CN114487945A - Scalar atom magnetometer without detection blind area and capable of eliminating optical frequency shift and method - Google Patents
Scalar atom magnetometer without detection blind area and capable of eliminating optical frequency shift and method Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 8
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 3
- IGLNJRXAVVLDKE-UHFFFAOYSA-N rubidium atom Chemical group [Rb] IGLNJRXAVVLDKE-UHFFFAOYSA-N 0.000 claims description 3
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/032—Measuring direction or magnitude of magnetic fields or magnetic flux using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/0011—Arrangements or instruments for measuring magnetic variables comprising means, e.g. flux concentrators, flux guides, for guiding or concentrating the magnetic flux, e.g. to the magnetic sensor
Abstract
The invention relates to a scalar atomic magnetometer without a detection blind zone and capable of eliminating optical frequency shift and a method. The invention puts a plane reflector in the middle of the atomic pool, establishes two vertical areas sensitive to the magnetic field, and achieves the purpose of eliminating the detection blind area. Meanwhile, the half-wave plate is arranged in the optical path of the atomic pool, the polarization direction of the pumping light in the atomic pool is reversed, the atomic pool is divided into two modules with opposite polarization directions, the light frequency shift caused by light detuning is counteracted, and the pointing error caused by the light frequency shift is eliminated.
Description
Technical Field
The invention relates to the field of atomic devices, in particular to a scalar atomic magnetometer based on optical power modulation and a method for eliminating a detection blind area by utilizing a bent optical path and eliminating optical frequency shift by adding a half-wave plate to reverse pump light polarization.
Background
In the optically pumped atomic magnetometer experiments, the magnitude of the external magnetic field can be obtained from the measured atom lamor precession frequency. The optical pump magnetometer based on the principle is widely applied to the fields of archaeology, geophysics, basic physics and the like. However, the response amplitude of the magnetometer to the magnetic field has a certain dependence on the relative angle between the propagation direction of the pumping light and the direction of the magnetic field, and in some regions, the magnetometer is not sensitive to the magnetic field and cannot accurately measure the measurement field, and such regions are called as detection blind regions. The detection blind area prevents the popularization of the magnetometer in application. Eliminating the detection blind area is one of the important improvement measures of the magnetometer.
Meanwhile, the atom precession frequency measured by experiments is often dependent on the relative angle between the propagation direction of the pumping light and the direction of the magnetic field for various reasons, which introduces a systematic error, namely a pointing error. This is another major cause of the decrease in measurement accuracy of magnetometers. The sources of pointing error are largely divided into three areas: on the first hand, the pointing error comes from the nonlinear Zeeman effect, and alkali metal atoms are subjected to nonlinear splitting under the action of a hyperfine structure and a magnetic field, which is one of main factors limiting the sensitivity of a magnetometer; secondly, pointing errors come from optical frequency shift, and circularly polarized light far away from the atomic transition resonance frequency can introduce the optical frequency shift effect, which is equivalent to a magnetic field, so that the measurement of an external magnetic field is influenced; in the third aspect, the pointing error comes from the linear nuclear Zeeman splitting effect, but the effect of the external magnetic field on the nuclear spin is three orders of magnitude smaller than that of the electron spin, so that the pointing error can be ignored. We mainly discuss pointing errors introduced by the optical frequency shift effect brought by circularly polarized light away from the atomic transition resonance frequency. A common method to suppress this pointing error is to depolarize the alkali metal atoms of two different spatial regions using two beams of pump light of opposite polarization. After the effects of the atoms in the two space regions are averaged, the influence on the direction dependence disappears, but the method increases the complexity of equipment, increases the additional optical power, and simultaneously needs the perfect matching between the two systems, so that the magnetometer brings a plurality of difficulties in the practical application process, and the application and the development of the magnetometer are hindered.
In 2010, the U.S. Romalis group modulated the pump light polarization using an electro-optical modulator, and eliminated the spin polarization along the magnetic field direction using symmetric, equal intensity, and oppositely polarized circularly polarized light. Meanwhile, the elimination of the detection blind zone corresponding to the optical frequency shift is realized by utilizing a method combining circularly polarized light pumping and linearly polarized light pumping, more power consumption is introduced by the method, and the structure is complex. Therefore, the simple and convenient scheme without additional power consumption is worthy of research and popularization.
