A raman light parallelism adjustment system and method for an atomic interferometer

Abstract

The present application belongs to the technical field of photoelectric servo control, and particularly relates to a Raman light parallelism adjusting system and adjusting method for an atomic interferometer. The system comprises an atomic preparation unit, a first Raman light unit, a second Raman light unit, a fluorescence detection unit and a host computer. The atomic preparation unit is used for preparation and directional projection of a cold atom group. The first Raman light unit is used for generating expanded-beam Raman laser, and the cold atom group has multiple internal state interference actions in the same laser light path, so as to change the internal state population of the cold atom group and have 2-degree-of-freedom light path adjusting function. The second Raman light unit is located below the first Raman light unit, and is used for generating another expanded-beam Raman laser, and the cold atom group has multiple internal state interference actions in the same laser light path, so as to change the internal state population of the cold atom group and have 4-degree-of-freedom light path adjusting function. The fluorescence detection unit is used for determination of the number of atoms in different internal states. The host computer is used for atomic contrast calculation and light path adjusting control.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic servo control technology, specifically relating to a Raman beam parallelism adjustment system and method for an atomic interferometer. Background Technology

[0002] Achieving high-precision measurements with atomic interferometers requires the combined action of multiple sets of bidirectional (reverse) Raman beams. The angular consistency between the Raman beams directly affects the contrast of the interference fringes of the atomic interferometer, further impacting the output phase accuracy and limiting the system's measurement precision. Current methods for calibrating the incident angle of Raman beams in atomic interferometers are either only applicable to single-beam Raman beam calibration and cannot effectively adjust the relative parallelism of multiple Raman beam combinations, leading to errors in high-precision alignment, or rely on the size and precision of the 90° Raman beam reflecting prism, which cannot meet the requirements for Raman beam parallelism alignment in large-loop atomic interferometers located far apart in space. Summary of the Invention

[0003] Objective of the invention: To provide a Raman beam parallelism adjustment system and method for an atomic interferometer, thereby improving the parallelism of the Raman beam and the returned beam, enhancing the contrast of the atomic interferometer, and thus improving measurement accuracy.

[0004] Technical solution:

[0005] A Raman beam parallelism adjustment system for an atomic interferometer includes: an atom preparation unit 1, a first Raman beam unit 2, a second Raman beam unit 3, a fluorescence detection unit 4, and a host computer 5, wherein...

[0006] Atom preparation unit 1 is used for the preparation and directional ejection of cold atomic clusters;

[0007] The first Raman optical unit 2 is used to generate expanded Raman laser, which interacts with the cold atom cluster multiple times within the same laser optical path, changing the internal state population of the cold atom cluster and having a 2-degree-of-freedom optical path adjustment function.

[0008] The second Raman optical unit 3 is located below the first Raman optical unit 2 and is used to generate another expanded Raman laser. It interacts with the cold atom cluster multiple times within the same laser optical path, changes the internal state population of the cold atom cluster, and has a 4-degree-of-freedom optical path adjustment function.

[0009] The fluorescence detection unit 4 is used to determine the number of atoms in different internal states;

[0010] The host computer 5 is used for atomic contrast calculation and optical path adjustment control.

[0011] Furthermore, the atom preparation unit 1 includes a vacuum cavity 11 and a magneto-optical trap 12, wherein the magneto-optical trap 12 is located at the bottom of the vacuum cavity 11, and the magneto-optical trap 12 realizes the cooling, confinement and directional ejection of metal atom clusters.

[0012] Further, the first Raman light unit includes: a first Raman light 21, a first quarter-wave plate 22, a first reflector 23, a first Raman return light 24, and a first piezoelectric displacement stage 25. The first Raman light 21 is incident from one side of the atom preparation unit 1. The first quarter-wave plate 22, the first reflector 23, and the first piezoelectric displacement stage 25 are located sequentially on the other side of the atom preparation unit 1. The first piezoelectric displacement stage 25 is fixedly connected to the first reflector 23. The first Raman light 21 has frequencies f1 and f2, both of which are negatively detuned from the resonant transition frequency. |f2-f1| is the energy level spacing of the atomic ground state. The polarization state of the first Raman light 21 is σ+ circular polarization. The first Raman return light 24 is obtained by the first Raman light 21 passing through the first quarter-wave plate 22, the first reflector 23, and then passing through the first quarter-wave plate 22 again, while the polarization state changes to σ- circular polarization.

