CN114966493A - Miniaturized atomic magnetometer - Google Patents
Miniaturized atomic magnetometer Download PDFInfo
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- CN114966493A CN114966493A CN202210850695.7A CN202210850695A CN114966493A CN 114966493 A CN114966493 A CN 114966493A CN 202210850695 A CN202210850695 A CN 202210850695A CN 114966493 A CN114966493 A CN 114966493A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/032—Measuring direction or magnitude of magnetic fields or magnetic flux using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
- A61B5/242—Detecting biomagnetic fields, e.g. magnetic fields produced by bioelectric currents
- A61B5/245—Detecting biomagnetic fields, e.g. magnetic fields produced by bioelectric currents specially adapted for magnetoencephalographic [MEG] signals
Abstract
The invention provides a miniaturized atomic magnetometer, which comprises an alkali metal atom gas chamber, a pumping light source component, a detection light source component and a photoelectric detection component, wherein a pumping light path of the miniaturized atomic magnetometer is vertical to a detection light path, detection laser of the detection light path penetrates through the alkali metal atom gas chamber to enter the photoelectric detection component, and the pumping light source component, the detection light source component and the photoelectric detection component are spatially arranged in a three-dimensional manner and are all positioned at the same side of the alkali metal atom gas chamber; the pumping optical path comprises a first optical path and a second optical path returning along the route of the first optical path; the first light path and the second light path penetrate through the alkali metal atom gas chamber to realize polarization pumping of the alkali metal atoms in high-temperature vaporization. Through the reasonable and ingenious structural design, the atomic polarizability uniformity and the detection sensitivity in the alkali metal atom gas chamber can be improved while miniaturization is realized, and further the magnetoencephalography detection efficiency and the detection quality are greatly improved.
Description
Technical Field
The invention relates to a diagnosis device in the medical field, in particular to a miniaturized atomic magnetometer for carrying out magnetoencephalography.
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.
Atomic magnetometers (also called optical pump magnetometers, i.e., OPMs, atomic magnetometers, and atomic magnetometers) are techniques for detecting magnetic fields using the interaction of light with atoms. The realization of the atomic magnetometer to the measurement of the extremely weak magnetic field mainly comprises optical pumping and atomic spin precession detection. Optical pumping is to microscopically change the distribution of out-core electrons of alkali metal atoms (generally K, Rb, Cs) on each energy level by using polarized laser, thereby realizing the macroscopic polarization of atomic spin. The spin polarizability of atoms is a physical quantity for representing the polarized degree of atoms, and is an important parameter for influencing an atomic magnetic field measuring device. The stability of atomic spin polarizability directly affects the stability of alkali metal atomic magnetometers.
The atomic magnetometer mainly detects a magnetic field perpendicular to two intersecting light (pumping light and detection laser) planes, and the structural design of the existing atomic magnetometer has a large detection magnetic sensitive area, so that the realization of miniaturization application and the realization of multi-channel detection cannot be realized better, the atomic polarizability uniformity in an alkali metal atomic gas chamber cannot be guaranteed, and the detection quality of magnetoencephalography is greatly reduced. For example, chinese patent (CN 113639883A) discloses an in-situ measurement system for spin polarizability spatial distribution of an alkali metal atom magnetometer, which comprises a detection light laser, a detection light laser stabilizing system, a polarizer, a plane mirror, a photoelastic modulator, a detection light quarter-wave plate, an alkali metal atom air chamber, an analyzer, and a photodetector, which are sequentially arranged in the forward 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.
