CN108287322B - Atomic magnetometer without response blind zone and method for measuring external magnetic field by atomic magnetometer - Google Patents
Atomic magnetometer without response blind zone and method for measuring external magnetic field by atomic magnetometer Download PDFInfo
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- CN108287322B CN108287322B CN201810083802.1A CN201810083802A CN108287322B CN 108287322 B CN108287322 B CN 108287322B CN 201810083802 A CN201810083802 A CN 201810083802A CN 108287322 B CN108287322 B CN 108287322B
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Abstract
The invention provides an atomic magnetometer without a response blind zone, which comprises a laser, a beam expanding and collimating device, a circularly polarized light conversion device, an acousto-optic modulator, a Helmholtz coil, an atomic gas chamber, a reflector group, a photoelectric detector, a lock-in amplifier, a signal processing system and a heating device. The atomic magnetometer is simple in structure; the method combines two excitation methods of applying an excitation magnetic field and modulating light, and realizes the measurement of the non-response blind area by detecting the components of the total spin angular momentum of the sensing atoms along two directions. The invention also discloses a method for measuring the external magnetic field by adopting the atomic magnetometer, which is simple and convenient in measuring method, free of response blind area, capable of quickly and accurately obtaining relevant data of the external magnetic field and strong in practicability.
Description
Technical Field
The invention relates to the technical field of weak magnetic field detection, in particular to an atomic magnetometer without a response blind area and a method for measuring an external magnetic field by the atomic magnetometer.
Background
In many critical fields, such as basic physical research, biomedicine, deep space exploration, geological exploration, earthquake prediction, nuclear magnetic resonance signal detection and the like, effective detection of a weak magnetic field is urgently needed. The conventional magnetometers mainly comprise a fluxgate, a Hall device, a proton magnetometer, a superconducting quantum interference device and an atomic magnetometer. Among them, the superconducting quantum interference device is the magnetometer which is currently put into practical use and has been realized to have the highest sensitivity
Sensitivity of order of magnitude. However, the superconducting quantum interference device requires a huge refrigeration device, so that the application range of the superconducting quantum interference device is limited due to inconvenience in use. Atomic magnetometers are magnetometers based on spin precession detection. For the sensing atom (alkali metal atom or4He), when the total spin angular momentum of the atoms precesses around the external magnetic field and performs magnetic resonance, the ratio of the precession frequency (namely the magnetic resonance frequency) to the external magnetic field is a constant gamma, and the external magnetic field can be detected by detecting the magnetic resonance frequency. Under the action of optical pumping, the sensitivity of the atomic magnetometer is extremely high because a large number of sensing atoms are in a coherent state. Its theoretical sensitivity is higher than that of superconducting quantum interference device, and at present in laboratory, the optimum sensitivity obtained by atomic magnetometer is reached
Magnitude. The atomic magnetometer does not need huge refrigeration equipment, so the atomic magnetometer is more widely applied than a superconducting quantum interference device.
The atomic magnetometer realizes the polarization of sensing atoms by an optical pumping method, and when a system is in a balanced state, the total spin angular momentum of the sensing atoms is along the direction of an external magnetic field and cannot precess around the external magnetic field, so that the external magnetic field cannot be detected. In order to realize that the total spin angular momentum of the sensing atoms precesses around the external magnetic field, that is, the component of the total spin angular momentum of the sensing atoms in the direction perpendicular to the external magnetic field is not zero, the atomic magnetometer generally adopts a method of applying an excitation magnetic field or modulating pumping light, and the excitation generates the total spin angular momentum component perpendicular to the external magnetic field. For the method of applying the excitation magnetic field, when the external magnetic field is perpendicular to the pumping light, the pumping light cannot realize effective polarization on the sensing atoms, so that effective detection on the external magnetic field cannot be realized; for the method of modulating the pumping light, when the external magnetic field is parallel to the pumping light, the modulated light cannot excite the sensing atoms to generate a total spin angular momentum component perpendicular to the direction of the external magnetic field, so that effective detection of the external magnetic field cannot be realized.
Atomic magnetometers typically employ light absorption or light rotation detection methods. After the detection light passes through the atom gas chamber filled with the sensing atoms, the light intensity (light absorption method) or the polarization plane (light rotation method) of the detection light is modulated by the component of the total spin angular momentum of the sensing atoms along the light propagation direction. When the external magnetic field is parallel to the detection light, the component of the total spin angular momentum of the sensing atoms along the light propagation direction cannot precess around the external magnetic field, so that the effective detection of the external magnetic field cannot be realized.
