CN113791370A - Magnetometer and magnetic field strength determination method - Google Patents
Magnetometer and magnetic field strength determination method Download PDFInfo
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Abstract
The present application relates to a magnetometer and a magnetic field strength determining method, the magnetometer including: at least two groups of parallel pump light processing optical paths, atomic gas chambers and signal processing circuits; each group of pump light processing optical paths correspondingly process different single-beam pump lights to obtain corresponding polarized pump lights; all polarized pump light enters the atomic gas chamber and outputs optical signals after reacting with alkali metal atoms in the atomic gas chamber; the optical signal enters a signal processing circuit so that the signal processing circuit processes the optical signal to obtain a frequency output signal; the frequency output signal is used for measuring and calculating the magnetic field intensity of the magnetic field to be measured; wherein the frequencies of the different single pump beams are different. The magnetometer improves the utilization rate of ground state atoms in the optical pumping process, so that the atomic polarizability is further improved, and the atomic pumping rate in the optical pump magnetometer is improved.
Description
Technical Field
The present disclosure relates to the field of magnetometer technology, and more particularly, to a magnetometer and a method for determining a magnetic field strength.
Background
The optical pump magnetometer has important application in the military and civil fields of magnetic target detection, space physics, biomedicine, geological exploration and the like.
The optical pump magnetometer is manufactured by utilizing the principle that circularly polarized light excites a gas atom system in a magnetic field to be measured to generate the particle number difference between Zeeman sub energy levels of the gas atom system so as to observe the magnetic resonance effect, and is mainly used for measuring a weak magnetic field. When applied, the atomic polarizability in the optical pump magnetometer is an important index, and the atomic polarizability directly influences the signal strength and the sensitivity of the magnetometer.
However, the optical pump magnetometer in the related art has a problem that the atomic pumping rate is low.
Disclosure of Invention
The embodiment of the application provides a magnetometer and a magnetic field strength determining method, which can improve the atomic pumping rate in an optical pump magnetometer.
In a first aspect, an embodiment of the present application provides a magnetometer, including: at least two groups of parallel pump light processing optical paths, atomic gas chambers and signal processing circuits;
each group of pump light processing light paths are used for correspondingly processing different single-beam pump lights to obtain corresponding polarized pump lights; wherein, the frequencies of different single beams of pump light are different;
all polarized pump light enters the atomic gas chamber and outputs optical signals after reacting with alkali metal atoms in the atomic gas chamber;
the optical signal enters a signal processing circuit, so that the signal processing circuit processes the optical signal to obtain a frequency output signal; the frequency output signal is used for measuring and calculating the magnetic field intensity of the magnetic field to be measured.
In one embodiment, the alkali metal atom is a rubidium atom, and the different single pump beams include a first pump beam and a second pump beam;
then, the frequency of the first beam of pump light is the same as the transition frequency of the rubidium atom D1 wire, and the frequency of the second beam of pump light is the same as the transition frequency of the rubidium atom D2 wire.
In one embodiment, the polarized pump light is circularly polarized pump light; each group of pump light processing optical paths comprises: the optical lens comprises a first optical lens, a first polarizer, an amplitude modulator and a quarter-wave plate;
the first optical lens is used for collimating and adjusting light spots of the corresponding single beam of pump light;
the first polarizer is used for aligning the pump light after the alignment and the light spot adjustment to perform linear polarization adjustment;
and the amplitude modulator is used for carrying out amplitude modulation on the pump light after linear polarization adjustment, and the output light after amplitude modulation is converted into circular polarization pump light through the quarter-wave plate.
In one embodiment, each group of pump light processing optical paths corresponds to one radio frequency driver;
the radio frequency driver is used for amplifying the frequency output signal to obtain a control signal scanned in a corresponding frequency range; the control signal is used for controlling the amplitude modulator to perform amplitude modulation on the pump light after linear polarization adjustment.
In one embodiment, the optical signal is a pump optical signal; the signal processing circuit comprises a detector, a first signal processor, a first phase-locked amplifier and a first frequency signal generator;
the detector is used for converting the pump light signal into a voltage signal;
the first signal processor is used for filtering and amplifying the voltage signal;
the first phase-locked amplifier is used for calculating according to the filtered and amplified voltage signal to obtain an error signal;
a first frequency signal generator for generating a frequency output signal in dependence on the error signal.
In one embodiment, the optical signal is a probe optical signal; the magnetometer also comprises a group of detection light processing light paths;
the detection light processing optical path is used for processing the single-beam detection light to obtain corresponding polarized detection light; the frequency of the single-beam probe light is different from the frequency of the single-beam pump light processed by the pump light processing optical paths of different groups;
the polarized detection light enters the atom gas chamber in the direction perpendicular to the polarized pump light, and outputs a detection light signal after the polarized detection light and the polarized pump light jointly react with alkali metal atoms.
In one embodiment, the alkali metal atoms are rubidium atoms, and the frequency of the probe light is shifted by a predetermined magnitude from the transition frequency of the rubidium atom D2 line.
In one embodiment, the detection light processing optical path comprises a second optical lens and a second polarizer;
the second optical lens is used for collimating the single-beam probe light and adjusting the light spot;
and the second polarizer is used for aligning the direct light and the detected light after the light spot adjustment to perform linear polarization adjustment.