[0013] Furthermore, the second Raman beam unit includes a second Raman beam 31, a second quarter-wave plate 32, a second reflector 33, a second piezoelectric displacement stage 34, a second Raman return beam 35, and a third piezoelectric displacement stage 36. The second Raman beam 31 is incident from one side of the atom preparation unit 1, the second piezoelectric displacement stage 34 is located on one side of the atom preparation unit 1, and the second quarter-wave plate 32, the second reflector 33, and the third piezoelectric displacement stage 36 are sequentially located on the other side of the atom preparation unit 1. The second piezoelectric displacement stage 34 is fixedly connected to the emitting device of the second Raman beam 31, and the third piezoelectric displacement stage 36 is fixedly connected to the second reflector 33.

[0014] The second Raman beam 31 has frequencies f1 and f2, both of which are negatively detuned from the resonant transition frequency. |f2-f1| represents the spacing between the atomic ground state energy levels. The polarization state of the second Raman beam 31 is σ+ circular polarization. The second Raman return beam 35 is obtained by passing the second Raman beam 31 through the second quarter-wave plate 32, the second mirror 33, and then through the second quarter-wave plate 32 again, while its polarization state changes to σ- circular polarization.

[0015] The first piezoelectric displacement stage 25, the second piezoelectric displacement stage 34, and the third piezoelectric displacement stage 36 respectively realize the orthogonal direction degree of freedom adjustment of the first Raman return light 24, the second Raman light 31, and the second Raman return light 35.

[0016] A method for adjusting the parallelism of Raman beams in an atomic interferometer, the method being executed by means of the aforementioned Raman beam parallelism adjustment system for an atomic interferometer, the method achieving parallelism adjustment of the first Raman beam 21, the first Raman return beam 24, the second Raman beam 31, and the second Raman return beam 35 through coarse alignment using two-pulse interference, including: first self-alignment S11, second self-alignment S12, vertical mutual alignment S13, and horizontal mutual alignment S14.

[0017] Furthermore, the first self-alignment of S11 is as follows:

[0018] Multiple atomic ejection processes are performed: In each ejection process, a single reverse Raman pulse interferometry measurement is performed, consisting of the first Raman beam 21 and the first Raman return beam 24, which are used to scan the Raman beam phase φ during multiple atomic ejection processes. laser The atomic interference fringe contrast K1 is obtained by adjusting the first piezoelectric displacement stage 25 until the atomic interference fringe contrast reaches its maximum value K1. max The first piezoelectric displacement stage 25 is fixed in position.

[0019] Furthermore, the second self-alignment of S12 is as follows:

[0020] Multiple atomic ejection processes are performed: A single reverse Raman pulse interferometry measurement is conducted by scanning the Raman light phase φ during multiple atomic ejection processes, using the atoms' single-flight over the second Raman light 31 and the second Raman return light 35. laser The atomic interference fringe contrast K2 was obtained by adjusting the third piezoelectric displacement stage 36 until the atomic interference fringe contrast reached its maximum value K2. max The third piezoelectric displacement stage 36 is fixed at the time.

[0021] Furthermore, S13 are vertically aligned with each other, specifically as follows:

[0022] In the atomic ejection trajectory, the first Raman interference (rising process) is performed in the second Raman light 31; the second and third Raman interferences are performed in the first Raman light 21, where the Raman pulse of the second Raman interference is a rising process and the Raman pulse of the third Raman interference is a falling process. The phase φ of the Raman light is scanned during multiple atomic ejection processes. laser The atomic interference fringe contrast K3 was obtained using this method;

[0023] By adjusting the second piezoelectric displacement stage 34, the maximum contrast K3 of the atomic interference fringes is achieved. max At that time, fix the second piezoelectric displacement stage 34;

[0024] Perform the second self-alignment step S12 to achieve the overlap of the second Raman beam 31 and the second returned Raman beam 35.

