An optical pumping magnetometer based on an alkali metal laser

Abstract

The present invention discloses an optical pumping magnetometer based on an alkali metal laser, comprising: a pump laser outputs pump light; an alkali metal vapor laser gas cell forms gain, and forms laser light under the action of a resonant cavity; the alkali metal magnetometer gas cell is internally sealed with the same kind of alkali metal atoms and buffer gas as those in the alkali metal vapor laser gas cell; a resonant cavity composed of a total reflection mirror and an output coupling mirror resonantly amplifies light corresponding to the wavelength of the 2 P 1 / 2 → 2 S 1 / 2 transition; a polarization beam splitter is used to couple the pump light with the gain region of the alkali metal laser; the laser light reciprocating in the resonant cavity of the alkali metal vapor laser forms circularly polarized light in two directions of σ+ and σ- in the alkali metal magnetometer gas cell; a photodetector is used to receive the laser light output by the output coupling mirror. This optical pumping magnetometer can achieve polarization laser frequency stabilization output without an additional optical path, uses the fundamental mode in the laser resonant cavity to polarize the atoms in the magnetometer gas cell, can effectively improve the sensitivity of the magnetometer, and has the advantage of low cost.

Description

Technical Field

[0001] The present invention relates to the field of atomic precision detection technology, and particularly relates to an optically pumped magnetometer based on an alkali metal laser. Background Art

[0002] An optically pumped magnetometer is a new type of magnetometer. Due to its characteristics such as small volume, large dynamic range, low cost, and high precision, it is widely used in fields such as geological exploration, environmental monitoring, and anti-submarine operations. The optically pumped magnetometer uses the Larmor precession of polarized alkali metal elements such as rubidium and cesium in a magnetic field to accurately measure the ambient magnetic field. Referring to Figure 1 As shown, traditional optically pumped magnetometers generally use radio frequency-excited alkali metal lamps (such as rubidium lamps, cesium lamps, etc.) to achieve the polarization of alkali metals. With the increasing requirements for volume, power consumption, and cost from application parties, more and more research institutions use vertical cavity surface emitting semiconductor lasers (VCSELs) to replace the original pump lamps as the pump source of the optically pumped magnetometer. However, directly using VCSEL lasers has problems such as high cost, unstable laser frequency / power, and unstable laser mode, and the problems of low power and large linewidth of VCSEL lasers also limit the further improvement of the accuracy of the optically pumped magnetometer.

[0003] Therefore, how to solve the problems of low accuracy, high cost, unstable polarization laser mode, and the need for additional frequency stabilization means in existing optically pumped magnetometers has become an urgent problem for those skilled in the art to solve. Summary of the Invention

[0004] In view of the above problems, the present invention proposes an optically pumped magnetometer based on an alkali metal laser that at least solves some of the above technical problems. This optically pumped magnetometer can achieve frequency stabilization without a frequency stabilization optical path. Since the fundamental mode in the laser resonator is used for multi-pass polarization, the sensitivity of the magnetometer can be effectively improved.

[0005] An embodiment of the present invention provides an optically pumped magnetometer based on an alkali metal laser, including: a pump laser and a shaping and focusing unit, as well as a total reflection cavity mirror, a polarization beam splitter, an alkali metal vapor laser gas cell, an alkali metal magnetometer gas cell, an output coupling mirror, and a photodetector sequentially arranged along the optical axis;

[0006] The pump laser is used to output the pump light of the alkali metal vapor laser;

[0007] The shaping and focusing unit is used to focus the pump light so that the beam waist position of the focused pump light is located at the central position of the alkali metal vapor laser gas cell;

[0008] The alkali metal vapor laser cell internally seals alkali metal atoms and buffer gas, acting as the gain medium of the laser. When the focused pump light passes through, gain is formed, and laser is formed under the action of the resonant cavity. Only the horizontally polarized D1 line light oscillates in the resonant cavity.

