Laser based on diffraction homogenization and closed-loop frequency stabilization control, atomic clock and implementation method

Abstract

The invention discloses a laser based on diffraction homogenization and closed-loop frequency stabilization control, an atomic clock and an implementation method, and belongs to the technical field of quantum precision measurement and atomic clocks. The laser comprises a laser light source, a light path optimization module and a closed-loop frequency stabilization control module. The core of the optical path optimization module is that the optical path optimization module is integrated with a diffraction homogenizer which is arranged in a laser optical path and is used for converting Gaussian distribution light beams output by a laser light source into flat-topped distribution light beams with uniform light intensity, so that optical frequency shift generated when the light intensity is not uniform and acts on atoms is eliminated fundamentally. Meanwhile, in combination with a closed-loop frequency stabilization control module based on a modulation transfer spectrum technology, high-precision locking and feedback adjustment are carried out on the laser frequency. Through the synergistic effect of light beam homogenization and electronic frequency stabilization, the system frequency shift of rubidium / hydrogen / strontium / cesium atomic clocks is remarkably reduced, the frequency stability and long-term timing accuracy of the atomic clocks are improved, and the key problem that in the prior art, optical frequency shift restricts the performance of the atomic clocks is solved.

Description

Technical Field

[0001] This application relates to the fields of quantum precision measurement and atomic clock technology, and in particular to a laser, atomic clock, and implementation method based on diffraction homogenization and closed-loop frequency stabilization control. Background Technology

[0002] As the core device for modern precision timekeeping and frequency standards, the performance of atomic clocks directly determines the upper limit of accuracy in many key fields such as satellite navigation, communication synchronization, deep space exploration, and fundamental physics research. Their working principle utilizes the extremely stable frequency corresponding to the transitions between atomic eigenlevels as a reference, and synchronizes the frequency of an external oscillator to this atomic reference frequency through frequency locking technology. In an atomic clock system, the frequency-stabilized laser used to excite atomic transitions is a key component determining overall performance; the laser's frequency stability, linewidth, and beam quality directly affect the frequency accuracy and long-term stability of the atomic clock.

[0003] Among the many physical effects affecting atomic clock performance, light shift is a long-standing and difficult-to-completely suppress critical problem. Light shift originates from the AC Stark shift of the light field on atomic energy levels. When the laser intensity applied to atoms is spatially uneven, atoms at different locations will experience different light field intensities, leading to differences in energy level shifts. This ultimately manifests as an overall shift and broadening of atomic transition frequencies. Commercial semiconductor lasers typically output lasers with a Gaussian distribution, exhibiting a significant intensity difference between the center and edges of the beam. This inherent intensity gradient is the primary physical source of light shift.

[0004] Traditional atomic clock optical systems have significant limitations in their methods for suppressing optical frequency shift. Common techniques, such as intensity feedback control, can only stabilize the total output power of the laser and cannot improve the uniformity of intensity distribution within the beam cross-section. Homogenization schemes using acousto-optic or electro-optic modulation for time averaging have limited response speeds and may introduce additional frequency noise. Furthermore, although frequency stabilization techniques such as saturated absorption spectroscopy (SAS) or Pound-Drever-Hall (PDH) cavity locking can achieve high frequency locking accuracy, they do not address the optical frequency shift problem at its physical source—the spatial characteristics of the beam.

[0005] On the other hand, existing frequency stabilization systems also have shortcomings in terms of environmental adaptability. External disturbances such as vibration and temperature drift can easily cause optical path distortion, leading to frequency lock point shift or even loss of lock. Traditional optical paths lack the ability to monitor and dynamically compensate for wavefront distortion in real time, making it difficult to maintain long-term stable operation in changing environments.

[0006] Therefore, there is an urgent need in this field for a laser frequency stabilization system that can simultaneously achieve highly uniform optical field distribution, high-precision frequency locking, and strong environmental adaptability, so as to fundamentally overcome the limitations of optical frequency shift on atomic clock performance and meet the higher-level requirements of future high-precision atomic clocks in terms of stability, accuracy, and reliability. Summary of the Invention

[0007] This application provides a laser, an atomic clock, and a method for implementing them based on diffraction homogenization and closed-loop frequency stabilization control, belonging to the field of quantum precision measurement and atomic clock technology. This solution aims to fundamentally solve the optical frequency shift problem caused by the uneven spatial distribution of laser intensity and achieve high-precision, high-stability laser frequency output, thereby significantly improving the long-term frequency stability and accuracy of the atomic clock.