The invention solves the problems: the scalar atom magnetometer and the method have the advantages that the detection blind area problem and the optical frequency shift effect are overcome, the scalar atom magnetometer without the detection blind area and capable of eliminating the optical frequency shift and based on optical power modulation are provided, the multi-reflection cavity is introduced into the atom pool, and the sensitivity is improved by increasing the interaction optical distance of light and atoms. A reflecting mirror is added in the atomic pool, and a bent light path is used for eliminating a detection blind area. Meanwhile, a half-wave plate is added in the atomic pool, and optical frequency shift is eliminated by reversing the polarization degree of pumping light. The scheme is simple and ingenious, the power consumption is low, and convenience is provided for realizing integration and miniaturization of the magnetometer in the future.
The technical scheme of the invention is as follows:
a Herriott multi-reflection cavity is added in an atom pool, so that the acting distance between light and atoms is increased, and the signal-to-noise ratio of the system is improved; in measurement, when the direction of a magnetic field is close to the direction of pumping light, the magnetometer is insensitive to the magnetic field, has no response signal, cannot realize the function of the magnetometer, and influences the measurement of the magnetic field; in order to eliminate the detection blind area, the invention arranges a plane mirror in the middle of the gas pool, bends the light path into two vertical parts, when the direction of the magnetic field is superposed with one part of the light path, the other part of the light path can ensure the normal work of the magnetometer; meanwhile, when the modulated pumping light is far away from the atomic transition resonance frequency, the response of the magnetometer has obvious dependency on the relative angle of a magnetic field and the pumping light, and the optical frequency shift effect caused by the detuning of the pumping light frequency enables the absorption signal of the magnetometer to be in an asymmetric dispersion line type, so that the measurement precision of an external magnetic field is influenced; in conclusion of the work of the two aspects, the problem of detection blind areas is solved, and when a magnetic field is in any direction, a magnetometer has considerable response to the magnetic field; meanwhile, the invention greatly reduces the dependence of the response of the magnetometer on the relative angle of the probe and the magnetic field, and more comprehensively realizes the function of the magnetometer.
The invention relates to an atomic magnetometer technology based on optical power modulation, which eliminates a detection blind area by using a bent optical path and eliminates optical frequency shift by adding a half-wave plate to reverse pumping light polarization. In experiments it was required to generate a lateral polarization with amplitude modulated pump light. When the modulation frequency is equal to the larmor precession frequency, the transverse polarization is the largest and the magnetometer has the strongest response signal to the magnetic field. In the measurement, when the included angle between the direction of the magnetic field and the direction of the pumping light is small, the response signal of the magnetometer is small, the signal-to-noise ratio is insufficient, and the measurement of the magnetic field is influenced. In order to eliminate the detection blind area, the invention arranges a plane mirror in the middle of the gas pool, and bends the light path into two vertical parts. When the direction of the magnetic field is overlapped with one part of the light path, the response signal of the magnetometer corresponding to the other part of the light path can ensure the normal high signal-to-noise ratio work of the magnetometer. Meanwhile, when the modulated pumping light is far away from the atomic transition resonance frequency, the response of the magnetometer has obvious dependence on the relative angle of the magnetic field and the pumping light. The optical frequency shift effect caused by the detuning of the pumping optical frequency enables the absorption signal of the magnetometer to present an asymmetric dispersion line type, and influences the measurement precision of the external magnetic field. The half-wave plate is arranged in the optical path of the atomic pool containing the three-mirror multi-reflection cavity system, the polarization direction of pump light in the atomic pool is reversed, the atomic pool is divided into two modules with opposite polarization directions of the optical path, light frequency shift caused by light detuning is counteracted, and pointing errors caused by the light frequency shift are eliminated.