For another example, chinese patent (CN 108490374A) discloses a hybrid optical pumping SERF atomic magnetometer device, which comprises a K/Rb mixed alkali metal gas chamber, an oven, a vacuum chamber, a three-dimensional magnetic compensation coil, a magnetic shielding barrel, a pumping light source, a beam expander, a linear polarizer, a 1/4 wave plate, a detection light source, a beam expander, a faraday modulator, a photodetector, a lock-in amplifier, and a data acquisition and analysis system, wherein: the K/Rb mixed alkali metal air chamber is fixed in the center of the boron nitride ceramic oven, the electric heating film is heated to 200 ℃ to ensure higher alkali metal atomic number density, the air chamber and the oven are placed in a vacuum cavity, the vacuum is utilized to isolate the outward diffusion of heat, the influence of heat is reduced, and the three-dimensional magnetic compensation coil and the magnetic shielding barrel are used for shielding a geomagnetic field and compensating residual magnetism; the pumping light source is a K atom D1 linear light source, and pumping light generated by the pumping light source is circularly polarized after passing through a beam expander, a linear polarizer and a 1/4 wave plate forming an angle of 45 degrees with the linear polarization direction, is used for polarizing K atoms in the alkali metal gas chamber, and polarizes Rb atoms through mutual collision between the K atoms and the Rb atoms; the detection light source is an Rb atom D1 linear light source, the detection light generated by the linear light source is linearly polarized after passing through a beam expander and a linear polarizer, and the other linear polarizer is used as an analyzer behind the alkali metal air chamber and is vertical to the first linear polarizer. When linearly polarized light passes through the alkali metal gas chamber, the linear polarization plane of the detection light is deflected due to atom precession caused by the change of the magnetic field, so that the light intensity transmitted through the analyzer is changed, and the light intensity is detected by the light detector; the Faraday modulator is used for modulating the light deflection angle, and the lock-in amplifier is used for extracting weak deflection angle signals, and finally the weak deflection angle signals enter the data acquisition and analysis system for processing.
The structural design of the atomic magnetometer disclosed in the prior art limits the realization of miniaturization application, cannot guarantee the atomic polarizability uniformity in the alkali metal atom air chamber, and greatly reduces the detection quality of magnetoencephalography.
Therefore, it is highly desirable for those skilled in the art to develop a miniaturized atomic magnetometer.
Disclosure of Invention
In view of this, in order to solve at least one of the above problems, an embodiment of the present invention provides a miniaturized atomic magnetometer, in which a pumping light source assembly, a detection light source assembly, and a photoelectric detection assembly are spatially and three-dimensionally arranged, and are structurally arranged at the same side of an alkali metal atom gas chamber, and a first light path in the pumping light path and a second light path returning along the first light path pass through the alkali metal atom gas chamber, so that a stroke of a pumping light beam in the atom gas chamber is increased, thereby solving technical problems that the structural design of the atomic magnetometer in the prior art is limited to achieve miniaturization application, atomic polarizability uniformity in the alkali metal atom gas chamber cannot be guaranteed, and quality of magnetoencephalography detection is greatly reduced.
In order to achieve the above object, an embodiment of the present invention provides a miniaturized atomic magnetometer, which includes an alkali metal atom air chamber, a pumping light source assembly, a detection light source assembly, and a photoelectric detection assembly, where a pumping light path emitted by the pumping light source assembly is perpendicular to a detection light path emitted by the detection light source assembly, detection laser of the detection light path passes through the alkali metal atom air chamber and enters the photoelectric detection assembly, and the pumping light source assembly, the detection light source assembly, and the photoelectric detection assembly are spatially and three-dimensionally arranged and are all located at the same side of the alkali metal atom air chamber; the pumping optical path comprises a first optical path and a second optical path returning along the route of the first optical path; the first light path and the second light path penetrate through the alkali metal atom gas chamber to realize polarization pumping of the alkali metal atoms in high-temperature vaporization.
Furthermore, a total reflection mirror is arranged on one inner side surface of the alkali metal atom gas chamber; the pumping light source assembly comprises a pumping source, a pumping light beam emitted by the pumping source penetrates through the alkali metal atom gas chamber to form the first light path, a first stroke light of the first light path irradiates on the holophote, a second light path is formed under the total reflection action of the holophote, and a second stroke light of the second light path penetrates through the alkali metal atom gas chamber.
Further, a first reflector is arranged on the pumping light path, the pumping light beam emitted by the pumping source irradiates on the first reflector, and the reflected light formed under the reflection action of the first reflector passes through the alkali metal atom gas chamber to form the first light path.
Further, the pump light source assembly further comprises a polarizing element disposed between the pump source and the first mirror.
Further, the pumping light source assembly further comprises a quarter wave plate and a beam expander, and the quarter wave plate and the beam expander are arranged between the reflecting mirror and the alkali metal atom gas chamber.
Further, be provided with second reflector and third reflector on the detection light path, second reflector, third reflector are located respectively the both sides of alkali metal atom air chamber, the detection laser of detection light path pass after the reflection of second reflector the alkali metal atom air chamber to shine on the third reflector, get into under the effect of third reflector in the photoelectric detector of photoelectric detection subassembly.
Further, the total reflection mirror is a total reflection prism.