In one embodiment, the signal processing circuit comprises a differential detector, a second signal processor, a second lock-in amplifier and a second frequency signal generator;
a differential detector for converting the detected optical signal into a voltage signal;
the second signal processor is used for filtering and amplifying the voltage signal;
the second lock-in amplifier is used for calculating according to the filtered and amplified voltage signal to obtain an error signal;
a second frequency signal generator for generating a frequency output signal based on the error signal.
In a second aspect, an embodiment of the present application provides a magnetic field strength determining method, which is applied to the magnetometer provided in any embodiment of the first aspect, and the method includes:
correspondingly processing different single-beam pump light through different groups of parallel pump light processing light paths to obtain corresponding polarized pump light; wherein, the frequencies of different single beams of pump light are different;
inputting all polarized pump light into an atomic gas chamber, and outputting optical signals after the polarized pump light reacts with alkali metal atoms in the atomic gas chamber;
inputting the optical signal into a signal processing circuit to enable the signal processing circuit to process the optical signal to obtain a frequency output signal; the frequency output signal is used for measuring and calculating the magnetic field intensity of the magnetic field to be measured.
The magnetometer and the magnetic field strength determining method provided by the embodiment of the application comprise the following steps: at least two groups of parallel pump light processing optical paths, atomic gas chambers and signal processing circuits; each group of pump light processing optical paths correspondingly process different single-beam pump lights to obtain corresponding polarized pump lights; all polarized pump light enters the atomic gas chamber and outputs optical signals after reacting with alkali metal atoms in the atomic gas chamber; the optical signal enters a signal processing circuit so that the signal processing circuit processes the optical signal to obtain a frequency output signal; the frequency output signal is used for measuring and calculating the magnetic field intensity of the magnetic field to be measured. Wherein the frequencies of the different single pump beams are different. Every group pump light handles the light path and corresponds the single beam pump light of handling the difference in this magnetometer, has used multiunit pump light to come with atom interact equivalently, can realize the pumping with the atom on a plurality of ground state energy levels simultaneously, has improved the utilization ratio of light pumping in-process ground state atom for atomic polarizability obtains further improvement, thereby improves the atomic pumping rate in the optical pump magnetometer. In addition, on the premise of adopting a plurality of groups of pump lights, when the modulation frequency of the pump lights and the Larmor precession frequency generated by atoms under a magnetic field with specific strength resonate, a magneto-optical resonance signal with larger amplitude can be obtained, so that the signal-to-noise ratio of the signal can be improved, and the sensitivity of the magnetometer is improved.
Drawings
FIG. 1 is a schematic diagram of an internal optical path configuration of a magnetometer according to one embodiment;
FIG. 2 is a schematic view of the configuration of the internal optical path of the magnetometer in another embodiment;
FIG. 3 is a diagram illustrating atomic polarization transition energy levels in another embodiment;
FIG. 4 is a schematic view of the configuration of the internal optical path of the magnetometer in another embodiment;
FIG. 5 is a schematic view of the configuration of the internal optical path of the magnetometer in another embodiment;
FIG. 6 is a schematic view of the configuration of the internal optical path of the magnetometer in another embodiment;
FIG. 7 is a schematic view of the configuration of the internal optical path of the magnetometer in another embodiment;
FIG. 8 is a schematic view of the configuration of the internal optical path of the magnetometer in another embodiment;
FIG. 9 is a schematic view of the configuration of the internal optical path of the magnetometer in another embodiment;
FIG. 10 is a schematic view of the configuration of the internal optical path of the magnetometer in another embodiment;
FIG. 11 is a schematic view showing the configuration of the internal optical path of the magnetometer in another embodiment;
FIG. 12 is a schematic view of the configuration of the internal optical path of the magnetometer in another embodiment;
fig. 13 is a flow chart of a magnetic field strength determination method in one embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application more clearly understood, the embodiments of the present application are described in further detail below with reference to the accompanying drawings and the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the application and are not intended to limit the embodiments of the application.
It is to be understood that the numbering scheme used herein for elements, such as "first", "second", etc., is used solely to distinguish one from another as may be described without any sequential or technical meaning. The term "connected" and "coupled" when used in this application, unless otherwise indicated, includes both direct and indirect connections (couplings). In the description of the present application, it is to be understood that the positional words, such as "upper", "lower", etc., indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present application and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the present application. In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through intervening media. In the present application, the difference in name is not used as a means for distinguishing elements, but the difference in function of elements is used as a principle of distinction.
First, before specifically describing the technical solution of the embodiment of the present application, a technical background or a technical evolution context on which the embodiment of the present application is based is described.
First, the related words in the technical background on which the embodiments of the present application are based are introduced:
an optical pumping magnetometer (optical sampling magnetometer) is a metrology term, and is a magnetometer manufactured by using the principle that a circular polarized light excites a gas atom system in a magnetic field to be measured to generate a particle number difference between zeeman sub-energy levels of the gas atom system, so that a magnetic resonance effect is observed.
Pumping: light acts on medium atoms to excite electrons with low energy level to high energy level, and the process is called pumping or pumping; i.e., pumping, is a process of raising (or "pumping") electrons from a lower energy level in an atom or molecule to a higher energy level using light. The pump light is emitted by a pump laser with an adjustable specific wavelength range.
Thermal atom: atoms in an excited state or with kinetic energy higher than the thermal energy of the surrounding environment may be generated by nuclear transformation processes or by other methods such as acceleration by chemical accelerators, interaction of radiation with matter.
Ensemble (ensemble): under certain macroscopic conditions, a large number of sets of independent systems with completely identical properties and structures in various motion states.
