An alkali metal vapor laser for use in array atomic magnetometers

Abstract

This invention relates to the fields of laser technology and quantum sensing technology, specifically an alkali metal vapor laser for array-type atomic magnetometers. This laser aims to solve the problems of low power, wide linewidth, mediocre beam quality, and frequency instability in existing lasers for measuring extremely weak magnetic fields. The main components include a semiconductor laser pump source, fast and slow axis collimating mirrors, a coupling lens, an alkali metal vapor chamber, a front cavity mirror and a rear cavity mirror, a polarization beam splitter, a built-in F-P cavity, and a λ / 4 waveplate. The semiconductor laser pump source provides a narrow-linewidth pump laser after linewidth compression. The fast and slow axis collimating mirrors are used for collimation and shaping of the pump beam. The coupling lens couples the pump light into the alkali metal vapor chamber, which provides the gain medium for laser formation. The front and rear cavity mirrors are used to form laser resonance and perform mode selection. The polarization beam splitter separates the laser from the pump light and controls the laser polarization direction. The λ / 4 waveplate is used for converting linearly polarized light to circularly polarized light.

Description

Technical Field

[0001] This invention belongs to the fields of novel laser technology and quantum sensing technology, and specifically relates to an alkali metal vapor laser (Diode Pumped Alkali Laser, DPAL) for array atomic magnetometers with extremely narrow output laser linewidth. Background Technology

[0002] In recent years, the measurement accuracy of extremely weak magnetic fields has reached the fT level. Instruments used for measuring extremely weak magnetic fields mainly include SERF (Spin-exchange Relaxation-free) atomic magnetometers and CPT (Coherent Population Trapping) magnetometers. The measurement of extremely weak magnetic fields is of great significance and has promising applications in many fields, such as the detection of magnetic signals in the heart and brain. Abroad, QUSPIN magnetometers are used to measure magnetic signals in the human heart and brain to diagnose and screen for heart and brain diseases. Each magnetic probe of this type of magnetometer contains a laser, which has drawbacks such as high operating temperature and high cost. (During operation, all lasers need to be powered simultaneously, resulting in excessively high temperatures and high costs.) In contrast, the laser of each magnetic probe in an array-type atomic magnetometer is obtained by splitting the beam through an external laser via optical fiber. This further reduces size, lowers cost, improves resolution, prevents excessive temperature, and maintains the consistency of each beam. It requires the laser being split to produce high-power, narrow-linewidth, and high-beam-quality laser light to ensure that each magnetometer in the array can obtain a narrow-linewidth laser with sufficient power and high beam quality. Currently, the lasers used in array-type atomic magnetometers are mostly semiconductor lasers (LDs), such as distributed Bragg reflector (DBR) semiconductor lasers and distributed feedback (DFB) semiconductor lasers. Compared to ordinary LDs, DBR-LDs and DFB-LDs have narrower linewidths and better beam quality, but their power is lower, only on the order of mW.

[0003] DPAL is a novel type of optically pumped gas laser with the potential to achieve high output power while maintaining high beam quality. The basic model of DPAL is a three-level system, as follows: Figure 1 As shown, the ground state energy level is 2 S 1 / 2 Excited state energy level 2 P 3 / 2 The metastable energy level is 2 P 1 / 2 The ground-state particle is excited and absorbed into an excited state.2 S 1 / 2 → 2 P 3 / 2 (Referred to as the D2 line), then rapidly relaxes to a metastable state, and finally undergoes stimulated radiation back to the ground state ( 2 P 1 / 2 → 2 S 1 / 2 It is referred to as the D1 line. Its pump source is an LD or a semiconductor laser array (LDAs); its gain medium is an alkali metal vapor, and alkali metals such as potassium (K), rubidium (Rb), and cesium (Cs) can be used to output laser light of three different wavelengths: 770.11 nm, 794.98 nm, and 894.59 nm. Compared with other lasers, DPAL has significant advantages such as high quantum efficiency (up to 95% or more), good beam quality, low thermal effect, and near-infrared spectrum. Notably, DPAL can use ordinary commercial LDs or LDAs as pump sources, converting the pump light they generate into high-quality, narrow-linewidth laser light of a specific wavelength.