It can be seen from the above that, when the external magnetic field is along some directions, some of the currently common atomic magnetometers cannot realize effective detection of the external magnetic field, i.e. there is a response blind area. In practical applications, the external magnetic field is generally in any direction. Therefore, the atomic magnetometer without the response blind zone has important application value.
Disclosure of Invention
The first purpose of the invention is to provide an atomic magnetometer with a simplified structure and no response blind area, and the specific technical scheme is as follows:
an atomic magnetometer without a response blind area comprises a laser, a beam expanding collimation device, a circularly polarized light conversion device, an acousto-optic modulator, a Helmholtz coil, an atomic air chamber, a reflector group, a photoelectric detector, a lock-in amplifier, a signal processing system and a heating device, wherein the laser, the beam expanding collimation device, the circularly polarized light conversion device and the acousto-optic modulator are sequentially arranged in series along the propagation direction of a light path, and the Helmholtz coil is arranged at the periphery of the atomic air chamber and used for providing an excitation magnetic field;
the laser is used for outputting laser beams along the x-axis direction;
the beam expanding and collimating device is used for carrying out beam expanding and collimating treatment on the laser beam output by the laser;
the circular polarized light conversion device is used for converting the laser beam after the beam expanding and collimating treatment into circular polarized light;
the acousto-optic modulator is used for modulating the amplitude of the circularly polarized light;
the atom gas chamber is filled with133Cs atoms and buffer gas;
the reflector group is used for changing the propagation direction of the circularly polarized light passing through the atomic gas chamber so that the circularly polarized light is emitted into the atomic gas chamber along the y-axis direction;
the photoelectric detector is used for detecting circularly polarized light passing through the atomic gas chamber;
the lock-in amplifier is used for demodulating a signal output by the photoelectric detector;
the acousto-optic modulator, the Helmholtz coil, the lock-in amplifier and the heating device are all connected with the signal processing system, the signal processing system is used for driving the acousto-optic modulator to perform amplitude modulation on circularly polarized light, the signal processing system controls an excitation magnetic field generated by the signal processing system by adjusting current input into the Helmholtz coil, and the signal processing system drives the heating device to heat the atom air chamber so as to improve the volume of the atom air chamber133A Cs atomic vapor density, the signal processing system to adjust a reference frequency of the lock-in amplifier and to acquire an output signal of the lock-in amplifier.
Preferably, in the above technical solution, the laser is 895nm DFB semiconductor laser adjusted to133The Cs atom D1 linearly transits the resonance frequency and outputs a laser beam.
Preferably, in the above technical solution, the beam expanding and collimating device is provided with two groups of convex lenses in series in turn from the light beam propagation direction.
Preferably, in the above technical solution, the reflector group includes three groups of reflectors, and the three groups of reflectors and the atomic gas chamber are located at four corners of the square.
Preferably, in the above technical solution, the circularly polarized light converting device is formed by combining a linear polarizer and a λ/4 glass slide, which are arranged in series in the propagation direction of the optical path.
Preferably, in the above technical solution, the helmholtz coil is wound by a copper wire and is used for generating an excitation magnetic field; heating device sets up the periphery of atom air chamber, heating device includes copper jig, no magnetism resistance heating plate and no magnetism temperature sensor, copper jig is used for fixing the atom air chamber, no magnetism resistance heating plate is used for right the atom air chamber heats in order to improve atom air chamberInner part133Cs atom steam density, no magnetism temperature sensor is used for measuring the temperature of atom air chamber, no magnetism resistance heating plate with no magnetism temperature sensor all with signal processing system connects.
Preferably, in the above technical solution, the signal processing system includes a data acquisition card and a computer, the data acquisition card is connected to the acousto-optic modulator, the helmholtz coil, the non-magnetic temperature sensor and the lock-in amplifier, and the computer is connected to the data acquisition card.