The scalar atom magnetometer without the detection blind area and capable of eliminating the optical frequency shift eliminates the detection blind area by utilizing the bent optical path, and simultaneously eliminates the optical frequency shift by adding the half-wave plate to reversely pump the optical polarization; the scalar atomic magnetometer includes: an atomic pool containing Herriott multi-reflection cavities, plane mirrors and half-wave plates, a heating unit, a magnetic field unit, an optical power modulated pumping light unit, a photoelectric detector and a 3d printing platform are assembled:
an atomic pool containing a Herriott multi-reflection cavity, a plane reflector and a half-wave plate, a heating unit, a magnetic field unit and a 3d printing platform are placed in a five-layer magnetic shielding barrel made of permalloy, and the magnetic shielding barrel shields interference of a geomagnetic field and an external stray magnetic field; the front cavity mirror and the rear cavity mirror which form the Herriott multi-reflection cavity are cylindrical mirrors, the cavity mirror and the plane mirror are fixed on a silicon wafer through an anodic bonding method, the two cavity mirrors are mutually vertically arranged, the plane mirror and the two cavity mirrors are arranged at an angle of 45 degrees, and the addition of the plane mirror bends a light path into two vertical light paths in an air pool, so that the introduction of multiple light paths is avoided, and the light power consumption is reduced; the sum of the distances from the two cavity mirrors to the center of the reflecting mirror is preferably 26.3mm, the relative rotation angle of the main shafts of the two cavity mirrors is preferably 50.7 degrees, the half-wave plates are positioned through a ceramic die and are respectively positioned at the middle points of the distances from the cavity mirrors to the reflecting mirror and are fixed by high-temperature-resistant glue, the polarization of a light path is reversed in the atomic pool due to the addition of the half-wave plates, the scheme is reliable, and the design is simple;
the heating unit is used for heating atoms in the atom pool; assembling the atomic pool and the heating unit together by using a 3d printed frame box;
the magnetic field unit comprises three magnetic field coils in x, y and z directions which are perpendicular to each other and used for providing a working bias magnetic field, the atom pool and the heating unit are positioned in the magnetic field unit, and the atom pool is close to the center of the magnetic field coils;
the pump light unit with modulated optical power directly generates transverse polarization; before entering an atomic pool, the circularly polarized light is subjected to amplitude modulation on the pumping light through an acousto-optic modulator, a 3d printing optical platform is introduced into an optical fiber, the circularly polarized light is emitted into a Herriott multi-reflection cavity and is emitted after being reflected for multiple times (preferably 14 times), and when the pumping light modulation frequency is close to the atomic lamor precession frequency, considerable transverse polarization is generated;
the photoelectric detector is used for detecting absorption signals of atoms in the atomic pool to light; the photoelectric detector detects the light power emitted from the Herriott multi-reflection cavity, the absorption signal has a certain dependence relation with the pumping light modulation frequency, in an experiment, the pumping light modulation frequency is scanned, when the modulation frequency is equal to the atom lamor precession frequency, the atom absorption signal is strongest, the resonance point of the signal is the atom lamor precession frequency, and the measurement of an external magnetic field is realized;
the 3d printing platform integrates the atomic pool, the heating unit, the pumping light unit and the photoelectric detector, completes heating and heat preservation assembly of the atomic pool, reduces and avoids complex light path adjustment, simplifies the system, and facilitates realization of miniaturization of the magnetometer in the future.
The front cavity mirror, the rear cavity mirror and the plane reflecting mirror in the Herriott multi-reflecting cavity are fixed on a silicon chip by an anodic bonding method, the two cavity mirrors, namely the front cavity mirror and the rear cavity mirror, are cylindrical mirrors and are positioned by using a ceramic die; placing a half-wave plate on each of two vertical light paths, fixing with high temperature resistant glue, sealing the glass cover and the silicon wafer by anodic bonding, filling atoms with natural abundance rubidium atoms (wherein the natural abundance rubidium atoms are filled in the atom pool)85Rb and87the contents of Rb were 72.2% and 27.8%, respectively), 350Torr nitrogen gas as a buffer gas; after all atoms are flushed into the atom pool, finally, the atom pool is taken down from the vacuum system through flame burning, and the atom pool containing the Herriott multi-reflection cavity and the half-wave plate is manufactured; the addition of the plane reflector bends one beam of light path into two vertical light paths in the atomic pool, thereby avoiding the introduction of a plurality of light paths and reducing the light power consumption; the addition of the half-wave plate achieves the purpose of reversing the polarization of the light path in the atomic pool, and the design is simple and the scheme is reliable.
