Miniaturized single-beam reflection type atom magnetometer probe and atom magnetometer

Abstract

The utility model discloses a miniaturized single-beam reflection-type atom magnetometer probe and an atom magnetometer. The atom magnetometer probe comprises a housing; an alkali metal atom gas cell; the combined prism is arranged on one side of the alkali metal atom gas chamber; the reflecting mirror is arranged on the other side of the alkali metal atom gas chamber; the photoelectric detector is arranged on one side, deviating from the alkali metal atom gas chamber, of the combined prism; the combined prism is used for converting collimated light received by the incident plane into circularly polarized light, the circularly polarized light is emitted to the alkali metal atom gas chamber through the emergent plane, and the reflector is used for reflecting pumping light passing through the alkali metal atom gas chamber back to the alkali metal atom gas chamber. The absorption optical path of the pumping light is remarkably improved, secondary polarization is achieved, meanwhile, the action intensity of the pumping light and alkali metal atoms is improved, the number of atoms is equivalently increased in a limited area, higher sensitivity can be achieved at a lower temperature, the performance of the single-beam atom magnetometer is remarkably improved, and miniaturization design is facilitated.

Description

Technical Field

[0001] This utility model belongs to the field of atomic magnetometer technology, specifically relating to a miniaturized single-beam reflective atomic magnetometer probe and atomic magnetometer. Background Technology

[0002] An atomic magnetometer is an optical instrument that measures magnetic fields using the polarization changes of alkali metal vapors. This instrument can operate in low-magnetic-shielded environments and employs conventional detector elements to achieve a low-cost, multi-channel configuration. Gradient detection technology further enhances measurement sensitivity. Among these, the spin-free exchange-relaxation (SERF) atomic magnetometer, as a novel sensor, operates in the SERF state, effectively avoiding the influence of spin exchange relaxation. It is currently the most sensitive type of magnetometer, with significant advantages including: operation at room temperature, high spatial resolution, and no reliance on expensive cooling equipment; its theoretical sensitivity can reach 2 aT / Hz. 1 / 2 .

[0003] In existing single-beam SERF atomic magnetometers, the minimum volume of the alkali metal atom gas cell is limited in order to ensure the absorption optical path of the pump light and alkali metal atoms. At the same time, the integration of the internal light source components of the magnetometer is low, making it difficult for existing single-beam SERF atomic magnetometers to achieve both miniaturization and high sensitivity, which is not conducive to their engineering application in cardiac and cerebrovascular magnetic resonance imaging (MRI). Utility Model Content

[0004] The purpose of this application is to provide a miniaturized single-beam reflective atomic magnetometer probe and atomic magnetometer to solve the technical problem that existing single-beam SERF atomic magnetometers are difficult to balance miniaturization and high sensitivity, which is not conducive to their engineering application in cardiac and cerebrovascular magnetic resonance imaging (MRI).

[0005] To achieve the above objectives, a first aspect of this application provides a miniaturized single-beam reflective atomic magnetometer probe, comprising:

[0006] case;

[0007] An alkali metal atom gas chamber is arranged inside the shell;

[0008] A combined prism is arranged on one side of the alkali metal atom gas cell, the combined prism including an exit surface facing the alkali metal atom gas cell and an incident surface distributed perpendicular to the exit surface;

[0009] A reflector is arranged on the other side of the alkali metal atom gas cell and is positioned opposite to the exit surface of the combined prism.

[0010] A photodetector is arranged on the side of the combined prism away from the alkali metal atom gas cell;

[0011] The combined prism is used to convert the collimated light received by the incident surface into circularly polarized light, and then direct it to the alkali metal atom gas cell via the exit surface. The reflector is used to reflect the pump light that has passed through the alkali metal atom gas cell back to the alkali metal atom gas cell.

[0012] In one or more embodiments, the combined prism includes:

[0013] Polarizing beam splitter;

[0014] A linear polarizer is arranged on one side of the polarizing beam splitter, and the incident surface is arranged on the side of the linear polarizer facing away from the polarizing beam splitter.

[0015] A quarter-wave plate is arranged on the other side of the polarizing beam splitter, and the exit surface is arranged on the side of the quarter-wave plate opposite to the polarizing beam splitter.

[0016] In one or more embodiments, the polarizing beam splitter, the linear polarizer, and the quarter-wave plate are glued together as a single unit.

[0017] In one or more embodiments, the reflector is embedded in the inner wall of the housing.