The invention relates to an atomic magnetometer which combines two excitation methods of applying an excitation magnetic field and modulating light, and obtains a measuring device without a response blind area by detecting the components of the total spin angular momentum of sensing atoms along two directions, which is specifically as follows: laser beams output by the 895nm DFB semiconductor laser are expanded and collimated after passing through the expanded beam collimating device, and then are converted into circularly polarized light by the circularly polarized light conversion device; then, performing amplitude modulation on the circularly polarized light by using an acousto-optic modulator, wherein the circularly polarized light with the amplitude modulated irradiates the atom air chamber along the x-axis direction; after the circularly polarized light passes through the atomic gas chamber, the propagation direction is changed by the reflector group, and then the atom gas chamber is irradiated along the y axis; circularly polarized light twice and in atomic gas chamber133After the Cs atoms have interacted with each other,133the Cs atom ensemble is polarized, and the light intensity of the circularly polarized light is modulated by spin polarization components in the x-axis direction and the y-axis direction; the circularly polarized light passing through the atomic gas chamber is detected by a photoelectric detector, and the output signal of the photoelectric detector reflects the change of the light intensity of the circularly polarized light; after the output signal of the photoelectric detector is demodulated by a lock-in amplifier, the amplitude of the output signal of the photoelectric detector output by the lock-in amplifier is collected by a signal processing system; the signal processing system drives and controls the heating device to heat the atomic gas chamber and keep the temperature of the atomic gas chamber stable; meanwhile, the signal processing system drives and controls the Helmholtz coil and the acousto-optic modulator, provides an excitation magnetic field and performs amplitude modulation on circularly polarized light, enables the frequency of the excitation magnetic field and the frequency of the optic modulation to track the magnetic resonance frequency, and obtains an external magnetic field at the atom air chamber according to the frequency. The specific principle is as follows:
the total spin angular momentum of the sense atoms of an atomic magnetometer is typically represented by the spin polarization vector of the sense atoms. Under the action of circularly polarized light, the ensemble of sensing atoms is polarized, and a large number of sensing atoms are in a coherent state and macroscopically represent spin polarization of the sensing atoms. When the method of applying an excitation magnetic field or modulating the pump light is adopted, when the excitation generates a spin polarization component perpendicular to the direction of the external magnetic field, the spin polarization component perpendicular to the direction of the external magnetic field will precess around the external magnetic field, and the frequency of the precession is equal to the frequency of the excitation magnetic field or the modulation frequency of the pump light. The amplitude of the spin-polarized component perpendicular to the direction of the external magnetic field is greatest when the frequency of the excitation magnetic field or the modulated light is equal to the magnetic resonance frequency. Therefore, the spin polarization component in the direction of the external magnetic field is detected by a light absorption or light rotation method, and the excitation magnetic field frequency or the modulation frequency of the pumping light when the amplitude of the signal is maximum is tracked, so that the magnetic resonance frequency can be obtained, and further the size of the external magnetic field can be obtained.
And selecting a three-dimensional rectangular coordinate system, wherein three axes of the coordinate system are an x axis, a y axis and a z axis respectively. The atomic magnetometer adopts a light absorption detection method, and pumping light and detection light are the same beam of circularly polarized light and firstly propagate along the x-axis direction. After the circularly polarized light passes through the atom air chamber filled with the sensing atoms along the x-axis direction, the transmission direction of the circularly polarized light is changed through the reflector, so that the circularly polarized light passes through the atom air chamber filled with the sensing atoms along the y-axis direction. Thus, the intensity of circularly polarized light is modulated by the components of the spin polarization vector in both the x-axis and y-axis directions.
When an excitation magnetic field is applied along the z-axis direction and simultaneously the circularly polarized light is subjected to amplitude modulation, and the light modulation frequency is equal to the frequency of the excitation magnetic field, if the external magnetic field is along the x-axis direction, under the action of the excitation magnetic field, a spin polarization component vertical to the x-axis direction is generated by excitation and precesses around the external magnetic field, and after the circularly polarized light passes through the atomic gas chamber, the intensity of the circularly polarized light is modulated by the spin polarization component in the y-axis direction; if the external magnetic field is along the y-axis direction, under the action of the excitation magnetic field, the excitation generates a spin polarization component vertical to the y-axis direction, the spin polarization component precesses around the external magnetic field, and after the circularly polarized light passes through the atomic gas chamber, the intensity of the circularly polarized light is modulated by the spin polarization component in the x-axis direction; if the external magnetic field is along the z-axis direction, under the action of the modulated light, the spin polarization component perpendicular to the z-axis direction is generated by excitation, the spin polarization component precesses around the external magnetic field, and after the circularly polarized light passes through the atomic gas chamber, the intensity of the circularly polarized light is modulated by the spin polarization component in the x-axis direction and the y-axis direction. In summary, it can be inferred that when the external magnetic field is along any direction, under the action of the excitation magnetic field and the modulated light, the spin polarization component perpendicular to the external magnetic field can be always excited and generated, the spin polarization component precesses around the external magnetic field, and the light intensity of the circularly polarized light is always modulated by the spin polarization component perpendicular to the external magnetic field, so that the atomic magnetometer without the response dead zone can be realized.