Further, when the pump light beam emitted by the pump light path propagates in the alkali metal atom gas chamber, the pump light beam is absorbed by the alkali metal atoms, so that a polarizability gradient is generated in the alkali metal atom gas chamber, and a differential equation of attenuation of the pump light beam when the pump light beam propagates in the alkali metal atom gas chamber is as follows:
the solution of this differential equation is:
；
wherein, in the formula, the w function is the real part of the Lambert complex function, n is the atomic number density of alkali metal, and σ (v) is the absorption section of the pump light,
in order to be the spin-destructive relaxation rate,
in order to be able to pump at a high rate,
in order to be the initial pumping rate,
the partial derivative of Rp to Z is the change of the pumping rate along with the depth of the light entering an alkali metal atom air chamber,
is the distribution of the pumping rate in the whole alkali metal atom air chamber.
Furthermore, the other side surface of the alkali metal atom gas chamber far away from the same side position is a magnetic detection surface of the atom magnetometer, and the magnetic detection surface is not on the same plane with the sections of the pumping light source assembly and the detection light source assembly.
Furthermore, the detection light source component comprises a detection laser, the detection laser emits the detection laser, the detection laser is emitted into the alkali metal atom gas chamber to be used for detecting the precession state of atomic spin, and then the optical signal of atomic spin detection is converted into an electric signal through the photoelectric detection component to be output.
The invention has the beneficial effects that:
according to the invention, the pumping light source assembly, the detection light source assembly and the photoelectric detection assembly are spatially and three-dimensionally arranged and are arranged at the same side of the alkali metal atom air chamber, the design of the structure can ensure that the magnetic detection surface of the atom magnetometer is not on the same plane with the cross sections of the pumping light source assembly and the detection light source assembly, the magnetic detection surface occupies a smaller surface area of the scalp, the miniaturized design is realized, meanwhile, the multichannel detection of the brain magnetism is more conveniently realized, and the detection quality of the brain magnetism is further improved.
Furthermore, the pumping light path is designed into a double-stroke light path of the first light path and the second light path returned along the first light path, and the double-stroke light path penetrates through the alkali metal atom air chamber, so that the stroke of the pumping light beam in the alkali metal atom air chamber can be increased in a certain space of the alkali metal atom air chamber, the uniformity and the sensitivity of the atomic polarizability in the alkali metal atom air chamber can be improved, and the detection quality of brain magnetism is greatly improved.
Drawings
The following drawings are included to provide a further understanding of the invention, are incorporated in and constitute a part of this application, and are provided for illustrative purposes only and are not intended to limit the scope of the invention. In the drawings:
FIG. 1 is a schematic top view of an atomic magnetometer illustrating an embodiment of the present application;
FIG. 2 is a schematic diagram of an internal perspective structure of an atomic magnetometer in an embodiment of the present application;
FIG. 3 is a schematic longitudinal sectional view of the pump beam path Z in FIG. 1;
FIG. 4 is a graph illustrating a comparison of a dual optical path gas cell depth atomic polarizability curve in an embodiment of the present application with a single optical path gas cell depth atomic polarizability curve in the prior art;
fig. 5 is a schematic diagram of a comparison curve between a depth-normalized sensitivity curve of a dual-optical-path gas chamber in the embodiment of the present application and a depth-normalized sensitivity curve of a single-optical-path gas chamber in the prior art.
Reference numerals:
1. an alkali metal atom gas cell; 2. a pump optical path; 3. detecting a light path; 10. a housing; 11. detecting a magnetic induction surface; 12. a heating coil; 15. the magnetic sensitivity direction to be measured; 20. a pump light source assembly; 21. a first optical path; 22. a second optical path; 24. a total reflection mirror; 25. a first reflector; a polarizing element; 30. detecting a light source assembly; 33. a second reflector; 34. a third reflector; 40. a photodetection component; 100a, a single-light path air chamber depth atom polarizability curve; 100b, a single-light path air chamber depth normalization sensitivity curve; 200a, a double-light-path air chamber depth atomic polarizability curve; 200b, double light path gas chamber depth normalization sensitivity curve.
Detailed Description
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.
It should be noted that, unless the directions indicated are individually defined, the directions of up, down, left, right, front, back, etc. referred to herein are based on the directions of up, down, left, right, etc. shown in fig. 2 of the embodiment of the present application, and if the specific posture is changed, the directional indication is changed accordingly. As used herein, the terms "first," "second," and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Further, in the various embodiments of the present disclosure, the same or similar reference numerals denote the same or similar components.