[0025] Furthermore, S14 are aligned horizontally, specifically as follows:

[0026] During the ascent of the atomic ejection trajectory, the first and second Raman interferences are performed in the second Raman beam 31, and the third and fourth Raman interferences are performed in the first Raman beam 21. The phase φ of the Raman beam is scanned during multiple atomic ejections. laser The atomic interference fringe contrast K4 was obtained using this method;

[0027] By adjusting the second piezoelectric displacement stage 34, the maximum contrast K4 of the atomic interference fringes is achieved. max At that time, fix the second piezoelectric displacement stage 34;

[0028] Perform the second self-alignment step S12 to achieve the overlap of the second Raman beam 31 and the second returned Raman beam 35.

[0029] Furthermore, during the first self-alignment process of S11, the applied Raman laser pulse type is a π pulse.

[0030] Beneficial effects:

[0031] This invention discloses a Raman beam parallelism adjustment system for an atomic interferometer, comprising an atom preparation unit, a first Raman beam unit, a second Raman beam unit, a fluorescence detection unit, and a host computer. The system supports multi-pulse interference processes, achieving a Raman beam and return beam parallelism better than 0.01 mrad through three angle adjustments. This invention utilizes a successive approximation method, leveraging the inherent Raman frequency spectrum characteristics of atomic interference to achieve stable and reliable adjustment, resulting in high-precision alignment. The adjustment device does not introduce additional electromagnetic actuators, contributing to the stability of the magnetic field in the atomic interference region. The system's simple structure facilitates the design of miniaturized atomic interferometers in space-constrained environments. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a Raman beam parallelism adjustment system for an atomic interferometer according to an embodiment of the present invention;

[0033] The system includes a vacuum cavity 11, a magneto-optical trap 12, a first Raman beam 21, a first quarter-wave plate 22, a first reflector 23, a first Raman return beam 24, a first piezoelectric displacement stage 25, a second Raman beam 31, a second quarter-wave plate 32, a second reflector 33, a second piezoelectric displacement stage 34, a second Raman return beam 35, a third piezoelectric displacement stage 36, a detection beam 41, a detector 42, and a host computer 5. Detailed Implementation

[0034] like Figure 1According to an embodiment of the present invention, a Raman beam parallelism adjustment system for an atomic interferometer includes: an atom preparation unit 1, a first Raman beam unit 2, a second Raman beam unit 3, a fluorescence detection unit 4, and a host computer 5. The atom preparation unit 1 is used for the preparation and directional ejection of cold atom clusters; the first Raman beam unit 2 is used to generate an expanded-beam Raman laser, which interferes with the cold atom cluster multiple times within the same laser beam path, changing the internal state population of the cold atom cluster, and has a 2-degree-of-freedom optical path adjustment function; the second Raman beam unit 3 is located below the first Raman beam unit 2 and is used to generate another expanded-beam Raman laser, which interferes with the cold atom cluster multiple times within the same laser beam path, changing the internal state population of the cold atom cluster, and has a 4-degree-of-freedom optical path adjustment function; the fluorescence detection unit 4 is used for determining the number of atoms in different internal states; and the host computer 5 is used for atom contrast calculation and optical path adjustment control.

[0035] By interfering with the internal states of atomic groups using Raman laser pulses, the population inversion rate of the internal states of atomic groups can be increased to 100%, and such Raman laser pulses are called π pulses; by interfering with the internal states of atomic groups using Raman laser pulses, the population inversion rate of the internal states of atomic groups can be increased to 50%, and such Raman laser pulses are called π / 2 pulses.