[0008] Firstly, this invention provides a laser based on diffraction homogenization and closed-loop frequency stabilization control. The laser comprises three core components: a laser source, an optical path optimization module, and an automatic frequency stabilization control module. The laser source employs a distributed feedback semiconductor laser (DFB-LD), whose output wavelength corresponds to specific transition lines of atoms such as rubidium, cesium, hydrogen, or strontium, and whose output power is adjustable within the range of 10-50mW. The optical path optimization module is responsible for collimating, expanding, splitting, and crucially homogenizing the laser beam. Its innovation lies in integrating a diffraction homogenizer. This device, designed based on the principle of micro-optical diffraction, is placed after the beam shaping module and can efficiently (homogenize efficiency ≥80%) convert the Gaussian intensity distribution beam output from the laser source into a flat-top distribution beam with intensity uniformity better than ±5% (preferably ≤±3%), thus eliminating the spatial intensity gradient from its physical source. The automatic frequency stabilization electronic control module achieves high-precision closed-loop control based on modulation transfer spectroscopy (MTS) technology. It receives the light signal after interaction with atoms through a photodetector, and after amplification, mixing and demodulation, it extracts the high signal-to-noise ratio dispersive error signal. Then, it generates control commands through a PID controller to adjust the driving current and / or temperature of the laser, thereby achieving precise locking of the laser frequency to the atomic reference spectral line.

[0009] Furthermore, the optical path optimization module may also include an optical path dynamic correction unit, which consists of a wavefront sensor and a spatial light modulator (SLM). The wavefront sensor monitors the wavefront distortion of the homogenized beam in real time, while the SLM performs dynamic phase modulation based on the monitoring signal to compensate for optical aberrations caused by environmental disturbances (such as vibration and temperature drift), ensuring the long-term stability of the flat-top beam quality.

[0010] Secondly, the present invention provides an atomic clock, which includes the aforementioned laser and an atomic physics module (including an atomic gas cell, a magnetic field system, etc.). The pump light and probe light generated by the laser and homogenized flat-top distributed are precisely guided into the atomic gas cell of the atomic physics module to interact with atoms for optical pumping and state detection of atoms, ultimately outputting a stable clock signal.

[0011] The atomic clock can be a rubidium atomic clock, a cesium atomic clock, a hydrogen atomic clock, or a strontium atomic clock.

[0012] Thirdly, the present invention provides a method for implementing diffraction homogenization and closed-loop frequency stabilization control, comprising:

[0013] Beam homogenization step: The Gaussian laser beam is converted into a flat-top beam with uniform intensity distribution using a diffraction homogenizer to eliminate the optical frequency shift caused by the spatial intensity gradient.

[0014] Frequency stabilization control steps: A high signal-to-noise ratio dispersive error signal is generated using modulation transfer spectroscopy technology, and the laser frequency is locked in a closed loop through an electronic feedback loop.

[0015] Furthermore, it also includes the atomic clock operation steps, which involve irradiating the atomic gas cell with the homogenized flat-top distributed pump light and probe light to complete the pumping and detection of atoms and output a stable clock signal.

[0016] Furthermore, before the beam homogenization step, there are also laser generation and optical path optimization steps: the laser generation step generates laser light corresponding to atomic line transitions from a laser source; the optical path optimization step collimates, expands, splits, and shapes the generated laser light; and then the beam homogenization step uses a diffraction homogenizer to convert the shaped pump laser beam with a Gaussian distribution into a flat-top distribution beam with uniform light intensity.

[0017] Furthermore, in the beam homogenization step, the diffraction homogenizer optimizes the intensity uniformity of the beam to ≤±3%.

[0018] Furthermore, the frequency stabilization control steps specifically include:

[0019] Modulation steps: Phase modulation of the pump light in the frequency-stabilized optical path is performed using an electro-optic modulator;

[0020] Interaction step: The modulated pump light and the probe light are incident collinearly into the atomic gas cell at a small angle;

[0021] Signal demodulation steps: The modulated and transferred probe light signal is received by a photodetector, converted into an electrical signal, and then extracted as a dispersion error signal after amplification, mixing, and low-pass filtering.