In the present invention, unless otherwise expressly stated or limited, the terms "connected," "secured," and the like are to be construed broadly, and for example, "connected" may be fixedly connected, detachably connected, or integral, unless otherwise expressly stated or limited. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination of technical solutions should not be considered to exist, and is not within the scope of the present invention as claimed.
Example one
Referring to fig. 1 to 3, a miniaturized atomic magnetometer in this embodiment includes a housing 10, and an alkali metal atom air chamber 1, a photoelectric detection component 40, a pumping light source component 20, a detection light source component 30, a pumping light path 2, and a detection light path 3 perpendicular to the pumping light path that are disposed in the housing, where detection laser of the detection light path 3 passes through the alkali metal atom air chamber 1 and enters the photoelectric detection component 40 to convert an optical signal of atomic spin detection into an electrical signal for output.
The pump light source assembly 20, the detection light source assembly 30 and the photoelectric detection assembly 40 in this embodiment are spatially and stereoscopically arranged. The meaning of the spatial arrangement of the present embodiment can be more clearly understood by referring to fig. 2, that is, the pump light source assembly 20, the detection light source assembly 30 and the photoelectric detection assembly are all located at the left side position of the alkali metal atom gas chamber 1, the detection light source assembly 30 is located at the front upper side of the pump light source assembly 20, and the photoelectric detection assembly 40 is located at the rear upper side of the pump light source assembly 20; further, the first mirror 25 disposed on the pumping optical path 2 in the present embodiment is located right below the alkali metal atom gas cell 1, and the second mirror 33 and the third mirror 34 disposed on the detection optical path 3 are located right in front of and right behind the alkali metal atom gas cell 1, respectively; the detection light source component 30, the second reflector 33, the alkali metal atom gas chamber 1, the third reflector 34 and the photoelectric detection component 40 are positioned on the same transverse plane, and a detection light path of the detection light source component 30 sequentially passes through the second reflector 33, the alkali metal atom gas chamber 1, the third reflector 34 and the photoelectric detection component 40; the pumping light source assembly 20, the first reflector 25 and the alkali metal atom gas chamber 1 are located on the same vertical plane.
It should be noted that the atomic magnetic force in this embodiment is a rectangular parallelepiped structure, and the arrangement of the internal structure enables the bottom surface to be the detection magnetic induction surface 11 directly contacting with the scalp; the pump light source component comprises a pump laser for emitting pump light beams and a pump optical element; the detection light source assembly includes a detection laser emitting detection laser light and a detection optical element.
The atomic magnetometer in the embodiment adopts the reasonable and ingenious structural design of spatial three-dimensional arrangement, and particularly, through the arrangement of the first reflector, the second reflector and the third reflector, two light source components which should be directly vertical to each other can be placed at the same side of the alkali metal atom air chamber, so that the miniaturization design can be fully realized; and the direction 15 (shown in fig. 3) of the magnetosensitive sensor to be detected is along the radial direction of the scalp, that is, as shown in fig. 1, the detection magnetosensitive surface 11 located on the bottom surface of the atomic magnetometer is directly contacted with the scalp, so as to ensure that more atomic magnetometers can be arranged on the scalp, better realize the multichannel detection of the brain magnetism, and further improve the detection quality of the brain magnetism.
Example two
In this embodiment, based on the structural arrangement of the miniaturized atomic magnetometer in the first embodiment, as shown in fig. 1 and fig. 2, the pumping optical path 2 in this embodiment includes a first optical path 21 and a second optical path 22 returning along the first optical path 21, where arrows in the illustrated optical path indicate the direction of laser light, and the first optical path 21 and the second optical path 22 pass through the alkali metal atom gas chamber 1 to realize polarized pumping of the alkali metal atoms vaporized at a high temperature.
As a preferred embodiment, a total reflection mirror 24 is disposed on one side surface of the alkali metal atom gas chamber 1 in this embodiment, and the total reflection mirror 24 is located on the other side of the alkali metal atom gas chamber 1 relative to the first reflection mirror, so that the pumping beam emitted by the pumping source can pass through the alkali metal atom gas chamber and then smoothly enter the total reflection mirror, the first stroke light of the first light path 21 returns along the route of the first light path under the total reflection action of the total reflection mirror to form the second light path 22, and the second stroke light of the second light path 22 that returns by total reflection enters the alkali metal atom gas chamber, so as to implement secondary return compensation polarization on the alkali metal atoms, thereby ensuring the polarization uniformity of the alkali metal atoms and improving the sensitivity of the atomic magnetometer.