[0009] The alkali metal magnetometer cell internally seals alkali metal atoms. The types of alkali metal atoms sealed inside the alkali metal magnetometer cell are the same as those sealed inside the alkali metal vapor laser cell. And the alkali metal magnetometer cell is internally filled with buffer gas for reducing collision relaxation.

[0010] The total reflection mirror and the output coupling mirror form the alkali metal laser resonant cavity for resonantly amplifying the light corresponding to the wavelength of the 2 P 1 / 2 → 2 S 1 / 2 transition of the alkali metal atoms.

[0011] The polarization beam splitter is used to couple the pump light with the alkali metal vapor laser cell.

[0012] The alkali metal magnetometer cell is placed inside the alkali metal laser resonant cavity.

[0013] The laser reciprocating inside the alkali metal laser resonant cavity forms circularly polarized light in two directions, σ+ and σ-, inside the alkali metal magnetometer cell.

[0014] The output coupling mirror is used to output the laser corresponding to the wavelength of the 2 P 1 / 2 → 2 S 1 / 2 transition of the alkali metal atoms.

[0015] The photodetector is used to receive the laser output by the output coupling mirror and convert the optical signal into an electrical signal.

[0016] Further, a magnetic field coil is arranged outside the alkali metal magnetometer cell.

[0017] Further, the polarization beam splitter is a polarization beam splitting prism.

[0018] Further, the wavelength of the pump light output by the pump laser is the same as the wavelength corresponding to the 2 P 3 / 2 → 2 S 1 / 2 transition of the alkali metal atoms.

[0019] Further, the linewidth of the pump light is the same as that of the alkali metal atoms after collision broadening by the buffer gas inside the alkali metal vapor laser cell for the 2 P 3 / 2 → 2S 1 / 2 Matched with the linewidth of the transition spectral line.

[0020] Furthermore, λ / 4 wave plates for the D1 line of the corresponding alkali metal atoms are respectively arranged at the front and rear ends of the alkali metal magnetometer gas cell.

[0021] The λ / 4 wave plate is used to convert the linearly polarized light oscillating in the resonator cavity of the alkali metal laser into circularly polarized light for atomic polarization in the alkali metal magnetometer gas cell.

[0022] Furthermore, the signal received by the photodetector includes a DC part and an AC part; the DC part is used for stable control of the alkali metal vapor laser power; the AC part is caused by the atomic Larmor precession induced by an external magnetic field; the AC part signal is amplified by the resonator cavity and used for the closed-loop control and magnetic field measurement of the magnetometer.

[0023] Furthermore, the polarization splitting ratio of the polarization beam splitter is higher than 500:1.

[0024] The beneficial effects of the above technical solutions provided by the embodiments of the present invention at least include:

[0025] An optical pumping magnetometer based on an alkali metal laser provided by an embodiment of the present invention includes: a pump laser outputs pump light; a shaping and focusing unit makes the waist position of the focused pump light located at the center of the gas cell of the alkali metal vapor laser; the gas cell of the alkali metal vapor laser forms gain, and forms laser under the action of the resonator cavity; the alkali metal magnetometer gas cell is internally sealed with the same type of alkali metal atoms and buffer gas as those in the gas cell of the alkali metal vapor laser; the resonator cavity composed of a total reflection mirror and an output coupling mirror resonantly amplifies the light corresponding to the wavelength of the 2 P 1 / 2 → 2 S 1 / 2 transition of the alkali metal atoms; a polarization beam splitter is used to couple the pump light with the gain region of the alkali metal laser; the laser reciprocating in the resonator cavity of the alkali metal vapor laser forms circularly polarized light in two directions of σ+ and σ- in the alkali metal magnetometer gas cell; a photodetector is used to receive the laser output by the output coupling mirror. This optical pumping magnetometer can achieve frequency stabilization of polarized light without an additional optical path, uses the fundamental mode in the laser resonator cavity to polarize atoms in the magnetometer gas cell, can effectively improve the sensitivity of the magnetometer, and has the advantage of low cost.

[0026] Other features and advantages of the present invention will be described in subsequent specifications, and, in part, will be obvious from the specifications, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures specifically pointed out in the written specifications, claims, and drawings.