The heating unit is composed of two nonmagnetic heating sheets, and heats the atomic pool by alternating current: the atomic pool is partially wrapped by a heat-insulating material during heating so as to play a role in heat insulation and heat preservation and reduce the need for heating power; the heating unit works at 60 deg.C, and the atoms are in gas state in the gas pool, so that the atoms are in stable high atomic number density of 3 × 1011/cm-3At room temperature (25 ℃), the atomic number density is 1X 1010/cm-3。
The 3d printing assembly platform can accurately realize the fixation of the atomic pool, and the experiment is started without complicated light path adjustment; the 3d printing also integrates an optical element and the photoelectric detector on a probe platform, so that the integration and miniaturization of the magnetometer are realized.
The invention discloses a method for realizing a scalar atom magnetometer without a detection blind area and capable of eliminating optical frequency shift, which comprises the following steps:
a Herriott multi-reflection cavity is added into the atom pool, so that the acting distance between light and atoms is increased, and the signal-to-noise ratio is improved; in measurement, when the direction of a magnetic field is close to the direction of pumping light, the magnetometer is insensitive to the magnetic field, has no response signal, cannot realize the function of the magnetometer, and influences the measurement of the magnetic field; in order to eliminate the detection blind area, a plane mirror is arranged in the middle of the atomic pool, the light path is bent into two vertical parts, two vertical regions sensitive to the magnetic field are established, and when the direction of the magnetic field is superposed with one part of the light path, the response signal of the magnetometer of the other part of the light path can ensure the high signal-to-noise ratio work of the magnetometer; meanwhile, when the modulated pumping light is far away from the atomic transition resonance frequency, the response of the scalar atomic magnetometer has obvious dependency on the relative angle of a magnetic field and the pumping light, and the optical frequency shift effect caused by the detuning of the pumping light frequency enables the absorption signal of the magnetometer to present an asymmetric dispersion line type and influence the measurement precision of an external magnetic field; the pumping light is subjected to amplitude modulation by an acousto-optic modulator in the process of atom polarization, so that transverse polarization is generated on a plane vertical to a bias magnetic field; under the condition of a bias magnetic field of 100mG, polarized alkali metal atoms precess in a direction vertical to the bias magnetic field at a lamor precession frequency, and when the pumping light modulation frequency is equal to the atom lamor precession frequency, an absorption signal detected by a photoelectric detector is strongest; obtaining atom lamor precession frequency by finding out a signal curve resonance point, namely measuring the size of an external magnetic field; the invention solves two common problems of a magnetometer, namely, the detection blind area and the optical frequency shift problem simultaneously under the design of not consuming extra optical power and being simple and easy to operate.
The invention has the advantages and positive effects that:
(1) the atomic pool composed of multi-reflection cavity, plane reflector and half-wave plate can eliminate both the detection blind area and optical frequency shift. In the conventional case (containing only multiple reflective cavities), when the magnetic field direction is near or coincident with the pump light, the probe is insensitive to the magnetic field direction and has no response signal. Such an area is a detection blind area of the magnetometer, is a disadvantage of performance of the magnetometer, and hinders popularization of the magnetometer in application. But the light path is bent into two perpendicular parts by adopting a method of adding a plane mirror. When the direction of the magnetic field is superposed with one part of the light path, the other part of the light path can ensure the normal work of the magnetometer, effectively eliminate the detection blind area and solve the blind area defect of the scalar magnetometer. In the conventional case (without the half-wave plate), the response of the magnetometer has a very clear dependence on the relative angle of the magnetic field and the pump light when the modulated pump light deviates from the atomic transition resonance frequency. The optical frequency shift effect caused by the detuning of the pumping optical frequency enables an absorption signal of the magnetometer to be in an asymmetric dispersion line type, the measurement precision of an external magnetic field is influenced, and the performance of the magnetometer is further limited. In the invention, because the atomic pool contains the half-wave plate, the optical frequency shift which generates asymmetric factors in signals can be counteracted, the dependence of the response of the magnetometer on the relative angle of the probe and the magnetic field is greatly reduced, and the function of the magnetometer is more comprehensively realized. The use of the multi-reflection cavity makes the absorption in the light path of single reflection negligible, so that the common phenomenon that light is continuously attenuated in the gas chamber in propagation is not considered when the half-wave plate is placed.