Specifically, a comparison curve diagram of a dual optical path gas cell depth atomic polarization rate curve of the embodiment of the present application and a single optical path gas cell depth atomic polarization rate curve in the prior art is shown in fig. 4. Firstly, analyzing a double-light-path gas chamber depth atomic polarizability curve 200a, wherein the double-stroke normalized atomic polarizability of the embodiment of the application is kept between 0.41 and 0.58 in an alkali metal atomic gas chamber; from the data of N times of exploration experiments of research personnel, it is known that when the atomic polarizability in the alkali metal atom gas chamber is between 0.4 and 0.6, especially when the atomic polarizability threshold values in the alkali metal atom gas chamber are 0.4, 0.41, 0.5, 0.58 and 0.6, higher detection efficiency can be achieved, and the detection quality of magnetoencephalography is guaranteed. Further, by analyzing the atomic polarizability curve 100a of the single-light-path gas chamber depth, it can be seen that after the single-stroke light enters a half of the gas chamber depth of the alkali metal atomic gas chamber, the atomic polarizability is obviously lower than the threshold of 0.4, and as the depth of the light entering the gas chamber increases, the atomic polarizability is smaller, which greatly affects the detection efficiency and the detection quality.
Then, by further combining the graph of the comparison curve between the depth normalization sensitivity curve of the dual-optical-path gas chamber in the embodiment of the present application and the depth normalization sensitivity curve of the single-optical-path gas chamber in the prior art shown in fig. 5, it can be known that the dual-optical-path detection sensitivity in the embodiment of the present application still maintains a higher sensitivity threshold (between 0.96 and 1.00) with the increase of the depth of the dual-optical-path detection sensitivity entering the gas chamber; however, in the prior art, the detection sensitivity threshold of the single light path is smaller and smaller with the increase of the depth of the single light path entering the air chamber, and particularly after the single light path enters half of the depth of the air chamber, the detection sensitivity threshold is sharply reduced, so that the detection efficiency and the detection quality are seriously influenced.
From this, the round trip double-circuit light beam that this embodiment adopted has increased the stroke of pumping light beam in the finite volume of atomic air chamber undoubtedly for the single-circuit light beam that adopts among the prior art, has ensured the interior atomic absorption energy of atomic air chamber and has produced the energy level transition, improves the degree of consistency and the detection sensitivity of atomic magnetometer of atomic polarizability greatly, and then has promoted the detection efficiency and the detection quality of brain magnetism greatly.
It should be noted that the pumping optical path in this embodiment preferably includes, but is not limited to, two travel optical paths including a first optical path and a second optical path, and may be designed as multiple round-trip optical paths according to practical situations. The round-trip double-stroke optical paths on the pumping optical path are all circularly polarized light which is applied to alkali metal atoms and has a wavelength corresponding to an excited state energy spectral line, the atoms absorb energy to generate energy level transition, and finally a large amount of energy levels are gathered in an ultra-fine energy level according to an optical pumping principle, so that high polarizability is realized. When a small magnetic field exists around the polarized atom spin, the atoms can do Larmor precession under the external magnetic field to generate a precession deflection angle, and the size of the precession deflection angle is in direct proportion to the magnetic field strength within a certain range. At the moment, one linear polarized light which is vertical to the double-stroke pump light beam on the pumping light path by one detection laser on the detection light path passes through the alkali metal atom air chamber, the polarization direction of the linear polarized light can slightly deflect due to the interaction of light and precession atoms, the change of the polarization angle is detected by the photoelectric detection assembly to directly reflect the size of a magnetic field, and the magnetoencephalography of the atomic magnetometer is accurately realized.
In addition, the detection laser emitted by the detection laser in the detection light source assembly 30 in this embodiment is emitted into the alkali metal atom gas chamber through the detection optical element for detecting the precession state of the atomic spins, and then the optical signal of the atomic spin detection is converted into an electrical signal by the photoelectric detection assembly 40 for output.