[0018] In one or more embodiments, the photodetector is embedded in the inner wall of the housing.

[0019] In one or more embodiments, a heating temperature measurement module and a triaxial magnetic compensation coil are further included, wherein the heating temperature measurement module includes:

[0020] An oven, enclosed outside the alkali metal atom gas chamber;

[0021] A non-magnetic electric heating circuit is used to heat the oven;

[0022] A temperature sensor is used to detect the temperature inside the oven;

[0023] The triaxial magnetic compensation coil is arranged inside the oven and is used to compensate the magnetic field of the alkali metal atom gas chamber.

[0024] In one or more embodiments, the non-magnetic electric heating circuit, the triaxial magnetic compensation coil, and the drive circuit of the photodetector are integrated on a flexible circuit board, which is disposed through the housing.

[0025] In one or more embodiments, a collimator is further included, which is disposed through the housing and includes a collimating light emitting end located inside the housing and opposite to the incident surface of the combined prism, and a laser incident end located outside the housing.

[0026] To achieve the above objectives, a second aspect of this application provides an atomic magnetometer, including the atomic magnetometer probe described in any of the above embodiments.

[0027] In one or more embodiments, it further includes:

[0028] A laser source is used to emit laser light into the atomic magnetometer probe;

[0029] The first control module is electrically connected to the laser source and is used to control the working state of the laser source;

[0030] The second control module is used to control the working state of the alkali metal atom gas chamber and to receive the electrical signals fed back by the photodetector.

[0031] The advantages of this application, which differ from existing technologies, are:

[0032] This application significantly improves the absorption path of the pump light through the mirror design, realizes secondary polarization, increases the interaction strength between the pump light and alkali metal atoms, and effectively increases the number of atoms in a limited region. It can achieve higher sensitivity at lower temperatures, significantly improve the performance of single-beam atomic magnetometers, and contribute to miniaturization design.

[0033] This application significantly improves the space utilization rate inside the housing through the integrated design of internal optical and electrical components;

[0034] This application balances miniaturization and sensitivity, with a probe size as low as 22×20×12mm, which improves the spatial resolution of array-type magnetic field measurement and has better measurement accuracy, making it of great significance in the field of heart and brain magnetometry. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of one embodiment of the miniaturized single-beam reflective atomic magnetometer probe of this application;

[0037] Figure 2 This is a schematic diagram of one embodiment of the atomic magnetometer of this application;

[0038] Figure 3 This is a graph showing the detection results of an embodiment of the atomic magnetometer of this application.

[0039] As shown in the figure:

[0040] Atomic magnetometer probe 10; housing 100; alkali metal atom gas cell 200; combined prism 300; exit surface 301; incident surface 302; polarizing beam splitter 303; linear polarizer 304; quarter-wave plate 305; reflector 400; photodetector 500; collimator 600; collimated light exit end 601; laser incident end 602; heating and temperature measurement module 700; oven 701; flexible circuit board 800;

[0041] Laser source 20;

[0042] 30mm polarization-maintaining fiber;

[0043] First control module 40;

[0044] Second control module 50;

[0045] Signal cable 60. Detailed Implementation

[0046] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of this utility model.

[0047] The SERF atomic magnetometer was initially based on a two-beam configuration, using a circularly polarized beam to polarize alkali metal atoms while simultaneously using a linearly polarized beam to detect atomic precession induced by an external magnetic field. However, this configuration is generally bulky and has a complex optical path, limiting its further development. Compared to the two-beam configuration, the single-beam magnetometer configuration has greater potential for miniaturization and higher resolution.

[0048] However, existing single-beam SERF atomic magnetometers require a sufficient pump light absorption path to ensure sensitivity, thereby guaranteeing the interaction strength between the pump light and alkali metal atoms and the polarizability of the alkali metal atoms. This limits the miniaturization of the alkali metal atom gas cell. At the same time, the internal structure of the atomic magnetometer is not highly integrated, making it impossible for the atomic magnetometer to achieve both high sensitivity and miniaturization.

[0049] To address the aforementioned issues, the applicant has developed a novel SERF atomic magnetometer probe. This probe achieves miniaturization of the atomic magnetometer through a reflective design and internal integration, while also improving detection sensitivity. This helps reduce the size of array-type magnetometers and enables higher spatial resolution for magnetic field measurements.

[0050] Specifically, please refer to Figure 1 , Figure 1 This is a schematic diagram of one embodiment of the miniaturized single-beam reflective atomic magnetometer probe of this application.