The second purpose of the invention is to disclose a method for measuring an external magnetic field by adopting the atomic magnetometer, which comprises the following steps:
firstly, a signal processing system generates high-frequency oscillation current far away from magnetic resonance frequency, the high-frequency oscillation current is input into a non-magnetic resistance heating sheet in a heating device to heat an atomic gas chamber, a non-magnetic temperature sensor in the heating device is collected to measure and obtain a temperature value of the atomic gas chamber, and the amplitude of the high-frequency oscillation current is adjusted through feedback control to stabilize the temperature of the atomic gas chamber;
step two, turning on the laser and adjusting the laser to133Cs atom D1 linear transition resonance frequency, the output laser beam is processed by the beam expanding collimation device and the circular polarization conversion device to obtain circular polarization light, the circular polarization light passes through the atom air chamber along the x-axis direction, the propagation direction of the circular polarization light is changed by the reflector group, and then the circular polarization light passes through the atom air chamber along the y-axis direction; detecting by a photoelectric detector, and starting to detect spin polarization component signals along the x axis and the y axis;
driving a Helmholtz coil to generate an excitation magnetic field in the z-axis direction by the signal processing system, and driving an acousto-optic modulator to perform amplitude modulation on circularly polarized light, wherein the modulation frequency of the light is consistent with the frequency of the excitation magnetic field; the locking amplifier demodulates a signal output by the photoelectric detector in the light path, the reference frequency of the locking amplifier is the frequency of the excitation magnetic field, and the signal processing system acquires the amplitude of the signal output by the photoelectric detector and demodulated by the locking amplifier;
fourthly, the signal processing system enables the amplitude of the collected output signal of the photoelectric detector to be maximum by adjusting the frequency of the excitation magnetic field and the modulation frequency of the light, and the frequency of the excitation magnetic field is equal to the magnetic resonance frequency omega at the moment0(ii) a From the resulting magnetic resonance frequency ω0Extracting to obtain the external magnetic field B ═ omega at the atom gas chamber0/γ。
The measuring method provided by the invention has the advantages of simple steps and capability of realizing effective detection of the external magnetic field.
In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic view showing the structure of an atomic magnetometer having no response dead zone in example 1;
wherein: 1. the device comprises a laser, 2, a beam expanding and collimating device, 2.1, a convex lens, 3, a circularly polarized light conversion device, 3.1, a linear polarizer, 3.2, a lambda/4 glass slide, 4, an acousto-optic modulator, 5, a Helmholtz coil, 6, an atom air chamber, 7, a reflector group, 7.1, a reflector, 8, a photoelectric detector, 9, a lock-in amplifier, 10, a signal processing system, 11 and a heating device.
Detailed Description
Embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways, which are defined and covered by the claims.
Example 1:
an atomic magnetometer without a response blind zone, see fig. 1, comprises a laser 1, a beam expanding collimator 2, a circularly polarized light conversion device 3, an acousto-optic modulator 4, a helmholtz coil 5, an atomic gas chamber 6, a reflector group 7, a photodetector 8, a lock-in amplifier 9, a signal processing system 10 and a heating device 11, wherein:
the laser 1, the beam expanding and collimating device 2, the circularly polarized light conversion device 3 and the acousto-optic modulator 4 are sequentially connected in series along the propagation direction of the light path.
The laser 1 is preferably an 895nm DFB semiconductor laser, and is used for outputting laser beams along the x-axis direction, specifically: adjusting 895nm DFB semiconductor laser to133Cs atom D1 line-transition resonance frequency, output laser beam).
The beam expanding and collimating device 2 performs beam expanding and collimating processing on the laser beam output by the laser 1, and preferably, two groups of convex lenses 2.1 are sequentially arranged in series in the beam expanding and collimating device 2 from the beam propagation direction.