[0004] The core sensing element of an atomic magnetometer is also an alkali metal gas cell. To polarize the alkali metal atoms within, a narrow-linewidth laser matching the D1 line of the alkali metal atoms is required for pumping. The wavelength of the DPAL output laser can be precisely matched to the D1 line of the alkali metal atoms, thereby greatly improving the polarization efficiency of the alkali metal atoms. Replacing a conventional LD ​​with a DPAL to pump the atomic magnetometer eliminates the need for frequency stabilization and does not limit the amplification of output power, which greatly contributes to the compact design of the atomic magnetometer.

[0005] In summary, DPAL can be considered a relatively ideal laser source for array-type atomic magnetometers. Its output laser combines the advantages of high power and high beam quality, and especially possesses the narrow linewidth and specific wavelength expected by atomic magnetometers. However, the linewidth of the laser output using a traditional single optical resonator is still limited. To further narrow the linewidth of the alkali metal laser output, improvements to its optical resonator are necessary. Summary of the Invention

[0006] To address the aforementioned issues of wide linewidth, generally poor beam quality, and mismatch between the output laser center wavelength and atomic magnetometer characteristics of commonly used domestic LDs, as well as the low power and embargo status of DBR_LD and DFB_LD, this paper proposes an alkali metal vapor laser for array-type atomic magnetometers with extremely narrow output laser linewidth. The aim is to utilize a commonly used commercial LD ​​as a pump source to generate a narrow-linewidth, high-power, high-beam-quality laser with a specific wavelength, thereby reducing domestic dependence on foreign LDs for array-type atomic magnetometers and breaking through foreign embargoes.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] This invention provides an alkali metal vapor laser for an array-type atomic magnetometer, comprising a semiconductor laser pump source, a fast-axis collimating lens, a slow-axis collimating lens, a first λ / 4 waveplate, a coupling lens, a front cavity mirror, an alkali metal vapor chamber, a heating furnace, a second λ / 4 waveplate, a polarizing beam splitter, a built-in FP cavity, and a rear cavity mirror. The semiconductor laser pump source internally includes a primary semiconductor laser, a first collimating lens, an interference filter, a focusing lens, a PZT output mirror, a second collimating lens, a first λ / 2 waveplate, and an optical isolator arranged sequentially according to the optical path direction. The primary LD narrows its linewidth using an interference filter and a cat's-eye structure, and the first λ / 2 waveplate is used to adjust the polarization direction, forming a pump light with a relatively narrow linewidth and predominantly vertical linear polarization.

[0009] When the laser output from the rear cavity mirror passes through the second λ / 2 waveplate, the polarization direction of the laser is changed and used as the detection light.

[0010] When the laser output from the rear cavity mirror passes through the third λ / 4 waveplate, the linearly polarized laser output is converted into a circularly polarized laser, which is then used as the pump light.

[0011] In the above scheme, the heating furnace is used to heat the alkali metal gas chamber and control the temperature inside the chamber to remain constant. Furthermore, the heating furnace is perforated or hollowed out in the middle, so that the temperature at both ends of the alkali metal gas chamber is higher than the temperature in the middle after heating. This prevents the alkanes in the buffer gas from reacting chemically with the alkali metal vapor to produce carbon particles that adhere to the inner surface of the glass at both ends of the alkali metal gas chamber, thus contaminating the glass window.

[0012] In the above scheme, the fast axis of the first λ / 4 waveplate is placed at a 45° angle to the horizontal direction to convert linearly polarized pump light into circularly polarized light so as to pump ground-state particles of alkali metal atoms; the slow axis of the second λ / 4 waveplate is placed at a 45° angle to the horizontal direction to convert circularly polarized light back into linearly polarized light so that the polarizing beam splitter can separate the pump light and the laser.

[0013] In the above scheme, the focal point of the coupling lens is located at the center of the alkali metal gas chamber, which is used to accurately couple the pump light into the alkali metal gas chamber.

[0014] In the above scheme, the front cavity mirror and the rear cavity mirror are placed parallel to each other. The front cavity mirror is a concave reflecting mirror and the rear cavity mirror is a plane mirror. Together, they form a plano-concave confocal laser resonator.

