阅读说明：本技术 一种碱金属原子磁强计自旋极化率空间分布原位测量系统及方法 (Alkali metal atom magnetometer spin polarizability spatial distribution in-situ measurement system and method ) 是由 李学文 郭强 张宁 王子轩 陆吉玺 孙畅 于 2021-08-18 设计创作，主要内容包括：本发明公开了一种碱金属原子磁强计自旋极化率空间分布的原位测量系统及方法,属于精密测量的技术领域,系统主要由激光器、激光稳定系统、激光扩束系统、分光棱镜、偏振元件、磁屏蔽系统、碱金属原子气室、光弹调制器、光电探测器、CMOS传感器、数据采集分析处理系统等组成,本发明理论依据合理,实验操作简单,对磁测量系统正常工作不会带来额外系统扰动,能实现准确测得碱金属原子气室工作状态的电子极化率分布,有利于基于极化率分布测量结果提高原子磁强计测量灵敏度,为超高灵敏极弱磁测量装置的研制提供了基础。(The invention discloses an in-situ measurement system and a method for spin polarizability spatial distribution of an alkali metal atom magnetometer, which belong to the technical field of precision measurement.)

1. An in-situ measurement system for spatial distribution of spin polarizability of an alkali metal atomic magnetometer, comprising: the device comprises a detection light laser, a detection light laser stabilizing system, a polarizer, a plane reflector, a photoelastic modulator, a detection light quarter-wave plate, an alkali metal atom air chamber, an analyzer and a photoelectric detector which are sequentially arranged according to the advancing direction of the detection light; the pumping light laser, the pumping light laser stabilizing system, the pumping light beam expanding system, the polarization beam splitter prism, the polaroid, the pumping light quarter-wave plate, the alkali metal atom air chamber and the second CMOS sensor are sequentially arranged in the other direction according to the advancing direction of the pumping light, and the other beam of refracted light of the polarization beam splitter prism enters the first CMOS sensor; the outer part of the alkali metal atom gas chamber is sequentially coated with a non-magnetic electric heating device, a heat insulation material cavity, a magnetic compensation coil and a magnetic shielding system from inside to outside; the photoelectric detector, the first CMOS sensor and the second CMOS sensor transmit data to the data acquisition, analysis and processing system.

2. The in-situ measurement system of the spatial distribution of the spin polarizability of the alkali metal atomic magnetometer of claim 1, wherein: the detection light laser and the pumping light laser are wavelength tunable semiconductor lasers working at lines corresponding to the alkali metal atoms D1 and D2 respectively, and the frequency power requirement of the alkali metal atom magnetometer on pumping/detection laser is met.

3. The in-situ measurement system of the spatial distribution of the spin polarizability of the alkali metal atomic magnetometer of claim 1, wherein: the detection light laser stabilizing system and the pumping light laser stabilizing system are stable in laser power, laser frequency, laser directivity and laser spot shape distribution.

4. The in-situ measurement system of the spatial distribution of the spin polarizability of the alkali metal atomic magnetometer of claim 1, wherein: the alkali metal atom air chamber is a cubic borosilicate glass bubble with the size of 25 multiplied by 25 mm, and the air chamber is filled with alkali metal atoms, buffer gas and quenching gas.

5. The in-situ measurement system for the spatial distribution of the spin polarizability of an alkali metal atomic magnetometer of claim 1, wherein: the effective receiving areas of the first CMOS sensor and the second CMOS sensor are 25 x 25 mm, the incident/transmission light spots can be completely received, the resolution is 2048 x 2048, 400 ten thousand pixel resolution, the size of a single pixel is 12.5 mu m, and micron-pixel-level ultrahigh-resolution data reading and storage of light spot energy distribution are realized.

6. The in-situ measurement system of the spatial distribution of the spin polarizability of the alkali metal atomic magnetometer of claim 1, wherein: the data acquisition, analysis and processing system comprises a phase-locked amplifier, a data acquisition system and a computer and is used for demodulating and amplifying the detection laser signal to realize the measurement of the extremely weak magnetic field; and reading and fitting the pumping laser attenuation information signal, and combining the function relation of the polarization rate and the pumping light intensity to realize the precise measurement of the spatial distribution of the spin polarization rate of the alkali metal atoms.