The circularly polarized light conversion device 3 is used for converting the laser beam after beam expanding and collimating treatment into circularly polarized light, and preferably, the circularly polarized light conversion device 3 is formed by combining a linear polarizer 3.1 and a lambda/4 glass slide 3.2 which are arranged in series in the propagation direction of an optical path.
The acousto-optic modulator 4 performs amplitude modulation on the circularly polarized light.
The Helmholtz coil 5 is wound by a copper wire and is used for generating an excitation magnetic field.
The atomic gas chamber 6 is filled with133Cs atoms and a buffer gas (here preferably nitrogen). The optical path being used in a polarized atomic gas cell133Cs atoms and detects the components of the spin polarization vector in both the x-axis and y-axis directions.
The reflector group 7 is used for changing the propagation direction of the circularly polarized light after passing through the atomic gas chamber 6, so that the circularly polarized light is emitted into the atomic gas chamber 6 along the y-axis direction. Preferably: the reflector group 7 comprises three groups of reflectors 7.1, and the three groups of reflectors and the atomic gas chamber 7 are positioned at four corners of a square.
The photodetector 8 is used to detect circularly polarized light passing through the atomic gas cell 6.
The lock-in amplifier 9 is used to adjust the signal output by the photodetector 8.
The signal processing system 10 is connected to the acousto-optic modulator 4, the helmholtz coil 5, the lock-in amplifier 9 and the heating device 11 at the same time, and the signal processing system 10 is used for driving the acousto-optic modulator 4, the helmholtz coil 5, the lock-in amplifier 9 and the heating device 11The acousto-optic modulator 4 modulates the amplitude of the circularly polarized light, the signal processing system 10 controls the excitation magnetic field generated by the Helmholtz coil 5 by adjusting the current input into the Helmholtz coil, and the signal processing system 10 drives the heating device 11 to heat the atomic gas chamber 6 so as to improve the temperature of the atomic gas chamber 6133Cs atomic vapor density, the signal processing system 10 is used to adjust the reference frequency of the lock-in amplifier 9 and to acquire the output signal of the lock-in amplifier 9.
It is preferred here that the signal processing system 10 comprises a data acquisition card connected to the acousto-optic modulator 4, the helmholtz coil 5, the non-magnetic temperature sensor and the lock-in amplifier 9, and a computer connected to the data acquisition card.
The technical scheme of the embodiment is specifically as follows: laser beams output by the 895nm DFB semiconductor laser are expanded and collimated after passing through two groups of convex lenses 2.1 in the expanded beam collimating device 2; it is converted into circularly polarized light by the linear polarizer 3.1 and the lambda/4 glass slide 3.2 in the circularly polarized light conversion means 3; the acousto-optic modulator 4 performs amplitude modulation on the circularly polarized light, and the circularly polarized light with the amplitude modulation irradiates the atom air chamber 6 along the x-axis direction; after the circularly polarized light passes through the atomic gas chamber 6, the circularly polarized light irradiates the atomic gas chamber 6 along the y axis after the propagation direction is changed by three groups of reflectors 7.1 in the reflector group 7 (the circularly polarized light is twice and in the atomic gas chamber 6)133After the Cs atoms have interacted with each other,133the Cs atomic ensemble is polarized while the intensity of the circularly polarized light is modulated by spin polarization components in both the x-axis and y-axis directions); the circularly polarized light passing through the atomic gas cell 6 is detected by the photodetector 8, and the output signal of the photodetector 8 reflectsThe change of the light intensity of circularly polarized light; after the output signal of the photoelectric detector 8 is demodulated by the lock-in amplifier 9, the amplitude of the output signal of the photoelectric detector 8 output by the lock-in amplifier 9 is collected by the signal processing system 10; the signal processing system 10 drives and controls the heating device 11 to heat the atomic gas chamber 6 and keep the temperature of the atomic gas chamber 6 stable; meanwhile, the signal processing system 10 drives and controls the helmholtz coil 5 and the acoustic-optical modulator 4, provides an excitation magnetic field and performs amplitude modulation on circularly polarized light, enables the frequency of the excitation magnetic field and the frequency of the optical modulation to track the magnetic resonance frequency, and obtains an external magnetic field at the atomic gas chamber 6 according to the frequency.