[0015] In the above scheme, the sidewall of the alkali metal gas chamber is made of metal material, and the two sides are glass, forming a robust structure of metal wall-glass cover. The glass window is coated with an anti-reflection film for the pump light and the center wavelength of the laser to reduce reflection loss.

[0016] In the above scheme, the built-in FP cavity is composed of a second plane mirror that is parallel to the first plane mirror, which is used to enhance the frequency selection of the oscillating laser and output a single longitudinal mode laser.

[0017] In the above scheme, the second plane mirror is also provided with piezoelectric ceramics for fine adjustment of the operation of the built-in FP cavity. Utilizing the positive piezoelectric effect of the piezoelectric ceramics, when an electric field is applied in the polarization direction of its dielectric, the piezoelectric ceramics will deform, thereby finely adjusting the FP cavity.

[0018] In the above scheme, both sides of the first and second plane mirrors are coated with a partial reflective film of the laser center wavelength, and the mirror size is smaller than the peripheral plano-confocal laser resonator.

[0019] In the above scheme, the alkali metal chamber is filled with any one of the alkali metals potassium, rubidium, and cesium, which turns into a vapor state upon heating. Simultaneously, a buffer gas is added to the alkali metal chamber to broaden the D2 absorption line of the alkali metal atoms and accelerate absorption. 2 P 3 / 2 and 2 P 1 / 2 The relaxation rate between the two fine energy levels is buffered by a mixture of helium and alkane gases.

[0020] The above-described technical solution provides an alkali metal vapor laser for array-type atomic magnetometers with an extremely narrow output laser linewidth, which has the following beneficial effects:

[0021] This invention uses a common commercial laser LD as the pump source, alkali metal vapor as the gain medium, and a plano-confocal laser resonator. These three elements constitute the three essential components for laser generation, transforming the original pump laser with a relatively wide linewidth and average beam quality into a high-power, high-beam-quality narrow-linewidth laser.

[0022] The pump source of this invention is a common commercial LD, and the power selection is not limited. The output laser power can be amplified by increasing the power of the pump source laser, which solves the problem of limited output laser power amplification in most lasers.

[0023] This invention uses an interference filter in conjunction with a PZT output mirror to form a cat's eye structure to narrow the pump beam width. This solves the problems of precise alignment and susceptibility to temperature and mechanical vibration when using common gratings to narrow the linewidth. It allows for easier adjustment of the pump beam frequency, narrowing of the pump beam width, increased alignment tolerance, and improved robustness and stability.

[0024] This invention improves upon the inadequacy of a single optical resonator in completely suppressing higher-order modes of oscillating light by adding a built-in FP cavity between the front and rear cavity mirrors of the optical resonator. This achieves further filtering of the oscillating light frequency, thereby enhancing the frequency selection effect of the oscillating light and ensuring that the final output laser is a single longitudinal mode.

[0025] This invention solves the problems of fixed output laser wavelength and complex wavelength transitions in ordinary lasers by filling the alkali metal gas chamber with different alkali metal gases, thus enabling the same laser to output lasers at three different frequencies. The alkali metal gas chamber containing potassium vapor can output a 770.11nm wavelength laser, containing rubidium vapor can output a 794.98nm wavelength laser, and containing cesium vapor can output an 894.59nm wavelength laser.

[0026] This invention controls the output laser of the rear cavity mirror to be horizontally linearly polarized light by using a polarizing beam splitter prism, which solves the problem of ambiguity in the polarization state or polarization direction of ordinary LD output lasers, making it convenient for subsequent use in array-type atomic magnetometers: by using a third λ / 4 waveplate to convert the output laser into circularly polarized light, it can be directly used to pump atomic magnetometers and other atomic measuring instruments; by using a second λ / 2 waveplate to adjust the polarization direction of the output laser, it can be directly used as the detection light for atomic magnetometers and other atomic measuring instruments. Attached Figure Description

[0027] Figure 1 It shows the fine energy level structure of alkali metal atoms and a schematic diagram of energy level transitions.

[0028] Figure 2 This is a schematic diagram of an alkali metal vapor laser for an array-type atomic magnetometer, which has an extremely narrow output laser linewidth.

[0029] Figure 3 This is a schematic diagram of the overall system formed by using the alkali metal laser of the present invention for pumping or detection in an array-type atomic magnetometer (the array-type atomic magnetometer is not part of the present invention).