(2) Unlike the commonly used method of eliminating optical frequency shifts. A common approach is to depolarize two different spatial alkali metal atoms using two pump lights of opposite polarization. The effect of the two space atoms is averaged, the influence on the direction dependence disappears, but the method increases the complexity of equipment, increases extra optical power, and simultaneously needs perfect matching between the two systems, so that a plurality of difficulties are brought to a magnetometer in the practical application process.
(3) Only add half-wave plate in normal atomic pool, need not extra consumption, also need not extra light beam, more need not consider the matching problem, the scheme is simple, and is practical again, and the magnetometer of being convenient for promotes in the aspect of the application.
(4) Under the assistance of 3d printing technology, the incident angle relation between pump light and the multiple reflection cavities can be accurately defined, tedious light path adjustment can be avoided, the system is simplified, and convenience is brought to integration and miniaturization of the magnetometer in the future.
Drawings
FIG. 1 is a schematic diagram of an atomic pool invented for a magnetometer for eliminating detection dead zones and eliminating optical frequency shift;
FIG. 2 is a graph of the overall result of the magnetometer system;
figure 3 is a schematic view of the 3d printing probe and the internal optical path.
Detailed Description
The present invention will be described in more detail with reference to the accompanying drawings.
As shown in figure 1, a front cavity mirror 1 and a rear cavity mirror 2 which form the Herriott multi-reflection cavity are cylindrical mirrors, a cavity mirror and a plane mirror 5 are fixed on a silicon chip 4 through an anodic bonding method, the distance between the two cavity mirrors is 26.3mm, the relative rotation angle of a main shaft is 50.7 degrees, and a half-wave plate 6 is positioned through a ceramic die and fixed by high-temperature-resistant glue. The glass cap 3 is also sealed to the silicon wafer 4 by anodic bonding. Filling atoms into the atom pool and injecting buffer gas, and finally taking down the atom pool from a vacuum system by flame burning, and completing the manufacturing of the atom pool with a plurality of reflection cavities. In the conventional case (containing only multiple reflective cavities), when the magnetic field direction is near or coincident with the pump light, the probe is insensitive to the magnetic field direction and has no response signal. Such an area is a detection blind area of the magnetometer, is a disadvantage of performance of the magnetometer, and is not beneficial to popularization of application. As shown in fig. 1, the light path is bent into two perpendicular portions by the addition of a plane mirror 5. When the direction of the magnetic field is superposed with one part of the light path, the other part of the light path can work normally, the detection blind area is effectively eliminated, and the blind area defect of the scalar magnetometer is overcome. Under the conventional condition (without a half-wave plate), the pump light is detuned to generate light frequency shift in the light propagation direction, and when a certain relative angle exists between the pump light and the magnetic field direction, a frequency response signal presents an asymmetric result, so that the precision of the magnetic field measurement of the magnetometer is reduced, and the performance of the magnetometer is further limited. However, in the present invention, as shown in fig. 1, a half-wave plate 6 is added to divide the atomic pool into two modules with opposite polarization, so as to cancel out the optical frequency shift effect, so that even if the pumping light is detuned and is not perpendicular to the magnetic field, the magnetic field can still be accurately measured, and the performance of the magnetometer is ensured.
As shown in fig. 2, the overall structure of the system of the present invention is schematically illustrated. Atomic pond, heating element, magnetic field unit, 3d printing optical platform place in five layers of magnetic screen buckets, and the magnetic screen bucket can avoid external stray magnetic field's interference, and other component units are placed on 3d printing optical platform, and the probe is close to the central point of magnetic field coil as far as possible and is put.
As shown in fig. 3, the probe 3d prints the platform and the internal optical path schematic. The optical fiber is led into the optical path, the optical fiber output head 7 is specially designed and manufactured by a 3d printing method, and the output collimating lens is integrated, so that the pumping light can be directly used without manual adjustment after being output by the optical fiber. Pumping light is injected into a Herriott multi-reflection cavity in the atomic pool and is emitted after 14 times of reflection, and the rear photoelectric detector 8 receives the power of the emitted light. The optical element and the detector are integrated on the 3d printing platform, the incidence relation between pumping light and the multiple reflection cavities can be accurately defined through the 3d printing technology, a fussy link for adjusting the light path is omitted, and the miniaturization and application popularization are facilitated.