Circularly polarized light: the light with circular trace drawn by the end point of the rotating electric vector is called circularly polarized light, which belongs to the special case of elliptically polarized light.
The ground state refers to such a stationary state that an atom is at the lowest energy level in a normal state, and then an electron moves on an orbit nearest to a nucleus.
Generally, the amplitude modulation type optical pump magnetometer based on single optical pumping mainly has two configurations: one is a configuration using only single-beam circularly polarized light as both the pump light and the probe light; the other is a configuration using one circularly polarized light as the pump light and another linearly polarized light as the probe light. Applicants have discovered in performing these two configurations of optical pump magnetometer applications and analyses:
the first configuration: the method is characterized in that only single-beam circularly polarized light is used as a configuration of pumping light and probe light at the same time, specifically, the single-beam circularly polarized light is used for acting on a thermal atom ensemble (namely, used as the pumping light) to realize atomic pumping, and the magnetic field intensity is measured and calculated by detecting the light intensity change after the single-beam circularly polarized light acts on atoms in a magnetic field environment.
The first configuration: the configuration using one circularly polarized light as the pump light and the other linearly polarized light as the probe light may be the same configuration using a single circularly polarized light to act on the thermal atomic ensemble (i.e., as the pump light), but using a linearly polarized light perpendicular to the circularly polarized light direction as the probe light, and then measuring the magnetic field strength by detecting the linear polarization plane deflection angle of the linearly polarized light after the action on the atomic ensemble.
For the optical pump magnetometer with the first configuration, the sensitivity is relatively low due to the influence of the amplitude modulation signal in the laser on the light intensity detection result, or the magnetometer is required to have a small volume in practical application, so that the atomic gas chamber is designed to be small, the atomic polarizability is influenced, and the sensitivity is also low. In the optical pump magnetometer of the second configuration, the probe light is used alone, and although the sensitivity is high, the atomic pumping rate is yet to be further improved. Therefore, how to ensure the sensitivity of the optical pump magnetometer and improve the atomic pumping rate becomes a difficult problem to be solved urgently at present. In addition, it should be noted that, from the deep analysis of the prior art to the determination of the technical problem and the technical solution described in the following embodiments, the applicant has paid a lot of creative efforts.
Next, a detailed description will be given of a specific optical path configuration in a magnetometer provided by an embodiment of the present application, with reference to the accompanying drawings.
As shown in fig. 1, an embodiment of the present application provides a magnetometer 10, where the magnetometer 10 includes: at least two groups of parallel pump light processing optical paths 101, an atomic gas chamber 102 and a signal processing circuit 103; each group of pump light processing optical paths 101 is used for correspondingly processing different single-beam pump lights to obtain corresponding polarized pump lights; wherein, the frequencies of different single beams of pump light are different; all polarized pump light enters the atom gas chamber 102 and outputs optical signals after reacting with alkali metal atoms in the atom gas chamber 102; the optical signal enters the signal processing circuit 103, so that the signal processing circuit 103 processes the optical signal to obtain a frequency output signal; the frequency output signal is used for measuring and calculating the magnetic field intensity of the magnetic field to be measured.
The pump light processing optical path 101 is an optical path for processing different single pump lights to obtain corresponding polarized pump lights. The single pump light refers to pump light output by one semiconductor laser, that is, the single pump light processed by each pump light processing optical path 101 is output by a different semiconductor laser.
For example, as shown in fig. 2, the pump light processing optical path 101 includes a first pump light processing optical path 1011 and a second pump light processing optical path 1012, so that the single pump light processed by the first pump light processing optical path 1011 is a first pump light, and the single pump light processed by the second pump light processing optical path 1012 is a second pump light, where the first pump light is output by the first semiconductor laser 1041, and the second pump light is output by the second semiconductor laser 1042.
Wherein the frequencies of the different single pump beams are different. Alternatively, the frequency of each beam of pump light may be set according to the alkali metal atoms in the atomic gas cell. The atomic gas cell may also be referred to as an alkali metal atomic gas cell, and it is naturally understood that the atomic gas cell includes alkali metal atoms, for example, rubidium atoms (Rb), cesium atoms (Cs), potassium atoms (K), and the like, which are not limited in this embodiment. Since the operating temperature of each atom is different and other parameters, such as laser, wavelength, and magnetic field, are determined from atom to atom, a magnetometer is typically designed to determine the alkali metal atoms to be used in the atomic gas cell and then determine the relevant parameters based on the alkali metal atoms used.
Taking rubidium atoms and two beams of pump light as an example, optionally, if the alkali metal atoms are rubidium atoms, the different single beams of pump light include a first beam of pump light and a second beam of pump light; then, the frequency of the first beam of pump light is the same as the transition frequency of the rubidium atom D1 wire, and the frequency of the second beam of pump light is the same as the transition frequency of the rubidium atom D2 wire.
In this embodiment, for example, Rb atoms are used as the working medium, the first pump beam is output by the semiconductor laser 1041 and has the same frequency as the transition frequency of Rb atom D1, and the second pump beam is output by the other semiconductor laser 1042 and has the same frequency as the transition frequency of Rb atom D2.
The polarized pump light corresponding to each beam of pump light is correspondingly obtained after the single beam of pump light is correspondingly processed by the different pump light processing optical paths 101, the polarized pump light obtained here may be circularly polarized light or linearly polarized light, and specifically, the circularly polarized light or the linearly polarized light may be adjusted according to actual requirements.