It should be noted that the total reflection mirror in this embodiment is preferably, but not limited to, a coated total reflection prism, and when light enters the prism from the hypotenuse of the isosceles triangle, the light passes through the prism and strikes one of the right-angled sides, because the incident light angle is greater than the critical angle (42 °) of the glass, total reflection occurs at this surface, the reflected light strikes the other right-angled side, total reflection occurs at this right-angled side, and finally the reflected light exits at the incident hypotenuse, and the reflected light exits in the same direction as the incident light. It may also be a pyramid prism, an isosceles prism, etc., which do not introduce significant power losses.
In addition, the pump laser, the polarization element, and the mirror 25 are sequentially disposed on the pump optical path 2 in this embodiment. That is, the pump beam emitted from the pump source passes through the PBS (polarization beam splitter prism), the reflector 25, the alkali metal atom gas chamber, and returns to the alkali metal atom gas chamber under the action of the silvered total-emission mirror, so as to achieve the purpose of two-pass.
Specifically, in the first optical path 21, the pump laser is configured to emit pump laser light, the polarization component preferably selects a polarization beam splitter to divide the pump laser light emitted from the pump laser into a main beam and a reference beam, where the reference beam is fed back to the pump laser controller and used to implement selection and stabilization of frequency and power of the pump laser light, the main beam sequentially passes through a reflector, a quarter-wave plate and a beam expander and then enters the alkali metal atom gas chamber 1 as a first stroke light, the quarter-wave plate is configured to convert linearly polarized laser light into circularly polarized laser light, and the beam expander is configured to expand the pump laser light and then irradiate the whole atom gas chamber. In the second light path 22, the first stroke light passes through the alkali metal atom gas chamber and then returns to form a second stroke light under the action of the silvered total-reflection mirror 24, the second stroke light passes through the alkali metal atom gas chamber 1 and returns to the polarization beam splitter prism along the route of the first stroke light, the first stroke light and the second stroke light have a coupling relation, power information of the driving light can be obtained from the second stroke light, and the return power is an important reference index for deducing whether the light intensity is proper or not.
As a preferred embodiment, the pump light beam emitted from the pump optical path in this embodiment is absorbed by the alkali metal atoms when propagating in the alkali metal atom gas cell, so as to generate a polarizability gradient in the alkali metal atom gas cell, and a differential equation of attenuation of the pump light beam when propagating in the alkali metal atom gas cell is:
，
the solution of this differential equation is:
；
wherein w in the formula is a real part of an enbo complex function, n is the atomic number density of alkali metal, and σ (v) is a pump light absorption section,
in order to be the spin-destructive relaxation rate,
in order to be able to pump at a high rate,
in order to be the initial pump rate,
the partial derivative of Rp to Z is the change of the pumping rate along with the depth of the light entering an alkali metal atom air chamber,
is the distribution of the pumping rate in the whole alkali metal atom air chamber.
It should be noted that, the above formula in this embodiment is a method for calculating a pumping rate in an alkali metal atom gas chamber, further, an atomic polarization rate = pumping rate/(pumping rate + spin damage relaxation rate), and a round-trip double-stroke pumping beam adopted in this embodiment of the pumping rate undoubtedly increases a stroke in a limited volume of the atom gas chamber, thereby ensuring stability of energy level transition generated by absorption energy of atoms in the atom gas chamber, making distribution of the pumping rate in the entire alkali metal atom gas chamber uniform, further improving uniformity of the atomic polarization rate in the entire alkali metal atom gas chamber and detection sensitivity of an atomic magnetometer, and greatly improving detection efficiency and detection quality of magnetoencephalography.
In conclusion, the pumping light source assembly, the detection light source assembly and the photoelectric detection assembly are spatially and three-dimensionally arranged and are arranged at the same side of the alkali metal atom air chamber, the design of the structure can ensure that the magnetic detection surface of the atomic magnetometer is not positioned on the same plane as the pumping light source assembly and the detection light source assembly, the magnetic detection surface occupies a smaller surface area of the scalp, the miniaturized design is realized, meanwhile, the multichannel detection of the magnetoencephalography is also conveniently and better realized, and the detection quality of the magnetoencephalography is further improved. Furthermore, the pumping light path is designed into a double-stroke light path of a first light path and a second light path returned along the first light path, the double-stroke light path penetrates through the alkali metal atom air chamber, the stroke of the pumping light beam in the alkali metal atom air chamber can be increased in a certain space of the alkali metal atom air chamber, the uniformity and the sensitivity of the atomic polarizability in the alkali metal atom air chamber are improved, the detection quality of the magnetoencephalography is greatly improved, the technical problems that the structural design of an atomic magnetometer in the prior art limits the realization of miniaturization application, the uniformity of the atomic polarizability in the alkali metal atom air chamber cannot be guaranteed, and the magnetoencephalography detection quality is greatly reduced are solved.