[0051] like Figure 1 As shown, the atomic magnetometer probe 10 includes a housing 100 and an alkali metal atom gas chamber 200, a combination prism 300, a reflector 400, and a photodetector 500 built into the housing 100.

[0052] In one embodiment, the housing 100 may be made of PEEK material; to facilitate component installation, the housing 100 may be designed as a split type, consisting of a top cover and a base that are fixed by bolts, clips or other structures.

[0053] The alkali metal atom gas chamber 200 is filled with alkali metal and high-purity nitrogen gas. The transverse relaxation time is increased by frequent collisions between nitrogen gas and alkali metal atoms. Under high temperature conditions, such as 130°C, alkali metal atoms can be in a spinless exchange relaxation (SERF) state.

[0054] The combined prism 300 is located on one side of the alkali metal atom gas cell 200, and includes an exit surface 301 facing the alkali metal atom gas cell 200 and an incident surface 302 perpendicular to the exit surface 301. Specifically, the combined prism 300 is used to convert the collimated light received by the incident surface 302 into circularly polarized light, and then direct it towards the alkali metal atom gas cell 200 via the exit surface 301.

[0055] The vertically distributed incident surface 302 and exit surface 301 can effectively reduce the space occupied in the optical axis direction of circularly polarized light, thereby reducing the volume of the housing 100.

[0056] In this embodiment, the combined prism 300 includes a polarizing beam splitter 303, a linear polarizer 304, and a quarter-wave plate 305; wherein, the linear polarizer 304 is arranged on one side of the polarizing beam splitter 303, and the incident surface 302 is arranged on the side of the linear polarizer 304 facing away from the polarizing beam splitter 303; the quarter-wave plate 305 is arranged on the other side of the polarizing beam splitter 303, and the exit surface 301 is arranged on the side of the quarter-wave plate 305 facing away from the polarizing beam splitter 303.

[0057] Understandably, after the collimated light passes through the linear polarizer 304, it is converted into linearly polarized light. Then, after being reflected by the polarizing beam splitter 303, it enters the quarter-wave plate 305. After being converted by the quarter-wave plate 305, the circularly polarized light is finally output and enters the alkali metal atom gas chamber 200.

[0058] Since alkali metal atoms absorb circularly polarized light passing through the gas cell, the relationship between the output intensity of the circularly polarized pump light and the atomic polarizability in the gas cell is expressed as follows:

[0059]

[0060] Among them, V PD I is the voltage signal output by the PD output signal after passing through the amplifier when using the optical absorption method. pump v is the initial incident light intensity of the pump light. pump Let η' be the frequency of the pump light, η' be the photoelectric conversion coefficient of the PD, and OD(v) be the frequency of the pump light. pump The optical depth of the pump light is denoted as P. When the alkali metal cell is in a near-zero magnetic field environment and the signal to be measured is a very weak magnetic field, the polarizability P induced by the magnetic field is... z The rate of change is relatively small. At this point, it can be assumed that the change in pump light intensity is related to the polarizability P. z The changes in polarizability are linearly related, thus enabling polarizability measurement.

[0061] In this embodiment, the polarizing beam splitter 303, the linear polarizer 304, and the quarter-wave plate 305 are glued together, thereby improving the integration of the internal optical components and contributing to miniaturization. Of course, in other embodiments, the polarizing beam splitter 303, the linear polarizer 304, and the quarter-wave plate 305 can also be designed as separate units with small gaps, achieving the same effect as this embodiment.

[0062] The reflector 400 is arranged on the other side of the alkali metal atom gas chamber 200 and is positioned opposite to the exit surface 301 of the combined prism 300; the photodetector 500 is arranged on the side of the combined prism 300 away from the alkali metal atom gas chamber 200.

[0063] Understandably, the pump light passes through the combined prism 300 and enters the alkali metal atom gas chamber 200. It then exits from the other side and is reflected by the reflector 400, re-entering the alkali metal atom gas chamber 200. Finally, it is received by the photodetector 500 and converted into an electrical signal to realize the detection of the polarizability signal.

[0064] By using a reflection design, the absorption path of the pump light can be significantly increased within a limited space, enabling secondary polarization of alkali metal atoms in the SERF state. This effectively increases the number of atoms within a limited area, greatly enhancing the limiting sensitivity of the miniaturized SERF atomic magnetometer.