7. An in-situ measurement method for the spatial distribution of the spin polarizability of an alkali metal atomic magnetometer is characterized by comprising the following steps of:

(1) the detection laser emits detection laser, the detection laser sequentially passes through a detection light laser stabilizing system, a polarizer, a plane reflector, a photoelastic modulator, a detection light quarter-wave plate, an alkali metal atom air chamber, an analyzer and a photoelectric detector, the influence of low-frequency noise on a rotation angle signal is reduced based on the high-frequency modulation effect of the photoelastic modulator, and the detection light modulated at high frequency is converted into a signal to be demodulated with light intensity change after passing through the analyzer and is received by the photoelectric detector;

(2) the pumping laser emits pumping laser, the pumping laser realizes stable output of laser power, frequency, light spot form and directivity through a pumping light laser stabilizing system, pumping light spot diameter is expanded to be matched with an alkali metal atom air chamber through a pumping light expanding system, the expanded pumping laser is divided into two beams according to a proportion through a polarization splitting prism, one beam is received by a first CMOS sensor and used for monitoring the light intensity of incident light, the other beam sequentially passes through a polaroid and a pumping light quarter-wave plate and then enters the alkali metal atom air chamber in a circular polarization state, polarization pumping of the alkali metal atoms in high-temperature steam is realized, and the transmitted light is received by a second CMOS sensor to monitor the light intensity of emergent light;

(3) the data acquisition, analysis and processing system collects data of the photoelectric detector, the first CMOS sensor and the second CMOS sensor, performs phase-locked amplification conversion on signals of the photoelectric detector and monitors that the atomic magnetometer system is in a normal working state; and reading corresponding pixel points in real time and fitting a functional relation to the dot matrix data recorded by the first CMOS sensor and the second CMOS sensor, and calculating to obtain the dot matrix distribution of the spin polarizability so as to realize the precise measurement of the spatial distribution of the polarizability micron pixel level of the alkali metal atom gas chamber.

8. The method for in-situ measurement of spatial distribution of spin polarizability of an alkali metal atomic magnetometer of claim 7, wherein: the first CMOS sensor and the second CMOS sensor have the same model.

Technical Field

The invention belongs to the technical field of precision measurement, and particularly relates to an in-situ measurement system and method for spin polarizability spatial distribution of an alkali metal atomic magnetometer.

Background

The alkali metal atom magnetometer based on the spin-exchange relaxation effect is widely applied to the advanced fields of basic physical research, biological magnetic measurement and the like due to the ultrahigh magnetic field measurement sensitivity potential. The realization of the atomic magnetic field meter for the measurement of the extremely weak magnetic field mainly comprises optical pumping and atomic spin precession detection. Optical pumping utilizes polarized laser to microscopically change the distribution of electrons outside the alkali metal atomic nucleus on each energy level, thereby realizing the macroscopic polarization of atomic spin. The spin polarizability is a physical quantity for characterizing the degree of polarization of atoms, and is an important parameter affecting the atomic magnetic field measuring device. The stability of atomic spin polarizability directly affects the stability of the scale factor of the alkali metal atomic magnetometer. The comprehensive influence of temperature gradient, alkali metal atom density gradient and optical field gradient in the measuring system causes gradient difference in spatial distribution of atomic spin polarizability. The most important problem to be solved while continuously improving the magnetic field measurement sensitivity of the alkali metal atom magnetometer at present is that the gradient difference of the spin polarizability of atoms is inhibited. Therefore, the accurate measurement of the spatial distribution of the spin polarizability of the alkali metal atoms is significant for improving the stability uniformity of the spin polarizability and further improving the sensitivity of magnetic field measurement.

At present, the commonly used methods for measuring the spin polarizability of alkali metal atoms include an electron paramagnetic resonance method, a pumping and attenuation transient method, a faraday optical rotation signal method, a slow-down factor transient response method and the like. However, these methods have certain limitations, either need to apply a large-intensity magnetic field additionally, or are only suitable for a low-temperature state, or have distortion of transient signals, which all affect the normal working state of the magnetic measurement device, and cannot realize in-situ measurement of the spatial distribution of the atomic spin polarizability.