The method for detecting the external magnetic field by applying the atomic magnetometer of the embodiment specifically comprises the following steps:
firstly, a signal processing system generates high-frequency oscillation current far away from magnetic resonance frequency, the high-frequency oscillation current is input into a non-magnetic resistance heating sheet in a heating device to heat an atomic gas chamber, a non-magnetic temperature sensor in the heating device is collected to measure and obtain a temperature value of the atomic gas chamber, and the amplitude of the high-frequency oscillation current is adjusted through feedback control to stabilize the temperature of the atomic gas chamber;
step two, turning on the laser and adjusting the laser to133Cs atom D1 linear transition resonance frequency, the output laser beam is processed by the beam expanding collimation device and the circular polarization conversion device to obtain circular polarization light, the circular polarization light passes through the atom air chamber along the x-axis direction, the propagation direction of the circular polarization light is changed by the reflector group, and then the circular polarization light passes through the atom air chamber along the y-axis direction; detecting by a photoelectric detector, and starting to detect spin polarization component signals along the x axis and the y axis;
driving a Helmholtz coil to generate an excitation magnetic field in the z-axis direction by the signal processing system, and driving an acousto-optic modulator to perform amplitude modulation on circularly polarized light, wherein the modulation frequency of the light is consistent with the frequency of the excitation magnetic field; the locking amplifier demodulates a signal output by the photoelectric detector in the light path, the reference frequency of the locking amplifier is the frequency of the excitation magnetic field, and the signal processing system acquires the amplitude of the signal output by the photoelectric detector and demodulated by the locking amplifier;
step four, the signal processing system is adjusted throughAdjusting the frequency of the excitation magnetic field and the modulation frequency of light to maximize the amplitude of the acquired output signal of the photoelectric detector, wherein the frequency of the excitation magnetic field is equal to the magnetic resonance frequency omega0(ii) a From the resulting magnetic resonance frequency ω0Extracting to obtain the external magnetic field B ═ omega at the atom gas chamber0/γ。
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. The utility model provides an atomic magnetometer of no response blind area which characterized in that: the device comprises a laser (1), a beam expanding collimation device (2), a circularly polarized light conversion device (3), an acousto-optic modulator (4), a Helmholtz coil (5), an atomic air chamber (6), a reflector group (7), a photoelectric detector (8), a lock-in amplifier (9), a signal processing system (10) and a heating device (11), wherein the laser (1), the beam expanding collimation device (2), the circularly polarized light conversion device (3) and the acousto-optic modulator (4) are sequentially arranged in series along the propagation direction of an optical path, and the Helmholtz coil (5) is arranged at the periphery of the atomic air chamber (6) and used for generating an excitation magnetic field along the direction of a z axis;
the laser (1) is used for outputting a laser beam along the x-axis direction;
the beam expanding and collimating device (2) is used for carrying out beam expanding and collimating treatment on the laser beam output by the laser (1);
the circular polarized light conversion device (3) is used for converting the laser beam after the beam expanding and collimating treatment into circular polarized light;
the acousto-optic modulator (4) performs amplitude modulation on the circularly polarized light;
the atomic gas chamber (6) is filled with133Cs atoms and buffer gas;
the reflector group (7) is used for changing the propagation direction of the circularly polarized light passing through the atomic gas chamber (6) so that the circularly polarized light is emitted into the atomic gas chamber (6) along the y-axis direction;
the photoelectric detector (8) is used for detecting circularly polarized light passing through the atomic gas chamber (6);
the lock-in amplifier (9) is used for demodulating the signal output by the photoelectric detector (8);
the acousto-optic modulator (4), the Helmholtz coil (5), the lock-in amplifier (9) and the heating device (11) are all connected with the signal processing system (10), the signal processing system (10) is used for driving the acousto-optic modulator (4) to perform amplitude modulation on circularly polarized light, the signal processing system (10) controls an excitation magnetic field generated by the Helmholtz coil (5) by adjusting current input into the Helmholtz coil, and the signal processing system (10) heats the atom air chamber (6) by driving the heating device (11) to improve the heating effect of the atom air chamber (6) inside133A Cs atomic vapor density, the signal processing system (10) for adjusting a reference frequency of the lock-in amplifier (9) and acquiring an output signal of the lock-in amplifier (9).
2. The atomic magnetometer without the dead zone of response of claim 1, characterized in that: the laser (1) is an 895nm DFB semiconductor laser adjusted to133The Cs atom D1 linearly transits the resonance frequency and outputs a laser beam.
