitted by the pumping laser 1 must be in the center of the alkali metal atom D1 line used; the laser frequency emitted by the detection laser 14 must be detuned by more than 100 GHz near the alkali metal atom D1 line used.

[0042] The alkali metal atoms in the alkali metal gas chamber 12 are one of potassium atoms, rubidium atoms, and cesium atoms, and should contain a buffer gas and a quenching gas at a total pressure of about 1 atm (atmospheric pressure). Both the buffer gas and the quenching gas are nitrogen.

[0043] The output signal of the subtractor 26 is amplified by the transimpedance amplifier 27 and then enters the phase-locked amplifier 28 to complete DC and first harmonic demodulation, and then enters the host computer 29 for calculation and data processing.

[0044] When the frequency of the magnetic field to be measured meets the bandwidth of the DC output, the lock-in amplifier 28 is used to demodulate the DC signal output; when the frequency of the magnetic field to be measured exceeds the bandwidth of the DC output, the lock-in amplifier 28 is used to demodulate the first harmonic signal output.

[0045] The signal generator 30 generates a high-frequency square wave signal to drive the acousto-optic modulator 2 to modulate the amplitude of the pumping light.

[0046] Any content not described in detail in this specification is prior art known to those skilled in the art. It should be noted that the above description is intended to help those skilled in the art understand the present invention, but does not limit the scope of protection of the present invention. Any equivalent substitution, modification, improvement, and / or simplification of the above description that does not depart from the essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A high-sensitivity all-optical atomic magnetometer device based on amplitude modulation, characterized in that: The invention comprises a pumping system and a detection system. The pumping system comprises a pumping laser and an acousto-optic modulator. The pumping light emitted by the pumping laser is amplitude-modulated by the acousto-optic modulator and then enters the alkali metal gas chamber along the positive direction of the z-axis to complete the polarization of the alkali metal atoms. The detection system comprises a detection laser, a differential detection device, a transimpedance amplifier and a lock-in amplifier. The detection light emitted by the detection laser passes through the alkali metal gas chamber along the negative direction of the y-axis and then outputs a differential detection signal through the differential detection device. The differential detection signal is amplified by the transimpedance amplifier and then enters the lock-in amplifier to complete DC demodulation and first harmonic demodulation. By switching the DC demodulation output and the first harmonic demodulation output, the all-optical atomic magnetometer can maintain fT / Hz within a bandwidth range of the order of kHz under high-frequency modulation. 1 / 2 High sensitivity performance of magnitude; When the frequency of the magnetic field to be measured meets the bandwidth of the DC output, the lock-in amplifier is used to demodulate the DC signal output; when the frequency of the magnetic field to be measured exceeds the bandwidth of the DC output, the lock-in amplifier is used to demodulate the first harmonic signal output; The DC component P of the output signal of the all-optical atomic magnetometer DC and the first harmonic component P ω The expression is as follows: Where R0 is the maximum pumping rate, γ e is the classical electron radius, B x is the residual magnetic field in the x-axis direction, Γ is the magnetic resonance linewidth, ω is the modulation frequency, q is the nuclear slowing factor, and t is time.

2. The high-sensitivity all-optical atomic magnetometer device based on amplitude modulation according to claim 1, characterized in that: The lock-in amplifier is respectively connected to a host computer, the acousto-optic modulator, and a signal generator. The acousto-optic modulator is connected to a first collimator via a polarization-maintaining optical fiber. The first collimator is connected to a second photodetector via a first 1 / 2 wave plate, a first polarization beam splitter, a first 1 / 4 wave plate, and the alkali metal gas chamber. The signal generator is respectively connected to a first three-axis magnetic field coil and a second three-axis magnetic field coil. The first three-axis magnetic field coil and the second three-axis magnetic field coil both surround a ceramic oven. A non-magnetic electric heating coil surrounding the alkali metal gas chamber is provided in the ceramic oven. The host computer calculates and processes data of the DC demodulation output and the first harmonic demodulation output of the lock-in amplifier.

3. The high-sensitivity all-optical atomic magnetometer device based on amplitude modulation according to claim 2, characterized in that: The signal generator generates a high-frequency square wave signal to drive the acousto-optic modulator to modulate the amplitude of the pumping light.

4. The high-sensitivity all-optical atomic magnetometer device based on amplitude modulation according to claim 1, characterized in that: The detection laser is connected to the second collimator through a polarization-maintaining optical fiber. The second collimator is connected to the incident end of the third polarization beam splitter prism through a second 1 / 2 wave plate, a second polarization beam splitter prism, a first reflector, a second reflector and a third 1 / 2 wave plate in sequence. The transmission end of the third polarization beam splitter prism is connected to the first input end of the subtractor through a fifth photodetector. The reflection end of the third polarization beam splitter prism is connected to the second input end of the subtractor through a third reflector and a fourth photodetector in sequence. The output end of the subtractor is connected to the lock-in amplifier via a transimpedance amplifier.

5. The high-sensitivity all-optical atomic magnetometer device based on amplitude modulation according to claim 2, characterized in that: The second three-axis magnetic field coil is used to compensate for the three-axis residual magnetic field, and the first three-axis magnetic field coil is used to apply a calibration magnetic field in the sensitive axis direction.

6. The high-sensitivity all-optical atomic magnetometer device based on amplitude modulation according to claim 1, characterized in that: The alkali metal atoms in the alkali metal gas chamber include one of potassium atoms, rubidium atoms, and cesium atoms, and nitrogen gas serving as a buffer gas and a quenching gas.

7. The high-sensitivity all-optical atomic magnetometer device based on amplitude modulation according to claim 1, characterized in that: The pumping light frequency emitted by the pumping laser is at the center of the alkali metal atom D1 line used; the detection light frequency emitted by the detection laser is detuned by more than 100 GHz near the alkali metal atom D1 line used.

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