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0028] The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention, but do not constitute a limitation to the present invention. In the accompanying drawings:

[0029] Figure 1 is a schematic structural diagram of a typical optically pumped magnetometer in the prior art provided by an embodiment of the present invention;

[0030] Figure 2 is a schematic structural diagram of an optically pumped magnetometer based on an alkali metal laser provided by an embodiment of the present invention.

[0031] In the accompanying drawings: 1 - pump laser; 2 - shaping and focusing unit; 3 - total reflection cavity mirror; 4 - polarization beam splitter; 5 - alkali metal vapor laser gas cell; 6 - alkali metal magnetometer gas cell; 7 - output coupling mirror; 8 - photodetector; 9 - magnetic field coil, 10 - λ / 4 wave plate. Detailed Embodiments

[0032] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0033] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "front end", "rear end", "both ends", "one end", "the other end", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0034] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and can be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0035] An embodiment of the present invention provides an optically pumped magnetometer based on an alkali metal laser, with reference to Figure 2As shown in the figure, it includes: a pump laser 1, a shaping and focusing unit 2, a total reflection cavity mirror 3, a polarization beam splitter 4, an alkali metal vapor laser gas cell 5, a λ / 4 wave plate 10, an alkali metal magnetometer gas cell 6, a λ / 4 wave plate 10, an output coupling mirror 7, and a photodetector 8, which are sequentially arranged along the optical axis;

[0036] The pump laser 1 is used to output the pump light of the alkali metal vapor laser;

[0037] The shaping and focusing unit 2 is used to focus the pump light so that the waist position of the focused pump light is located at the center of the alkali metal vapor laser gas cell 5;

[0038] The alkali metal vapor laser gas cell 5 is internally sealed with alkali metal atoms and buffer gas, acting as the gain medium of the laser. When the focused pump light passes through, gain is formed, and laser is formed under the action of the resonant cavity; only the horizontally polarized D1 line light oscillates in the resonant cavity;

[0039] The alkali metal magnetometer gas cell 6 is internally sealed with alkali metal atoms; the types of alkali metal atoms sealed inside the alkali metal magnetometer gas cell 6 are the same as those sealed inside the alkali metal vapor laser gas cell 5; and the alkali metal magnetometer gas cell 6 is filled with buffer gas for reducing collision relaxation;

[0040] The total reflection cavity mirror 3 and the output coupling mirror 7 form the alkali metal laser resonant cavity, which is used for resonant amplification of the light corresponding to the P 2 P 1 / 2 → 2 S 1 / 2 transition corresponding wavelength;

[0041] The polarization beam splitter 4 is used to couple the pump light with the alkali metal vapor laser gas cell 5;

[0042] The alkali metal magnetometer gas cell 6 is placed inside the alkali metal laser resonant cavity;

[0043] The laser reciprocating inside the alkali metal laser resonant cavity forms circularly polarized light in two directions of σ+ and σ- inside the alkali metal magnetometer gas cell 6;

[0044] The output coupling mirror 7 is used to output the laser corresponding to the P 2 P 1 / 2 → 2 S 1 / 2 transition corresponding wavelength;

[0045] The photodetector 8 is used to receive the laser output by the output coupling mirror 7 and convert the optical signal into an electrical signal.

[0046] The optically pumped magnetometer based on an alkali metal laser provided in this embodiment uses in-laser polarization, and is a new type of magnetometer system with low cost, no need for pump source frequency stabilization, and can effectively improve the sensitivity of the magnetometer. This optically pumped magnetometer features low cost and high precision.

[0047] Among them, the shaping and focusing unit 2 is located between the polarization beam splitter 4 and the semiconductor laser (i.e., the pump laser 1), and is used for beam shaping of the pump laser 1. The pump light turns the pump beam onto the system optical axis through the polarization beam splitting prism. Along the beam propagation direction on the system optical axis, a total reflection cavity mirror 3, a polarization beam splitter 4 (which can be set as a polarization beam splitting prism), an alkali metal laser gas cell, a λ / 4 wave plate 10, a magnetometer gas cell (which can be set as an alkali metal magnetometer gas cell 6), a λ / 4 wave plate 10, an output coupling mirror 7, and a photodetector 8 are sequentially placed.