Whether the output of each pump light processing optical path 101 is circularly polarized (pump) light or linearly polarized (pump) light, each polarized pump light enters the atomic gas cell 102 and reacts with the alkali metal atoms in the atomic gas cell 102. The action of the pump light and the alkali metal atoms refers to the phenomenon that polarized light which resonates with atomic absorption lines generates uneven distribution of atoms between ground energy levels through optical pumping, the pumping is the process that the pump light raises electrons from a lower energy level (or 'pump') in the alkali metal atoms to a higher energy level, the atoms can do Larmor precession along the direction of a magnetic field after being polarized by the pump light, wherein the Larmor precession refers to the precession of the magnetic moment of the atoms under the action of an external magnetic field.
For example, as shown in fig. 3, fig. 3 is a schematic diagram of a transition channel when a pump light interacts with an atom. Assuming that the lines D1 and D2 in fig. 3 are the lines Rb atom D1 and D2, the first pump beam is represented as pump beam 1 in fig. 3, and the second pump beam is represented as pump beam 2 in fig. 3, then since the frequency of pump beam 1 is the same as the transition frequency of the line Rb atom D1 and the frequency of pump beam 2 is the same as the transition frequency of the line Rb atom D2, in fig. 3 (a), the pump beam 1 will be 52S1/2F-1 level pumped to 5 higher than it2P1/2At level F1, pump light 2 will be 52S1/2F2 level pumped to 5 higher than it2P3/2F is at the 1 level; and in fig. 3 (b), the pump light 1 is 52S1/2F-1 level pumped to 5 higher than it2P1/2At level F1, pump light 2 will be 52S1/2F2 level pumped to 5 higher than it2P1/2F is at the 2 level; it is understood that (a) and (b) in fig. 3 are examples of energy level transitions in practical applications, and are not intended to be limiting. Therefore, as can be seen from both (a) and (b) in fig. 3, it is possible to achieve simultaneous pumping of atoms at different low energy levels to other higher energy levels by the double pump light, which results in an increase in the polarization rate of the atoms.
After the polarized pump light input into the atomic gas cell 102 and the alkali metal atoms in the atomic gas cell 102 have the above-mentioned effect, the optical signal output from the atomic gas cell may be the acted pump optical signal in one case; but in another case it may be other optical signals, for example if the polarized probe light enters in addition to the polarized pump light, which enters the atomic gas cell, in which case it may also be a probe optical signal that is output from the atomic gas cell 102. For these two cases, the present application will provide different examples for illustration hereinafter, and will not be described again here.
With reference to fig. 1, the optical signal output from the atomic gas cell 102 is input into a signal processing circuit 103 disposed at the rear, and the signal processing circuit 103 processes the optical signal, for example, signal type conversion, signal filtering, signal calculation, and the like, and the processing procedure and the type of the signal processing circuit 103 are not limited in the embodiment of the present application. The optical signal is processed by the signal processing circuit 103 to obtain a frequency output signal, which is a signal for measuring and calculating the magnetic field strength of the magnetic field to be measured. Because the optical signal output by the atomic gas chamber 102 can reflect the light intensity change of the magnetic field to be measured after the pumping light and the alkali metal atoms are reacted, the frequency output signal obtained after the processing also corresponds to the light intensity change, and the magnetic field intensity of the magnetic field to be measured can be accurately measured according to the frequency output signal.
For example, the magnetic field strength of the magnetic field to be measured is measured and calculated according to the frequency output signal, which may be calculated by using an external algorithm model, that is, the frequency output signal is input into a pre-trained algorithm model, and the obtained output is the magnetic field strength; of course, a calculation processing chip may be disposed inside the magnetometer, the frequency output signal output by the signal processing circuit 103 may be directly input to the calculation processing chip, and the calculation processing chip outputs the magnetic field strength, so that for the magnetometer, the magnetic field strength value of the magnetic field to be measured is directly obtained during the measurement. The embodiment of the present application does not limit the manner of measuring and calculating the magnetic field strength of the magnetic field to be measured according to the frequency output signal, and any manner may be used.
The present embodiment provides a magnetometer, comprising: at least two groups of parallel pump light processing optical paths, atomic gas chambers and signal processing circuits; each group of pump light processing optical paths correspondingly process different single-beam pump lights to obtain corresponding polarized pump lights; all polarized pump light enters the atomic gas chamber and outputs optical signals after reacting with alkali metal atoms in the atomic gas chamber; the optical signal enters a signal processing circuit so that the signal processing circuit processes the optical signal to obtain a frequency output signal; the frequency output signal is used for measuring and calculating the magnetic field intensity of the magnetic field to be measured. Wherein the frequencies of the different single pump beams are different. Every group pump light handles the light path and corresponds the single beam pump light of handling the difference in this magnetometer, has used multiunit pump light to come with atom interact equivalently, can realize the pumping with the atom on a plurality of ground state energy levels simultaneously, has improved the utilization ratio of light pumping in-process ground state atom for atomic polarizability obtains further improvement, thereby improves the atomic pumping rate in the optical pump magnetometer.
In addition, on the premise of adopting a plurality of groups of pump lights, when the modulation frequency of the pump lights and the Larmor precession frequency generated by atoms under a magnetic field with specific strength resonate, a magneto-optical resonance signal with larger amplitude can be obtained, so that the signal-to-noise ratio of the signal can be improved, and the sensitivity of the magnetometer is improved.