[0030] Figure 4 This is a schematic diagram of the cat's-eye structure of the semiconductor pump source with narrow LD linewidth and internal pressure of the present invention.

[0031] Figure 5 This is a schematic diagram of mode matching between the pump light and the resonant cavity in this invention.

[0032] The marks in the diagram indicate the following:

[0033] 1-Ordinary semiconductor laser pump source; 2-Fast axis collimating lens; 3-Slow axis collimating lens; 4-First λ / 4 waveplate; 5-Coupled lens; 6-Front cavity mirror; 7-Alkali metal gas chamber; 8-Heating furnace; 9-Second λ / 4 waveplate; 10-Polarizing beam splitter; First plane mirror 11 and second plane mirror 12, 11, 12-Built-in FP cavity; 13-Piezoelectric ceramic; 14-Rear cavity mirror; 15-Pristine semiconductor laser; 16-First collimating lens; 17-Interference filter; 18-Focusing lens; 19-PZT output mirror; 20-Second collimating lens; 21-First λ / 2 waveplate; 22-Optical isolator; 23-Second λ / 2 waveplate (for detection) or third λ / 4 waveplate (for pumping). Detailed Implementation

[0034] The embodiments of the present invention will be described in detail below. Although the present invention will be described and illustrated in conjunction with some specific embodiments, it should be noted that the present invention is not limited to these embodiments. On the contrary, any modifications or equivalent substitutions made to the present invention should be covered within the scope of the claims of the present invention.

[0035] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art will understand that the present invention can be practiced without these specific details.

[0036] To achieve this objective, the present invention proposes an alkali metal vapor laser for array-type atomic magnetometers with extremely narrow output laser linewidth. The specific technical solution is as follows:

[0037] An alkali metal vapor laser for an array-type atomic magnetometer with extremely narrow output laser linewidth includes: a semiconductor laser pump source 1, a fast-axis collimating lens 2, a slow-axis collimating lens 3, a first λ / 4 waveplate 4, a coupling lens 5, a front cavity mirror 6, an alkali metal gas chamber 7, a heating furnace 8, a second λ / 4 waveplate 9, a polarizing beam splitter 10, built-in FP cavities 11, 12, a piezoelectric ceramic 13, and a rear cavity mirror 14.

[0038] The semiconductor laser pump source 1 internally includes a raw semiconductor laser 15, a first collimating lens 16 and a second collimating lens 20, a focusing lens 18, an interference filter (IF) 17, a PZT output mirror 19, a first λ / 2 waveplate 21, and an optical isolator 22. The raw semiconductor laser 15 uses the interference filter and a cat's-eye mirror to narrow the linewidth of the LD, and the first λ / 2 waveplate 21 adjusts the polarization direction, ultimately forming a pump light with a relatively narrow linewidth and predominantly vertical linear polarization. The interference filter 17 is based on the principle of multi-beam interference, allowing only light within a specific spectral range to pass through, possessing the advantages of high transmittance and narrow bandwidth (existing technology). The optical isolator 22 allows the forward-propagating pump light to pass through while isolating the reverse-propagating light, preventing reflected light from affecting the stability of the semiconductor laser pump source 1.

[0039] The fast-axis collimating lens 2 and the slow-axis collimating lens 3 work together to collimate and optimize the pump light, and limit the divergence angle of the pump laser in the fast and slow axis directions to ensure accurate and efficient transmission of the laser beam.

[0040] The first λ / 4 waveplate 4 is placed at a 45° angle to the horizontal along its fast axis, and is used to convert linearly polarized pump light into circularly polarized light to pump ground-state particles of alkali metal atoms; the second λ / 4 waveplate 9 is placed at a 45° angle to the horizontal along its slow axis, and is used to convert circularly polarized light back into linearly polarized light, so that the polarizing beam splitter prism 10 can separate the pump light and the laser, and ensure that the output laser is horizontally linearly polarized light.

[0041] The focal point of the coupling lens 5 is located at the center of the alkali metal gas chamber 7, and is used to accurately couple the pump light into the alkali metal gas chamber 7 so that the pump light can achieve optimal mode matching with the resonant cavity.