[0048] The semiconductor laser (i.e., the pump laser 1) outputs pump light, which first passes through the shaping and focusing unit 2. The shaping and focusing unit 2 focuses the pump light so that the waist position of the focused pump light is located at the center of the alkali metal vapor laser gas cell 5, and the excited state energy level of the alkali metal atoms 2 P 1 / 2 and the ground state energy level 2 S 1 / 2 have population inversion. The polarization beam splitter 4 is of a polarization cube structure. The polarization beam splitter 4 couples the pump light with the alkali metal vapor laser gas cell 5. The alkali metal laser resonator formed by the total reflection cavity mirror 3 and the output coupling mirror 7 is used to achieve optical resonance amplification of the light corresponding to the 2 P 1 / 2 → 2 S 1 / 2 transition of the alkali metal atoms, and outputs the laser corresponding to the 2 P 1 / 2 → 2 S 1 / 2 transition of the alkali metal atoms through the output coupling mirror 7. The total reflection cavity mirror and the output coupling mirror form an alkali metal laser resonator. After the pump light makes the alkali metal laser gas cell form the condition of population inversion, the spontaneous emission will be reciprocally resonantly amplified under the action of the resonator and the gain medium.

[0049] The transmittance of the output coupling mirror 7 can be optimized for the atomic polarizability of the alkali metal magnetometer gas cell 6. Preferably, using an output coupling mirror with a low transmittance (<30%) is beneficial to improving the atomic polarizability in the magnetometer atomic gas cell.

[0050] The wavelength of the output pump light is the same as that of the 2 P 3 / 2 → 2 S 1 / 2The wavelengths corresponding to the transitions are the same; the linewidth of the pump light matches the linewidth of the spectral line of the 2 P 3 / 2 → 2 S 1 / 2 transition of the alkali metal atoms broadened by the buffer gas in the alkali metal vapor laser cell 5 (i.e., the alkali metal laser cell).

[0051] Specifically, the linewidth of the pump light is greater than the linewidth of the spectral line of the 2 P 3 / 2 → 2 S 1 / 2 transition of the alkali metal atoms in the alkali metal vapor laser cell 5 broadened by collisions; the preferred value of the ratio of the linewidth of the pump light to the linewidth of the spectral line of the 2 P 3 / 2 → 2 S 1 / 2 transition of the alkali metal atoms in the alkali metal vapor laser cell 5 broadened by collisions is 3:1.

[0052] After the pump light passes through the shaping and focusing unit 2, the size of the focused beam waist is 0.3 mm to 2 mm, and gain is formed in the alkali metal vapor laser cell 5 (the gain medium can be potassium, rubidium, or cesium), and laser is formed under the action of the resonant cavity. The vertically polarized pump light is reflected by the polarization beam splitter prism and enters the alkali metal vapor laser cell. Since the parallel polarized laser can resonate in the resonant cavity composed of the total reflection mirror and the output coupling mirror through the transmission of the polarization beam splitter prism, the polarization state of the alkali metal laser is linearly polarized in parallel. The transmittance of the polarization beam splitter 4 for the parallel polarized light is between 95% and 100%; the reflectance of the polarization beam splitter 4 for the vertically polarized light is between 95% and 100%, ensuring that only the parallel polarized D1 line light oscillates in the cavity. Among them, the reflectance of the total reflection mirror 3 is 99% to 100%; the output coupling rate of the output coupling mirror 7 is 15% to 90%.

[0053] The alkali metal atoms and the buffer gas are sealed inside the alkali metal vapor laser cell 5. The buffer gas is preferably CH4 to increase the fine energy level mixing rate. A magnetic field coil 9 is arranged outside the alkali metal magnetometer cell 6 for the closed-loop control of the magnetometer.