[0022] Feedback execution steps: The error signal is input to the PID controller, and its output is fed back to the drive current of the laser source to complete the frequency-locked closed-loop control.

[0023] The laser, atomic clock, and implementation method based on diffraction homogenization and closed-loop frequency stabilization control provided in the first, second, and third aspects of this application are innovative in the following ways compared with the prior art: (1) Source suppression of optical frequency shift: The diffraction homogenizer is statically introduced into the laser optical path of the atomic clock, and the Gaussian beam is directly converted into a flat-top beam, eliminating the optical frequency shift caused by uneven spatial distribution of light intensity from the physical source. The method is more thorough and fundamental. (2) Dynamic optical path compensation: A dynamic correction unit that links the wavefront sensor and the spatial light modulator is introduced into the homogenization optical path, which can monitor and compensate for wavefront distortion caused by environmental factors in real time, solve the problem of poor anti-interference ability of static homogenization devices, and significantly improve the environmental adaptability and long-term stability of the system. (3) Optical-electric synergistic optimization: The combination of "beam spatial quality hardware optimization" and "modulation transfer spectral electronic frequency stabilization" technology forms a synergistic enhancement effect. The homogenized light field not only reduces the frequency shift, but also improves the signal-to-noise ratio and narrows the spectral linewidth due to the increased volume and reduced transition width, creating better conditions for subsequent electronic frequency stabilization, thereby improving the overall system performance. (4) Fully automatic frequency stabilization control: The automatic frequency stabilization electronic control module, together with dedicated software, can realize the full-process automated control from power-on, parameter configuration, phase recognition, automatic locking, lockout and relock to power-off, which greatly reduces the difficulty of operation and improves practicality and reliability.

[0024] The laser, atomic clock, and implementation method provided by this invention have the following significant advantages: (1) Greatly reduces system frequency shift: It fundamentally suppresses optical frequency shift, a key factor restricting the performance of atomic clocks, and improves frequency accuracy. (2) Improves frequency stability: The high uniformity of the optical field combined with high-precision modulation transfer spectrum frequency stabilization technology significantly improves the stability of laser frequency and the long-term stability of atomic clocks. (3) Enhances system robustness: The dynamic optical path correction function effectively combats environmental disturbances, enabling the system to maintain stable operation in more complex environments. (4) High practicality and easy integration: The diffraction homogenizer is small in size and easy to embed into the optical path of existing optically pumped atomic clocks. The modification cost is low, and it has high promotion value and application prospects. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0026] Figure 1 This is a schematic diagram illustrating the working principle of the diffraction homogenizer in this invention, showing a comparison of the intensity distribution between the input Gaussian beam and the output flat-top beam;

[0027] Figure 2 A schematic diagram of the overall optically pumped atomic clock system structure provided in an embodiment of the present invention (taking a cesium clock as an example);

[0028] Figure 3 This is a diagram of the automatic frequency locking program architecture for a laser provided in an embodiment of the present invention;

[0029] Figure 4 This is a diagram showing the spectral lines and error signal status of an 852nm laser after power-on, as provided in Embodiment 1 of the present invention.

[0030] Figure 5 A screenshot of the oscilloscope after the 852nm laser provided in Embodiment 1 of the present invention has been locked.

[0031] Figure 6 The signal status diagram of the 852nm laser after unlocking is provided in Embodiment 1 of the present invention.

[0032] Figure labeling: 1-Laser source, 2-Collimating lens, 3-Optical isolator, 4-Beam expander module, 5, 6, 8-Polarization beam splitter (PBS), 7-Acousto-optic modulator (AOM), 9-Electro-optic modulator (EOM), 10-Atomic gas cell, 11-Photodetector (PD), 12-Beam shaping module, 13-Diffraction homogenizer, 14-Wavefront sensor, 15-Spatial light modulator, 16-Laser system drive module, 17-Frequency stabilization electronic control module, 18-Atomic physics drive module, 19, 20-Optical windows. L1-Main laser, L2-Frequency stabilized light, L3-Probe light, L4-Homogenized pump light, L5-Frequency stabilized pump light, L6-Frequency stabilized probe light.

[0033] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0034] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0035] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments.