Based on the foregoing embodiments, an example of a specific implementation configuration in the pump light processing optical path 101 is provided below, as shown in fig. 4, fig. 4 is a schematic diagram provided on the basis of fig. 1, and in practical applications, the schematic diagram may also be provided in combination with fig. 2, which is not limited herein. In one embodiment, each set of pump light processing optical paths 101 includes: a first optical lens 1013, a first polarizer 1014, an amplitude modulator 1015, and a quarter-wave plate 1016; the first optical lens 1013 is configured to collimate and adjust a light spot of the corresponding single beam of pump light; a first polarizer 1014 for aligning the pump light after the alignment and spot adjustment to perform linear polarization adjustment; the amplitude modulator 1015 is configured to perform amplitude modulation on the pump light after linear polarization adjustment, and output light after amplitude modulation is converted into circularly polarized pump light through the quarter-wave plate 1016.
It should be noted that, on the basis of the specific implementation configuration in the pump light processing optical path 101 provided in this embodiment, the obtained polarized pump light may be adjusted to be the circularly polarized pump light, the linearly polarized pump light, and the elliptically polarized pump light according to the requirement, but in this embodiment, the description is given by taking as an example that the polarized pump light obtained correspondingly after the single beam of pump light is processed by the pump light processing optical path 101 is the circularly polarized pump light.
It should be emphasized that the second in the embodiment is only used to distinguish the same device in different embodiments when the first and the rear optical signals are detection optical signals, and information such as a model, a structure, and parameters of the device itself is not limited.
The first optical lens 1013 is an optical element made of a transparent material and having a surface that is a part of a spherical surface, and may be a plastic lens or a glass lens, which is not limited in this embodiment. After entering the first optical lens 1013, the pump light passes through the first optical lens 1013 for collimation and spot adjustment, and then the pump light after collimation and spot adjustment enters the first polarizer 1014, which is a device that obtains polarized light from natural light emitted from a common light source, so the first polarizer 1014 aligns the pump light after the collimation and spot adjustment for linear polarization adjustment. The polarizer may be a polarizer, a nicol prism, or the like, which is not limited in the embodiments of the present application.
Referring to fig. 4, the pump light after linear polarization adjustment by the first polarizer 1014 is input to the amplitude modulator 1015 arranged at the rear end, the amplitude modulator 1015 performs amplitude modulation on the pump light after linear polarization adjustment, and output light after amplitude modulation enters the quarter-wave plate 1016 and is converted into circular polarization pump light by the quarter-wave plate 1016.
The quarter-wave plate 1016 is a quarter retardation plate, and when light of a certain wavelength is vertically incident and passes through, the outgoing ordinary light and extraordinary light have a phase difference 1/4. Quarter-wave plates are often used in the optical path to change linearly polarized light into circularly or elliptically polarized light, or vice versa. In practice, quarter-wave plate 1016 may be formed as a parallel plane plate cut parallel to the optical axis using a birefringent material, with a thickness that is precisely an odd multiple of the product of the difference between the two principal axes of the birefringent material and a given wavelength 1/4; there may be a wave plate made of an optically active material capable of rotating the polarization plane of incident light by an odd multiple of x/2, which is not limited in the embodiments of the present application.
The amplitude modulator 1015 may be an Acousto-optic modulator (AOM), and amplitude-modulates the pump light after linear polarization adjustment by the AOM. The principle can be understood as follows: when an external signal acts on the acousto-optic device through the driving power supply, the ultrasonic intensity changes along with the signal, and the diffraction light intensity also changes along with the signal, so that the amplitude or intensity modulation of the laser is realized.
Therefore, the AOM can realize the function of amplitude modulation of the pump light after linear polarization adjustment by driving with an external signal. Based on this, in one embodiment, as shown in fig. 5, each set of pump light processing optical paths corresponds to one rf driver 105; the rf driver 105 is configured to amplify the frequency output signal to obtain a control signal scanned in a corresponding frequency range; the control signal is used for controlling the amplitude modulator to perform amplitude modulation on the pump light after linear polarization adjustment.
The frequency output signal is output by the signal processing circuit, and the rf driver 105 is used for amplifying the frequency signal output by the signal processing circuit to obtain a control signal scanned in a corresponding frequency range.
Specifically, the rf driver 105 is used to provide an external signal, i.e. a control signal, to the AOM, so that the ultrasonic intensity of the AOM changes with the control signal under the action of the control signal, and the diffracted light intensity also changes with the control signal, thereby performing amplitude modulation on the pump light after linear polarization adjustment. The rf driver 105 amplifies the frequency output signal according to the frequency output signal outputted from the signal processing circuit 103, the amplified signal is called a control signal, and the control signal needs to be a control signal scanned in a corresponding frequency range, which refers to a frequency corresponding to the frequency output signal. It can be understood that, since the rf driver 105 plays a role of amplifying the frequency output signal, it is equivalent to that the frequency output signal outputted by the signal processing circuit 103 belongs to the control signal capable of controlling the AOM, and is only called the frequency output signal, and therefore, the relationship between the control signal and the frequency output signal is that the control signal is the amplified signal of the frequency output signal.
As shown in fig. 6, fig. 6 is based on the above-mentioned embodiments of fig. 4 and 5 to include two sets of pump light processing optical paths 101: the first pump light processing optical path 1011 and the second pump light processing optical path 1012 are taken as an example, and correspondingly, one optical lens, one polarizer, one amplitude modulator and one quarter wave plate are arranged in each pump light processing optical path, and the radio frequency driver (shown as an RF driver) is also taken as an example and comprises a first RF driver 1051 and a second RF driver 1052, so as to provide an optical path configuration of the magnetometer.