[0036] The atom preparation unit 1 includes a vacuum cavity 11 and a magneto-optical trap 12, wherein the magneto-optical trap 12 is located at the bottom of the vacuum cavity 11, and the magneto-optical trap 12 realizes the cooling, confinement and directional ejection of metal atom clusters.

[0037] The magneto-optical trap 12 generates atomic ejection trajectories with a divergence angle of less than 1 mrad.

[0038] The atoms are alkali metal atoms.

[0039] The first Raman light unit 2 includes: a first Raman light 21, a first quarter-wave plate 22, a first reflector 23, a first Raman return light 24, and a first piezoelectric displacement stage 25. The first Raman light 21 is incident from one side of the atom preparation unit 1. The first quarter-wave plate 22, the first reflector 23, and the first piezoelectric displacement stage 25 are located on the other side of the atom preparation unit 1. The first piezoelectric displacement stage 25 is fixedly connected to the first reflector 23. The first Raman light 21 has frequencies f1 and f2, both of which are negatively detuned from the resonant transition frequencies. |f2-f1| is the distance between the atomic ground state energy levels. The polarization state of the first Raman light 21 is σ+ circular polarization. The first Raman return light 24 is obtained by passing the first Raman light 21 through the first quarter-wave plate 22, the first reflector 23, and then through the first quarter-wave plate 22 again, while the polarization state changes to σ- circular polarization.

[0040] The negative detuning of the resonant transition frequency of the first Raman light 21 is preferably 0.5-2 GHz.

[0041] The second Raman light unit 3 includes a second Raman light 31, a second quarter-wave plate 32, a second reflector 33, a second piezoelectric displacement stage 34, a second Raman return light 35, and a third piezoelectric displacement stage 36. The second Raman light 31 is incident from one side of the atom preparation unit 1, the second piezoelectric displacement stage 34 is located on one side of the atom preparation unit 1, the second quarter-wave plate 32, the second reflector 33, and the third piezoelectric displacement stage 36 are located on the other side of the atom preparation unit 1, the second piezoelectric displacement stage 34 is fixedly connected to the emitting device of the second Raman light 31, and the third piezoelectric displacement stage 36 is fixedly connected to the second reflector 33.

[0042] The second Raman light 31 has frequencies f3 and f4, both of which are negatively detuned from the resonant transition frequency. |f4-f3| is the spacing between the atomic ground state energy levels. The polarization state of the second Raman light 31 is σ+ circular polarization. The second Raman return light 35 is obtained by passing the second Raman light 31 through the second quarter-wave plate 32, the second mirror 33, and then through the second quarter-wave plate 32 again, while the polarization state changes to σ- circular polarization.

[0043] The first piezoelectric displacement stage 25, the second piezoelectric displacement stage 34, and the third piezoelectric displacement stage 36 respectively realize the orthogonal direction degree of freedom adjustment of the first Raman return light 24, the second Raman light 31, and the second Raman return light 35.

[0044] Preferably, the adjustment step is better than 1 μrad. More preferably, it is 0.4 μrad.

[0045] The fluorescence detection unit 4 includes a detection light 41 and a detector 42. The detection light 41 is a parallel laser beam with a laser frequency equal to the resonant excitation transition frequency of the outer electrons of the atom. The detector 42 detects the fluorescence signal intensity I of atoms in different internal states flying through the region of the detection light 41. a (t) and I b (t), calculate the probability P that the atom is in state a. a =∫I a (t) / (∫I a (t)+∫I b (t)). Further, by scanning the corresponding Raman phase φ during multiple atomic ejection processes... laser The method of obtaining interference fringes P a (φ laser The difference between the maximum and minimum values ​​of the interference fringes is the fringe contrast.

[0046] A method for adjusting the parallelism of Raman beams in an atomic interferometer, the method being performed using the aforementioned Raman beam parallelism adjustment system for an atomic interferometer, the method comprising:

[0047] Parallel adjustment of the first Raman beam 21, the first Raman return beam 24, the second Raman beam 31, and the second Raman return beam 35 is achieved through the first self-alignment S11, the second self-alignment S12, the vertical mutual alignment S13, and the horizontal mutual alignment S14.