[0065] To further improve the space utilization rate inside the housing 100, in this embodiment, the reflectors 400 and photodetectors 500 located at both ends are embedded in the inner wall of the housing 100, thereby optimizing the spatial layout in the optical axis direction of the pump light. Of course, in other embodiments, only the reflectors 400 or only the photodetectors 500 may be embedded in the inner wall of the housing 100, which can achieve the effect of this embodiment to a certain extent.

[0066] In this embodiment, the atomic magnetometer probe 10 also includes a collimator 600, which is arranged to penetrate the housing 100, further reducing the space occupied inside the housing 100.

[0067] Specifically, the collimator 600 includes a collimating light emitting end 601 located inside the housing 100 and opposite to the incident surface 302 of the combined prism 300, and a laser incident end 602 located outside the housing 100; the collimator 600 can convert the laser light incident through the laser incident end 602 into collimated light and send it into the combined prism 300.

[0068] In this embodiment, the atomic magnetometer probe 10 also includes a heating and temperature measurement module 700 for heating the alkali metal atom gas chamber 200 and a triaxial magnetic compensation coil (not shown in the figure) for magnetic field compensation.

[0069] Specifically, the heating and temperature measurement module 700 includes an oven 701 enclosed in an alkali metal atom gas chamber 200, a non-magnetic electric heating circuit (not shown in the figure) for heating the oven 701, and a temperature sensor (not shown in the figure) for detecting the temperature inside the oven 701.

[0070] A triaxial magnetic compensation coil is arranged inside the oven 701 to compensate the magnetic field of the alkali metal atom gas chamber 200, so as to cancel the residual magnetic field signal in the environment and apply a modulated magnetic field.

[0071] To further integrate the design, in this embodiment, the non-magnetic heating circuit, the triaxial magnetic compensation coil, and the drive circuit of the photodetector 500 are integrated on a flexible circuit board 800. The flexible circuit board 800 is installed through the housing 100, which facilitates external control. The integrated design of the flexible circuit board 800 helps to further improve the space utilization inside the housing 100 and contributes to miniaturization design.

[0072] The atomic magnetometer probe 10 based on the above embodiments significantly improves the absorption optical path of the pump light through the design of the reflector 400, achieving secondary polarization. It also increases the interaction intensity between the pump light and alkali metal atoms and effectively increases the number of atoms in a limited area, enabling higher sensitivity at lower temperatures and significantly improving the performance of the single-beam atomic magnetometer. On the other hand, the integrated design of internal optical and electrical components significantly improves the space utilization rate inside the housing 100. This allows for both miniaturization and sensitivity, with the probe size as low as 22×20×12mm. This enhances the spatial resolution of array-type magnetic field measurements and provides superior measurement accuracy, which is of great significance in the field of heart and brain magnetometry.

[0073] This application also provides an atomic magnetometer that employs the atomic magnetometer probe 10 of any of the above embodiments. Please refer to [link to relevant documentation]. Figure 2 , Figure 2 This is a schematic diagram of one embodiment of the atomic magnetometer of this application.

[0074] like Figure 2 As shown, the atomic magnetometer includes a laser source 20, which is connected to the laser incident end 602 of the collimator 600 via a polarization-maintaining fiber 30, thereby realizing laser injection.

[0075] The atomic magnetometer also includes a first control module 40, which is electrically connected to the laser source 20 and is used to control the working state of the laser source 20.

[0076] The atomic magnetometer also includes a second control module 50, which is used to control the working state of the alkali metal atom gas chamber 200 and to receive electrical signals fed back by the photodetector 500.

[0077] Specifically, the second control module 50 can be connected to the flexible circuit board 800 via the signal cable 60, thereby controlling the heating and temperature measurement module 700 to heat the alkali metal gas chamber to the target temperature, controlling the triaxial magnetic compensation coil to work to cancel the ambient magnetic field or apply a modulated magnetic field, and receiving the electrical signal fed back by the photodetector 500. After demodulation and other processing, the final magnetic field information to be measured is obtained.

[0078] The specific workflow of the atomic magnetometer in this embodiment is as follows:

[0079] S1. First, fix the atomic magnetometer probe 10 in the custom fixture and place it in the magnetic shielding cylinder, and connect the signal cable 60 and the polarization-maintaining fiber 30.

[0080] S2. A start command is sent via computer. The first electronic control module receives the command and adjusts the laser to emit light normally.