[0054] The same type of alkali metal element as that sealed inside the alkali metal vapor laser cell 5 is sealed inside the alkali metal magnetometer cell 6, and a buffer gas for slowing down the collision relaxation is filled, and the buffer gas is preferably N2, He, etc.

[0055] At both ends of the alkali metal magnetometer gas chamber 6, λ / 4 wave plates 10 for the corresponding D1 line of the alkali metal element are placed, which are used to convert the linearly polarized light oscillating in the resonant cavity of the laser (i.e., the alkali metal vapor laser) into circularly polarized light for atomic polarization in the alkali metal magnetometer gas chamber 6. A beam of linearly polarized light is converted into circularly polarized light after passing through the first λ / 4 wave plate, and then becomes linearly polarized light again after passing through the second λ / 4 wave plate. After being reflected by the resonant cavity mirror, it becomes circularly polarized light again after passing through the second λ / 4 wave plate, and so on.

[0056] The laser reciprocating in the resonant cavity of the alkali metal vapor laser forms circularly polarized light in two directions, σ+ and σ-, in the alkali metal magnetometer gas chamber 6. This characteristic light beam is used to polarize alkali metal atoms, which can effectively improve the atomic polarization rate and thus the sensitivity of the magnetometer. The alkali metal vapor laser gas chamber 5 and the alkali metal magnetometer gas chamber 6 can be heated to the same temperature by a set of heating systems.

[0057] Optionally, the alkali metal magnetometer gas chamber 6 can be placed inside or outside the resonant cavity of the alkali metal vapor laser gas chamber 5. This embodiment does not limit it.

[0058] The signal received by the photodetector 8 contains a DC part and an AC part. The DC part is used for stable control of the alkali metal vapor laser power; the AC part is caused by the atomic Larmor precession induced by the external magnetic field. This signal can be used for the closed-loop control and magnetic field measurement of the magnetometer after being amplified by the resonant cavity.

[0059] Optionally, the resonant cavity can be a stable cavity type such as a plano-concave cavity or a plano-plano cavity. This embodiment does not limit it.

[0060] Optionally, the types of alkali metal magnetometers include Mx and Mz configurations and other all-optical probe configurations.

[0061] The following is a specific embodiment described based on a system using alkali metal Rb:

[0062] The semiconductor laser outputs pump light. Preferably, an LD diode with an output power of 500 mW, a line width of 1 GHz, and a wavelength of 780 nm is used; the pump light first passes through the shaping and focusing unit 2. The shaping and focusing unit 2 focuses the pump light. Preferably, a plano-convex lens coated with an antireflection film of 780 nm and a focal length of 5 - 10 mm is used as the shaping and focusing unit 2, so that the waist position of the focused pump light is located at the center of the alkali metal vapor laser gas chamber 5, exciting the energy levels of the alkali metal atoms 2 P 1 / 2 and the ground state energy level 2 S 1 / 2Population inversion between them, the polarization beam splitter 4 couples the pump light with the alkali metal vapor laser cell. Preferably, a polarization beam splitting prism with a polarization splitting ratio higher than 500:1 is used, and the total reflection mirror 3 is used to achieve the 2 P 1 / 2 → 2 S 1 / 2 optical amplification corresponding to the wavelength (795 nm, D1 line) of the transition, and outputs the laser corresponding to the wavelength of the 2 P 1 / 2 → 2 S 1 / 2 transition of the alkali metal atoms through the output coupling mirror 7.

[0063] The wavelength of the output pump light is the same as the 2 P 3 / 2 → 2 S 1 / 2 corresponding wavelength (780 nm) of the transition, and the line width of the pump light is the same as that of the alkali metal atoms broadened by the buffer gas in the alkali metal vapor laser cell 5 2 P 3 / 2 → 2 S 1 / 2 transition spectral line width. Preferably, the alkali metal vapor laser cell 5 is filled with 300 torr of methane, and the alkali metal magnetometer cell 6 is filled with 100 torr of N2. The temperatures of the two cells are both 70 - 90 °C under the working state. The line width of the pump light is greater than the 2 P 3 / 2 → 2 S 1 / 2 line width of the transition spectral line of the alkali metal atoms broadened by collision; the preferred value of the ratio of the line width of the pump light to the 2 P 3 / 2 → 2 S 1 / 2 line width of the transition spectral line of the alkali metal atoms in the alkali metal vapor laser cell 5 broadened by collision is 3:1.