While the above description shows and describes the preferred embodiments of the application, it is to be understood, as noted above, that the application is not limited to the forms disclosed herein, but is not intended to be exhaustive of other embodiments, and is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the subject matter disclosed above, as determined by the teachings or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the application, which is to be protected by the claims appended hereto.
Claims (10)
1. A miniaturized atomic magnetometer comprises an alkali metal atom air chamber, a pumping light source component, a detection light source component and a photoelectric detection component, wherein a pumping light path emitted by the pumping light source component is perpendicular to a detection light path emitted by the detection light source component, and detection laser of the detection light path penetrates through the alkali metal atom air chamber to enter the photoelectric detection component;
the pumping optical path comprises a first optical path and a second optical path returning along the route of the first optical path;
the first light path and the second light path penetrate through the alkali metal atom gas chamber to realize polarization pumping of the alkali metal atoms in high-temperature vaporization.
2. The miniaturized atomic magnetometer of claim 1, wherein a total reflection mirror is provided on one side surface of the alkali metal atom gas cell;
the pumping light source assembly comprises a pumping source, a pumping light beam emitted by the pumping source penetrates through the alkali metal atom gas chamber to form the first light path, a first stroke light of the first light path irradiates on the holophote, a second light path is formed under the total reflection action of the holophote, and a second stroke light of the second light path penetrates through the alkali metal atom gas chamber.
3. The miniaturized atomic magnetometer of claim 2, wherein a first reflecting mirror is disposed on the pumping light path, the pumping light beam emitted from the pumping source is irradiated on the first reflecting mirror, and the first light path is formed after the reflected light formed by the reflection of the first reflecting mirror passes through the alkali metal atom gas chamber.
4. The miniaturized atomic magnetometer of claim 3, wherein the pump light source assembly further comprises a polarizing element disposed between the pump source and the first mirror.
5. The miniaturized atomic magnetometer of claim 3, wherein the pump light source assembly further comprises a quarter wave plate and a beam expander, the quarter wave plate and the beam expander being disposed between the reflecting mirror and the alkali metal atom gas cell.
6. The miniaturized atomic magnetometer of claim 1, wherein a second reflecting mirror and a third reflecting mirror are disposed on the detection light path, the second reflecting mirror and the third reflecting mirror are respectively disposed at two sides of the alkali metal atom air chamber, and the detection laser of the detection light path passes through the alkali metal atom air chamber after being reflected by the second reflecting mirror, and irradiates on the third reflecting mirror, and enters the photodetector of the photodetection assembly under the action of the third reflecting mirror.
7. The miniaturized atomic magnetometer of claim 2, wherein the total reflection mirror is a total reflection prism.
8. The miniaturized atomic magnetometer of claim 1, wherein the pump beam emitted from the pump optical path is absorbed by the alkali metal atoms while propagating in the alkali metal atom gas cell, so as to generate a polarizability gradient in the alkali metal atom gas cell, and a differential equation of attenuation of the pump beam while propagating in the alkali metal atom gas cell is:
the solution of the differential equation is:
(ii) a Wherein, in the formula, the w function is the real part of the Lambert complex function, n is the atomic number density of alkali metal, and σ (v) is the absorption section of the pump light,
in order to be the spin-destructive relaxation rate,
in order to be able to pump at a high rate,
in order to be the initial pump rate,
the partial derivative of Rp to Z is the change of the pumping rate along with the depth of the light entering an alkali metal atom air chamber,
is the distribution of the pumping rate in the whole alkali metal atom air chamber.
9. The miniaturized atomic magnetometer of claim 1, wherein the other side surface of the alkali metal atom gas cell away from the same-side position is a magnetism detection surface of the atomic magnetometer.
10. The miniaturized atomic magnetometer of claim 1, wherein the detection light source assembly comprises a detection laser, the detection laser emits the detection laser, the detection laser is injected into the alkali metal atom gas chamber to detect the precession state of the atomic spins, and then the optical signal detected by the atomic spins is converted into an electrical signal by the photoelectric detection assembly to be output.
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