[0042] The front cavity mirror 6 and the rear cavity mirror 14 are placed parallel to each other. The front cavity mirror 6 is a concave reflector, and the rear cavity mirror 14 is a plane mirror. Together, they form a plano-concave confocal laser resonant cavity. The optical axis of the front cavity mirror 6 is perpendicular to the rear cavity mirror, and the radius of curvature of the concave reflector is equal to twice the cavity length between the two, making it a stable resonant cavity. The surface of the front cavity mirror 6 facing the coupling lens is coated with an antireflection film with a center wavelength of the pump light wavelength, and the surface facing the alkali metal gas cell is coated with an antireflection film with a center wavelength of the pump light wavelength and a total internal reflection film with a center wavelength of the laser wavelength. The surface of the rear cavity mirror 14 facing into the cavity is coated with a partial reflection film (70% reflectivity) with a center wavelength of the alkali metal atom D1 line, and the other side is coated with an antireflection film with a center wavelength of the alkali metal atom D1 line.

[0043] The heating furnace 8 is used to heat the alkali metal gas chamber 7 and control the temperature inside the gas chamber to be constant. The alkali metal gas chamber is placed in the center of the furnace and does not contact the furnace wall. Light-transmitting holes are provided at both ends.

[0044] The alkali metal gas chamber has metal sidewalls and glass sides, forming a robust metal-glass cover structure. The glass windows are coated with an anti-reflection film targeting the pump light and laser center wavelength to reduce reflection loss. The chamber is filled with one of the alkali metals potassium, rubidium, or cesium, which vaporizes upon heating. A buffer gas is also added to the chamber to broaden the D2 absorption line of the alkali metal atoms and accelerate... 2 P 3 / 2 and 2 P 1 / 2 The relaxation rate between two fine energy levels. The buffer gas can be helium alone, or a mixture of helium and alkane gases.

[0045] The built-in FP cavity (Fabry-Perot etalon) consists of two plane mirrors, a first plane mirror 11 and a second plane mirror 12, placed parallel to each other to enhance the frequency selection of the oscillating laser and ensure that the final output is a single longitudinal mode laser. Both sides of the first plane mirror 11 and the second plane mirror 12 are coated with a partially reflective film of the laser's center wavelength, and the mirror surface is smaller than the surrounding plano-confocal cavity. Fine adjustment of the built-in FP cavity is performed by the piezoelectric ceramic 13. Utilizing the positive piezoelectric effect of the piezoelectric ceramic, when an electric field is applied in the polarization direction of its dielectric, the piezoelectric ceramic deforms, thereby finely adjusting the FP cavity.

[0046] Based on the alkali metal laser constructed by the above scheme, by adding a third λ / 4 waveplate or a second λ / 2 waveplate, it can be directly used for pumping or detection by an atomic magnetometer.

[0047] Figure 2 This is a schematic diagram of an alkali metal vapor laser for an array-type atomic magnetometer, exhibiting an extremely narrow output laser linewidth. The invention, starting from the emission of light from the original semiconductor laser 15 and ending with the emission of laser light from the rear cavity mirror 14, essentially completes the conversion from a common commercial laser to a high-quality laser. Using only a common commercial semiconductor laser, this invention can transform the originally low-power, wide-linewidth, and low-beam-quality pump light into a higher-power, extremely narrow-linewidth, precise-frequency, and high-beam-quality laser. Following the optical path, the conversion process mainly involves the following steps:

[0048] Step 1: After the original semiconductor laser 15 emits light, it is initially collimated by the first collimating lens 16, so that the beam passes through the interference filter 17 in a parallel manner. By adjusting the angle α between the interference filter and the incident light, the center wavelength of the emitted laser can be tuned to the D2 line of the alkali metal atom. At the same time, only light in a specific spectral range can be output, thereby narrowing the linewidth of the pump light.

[0049] Step Two: The pump light, with its linewidth narrowed, is then automatically calibrated and its mechanical robustness improved by the cat's-eye reflector structure, significantly reducing frequency noise and sensitivity to vibration. The cat's-eye reflector structure consists of the focusing lens 18, the PZT output mirror 19, and the second collimating lens 20. Finally, the first λ / 2 waveplate 21 is used to adjust the polarization direction of the pump light, making it vertically linearly polarized. Furthermore, constrained by the optical isolator 22, the pump light can only be output in one direction.