[0064] After the pump light passes through the shaping and focusing unit 2, the size of the focused beam waist is 0.3 mm to 2 mm, forming gain in the alkali metal vapor laser cell 5, and forming laser under the action of the resonant cavity. The length of the alkali metal vapor laser cell 5 is preferably 8 mm. Since the polarization state of the pump light is vertical linear polarization and the polarization state of the alkali metal laser is parallel linear polarization; the transmittance of the polarization beam splitter 4 for parallel polarized light is between 95% and 100%, and the reflectivity of the polarization beam splitter 4 for vertical polarized light is between 95% and 100%, ensuring that only the parallel polarized D1 line light oscillates in the cavity. The reflectivity of the total reflection mirror 3 is 99% - 100%; the output coupling rate of the output coupling mirror 7 is 15% - 90%.

[0065] The alkali metal magnetometer gas chamber 6 and the alkali metal vapor laser gas chamber 5 are hermetically sealed inside. 87 For the Rb alkali metal element, λ / 4 wave plates 10 for the D1 line of the corresponding alkali metal element are respectively placed at both ends of the alkali metal magnetometer gas chamber 6, which are used to convert the linearly polarized light oscillating in the laser resonator into circularly polarized light for atomic polarization in the alkali metal magnetometer gas chamber 6. Preferably, the λ / 4 wave plates 10 with an antireflection coating at 795 nm are selected.

[0066] The laser reciprocating in the alkali metal vapor laser resonator forms circularly polarized light in two directions, σ+ and σ-, in the alkali metal magnetometer gas chamber 6. This characteristic light beam is used to polarize alkali metal atoms, which can effectively improve the atomic polarization rate and thus the sensitivity of the magnetometer.

[0067] The signal received by the photodetector 8 contains a DC part and an AC part. The DC part is used for the stable control of the alkali metal vapor laser power, and the AC part is caused by the atomic Larmor precession induced by the external magnetic field. This signal can be used for the closed-loop control and magnetic field measurement of the magnetometer after being amplified by the resonator.

[0068] The optically pumped magnetometer based on an alkali metal laser provided in this embodiment can achieve the following beneficial effects:

[0069] 1) An alkali metal vapor laser is used to polarize the atoms in the magnetometer atomic gas chamber (i.e., the alkali metal magnetometer gas chamber 6). Since the output wavelength of the alkali metal vapor laser strictly corresponds to the D1 line of the alkali metal element, that is, the wavelength required for atomic polarization in the magnetometer, the technical means of laser frequency stabilization are omitted, which reduces the technical difficulty and improves the reliability of the magnetometer at the same time.

[0070] 2) The alkali metal vapor laser uses a common commercial wide-spectrum LD diode, and the cost is greatly reduced compared with the VCSEL laser used in the conventional technology.

[0071] 3) The magnetometer atomic gas chamber is placed in the alkali metal vapor laser resonator, and the stable mode in the laser cavity is used for polarization. Compared with the VCSEL laser, the mode is more stable and the polarization is more uniform.

[0072] 4) The laser in the magnetometer atomic gas chamber is multi-pass polarized by the reciprocating laser in the laser resonator, and extremely high polarization efficiency can be achieved in a limited space, thereby improving the sensitivity of the magnetometer.

[0073] 5) The magnetometer signal is repeatedly amplified by the resonator, and has a higher signal-to-noise ratio than the single-pass optical path.

[0074] 6) The DC component in the laser signal output by the alkali metal vapor laser contains atomic polarization information and can be used for the stable control of the atomic polarization rate.