In summary, the present invention provides a scalar atom magnetometer and a method thereof, which have no detection blind area and can eliminate optical frequency shift. A Herriott multi-reflection cavity is introduced into an atom pool, the sensitivity and stability are improved by increasing the interaction optical path of light and atoms, and alkali metal atoms and nitrogen atoms are filled. A plane reflector is added in the middle of the multi-reflection cavity to turn the light path by 90 degrees, which is equivalent to divide the cavity into two parts which are vertical to each other. Even if one part of the light path is overlapped with the direction of the magnetic field, the other part of the perpendicular light path can work normally, and the purpose of eliminating the detection blind area of the magnetometer is achieved. Meanwhile, two half-wave plates are respectively added to two optical paths in the gas pool, so that the two vertical optical paths are respectively changed into two parts, atoms of one module are pumped by left-handed light, and atoms of the other module are pumped by right-handed light. Since the system directly measures the signal summation effect within the atomic pool, the optical frequency shift effect due to optical detuning is cancelled out in the process. Therefore, the response curve of the magnetometer signal to the modulation frequency is in a symmetrical spectral line type, the dependence of the measurement value on the relative angle of the probe and the magnetic field is greatly reduced, and the measurement precision is improved.
Claims (5)
1. A scalar atom magnetometer without detection blind area and capable of eliminating optical frequency shift is characterized by comprising: the device comprises an atomic pool containing Herriott multi-reflection cavities, a plane mirror and a half-wave plate, a heating unit, a magnetic field unit, an optical power modulation pumping light unit, a photoelectric detector and an assembled 3d printing platform:
an atomic pool containing a Herriott multi-reflection cavity, a plane reflector and a half-wave plate, a heating unit, a magnetic field unit and a 3d printing platform are placed in a five-layer magnetic shielding barrel made of permalloy, and the magnetic shielding barrel shields interference of a geomagnetic field and an external stray magnetic field; the front cavity mirror and the rear cavity mirror which form the Herriott multi-reflection cavity are cylindrical mirrors, the cavity mirror and the plane mirror are fixed on a silicon wafer through an anodic bonding method, the front cavity mirror and the rear cavity mirror are mutually and vertically arranged, the plane mirror, the front cavity mirror and the rear cavity mirror are arranged at an angle of 45 degrees, and a light path is bent into two vertical light paths in an atomic pool by adding the plane mirror, so that the introduction of multiple light paths is avoided, and the light power consumption is reduced; the half-wave plate is positioned by the ceramic mould, is respectively positioned at the midpoint position of the distance from the front cavity mirror and the rear cavity mirror to the reflecting mirror, is fixed by adopting high-temperature-resistant glue, and the polarization of a light path is reversed in the atomic pool due to the addition of the half-wave plate, so that the scheme is reliable and the design is simple;
the heating unit is used for heating atoms in the atom pool; assembling the atomic pool and the heating unit together by using a 3d printed frame box;
the magnetic field unit comprises three magnetic field coils in x, y and z directions which are perpendicular to each other and provides a working bias magnetic field, the atom pool and the heating unit are positioned in the magnetic field unit, and the atom pool is close to the center of the magnetic field coils;
the pump light unit with modulated optical power directly generates transverse polarization; before entering an atomic pool, the circularly polarized light is subjected to amplitude modulation on the pumping light through an acousto-optic modulator, a 3d printing optical platform is introduced into an optical fiber, the circularly polarized light is emitted into a Herriott multi-reflection cavity and is emitted after being reflected for multiple times, and when the pumping light modulation frequency is close to the atom lamor precession frequency, considerable transverse polarization is generated;
the photoelectric detector is used for detecting absorption signals of atoms in the atomic pool to light; the photoelectric detector detects the light power emitted from the Herriott multi-reflection cavity, the absorption signal and the pumping light modulation frequency have a certain dependence relationship, in an experiment, the pumping light modulation frequency is scanned, when the modulation frequency is equal to the atomic lamor precession frequency, the atomic absorption signal is strongest, the resonance point of the signal is the atomic lamor precession frequency, and the measurement of an external magnetic field is realized;
the 3d printing platform integrates the atomic pool, the heating unit, the pumping light unit and the photoelectric detector, completes heating and heat preservation assembly of the atomic pool, reduces and avoids complex light path adjustment, simplifies the system, and facilitates realization of miniaturization of the magnetometer in the future.