[0050] Step 3: After the semiconductor laser pump source 1 emits light through steps 1 and 2 to narrow the linewidth, the fast-axis collimating lens 2 and the slow-axis collimating lens 3 successively constrain and adjust the divergence angle of the pump light in the fast and slow axis directions to optimize the shape of the laser beam.

[0051] Step 4: To achieve the transition of alkali metal atoms from the ground state to the excited state using circularly polarized light, completing the D1 line transition, the pump light is converted into circularly polarized light using the first λ / 4 waveplate 4. Furthermore, the first λ / 4 waveplate 4 must be positioned before the coupling lens 5 to prevent the focusing effect of the coupling lens 5 from damaging the first λ / 4 waveplate 4. Afterwards, the circularly polarized pump light is coupled into the alkali metal gas chamber 7 by the coupling lens 5. The focal point of the coupling lens 5 is precisely located at the center of the alkali metal gas chamber to ensure that the pump light and the resonant cavity achieve the aforementioned transition. Figure 5 The optimal mode matching shown allows the pump light energy to be utilized to the maximum extent, thereby improving pump power efficiency.

[0052] Step 5: The solid alkali metal in the alkali metal gas chamber 7 has been pre-evaporated into a gaseous state by the heating furnace 8. When the pump light couples into the alkali metal gas chamber 7, its interior is already a mixture of alkali metal vapor and buffer gas. The ground-state alkali metal atoms are pumped to an excited state by the pump light, completing population inversion, and then rapidly relax to a metastable energy level, finally undergoing stimulated emission to achieve optical amplification. Due to the continuous action of the pump light, photons also accumulate continuously. The laser resonant cavity formed by the front cavity mirror 6 and the rear cavity mirror 14 controls the oscillating beam and provides positive optical feedback, ultimately forming coherent radiation light, i.e., laser light.

[0053] Step Six: The second λ / 4 waveplate 9 and the polarizing beam splitter 10 are used to filter out the residual pump light mixed in with the intracavity laser. The fast and slow axes of the second λ / 4 waveplate 9 are exactly opposite to those of the first λ / 4 waveplate 4, adjusting the residual pump light back to vertically linearly polarized light. The polarizing beam splitter 10, in conjunction with the second λ / 4 waveplate 9, filters out the residual pump light and simultaneously limits the final horizontally linearly polarized light output of the laser.

[0054] Step 7: The built-in FP cavities 11 and 12 are controlled by the piezoelectric ceramic 13 to further refine the mode selection of the oscillating light in the larger peripheral laser resonant cavity, ensuring that the laser is output in a single longitudinal mode. Furthermore, the cavity mirror surfaces are all coated with a partially reflective film with a center wavelength at the D1 line of alkali metal atoms. Combined with the large peripheral laser resonant cavity, this forms a multi-layered filtering effect on the oscillating light frequency, further narrowing the linewidth of the output laser and enabling a better match between the center wavelength of the output laser and the D1 line of alkali metal atoms.

[0055] Step 8: After steps one through seven, the final output laser light, passing through the third λ / 4 waveplate or the second λ / 2 waveplate 23, can be directly used for pumping or detection by the atomic magnetometer. When the third λ / 4 waveplate or the second λ / 2 waveplate 23 is a λ / 4 waveplate, the output linearly polarized laser light can be converted into circularly polarized laser light for use as pump light; when the third λ / 4 waveplate or the second λ / 2 waveplate 23 is a λ / 2 waveplate, the laser polarization direction can be changed as needed for use as detection light. Figure 3 As shown, the alkali metal laser output of this invention, after being split, can be directly used in an array-type atomic magnetometer. Only the power of the original semiconductor laser needs to be sufficiently high; frequency stabilization and beam quality improvement are no longer required. Ultimately, this constitutes an integrated system of an alkali metal vapor laser and an array-type atomic magnetometer that satisfies the objectives of this invention.