[0075] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. An optically pumped magnetometer based on an alkali metal laser, characterized in that, Including: A pump laser (1) and a shaping and focusing unit (2), as well as a total reflection cavity mirror (3), a polarization beam splitter (4), an alkali metal vapor laser gas cell (5), an alkali metal magnetometer gas cell (6), an output coupling mirror (7) and a photodetector (8) arranged in sequence along the optical axis; The pump laser (1) is used to output the pump light of the alkali metal vapor laser; The shaping and focusing unit (2) is used to focus the pump light so that the waist position of the focused pump light is located at the central position of the alkali metal vapor laser gas cell (5); The alkali metal vapor laser gas cell (5) is internally sealed with alkali metal atoms and buffer gas, serving as the gain medium of the laser. When the focused pump light passes through, gain is formed, and laser is formed under the action of the resonant cavity; only the horizontally polarized D1-line light oscillates in the resonant cavity; The alkali metal magnetometer gas cell (6) is internally sealed with alkali metal atoms; the alkali metal atoms are of the same type as those sealed inside the alkali metal vapor laser gas cell (5); and the alkali metal magnetometer gas cell (6) is filled with buffer gas for slowing down collision relaxation; The total reflection mirror (3) and the output coupling mirror (7) form a resonant cavity of an alkali metal laser, which is used for resonantly amplifying light with a wavelength corresponding to the 2 P 1 / 2 → 2 S 1 / 2 transition of the alkali metal atoms in the alkali metal vapor laser gas cell (5); The polarization beam splitter (4) is used to couple the pump light with the alkali metal vapor laser gas cell (5); The alkali metal magnetometer gas cell (6) is placed inside the alkali metal laser resonant cavity; The laser reciprocating inside the alkali metal laser resonant cavity forms circularly polarized light in two directions, σ+ and σ-, inside the alkali metal magnetometer gas cell (6); The output coupling mirror (7) is used to output the laser with a wavelength corresponding to the 2 P 1 / 2 → 2 S 1 / 2 transition of the alkali metal atoms in the alkali metal vapor laser cavity (5). The photodetector (8) is used to receive the laser output by the output coupling mirror (7) and convert the optical signal into an electrical signal.

2. The optically pumped magnetometer based on an alkali metal laser according to claim 1, characterized in that, A magnetic field coil (9) is arranged outside the alkali metal magnetometer gas cell (6).

3. The optically pumped magnetometer based on an alkali metal laser according to claim 1, wherein The polarization beam splitter (4) is a polarization beam splitting prism.

4. The optically pumped magnetometer based on an alkali metal laser according to claim 1, characterized in that, The wavelength of the pump light output by the pump laser (1) is the same as that corresponding to the 2 P 3 / 2 → 2 S 1 / 2 transition of the alkali metal atoms in the alkali metal vapor laser cell (5).

5. The optically pumped magnetometer based on an alkali metal laser according to claim 1, wherein The linewidth of the pump light matches the linewidth of the spectral line of the transition of the alkali metal atoms broadened by collision with the buffer gas in the alkali metal vapor laser gas cell (5). 2 P 3 / 2 → 2 S 1 / 2 ​ 6. The optically pumped magnetometer based on an alkali metal laser according to claim 1, wherein λ / 4 wave plates (10) for the D1 line of the corresponding alkali metal atoms are respectively arranged at the front and rear ends of the alkali metal magnetometer gas cell (6); The λ / 4 wave plates (10) are used to convert the linearly polarized light oscillating in the alkali metal laser resonant cavity into circularly polarized light for atomic polarization in the alkali metal magnetometer gas cell (6).

7. A optically pumped magnetometer based on an alkali metal laser according to claim 1, characterized in that, The signal received by the photodetector (8) includes a DC part and an AC part; the DC part is used for stable control of the alkali metal vapor laser power; the AC part is caused by the atomic Larmor precession induced by an external magnetic field; the AC part signal is amplified by the resonant cavity and used for the closed-loop control and magnetic field measurement of the magnetometer.

8. The optically pumped magnetometer based on an alkali metal laser according to claim 3, characterized in that, The polarization splitting ratio of the polarization beam splitting prism is higher than 500:1.

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