Disclosure of Invention

The invention aims to provide an in-situ measurement system and method for the spatial two-dimensional distribution of the spin polarizability of an alkali metal atom magnetometer, aiming at the problems in the prior art.

The purpose of the invention is realized by the following technical scheme: an in-situ measurement system for spin polarizability spatial two-dimensional distribution of an alkali metal atom magnetometer comprises a detection light laser, a detection light laser stabilizing system, a polarizer, a plane reflector, a photoelastic modulator, a detection light quarter wave plate, an alkali metal atom air chamber, an analyzer and a photoelectric detector which are sequentially arranged according to the advancing direction of detection light; the pumping light laser, the pumping light laser stabilizing system, the pumping light beam expanding system, the polarization beam splitter prism, the polaroid, the pumping light quarter-wave plate, the alkali metal atom air chamber and the second CMOS sensor are sequentially arranged in the other direction according to the advancing direction of the pumping light, and the other beam of refracted light of the polarization beam splitter prism enters the first CMOS sensor; the outer part of the alkali metal atom gas chamber is sequentially coated with a non-magnetic electric heating device, a heat insulation material cavity, a magnetic compensation coil and a magnetic shielding system from inside to outside; the photoelectric detector, the first CMOS sensor and the second CMOS sensor transmit data to the data acquisition, analysis and processing system.

Preferably, the detection laser and the pumping laser are wavelength-tunable semiconductor lasers working at lines corresponding to the alkali metal atoms D1 and D2, respectively, and meet the frequency power requirement of the alkali metal atom magnetometer on the pumping/detection laser.

Preferably, the detection light laser stabilization system and the pumping light laser stabilization system both include laser power stabilization, laser frequency stabilization, laser directivity stabilization, and laser spot form distribution stabilization.

Preferably, the alkali metal atom air chamber is a cubic borosilicate glass bubble with the size of 25 × 25 × 25 mm, and the air chamber is filled with alkali metal atoms, buffer gas and quenching gas.

Preferably, the effective receiving area of the first CMOS sensor and the effective receiving area of the second CMOS sensor are 25 x 25 mm, so that the incident/transmitted light spot can be completely received, the resolution is 2048 x 2048, 400 ten thousand pixels, the size of a single pixel is 12.5 mu m, and micron-pixel-level ultrahigh-resolution data reading and storing of light spot energy distribution are realized.

Preferably, the data acquisition, analysis and processing system comprises a phase-locked amplifier, a data acquisition system and a computer, and is used for demodulating and amplifying the detection laser signal to realize the measurement of the extremely weak magnetic field; and reading and fitting the pumping laser attenuation information signal, and combining the function relation of the polarization rate and the pumping light intensity to realize the precise measurement of the spatial distribution of the spin polarization rate of the alkali metal atoms.

The invention also provides an in-situ measurement method of the spatial two-dimensional distribution of the spin polarizability of the alkali metal atomic magnetometer based on the system, which comprises the following steps:

(1) the detection laser emits detection laser, the detection laser sequentially passes through a detection light laser stabilizing system, a polarizer, a plane reflector, a photoelastic modulator, a detection light quarter-wave plate, an alkali metal atom air chamber, an analyzer and a photoelectric detector, the influence of low-frequency noise on a rotation angle signal is reduced based on the high-frequency modulation effect of the photoelastic modulator, and the detection light modulated at high frequency is converted into a signal to be demodulated with light intensity change after passing through the analyzer and is received by the photoelectric detector;

(2) the pumping laser emits pumping laser, the pumping laser realizes stable output of laser power, frequency, light spot form and directivity through a pumping light laser stabilizing system, pumping light spot diameter is expanded to be matched with an alkali metal atom air chamber through a pumping light expanding system, the expanded pumping laser is divided into two beams according to a proportion through a polarization splitting prism, one beam is received by a first CMOS sensor and used for monitoring the light intensity of incident light, the other beam sequentially passes through a polaroid and a pumping light quarter-wave plate and then enters the alkali metal atom air chamber in a circular polarization state, polarization pumping of the alkali metal atoms in high-temperature steam is realized, and the transmitted light is received by a second CMOS sensor to monitor the light intensity of emergent light;