Claims

1. An alkali metal vapor laser for use in an array-type atomic magnetometer, characterized in that, The system includes a semiconductor laser pump source (1), a fast-axis collimating lens (2), a slow-axis collimating lens (3), a first λ / 4 waveplate (4), a coupling lens (5), a front cavity mirror (6), an alkali metal gas chamber (7), a heating furnace second λ / 4 waveplate (9), a polarizing beam splitter (10), an internal FP cavity (11,12), and a rear cavity mirror (14), arranged sequentially along the optical path. The semiconductor laser pump source (1) includes a raw semiconductor laser (15), a first collimating lens (16), an interference filter (17), a focusing lens (18), a PZT output mirror (19), a second collimating lens (20), a first λ / 2 waveplate (21), and an optical isolator (22), arranged sequentially along the optical path. The raw semiconductor laser (15) narrows the linewidth of the LD through the interference filter and the cat's eye structure, and uses the first λ / 2 waveplate (21) to adjust the polarization direction, forming a pump light with a relatively narrow linewidth and vertical linear polarization. When the laser output from the rear cavity mirror (14) passes through the second λ / 2 waveplate, the laser polarization direction is changed and used as the detection light; When the laser output from the rear cavity mirror (14) passes through the third λ / 4 waveplate, the linearly polarized laser output is converted into a circularly polarized laser and used as pump light.

2. The alkali metal vapor laser for an array-type atomic magnetometer according to claim 1, characterized in that, A heating furnace (8) is also provided to heat the alkali metal gas chamber (7) and control the temperature inside the gas chamber to be constant.

3. The alkali metal vapor laser for an array-type atomic magnetometer according to claim 1, characterized in that, The first λ / 4 waveplate (4) is placed at a 45° angle to the horizontal direction along its fast axis, and is used to convert linearly polarized pump light into circularly polarized light so as to pump ground-state particles of alkali metal atoms; the second λ / 4 waveplate (9) is placed at a 45° angle to the horizontal direction along its slow axis, and is used to convert circularly polarized light back into linearly polarized light so that the polarizing beam splitter (10) can separate the pump light and the laser.

4. An alkali metal vapor laser for an array-type atomic magnetometer according to claim 1, characterized in that, The focal point of the coupling lens (5) is located at the center of the alkali metal gas chamber (7) to accurately couple the pump light into the alkali metal gas chamber.

5. An alkali metal vapor laser for an array-type atomic magnetometer according to claim 1, characterized in that, The front cavity mirror (6) and the rear cavity mirror (14) are placed parallel to each other. The front cavity mirror is a concave reflecting mirror and the rear cavity mirror is a plane mirror. Together, they form a plano-concave confocal laser resonator.

6. An alkali metal vapor laser for an array-type atomic magnetometer according to claim 1, characterized in that, The sidewall of the alkali metal gas chamber (7) is made of metal, and the two sides are made of glass, forming a robust structure of metal wall-glass cover. The outer side of the glass cover is coated with an anti-reflection film for the pump light and the center wavelength of the laser to reduce reflection loss.

7. An alkali metal vapor laser for an array-type atomic magnetometer according to claim 1, characterized in that, The built-in FP cavity (11, 12) is composed of a second plane mirror (12) parallel to the first plane mirror (11), which is used to enhance the frequency selection of the oscillating laser and output a single longitudinal mode laser.

8. An alkali metal vapor laser for an array-type atomic magnetometer according to claim 7, characterized in that, The second plane mirror (12) is also provided with a piezoelectric ceramic (13) for fine adjustment of the operation of the built-in FP cavity. By utilizing the positive piezoelectric effect of the piezoelectric ceramic, when an electric field is applied in the polarization direction of its dielectric, the piezoelectric ceramic will deform, thereby finely adjusting the FP cavity.

9. An alkali metal vapor laser for an array-type atomic magnetometer according to claim 7, characterized in that, Both sides of the first plane mirror (11) and the second plane mirror (12) are coated with a partial reflective film of the laser center wavelength, and the mirror size is smaller than the peripheral plano-confocal laser resonator.

10. An alkali metal vapor laser for an array-type atomic magnetometer according to claim 6, characterized in that, The alkali metal chamber (8) is filled with any one of the alkali metals potassium, rubidium, and cesium, which turns into vapor upon heating. Simultaneously, a buffer gas is added to the alkali metal chamber (8) to broaden the D2 absorption line of the alkali metal atoms and accelerate absorption. 2 P 3 / 2 and 2 P 1 / 2 The relaxation rate between the two fine energy levels is buffered by a mixture of helium and alkane gases.

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