[0048] In S11, the first self-alignment involves multiple atomic ejection processes: during each ejection, a single reverse Raman pulse interferometry measurement is performed, consisting of the first Raman light 21 and the first Raman return light 24, and the Raman light phase φ is scanned during the multiple atomic ejection processes. laser The atomic interference fringe contrast K1 is obtained by means of a π-pulse applied Raman laser pulse. The horizontal emission angle θ of the first Raman return light 24 is scanned by adjusting the first piezoelectric displacement stage 25. i1 and vertical exit angle θ j1 Record the atomic interference fringe contrast K1(θ) under each angular condition. i1 ,θ j1 The first piezoelectric displacement stage 25 is fixed at the point where the contrast of the atomic interference fringes reaches its maximum value K1. max At this time, the first Raman return light 24 and the first Raman light 21 are in a state of overlap (parallelism).

[0049] S12 second self-alignment, performing multiple atomic ejection processes: This is achieved through single-pass reverse Raman pulse interferometry measurement of the atoms during a single ejection, consisting of the second Raman light 31 and the second Raman return light 35, with the applied Raman laser pulse type being π pulse. The Raman light phase φ is scanned during multiple atomic ejection processes. laser The atomic interference fringe contrast K2 was obtained by means of this method.

[0050] The horizontal emission angle θ of the second Raman return light 35 is scanned by adjusting the third piezoelectric displacement stage 36. i2 and vertical exit angle θ j2 Record the atomic interference fringe contrast K2(θ) under each angular condition. i2 ,θ j2 The third piezoelectric displacement stage 36 is fixed at the point where the contrast of the atomic interference fringes reaches its maximum value K2. max At this time, the second Raman return light 35 and the second Raman light 31 are in a state of overlap (parallelism).

[0051] After achieving self-alignment of the two Raman beams separately, mutual alignment is further completed through multiple pulse interferometry measurements. The specific method is as follows:

[0052] After vertical alignment of S13 and completion of self-alignment in S11 and second self-alignment in S12, the first Raman interference (rising process) is performed in the second Raman light 31 within the atomic ejection trajectory, where the Raman pulse is a π / 2 pulse; the second and third Raman interferences are performed in the first Raman light 21, where the Raman pulse of the second Raman interference is a π pulse (rising process) and the Raman pulse of the third Raman interference is a π / 2 pulse (falling process). The Raman light phase φ is scanned during multiple atomic ejection processes. laser The atomic interference fringe contrast K3 was obtained by adjusting the vertical emission angle θ of the second Raman beam 31 by adjusting the second piezoelectric displacement stage 34. j3 Record the atomic interference fringe contrast K3(θ) under each angular condition. j3 The vertical emission angle θ of the second Raman beam 31 is fixed. j3* The maximum contrast K3 appears at the atomic interference fringes. max At this time, the vertical angle between the second Raman beam 35 and the first Raman beam 31 is the smallest. Simultaneously, the second self-alignment step S12 is executed to achieve the overlap of the second Raman beam 31 and the second returned Raman beam 35.

[0053] After horizontal alignment in S14 and vertical alignment in S13, the first and second Raman interferences are performed in the second Raman beam 31 during the atomic ejection trajectory (ascent), with Raman pulses of π / 2 pulses and π / 2 pulses respectively. The third and fourth Raman interferences are performed in the first Raman beam 21, with Raman pulses of π / 2 pulses and π / 2 pulses respectively. The phase φ of the Raman beam is scanned during multiple atomic ejections. laser The atomic interference fringe contrast K4 was obtained by adjusting the horizontal emission angle θ of the second Raman beam 31 using the second piezoelectric displacement stage 34. i4 Record the atomic interference fringe contrast K4(θ) under each angular condition. i4 The horizontal emission angle θ of the second Raman beam 31 is fixed. i4* The maximum contrast of the atomic interference fringes is K4. max At this time, the horizontal angle between the second Raman beam 35 and the first Raman beam 31 is the smallest. Then, the second self-alignment step S12 is executed to achieve the overlap of the second Raman beam 31 and the second returned Raman beam 35.