(3) the data acquisition, analysis and processing system collects data of the photoelectric detector, the first CMOS sensor and the second CMOS sensor, performs phase-locked amplification conversion on signals of the photoelectric detector and monitors that the atomic magnetometer system is in a normal working state; and reading corresponding pixel points in real time and fitting a functional relation to the dot matrix data recorded by the first CMOS sensor and the second CMOS sensor, and calculating to obtain the dot matrix distribution of the spin polarizability so as to realize the precise measurement of the spatial distribution of the polarizability micron pixel level of the alkali metal atom gas chamber.

Preferably, the first CMOS sensor and the second CMOS sensor are the same type.

The method is based on the absorption effect of alkali metal atoms on light, the polarizability is measured by obtaining attenuation information after the action of circularly polarized pumping light and the alkali metal atoms, the pixel-level extraction is carried out on pumping light attenuation signals by using a large-size high-resolution CMOS sensor, and the in-situ measurement of two-dimensional spatial distribution of polarizability pixel-level is realized by analyzing and fitting collected data. The polarizability measuring method does not damage the normal working state of the atomic magnetometer and bring system disturbance which affects the measuring sensitivity. The method has reasonable theoretical basis and simple experimental operation, does not have any system disturbance on the normal work of the magnetic measurement system, is favorable for accurately measuring the electron polarizability distribution of the alkali metal atoms, and provides a foundation for the development of an ultrahigh-sensitivity extremely weak magnetic measurement device.

Drawings

FIG. 1 is a schematic diagram of the system of the present invention;

fig. 2 is a schematic diagram of a pixel array structure and data distribution of the first CMOS sensor and the second CMOS sensor.

In the figure: 1-detection light laser, 2-detection light laser stabilizing system, 3-polarizer, 4-plane reflector, 5-photoelastic modulator, 6-detection light quarter wave plate, 7-magnetic shielding system, 8-magnetic compensation coil, 9-heat insulation material cavity, 10-non-magnetic electric heating device, 11-alkali metal atom air chamber, 12-pumping light laser, 13-pumping light laser stabilizing system, 14-laser beam expanding system, 15-polarization beam splitter prism, 16-polaroid, 17-pumping light quarter wave plate, 18-first CMOS sensor, 19-analyzer, 20-photoelectric detector, 21-second CMOS sensor, 22-data acquisition analysis processing system.

Detailed Description

The invention is further illustrated by the accompanying drawings and the detailed description.

As shown in fig. 1, the present invention provides an in-situ measurement system for spin polarizability spatial two-dimensional distribution of an alkali metal atom magnetometer, which comprises a detection light laser 1, a detection light laser stabilizing system 2, a polarizer 3, a plane mirror 4, a photoelastic modulator 5, a detection light quarter-wave plate 6, an alkali metal atom gas chamber 11, an analyzer 19, and a photodetector 20, which are sequentially arranged in the advancing direction of detection light; the pumping light laser 12, the pumping light laser stabilizing system 13, the pumping light beam expanding system 14, the polarization beam splitter prism 15, the polaroid 16, the pumping light quarter-wave plate 17, the alkali metal atom air chamber 11 and the second CMOS sensor 21 are sequentially arranged in the other direction according to the advancing direction of the pumping light, and the other beam of refracted light of the polarization beam splitter prism 15 enters the first CMOS sensor 18; the outside of the alkali metal atom gas chamber 11 is coated with a non-magnetic electric heating device 10, a heat insulation material chamber 9, a magnetic compensation coil 8 and a magnetic shielding system 7 in sequence from inside to outside; the photoelectric detector 20, the first CMOS sensor 18 and the second CMOS sensor 21 transmit data to the data acquisition, analysis and processing system 22.