In this embodiment, the functions and principles of each device and the processing manner of light have been described in the foregoing embodiments, and are not described herein again. In the embodiment, different amplitude modulators are used for simultaneously carrying out amplitude modulation on different polarized pump lights, and when the modulation frequency of the pump lights is in resonance with the Larmor precession frequency generated by atoms in a magnetic field with specific intensity, a magneto-optical resonance signal with larger amplitude can be obtained, so that the signal-to-noise ratio of the signal is improved, and the sensitivity of the magnetometer is improved.
As mentioned above, the optical signal output from the atomic gas cell 102 is a pump optical signal in one case and a probe optical signal in the other case, and then, the internal configuration of the signal processing circuit 103 will be described in detail by providing an example for each of the two cases.
In one embodiment, the case where the optical signal is a pump optical signal is described, which indicates that there is no probe light and that only pump polarized light enters the atomic gas cell 102. As shown in fig. 7, in this embodiment, the signal processing circuit 103 includes a detector 1031, a first signal processor 1032, a first phase-lock amplifier 1033, and a first frequency signal generator 1034; a detector 1031 for converting the pump light signal into a voltage signal; a first signal processor 1032 for filtering and amplifying the voltage signal; a first phase-locked amplifier 1033, configured to calculate an error signal according to the filtered and amplified voltage signal; a first frequency signal generator 1034 for generating a frequency output signal in accordance with the error signal.
It is emphasized again that the second in the embodiment is only to distinguish the same device in different embodiments when the first and the rear optical signals in this embodiment are detection optical signals, and information such as a model, a structure, and parameters of the device itself is not limited.
In this embodiment, referring to fig. 7, the pump light signal output from the atomic gas cell 102 is detected by a detector 1031, and the detector 1031 may be any type of detector. The output of the detector 1031 is a converted voltage signal, which enters the first signal processor 1032, and after being filtered and amplified by the first signal processor 1032, the filtered and amplified voltage signal is input to the first phase-lock amplifier 1033, an error signal is calculated by the first phase-lock amplifier 1033, the error signal is input to the first frequency signal generator 1034, and the first frequency signal generator 1034 is configured to control the frequency value of the frequency output signal, that is, the frequency value of the frequency output signal is a value controlled by the first frequency signal generator 1034.
Referring to fig. 8, fig. 8 is a schematic diagram showing an internal configuration of a magnetometer provided by combining the above fig. 6 and fig. 7. In fig. 8, the output frequency output signal of the first frequency signal generator 1034 is input to the RF driver 105 (when two RF drivers are input, both of the two RF drivers input the complete frequency output signal), and the output frequency signal of the first frequency signal generator 1034 is a square wave or a sinusoidal signal scanned in a certain frequency range, so that after the output frequency output signal is input to the RF driver, the RF driver performs power amplification according to the output frequency output signal to obtain a power-amplified frequency output signal, which is called a control signal; since the RF driver only performs power amplification, the control signal is also a square wave or sinusoidal signal that is swept over a range of frequencies, and then the control signal (power amplified signal) is provided to the AOM to amplitude modulate the pump light. For the principle, configuration and optical path of other devices in fig. 8, the description of the foregoing embodiments can be referred to, and details are not repeated herein.
In another embodiment, a case where the optical signal is a probe optical signal is described, in which case probe light is present and the probe light enters the atomic gas cell 102 in addition to the pump polarized light.
First, the case of detecting light when there is detecting light, and the case of the atomic gas cell 102 will be described. As shown in FIG. 9, in one embodiment, magnetometer 10 further comprises a set of probe light processing optical paths 106; the detection light processing optical path 106 is used for processing the single-beam detection light to obtain corresponding polarized detection light; the frequency of the single-beam probe light is different from the frequency of the single-beam pump light processed by the pump light processing optical path processing 101 of different groups; the polarized probe light enters the atom gas cell 102 in a direction perpendicular to the polarized pump light, and outputs a probe light signal after the polarized probe light and the polarized pump light jointly react with the alkali metal atoms.
The probe light processing optical path 106 is an optical path for processing the single probe light beam to obtain corresponding polarized probe light. The single probe light beam is probe light output by one semiconductor laser, that is, the semiconductor laser outputting the probe light is different from the semiconductor laser outputting the pump light in front.
The frequency setting of the probe light is also different from the frequency of the pump light, and the frequency of the probe light is different from the frequency of the single pump light of the different groups of pump light processing optical path processing 101.
Optionally, still taking the alkali metal atom as the rubidium atom as an example, the frequency of the probe light is a frequency after shifting the transition frequency of the rubidium atom D2 line by a preset magnitude.
The frequency of the probe light can be set to a frequency that is on the order of GHz detuned from the Rb atom D2 wire transition frequency. The frequencies of the front pumping light are the same as the transition frequency of the Rb atom D1 wire, the frequencies of the front pumping light and the Rb atom D2 wire, and the frequencies of the front pumping light and the Rb atom D2 wire are different after the frequency of the probe light is set to be a frequency which is detuned in a GHz order with the transition frequency of the Rb atom D2 wire.