3. The atomic magnetometer without the dead zone of response of claim 1, characterized in that: and the beam expanding and collimating device (2) is sequentially provided with two groups of convex lenses (2.1) in series from the light beam propagation direction.
4. The atomic magnetometer without the dead zone according to any one of claims 1 to 3, wherein: the reflector group (7) comprises three groups of reflectors (7.1), and the three groups of reflectors and the atom gas chamber (7) are positioned at four corners of a square.
5. The atomic magnetometer without the dead zone of response of claim 4, wherein: the circularly polarized light conversion device (3) is formed by combining a linear polarizer (3.1) and a lambda/4 glass sheet (3.2) which are arranged in series in the light path transmission direction.
6. The atomic magnetometer without the dead zone of response of claim 4, wherein: the Helmholtz coil (5) is wound by a copper wire and is used for generating an excitation magnetic field; heating device (11) set up atom air chamber (6) are peripheral, heating device (11) include copper anchor clamps, no magnetism resistance heating piece and no magnetism temperature sensor, the copper anchor clamps are used for fixing atom air chamber (6), no magnetism resistance heating piece is used for right atom air chamber (6) are heated in order to improve atom air chamber (6) in133Cs atom steam density, no magnetism temperature sensor is used for measuring the temperature of atom air chamber (6), no magnetism resistance heating piece with no magnetism temperature sensor all with signal processing system (10) are connected.
7. The atomic magnetometer without the dead zone of response of claim 6, wherein: the signal processing system (10) comprises a data acquisition card and a computer, the data acquisition card is connected with the acousto-optic modulator (4), the Helmholtz coil (5), the nonmagnetic temperature sensor and the lock-in amplifier (9), and the computer is connected with the data acquisition card.
8. A method for measuring an external magnetic field by an atomic magnetometer without a response blind area is characterized in that: the method comprises the following steps:
firstly, a signal processing system generates high-frequency oscillation current far away from magnetic resonance frequency, the high-frequency oscillation current is input into a non-magnetic resistance heating sheet in a heating device to heat an atomic gas chamber, a non-magnetic temperature sensor in the heating device is collected to measure and obtain a temperature value of the atomic gas chamber, and the amplitude of the high-frequency oscillation current is adjusted through feedback control to stabilize the temperature of the atomic gas chamber;
step two, turning on the laser and adjusting the laser to133Cs atom D1 linear transition resonance frequency, processing the output laser beam by beam expanding collimation device and circular polarization conversion device to obtain circular polarization light, passing the circular polarization light through atom air chamber along x-axis direction, changing propagation direction of the circular polarization light by reflector set, and passing through atom air chamber along y-axis direction(ii) a Detecting by a photoelectric detector, and starting to detect spin polarization component signals along the x axis and the y axis;
driving a Helmholtz coil to generate an excitation magnetic field in the z-axis direction by the signal processing system, and driving an acousto-optic modulator to perform amplitude modulation on circularly polarized light, wherein the modulation frequency of the light is consistent with the frequency of the excitation magnetic field; the locking amplifier demodulates a signal output by the photoelectric detector in the light path, the reference frequency of the locking amplifier is the frequency of the excitation magnetic field, and the signal processing system acquires the amplitude of the signal output by the photoelectric detector and demodulated by the locking amplifier;
fourthly, the signal processing system enables the amplitude of the collected output signal of the photoelectric detector to be maximum by adjusting the frequency of the excitation magnetic field and the modulation frequency of the light, and the frequency of the excitation magnetic field is equal to the magnetic resonance frequency omega at the moment0(ii) a From the resulting magnetic resonance frequency ω0Extracting to obtain the external magnetic field B ═ omega at the atom gas chamber0/γ。
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| CN109358302B (en) * | 2018-09-25 | 2020-02-18 | 中国科学院武汉物理与数学研究所 | Passive magnetic shielding-free atomic magnetometer device and magnetism measuring method |
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| CN113447862A (en) * | 2021-06-30 | 2021-09-28 | 北京量子信息科学研究院 | Magnetic field gradient measuring device |
| CN114487945B (en) * | 2021-12-29 | 2024-05-14 | 中国科学技术大学 | Scalar atomic magnetometer without detection dead zone and capable of eliminating optical frequency shift and method |
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