The detection laser emitted by the detection light laser 1 sequentially passes through a detection light laser stabilizing system 2, a polarizer 3, a plane reflector 4, a photoelastic modulator 5, a detection light quarter-wave plate 6, an alkali metal atom air chamber 11, an analyzer 19 and a photoelectric detector 20, the influence of low-frequency noise on a rotation angle signal is reduced based on the high-frequency modulation effect of the photoelastic modulator, and the detection light modulated at high frequency is converted into a signal to be demodulated with light intensity change after passing through the analyzer and is received by the photoelectric detector 20. The signal is finally stored by the data acquisition, analysis and processing system 22 and is demodulated and amplified to realize the measurement of the extremely weak magnetic field signal.

Pumping light laser 12 outgoing laser beam realizes laser power through pumping light laser stabilization system 13, the frequency, the stable output of facula form and directive property, it expands to expand to with alkali metal atom air chamber 11 phase-match size to realize pumping facula diameter through laser beam expanding system 14, the laser divides into two bundles through polarization beam splitter prism 15 after expanding the beam, a bundle of laser is received by first CMOS sensor 18, be used for monitoring incident light intensity, another bundle of laser then passes through polaroid 16 successively, pump light quarter wave plate 17 back is with circular polarization state incident alkali metal atom air chamber 11, realize the polarization pump to the alkali metal atom that is located the high temperature vaporization, the transmitted light is then received in order to monitor emergent light intensity by another same second CMOS sensor 21. The polarization beam splitter prism 15 performs an energy beam splitting function on the pump laser, the beam splitting only performs beam splitting on the laser power in proportion, the power beam splitting proportion is stable, and the laser frequency, the polarization state and the light spot form are not affected.

After the absorption polarization of high-density alkali metal atoms and pumping light, the attenuation process of the circularly polarized pumping light when the circularly polarized pumping light is transmitted in an alkali metal gas chamber is as follows:

；

wherein n is the atomic number density of alkali metal,i (z) is the pump light intensity in the z-direction of the pump light propagation direction,is the spin relaxation rate of the alkali metal atom.

According to the relationship between the atomic polarizability and the laser pumping rate and the relationship between the atomic spin relaxation rate and the laser intensity, the polarizability p (z) of the alkali metal atoms can be expressed as:

；

therefore, the polarizability in the alkali metal atomic gas chamber can be measured by respectively monitoring the incident light intensity I (0) and the emergent light intensity I (z) and comparing the function fitting relationship of the incident light intensity I (0) and the emergent light intensity I (z).

The first CMOS sensor 18 and the second CMOS sensor 21 have photosensitive areas of 25 mm multiplied by 25 mm, so that light spots of the incident alkali metal atom gas chamber 11 can be completely received without focusing and beam shrinking, and monitoring data are more real and accurate. The sensor has a resolution of 2048 x 2048 million pixels with global shutter guaranteeThe simultaneity of the pixel array data acquisition is improved. The schematic diagram of the pixel array structure and the data distribution of the first CMOS sensor 18 and the second CMOS sensor 21 is shown in fig. 2, each pixel unit corresponds to an effective data, and the incident light intensity collected and recorded by each pixel unit of the first CMOS sensor 18 is respectively marked as (I)₁₁，I₁₂，……，I_nn) Correspondingly, the light intensity of the emergent light transmitted through the alkali metal atom gas chamber is collected and recorded by each pixel unit of the second CMOS sensor 21 and is respectively recorded as (I)^’ ₁₁，I^’ ₁₂，……，I^’ _nn）。

The data acquisition, analysis and processing system 22 records and stores the incident light intensity (I) by reading₁₁，I₁₂，……，I_nn) And the intensity of the emergent light (I)^’ ₁₁，I^’ ₁₂，……，I^’ _nn) Thus, as described above, the polarizability values can be measured by comparing the data function fitting relationship between the incident light intensity and the emergent light intensity, i.e. Pair (I)₁₁，I^’ ₁₁）（I₁₂，I^’ ₁₂）……（I_nn，I^’ _nn) And fitting and analyzing data points corresponding to each group of spatial pixels to measure the polarizability distribution (P11, P12, … … and Pnn), thereby realizing precise measurement of the polarizability micron-pixel-level spatial distribution of the alkali metal atom gas chamber.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the invention and are not to be construed as limiting the embodiments of the present invention, and it will be apparent to those skilled in the art that other variations and modifications can be made on the basis of the above description.