Referring to fig. 9, the detection light processing optical path 106 processes the single-beam detection light to obtain corresponding polarized detection light, where the polarized detection light is linearly polarized detection light, and the polarized detection light (i.e., the linearly polarized detection light) enters the atom gas cell 102 in a direction perpendicular to the polarized pump light, and then, the polarized detection light and the polarized pump light jointly react with the alkali metal atoms to output a detection light signal.
In fig. 9, the linear polarization probe light enters the atomic gas cell 102 in a direction perpendicular to the polarization pump light, and in this case, the atomic gas cell 102 outputs a probe light signal, so in this case, the polarization pump light entering the atomic gas cell 102 is in a direction perpendicular to the polarization probe light, and may be absorbed by an extinction plate or naturally dissipated.
It should be noted here that the detection light does not polarize the atoms, that is, the detection light enters the atom gas cell 102, only because the pumping light in the atom gas cell 102 and the alkali metal atoms act to polarize the alkali metal atoms, the detection light irradiates the polarized atoms, and the light intensity thereof changes to some extent, so that the polarization plane of the detection light signal line output from the atom gas cell 102 has a deflection angle, and the magnetic field intensity of the magnetic field to be measured can be determined according to the deflection angle of the linear polarization plane.
The specific process of determining the magnetic field strength of the magnetic field to be measured according to the deflection angle of the linear polarization plane may be obtained by processing the magnetic field strength with the signal processing circuit 103.
In an embodiment, which is an internal configuration embodiment of the signal processing circuit 103 in the case that the optical signal is a detection optical signal, as shown in fig. 10, the signal processing circuit 103 includes a differential detector 1035, a second signal processor 1036, a second lock-in amplifier 1037, and a second frequency signal generator 1038; a differential detector 1035 for converting the detected light signal into a voltage signal; a second signal processor 1036 for filtering and amplifying the voltage signal; a second lock-in amplifier 1037, configured to calculate according to the filtered and amplified voltage signal to obtain an error signal; a second frequency signal generator 1038 for generating a frequency output signal based on the error signal.
In this embodiment, referring to fig. 10, the detection light signal output from the atomic gas cell 102 is detected by a differential detector 1035, and the differential detector 1035 must be a differential detector. The output of the differential detector 1035 is a converted voltage signal, the voltage signal enters the second signal processor 1036, after being filtered and amplified by the second signal processor 1036, the filtered and amplified voltage signal is input to the second lock-in amplifier 1037, the second lock-in amplifier 1037 calculates an error signal, the error signal is input to the second frequency signal generator 1038, and the second frequency signal generator 1038 is used to control the frequency value of the frequency output signal, that is, the frequency value of the frequency output signal is the value controlled by the second frequency signal generator 1038.
That is, in the case where the optical signal is a detection optical signal, only the type of the detector (differential detector) is different from that in the case where the optical signal is a pump optical signal, and the functions of the other signal processor, the lock-in amplifier, and the frequency signal generator are the same, and other information and parameters may be the same.
In one embodiment, as shown in fig. 11, the probe light processing optical path 106 includes a second optical lens 1061 and a second polarizer 1062; the second optical lens 1061 is used for collimating and spot-adjusting the single-beam probe light; and the second polarizer 1062 is used for aligning the detected light after the straight light spot adjustment and the light spot adjustment to perform linear polarization adjustment and output.
The second optical lens 1061 is an optical element made of a transparent material and having a surface that is a part of a spherical surface, and may be a plastic lens or a glass lens, which is not limited in this embodiment. After entering the second optical lens 1061, the probe light is collimated and spot-adjusted by the second optical lens 1061, and then the probe light after the collimation and spot adjustment enters the second polarizer 1062, which is a device for obtaining polarized light from natural light emitted from a common light source, so that the second polarizer 1062 performs linear polarization adjustment on the pump light after the collimation and spot adjustment. The polarizer may be a polarizer, a nicol prism, or the like, which is not limited in the embodiments of the present application.
Referring to fig. 12, fig. 12 is a schematic view showing an internal configuration of a magnetometer provided by combining the above fig. 6, 10 and 11. In fig. 12, the frequency output signal output by the second frequency signal generator 1038 is input to the RF driver 105 (when two RF drivers are input, both of the two RF drivers are input, and the two RF drivers input the frequency output signal complete signal), and the frequency output signal output by the second frequency signal generator 1038 is also a square wave or a sinusoidal signal scanned in a certain frequency range, so that after the output frequency output signal is input to the RF driver, the RF driver performs power amplification according to the frequency output signal to obtain a power amplified frequency output signal, which is called a control signal. For the principle, configuration and optical path of other devices in fig. 12, the description of the foregoing embodiments can be referred to, and details are not repeated herein.
So far, the internal optical path configuration of the magnetometer and the principle and optical direction in each optical path configuration in various embodiments have been described.
In addition, the present application also provides an embodiment of a magnetic field strength determination method, which can be applied to a magnetometer configured in any one of the above embodiments, and as shown in fig. 13, the method includes the following steps:
s101, correspondingly processing different single-beam pump light through different groups of parallel pump light processing light paths to obtain corresponding polarized pump light; wherein the frequencies of the different single pump beams are different.
And S102, inputting all polarized pump light into the atomic gas chamber, and outputting optical signals after the polarized pump light reacts with alkali metal atoms in the atomic gas chamber.
S103, inputting the optical signal into a signal processing circuit to enable the signal processing circuit to process the optical signal to obtain a frequency output signal; the frequency output signal is used for measuring and calculating the magnetic field intensity of the magnetic field to be measured.