[0081] S3. The computer sends a temperature adjustment command. After receiving the command, the second electronic control module sends a heating and temperature measurement command to the flexible circuit board 800, so that the heating and temperature measurement module 700 heats the alkali metal atom gas chamber 200 to 130°C, thereby allowing the alkali metal atoms to work in the SERF state.

[0082] S4. Adjust the operating temperature of the laser through the first electronic control module, thereby fine-tuning the output wavelength of the laser;

[0083] S5. The computer issues a magnetic field compensation command, and the first control module 40 generates a low-frequency sine wave signal, which is transmitted to the triaxial magnetic compensation coil through the signal cable 60, thereby performing triaxial magnetic field compensation on the alkali metal gas chamber in sequence to cancel the remaining magnetic field signal in the environment.

[0084] S6. The computer issues a modulation / demodulation command, and the first control module 40 generates a sinusoidal signal, which is transmitted to the coil of the triaxial magnetic compensation coil in the direction to be measured. A modulated magnetic field is applied in the direction to be measured in the alkali metal atom gas cell 200. The laser passes through the gas cell twice and then enters the photodetector 500, thus being converted into an electrical signal. The electrical signal is transmitted to the first control module 40 via the signal cable 60. After demodulation and other processing, the final magnetic field information to be measured is obtained, such as... Figure 3 As shown, Figure 3 This is a graph showing the detection results of an embodiment of the atomic magnetometer of this application.

[0085] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0086] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A miniaturized single-beam reflective atomic magnetometer probe, characterized in that, include: case; An alkali metal atom gas chamber is arranged inside the shell; A combined prism is arranged on one side of the alkali metal atom gas cell, the combined prism including an exit surface facing the alkali metal atom gas cell and an incident surface distributed perpendicular to the exit surface; A reflector is arranged on the other side of the alkali metal atom gas cell and is positioned opposite to the exit surface of the combined prism. A photodetector is arranged on the side of the combined prism away from the alkali metal atom gas cell; The combined prism is used to convert the collimated light received by the incident surface into circularly polarized light, and then direct it to the alkali metal atom gas cell via the exit surface. The reflector is used to reflect the pump light that has passed through the alkali metal atom gas cell back to the alkali metal atom gas cell.

2. The atomic magnetometer probe according to claim 1, characterized in that, The combined prism includes: Polarizing beam splitter; A linear polarizer is arranged on one side of the polarizing beam splitter, and the incident surface is arranged on the side of the linear polarizer facing away from the polarizing beam splitter. A quarter-wave plate is arranged on the other side of the polarizing beam splitter, and the exit surface is arranged on the side of the quarter-wave plate opposite to the polarizing beam splitter.

3. The atomic magnetometer probe according to claim 2, characterized in that, The polarizing beam splitter, the linear polarizer, and the quarter-wave plate are glued together as a single unit.

4. The atomic magnetometer probe according to claim 1, characterized in that, The reflector is embedded in the inner wall of the housing.

5. The atomic magnetometer probe according to claim 1, characterized in that, The photodetector is embedded in the inner wall of the housing.

6. The atomic magnetometer probe according to claim 1, characterized in that, It also includes a heating temperature measurement module and a triaxial magnetic compensation coil, wherein the heating temperature measurement module includes: An oven, enclosed outside the alkali metal atom gas chamber; A non-magnetic electric heating circuit is used to heat the oven; A temperature sensor is used to detect the temperature inside the oven; The triaxial magnetic compensation coil is arranged inside the oven and is used to compensate the magnetic field of the alkali metal atom gas chamber.

7. The atomic magnetometer probe according to claim 6, characterized in that, The non-magnetic electric heating circuit, the triaxial magnetic compensation coil, and the photodetector driving circuit are integrated on a flexible circuit board, which extends through the housing.

8. The atomic magnetometer probe according to claim 1, characterized in that, It also includes a collimator that extends through the housing and includes a collimating light emitting end located inside the housing and opposite to the incident surface of the combined prism, and a laser incident end located outside the housing.

9. An atomic magnetometer, characterized in that, Includes the atomic magnetometer probe as described in any one of claims 1 to 8.

10. The atomic magnetometer according to claim 9, characterized in that, Also includes: A laser source is used to emit laser light into the atomic magnetometer probe; The first control module is electrically connected to the laser source and is used to control the working state of the laser source; The second control module is used to control the working state of the alkali metal atom gas chamber and to receive the electrical signals fed back by the photodetector.

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