[0054] After the parallelism adjustment described above is completed, atomic interferometry can be used for angular velocity measurement. The specific interferometry process is as follows:

[0055] At the trajectory r1 of the atom's upward trajectory, a Raman laser π / 2 pulse interference is performed in the second Raman beam 31; at the trajectory r2 of the atom's upward trajectory, a Raman laser π pulse interference is performed in the first Raman beam 21; at the trajectory r3 of the atom's downward trajectory, a Raman laser π pulse interference is performed in the first Raman beam 21; and at the trajectory r4 of the atom's downward trajectory, a Raman laser π / 2 pulse interference is performed in the second Raman beam 31. Here, r1 and r4 are located within the region of the second Raman beam 31, and r2 and r3 are located within the region of the first Raman beam 21. Based on the parallelism alignment method provided by S11-S14, the atomic interference angular velocity measurement result can be obtained by the formula Δφ=4Ω·k. eff ·g·T 3 The solution is then implemented. Here, Δφ represents the atomic interference fringe measurement result, Ω represents the carrier angular velocity, and k... eff Let g be the Raman laser wave vector, and g be the gravitational acceleration.

[0056] In summary, this invention supports multi-pulse interferometry, achieving a parallelism of Raman and returned light better than 0.01 mrad through multiple angle adjustments. By employing a successive approximation method and leveraging the inherent Raman frequency spectrum characteristics of atomic interferometry, this invention improves the parallelism of Raman and returned light, enhances the contrast of the atomic interferometer, and ensures stable and reliable adjustment, thereby improving measurement accuracy.

[0057] This application proposes an atomic interferometer Raman beam parallelism adjustment system and method based on atomic interference contrast evaluation. Based on the physical characteristics of the atomic interferometer itself, it has the advantages of high adjustment accuracy and large degree of freedom.

Claims

1. A method for adjusting the parallelism of Raman beams in an atomic interferometer, characterized in that, The method is executed using a Raman beam parallelism adjustment system, which includes a first Raman beam unit and a second Raman beam unit located below the first Raman beam unit. The method achieves coarse alignment and parallelism adjustment of the first Raman beam, the first Raman return beam, the second Raman beam, and the second Raman return beam through two-pulse interference, including: S11 First Self-Alignment, Performing Multiple Atom Ejection Processes: During each ejection process, a single reverse Raman pulse interferometry measurement is performed, consisting of the first Raman beam and the first Raman return beam, by scanning the Raman beam phase φ during multiple atom ejection processes. laser The atomic interference fringe contrast K1 is obtained by adjusting the first piezoelectric displacement stage until the atomic interference fringe contrast reaches its maximum value K1. max The first piezoelectric displacement stage is fixed in position; S12 second self-alignment, performing multiple atomic ejection processes: This is achieved through single-stage reverse Raman pulse interferometry measurement of the atoms' single-flight over the second Raman beam and the second Raman return beam during a single ejection process, and by scanning the Raman beam phase φ during multiple atomic ejection processes. laser The atomic interference fringe contrast K2 was obtained by adjusting the third piezoelectric displacement stage until the atomic interference fringe contrast reached its maximum value K2. max The third piezoelectric displacement stage is fixed at the time; S13 are vertically aligned. Within the atomic ejection trajectory, the first Raman interference is performed in the second Raman beam; the second and third Raman interferences are performed in the first Raman beam. The Raman pulse of the second Raman interference is a rising phase, and the Raman pulse of the third Raman interference is a falling phase. The phase φ of the Raman beam is scanned during multiple atomic ejections. laser The atomic interference fringe contrast K3 was obtained using this method; By adjusting the second piezoelectric displacement stage, the maximum contrast K3 of the atomic interference fringes is achieved. max At that time, fix the second piezoelectric displacement stage; Perform the second self-alignment step S12 to achieve the overlap of the second Raman beam and the second returned Raman beam; S14 are horizontally aligned. During the ascent of the atomic ejection trajectory, the first and second Raman interferences are performed in the second Raman beam, and the third and fourth Raman interferences are performed in the first Raman beam. The phase φ of the Raman beam is scanned during multiple atomic ejections. laser The atomic interference fringe contrast K4 was obtained using this method; By adjusting the second piezoelectric displacement stage, the maximum contrast K4 of the atomic interference fringes is achieved. max At that time, fix the second piezoelectric displacement stage; Perform the second self-alignment step S12 to achieve the overlap of the second Raman beam and the second returned Raman beam.