For specific limitations of the method for determining the magnetic field strength, reference may be made to the limitations of the magnetometer described above, and details thereof will not be repeated here.
It should be understood that, although the steps in the flowchart of fig. 13 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least a portion of the steps in fig. 13 may include multiple steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of performing the steps or stages is not necessarily sequential, but may be performed alternately or alternately with other steps or at least a portion of the steps or stages in other steps.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database or other medium used in the embodiments provided herein may include at least one of non-volatile and volatile memory. Non-volatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical storage, or the like. Volatile Memory can include Random Access Memory (RAM) or external cache Memory. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM), among others.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express a few embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for those skilled in the art, variations and modifications can be made without departing from the concept of the embodiments of the present application, and these embodiments are within the scope of the present application. Therefore, the protection scope of the embodiments of the present application shall be subject to the appended claims.
Claims (10)
1. A magnetometer, characterized in that it comprises: at least two groups of parallel pump light processing optical paths, atomic gas chambers and signal processing circuits;
each group of the pump light processing light paths is used for correspondingly processing different single-beam pump lights to obtain corresponding polarized pump lights; wherein, the frequencies of different single beams of pump light are different;
all the polarized pump light enters the atomic gas chamber and outputs optical signals after reacting with alkali metal atoms in the atomic gas chamber;
the optical signal enters the signal processing circuit, so that the signal processing circuit processes the optical signal to obtain a frequency output signal; the frequency output signal is used for measuring and calculating the magnetic field intensity of the magnetic field to be measured.
2. The magnetometer of claim 1, wherein the alkali metal atoms are rubidium atoms, and the different single beams of pump light comprise a first beam of pump light and a second beam of pump light;
then, the frequency of the first beam of pump light is the same as the transition frequency of the rubidium atom D1 wire, and the frequency of the second beam of pump light is the same as the transition frequency of the rubidium atom D2 wire.
3. The magnetometer of claim 1, wherein the polarized pump light is a circularly polarized pump light; each set of the pump light processing optical paths includes: the optical lens comprises a first optical lens, a first polarizer, an amplitude modulator and a quarter-wave plate;
the first optical lens is used for collimating and adjusting light spots of the corresponding single beam of pump light;
the first polarizer is used for aligning the pump light after the alignment and the light spot adjustment to perform linear polarization adjustment;
the amplitude modulator is used for carrying out amplitude modulation on the pump light after linear polarization adjustment, and output light after amplitude modulation is converted into the circularly polarized pump light through the quarter-wave plate.
4. The magnetometer of claim 3, wherein each set of the pump light processing optical paths corresponds to one rf driver;
the radio frequency driver is used for amplifying the frequency output signal to obtain a control signal scanned in a corresponding frequency range; the control signal is used for controlling the amplitude modulator to perform amplitude modulation on the pump light after the linear polarization adjustment.
5. The magnetometer of any one of claims 1-5, wherein the optical signal is a pump optical signal; the signal processing circuit comprises a detector, a first signal processor, a first phase-locked amplifier and a first frequency signal generator;
the detector is used for converting the pump light signal into a voltage signal;
the first signal processor is used for filtering and amplifying the voltage signal;
the first phase-locked amplifier is used for calculating according to the filtered and amplified voltage signal to obtain an error signal;
the first frequency signal generator is configured to generate the frequency output signal according to the error signal.
6. A magnetometer according to any one of claims 1 to 5 wherein the optical signal is a probe optical signal; the magnetometer further comprises a group of detection light processing light paths;
the detection light processing optical path is used for processing the single-beam detection light to obtain corresponding polarized detection light; the frequency of the single-beam probe light is different from the frequency of the single-beam pump light processed by the pump light processing optical paths of different groups;
the polarized detection light enters the atom gas chamber in a direction perpendicular to the polarized pump light, and the polarized detection light and the polarized pump light jointly react with the alkali metal atoms to output the detection light signal.
7. The magnetometer of claim 6, wherein the alkali metal atoms are rubidium atoms, and the frequency of the probe light is a frequency shifted by a predetermined magnitude from a transition frequency of a D2 line of the rubidium atoms.
8. The magnetometer of claim 6, wherein the probe light processing optical path comprises a second optical lens and a second polarizer;
the second optical lens is used for collimating and adjusting the light spot of the single-beam probe light;
and the second polarizer is used for aligning the direct light and the detected light after the light spot adjustment to perform linear polarization adjustment.
9. The magnetometer of claim 6, wherein the signal processing circuitry comprises a differential detector, a second signal processor, a second lock-in amplifier, and a second frequency signal generator;
the differential detector is used for converting the detection light signal into a voltage signal;
the second signal processor is used for filtering and amplifying the voltage signal;
the second lock-in amplifier is used for calculating according to the filtered and amplified voltage signal to obtain an error signal;
the second frequency signal generator is configured to generate the frequency output signal according to the error signal.
10. A magnetic field strength determination method applied to the magnetometer of any one of claims 1 to 9, the method comprising:
correspondingly processing different single-beam pump light through different groups of parallel pump light processing light paths to obtain corresponding polarized pump light; wherein, the frequencies of different single beams of pump light are different;
inputting all the polarized pump light into an atomic gas chamber, and outputting optical signals after the polarized pump light and alkali metal atoms in the atomic gas chamber react;
inputting the optical signal into a signal processing circuit, so that the signal processing circuit processes the optical signal to obtain a frequency output signal; the frequency output signal is used for measuring and calculating the magnetic field intensity of the magnetic field to be measured.
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