2. The scalar atomic magnetometer of claim 1, which has no detection dead zone and can eliminate optical frequency shift, wherein: the front cavity mirror, the rear cavity mirror and the plane reflecting mirror in the Herriott multi-reflecting cavity are fixed on a silicon chip by an anodic bonding method, the two cavity mirrors, namely the front cavity mirror and the rear cavity mirror, are cylindrical mirrors and are positioned by using a ceramic die; placing a half-wave plate on each of the two vertical light paths, fixing the half-wave plates by using high-temperature-resistant glue, sealing the glass cover and the silicon wafer by using an anodic bonding method, filling atoms by using a tail pipe on the glass cover, filling natural abundance rubidium atoms into an atom pool, and using 350Torr nitrogen as buffer gas; and after all atoms are flushed into the atom pool, finally, taking down the atom pool from the vacuum system through flame burning, and completing the manufacturing of the atom pool containing the Herriott multi-reflection cavity and the half-wave plate.
3. The kit of claim 1Detect the blind area and can eliminate scalar atom magnetometer of optical frequency shift, its characterized in that: the heating unit is composed of two nonmagnetic heating sheets, and heats the atomic pool by alternating current: the atomic pool is partially wrapped by a heat-insulating material during heating so as to play a role in heat insulation and heat preservation and reduce the need for heating power; the heating unit works at 60 deg.C, and the atoms are in gas state in the gas pool, so that the atoms are in stable high atomic number density of 3 × 1011/cm-3Atomic number density of 1X 10 at room temperature of 25 deg.C10/cm-3。
4. The scalar atomic magnetometer of claim 1, which has no detection dead zone and can eliminate optical frequency shift, wherein: the 3d printing assembly platform can accurately realize the fixation of the atomic pool, and the experiment is started without complicated light path adjustment; the 3d printing also integrates an optical element and the photoelectric detector on the probe platform, so that the integration and miniaturization of the magnetometer are realized.
5. A method for implementing a scalar atomic magnetometer without detection dead zone and capable of eliminating optical frequency shift according to claim 1, comprising the steps of:
a Herriott multi-reflection cavity is added into the atom pool, so that the acting distance between light and atoms is increased, and the signal-to-noise ratio is improved; in measurement, when the direction of a magnetic field is close to the direction of pumping light, the magnetometer is insensitive to the magnetic field, has no response signal, cannot realize the function of the magnetometer, and influences the measurement of the magnetic field; in order to eliminate the detection blind area, a plane mirror is arranged in the middle of the atomic pool, the light path is bent into two vertical parts, two vertical regions sensitive to the magnetic field are established, and when the direction of the magnetic field is superposed with one part of the light path, the response signal of the magnetometer of the other part of the light path ensures the high signal-to-noise ratio work of the magnetometer; meanwhile, when the modulated pumping light is far away from the atomic transition resonance frequency, the response of the scalar atomic magnetometer has obvious dependency on the relative angle of a magnetic field and the pumping light, and the optical frequency shift effect caused by the detuning of the pumping light frequency enables the absorption signal of the magnetometer to present an asymmetric dispersion line type and influence the measurement precision of an external magnetic field; the pumping light is subjected to amplitude modulation by an acousto-optic modulator in the process of atom polarization, so that transverse polarization is generated on a plane vertical to a bias magnetic field; under the condition of a bias magnetic field of 100mG, polarized alkali metal atoms precess in the direction vertical to the bias magnetic field at the lamor precession frequency, when the pumping light modulation frequency is equal to the atom lamor precession frequency, the absorption signal detected by a photoelectric detector is strongest, and the atom lamor precession frequency is obtained by finding a signal curve resonance point, namely the size of an external magnetic field is measured.
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