2. The method according to claim 1, characterized in that, During the first self-alignment process of S11, the applied Raman laser pulse type is a π pulse.

3. The method according to claim 1, characterized in that, The system also includes: an atomic preparation unit, a fluorescence detection unit, and a host computer, wherein... The atomic preparation unit is used for the preparation and directional ejection of cold atomic clusters; The first Raman optical unit is used to generate expanded Raman laser, which interacts with the cold atom cluster multiple times within the same laser optical path, changing the internal state population of the cold atom cluster and having a 2-degree-of-freedom optical path adjustment function. The second Raman optical unit is used to generate another expanded Raman laser, which interacts with the cold atom cluster multiple times within the same laser optical path, changing the internal state population of the cold atom cluster and having a 4-degree-of-freedom optical path adjustment function. The fluorescence detection unit is used to determine the number of atoms in different internal states; The host computer is used for atomic contrast calculation and optical path adjustment control.

4. The method according to claim 3, characterized in that, The atom preparation unit includes a vacuum cavity and a magneto-optical trap, wherein the magneto-optical trap is located at the bottom of the vacuum cavity and realizes the cooling, confinement and directional ejection of metal atom clusters.

5. The method according to claim 4, characterized in that, The first Raman light unit includes: a first Raman light, a first quarter-wave plate, a first reflector, a first Raman return light, and a first piezoelectric displacement stage. The first Raman light is incident from one side of the atom preparation unit. The first quarter-wave plate, the first reflector, and the first piezoelectric displacement stage are located sequentially on the other side of the atom preparation unit. The first piezoelectric displacement stage is fixedly connected to the first reflector. The first Raman light has frequencies f1 and f2, both of which are negatively detuned from the resonant transition frequencies. |f2-f1| is the spacing between the ground state energy levels of the atoms. The polarization state of the first Raman light is σ+ circular polarization. The first Raman return light is obtained by passing the first Raman light through the first quarter-wave plate, the first reflector, and then through the first quarter-wave plate again, while the polarization state changes to σ- circular polarization.

6. The method according to claim 5, characterized in that, The second Raman beam unit includes a second Raman beam, a second quarter-wave plate, a second mirror, a second piezoelectric displacement stage, a second Raman return beam, and a third piezoelectric displacement stage. The second Raman beam is incident from one side of the atom preparation unit, and the second piezoelectric displacement stage is located on the same side. The second quarter-wave plate, the second mirror, and the third piezoelectric displacement stage are sequentially located on the other side of the atom preparation unit. The second piezoelectric displacement stage is fixedly connected to the emitting device of the second Raman beam, and the third piezoelectric displacement stage is fixedly connected to the second mirror. The second Raman beam has frequencies f1 and f2, both of which are negatively detuned to the resonant transition frequencies. |f2-f1| represents the spacing between the atomic ground state energy levels. The polarization state of the second Raman beam is σ+ circularly polarized. The second Raman return beam is obtained by passing the second Raman beam through a second quarter-wave plate, a second mirror, and then through another second quarter-wave plate, during which the polarization state changes to σ- circularly polarized. The first piezoelectric displacement stage, the second piezoelectric displacement stage, and the third piezoelectric displacement stage respectively realize the adjustment of the orthogonal direction degrees of freedom of the first Raman returned light, the second Raman light, and the second Raman returned light.

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