[0036] Before introducing specific embodiments, we will first introduce the background technology to better understand each embodiment.

[0037] In recent years, quantum precision measurement has become a unique and rapidly growing research branch in the field of quantum information science and technology, with atomic clocks occupying a central position due to their superior stability and accuracy. As a key component of atomic clock systems, the performance of frequency-stabilized lasers directly affects the timing accuracy and frequency stability of the atomic clock. Among the many factors affecting atomic clock performance, optical frequency shift is a problem that cannot be ignored. It causes minute changes in atomic energy levels, leading to a drift in the atomic clock's output frequency, severely limiting the performance of atomic clocks in applications requiring extremely high time and frequency accuracy, such as satellite navigation, communication network synchronization, and high-precision scientific experiments.

[0038] Traditional frequency-stabilized lasers often achieve frequency stability through frequency locking (such as saturable absorption spectroscopy and PDH technology), but they do not specifically address the frequency shift caused by uneven intensity distribution. In terms of optical path design, existing frequency-stabilized lasers have relatively simple optical path systems, lacking effective optimization methods for beam quality and intensity distribution. In common optical paths, the laser beam is easily affected by various factors during transmission, such as beam divergence and intensity non-uniformity. These problems further exacerbate the frequency shift phenomenon of atomic clocks. Specifically, atomic clocks achieve frequency standardization by detecting hyperfine energy level transitions in atoms. However, since the laser output spot typically exhibits a Gaussian distribution with higher intensity at the center and weaker intensity at the edges, when such a beam acts on atoms, it leads to uneven optical field interaction, resulting in varying degrees of frequency shift and severely challenging the frequency stability of the atomic clock. Furthermore, existing optical paths often lack devices for effective beam shaping and homogenization, making it impossible to precisely control the beam shape and intensity distribution, and thus failing to meet the stringent requirements of atomic clocks for laser beam quality.

[0039] In summary, existing frequency-stabilized lasers, when used in atomic clocks, suffer from numerous shortcomings in optical path design and optical frequency shift elimination, resulting in an inability to provide sufficiently stable laser frequencies for atomic clocks. This severely limits the further development of atomic clocks in high-precision applications. Therefore, developing a novel frequency-stabilized laser that can effectively eliminate optical frequency shift in atomic clocks and optimize optical path design is both an urgent practical need and of significant scientific importance.

[0040] The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below.

[0041] Example 1

[0042] This embodiment 1 provides a laser based on diffraction homogenization and closed-loop frequency stabilization control, the specific structure of which is as follows: Figure 2 The component structure within the dashed box of the laser.

[0043] The laser source 1 is a distributed feedback semiconductor laser with an output power greater than 30mW. Its driving current and temperature can be adjusted by the laser driving module 16 to output a continuously tuned frequency.

[0044] The laser beam emitted from the laser first passes through a numerically aperture-matched aspherical collimating lens 2, where it is collimated into a parallel beam. The beam then passes through an optical isolator 3 to prevent reflected light from interfering with the laser's stability. The collimated beam then enters a telescope system (beam expander module 4) consisting of two lenses, which increases the beam diameter by a factor of three to reduce the laser's divergence angle and increase the volume of light interacting with atoms.

[0045] The expanded beam is split into two paths by the first polarizing beam splitter 5: most of the transmitted light intensity (about 90%) is used as the main laser L1 for the atomic clock system; a small portion of the reflected light intensity (about 10%) is used as the frequency-stabilized light L2 for frequency locking.

[0046] The main laser L1 continues to propagate and is split again by the second polarizing beam splitter 6: the reflected light serves as the probe light L3 for the atomic clock and enters the atomic physics module directly through the optical window 19; the transmitted light enters the acoustic-optical modulator 7. The AOM 7 is used for frequency shifting and switching control of the pump light. The +1 order light diffracted by the AOM is used as the source of the pump light, and its optical path is sequentially equipped with a shaping module 12 and a diffraction homogenizer 13. The shaping module 12 consists of a pair of cylindrical mirrors or other beam shapers, used to pre-shape the elliptical spot into a circular spot. The diffraction homogenizer 13 is the core of this embodiment; it is designed using microstructured diffraction optical elements on a quartz substrate, targeting an input beam diameter (3mm, 1 / e). 2 Optimize the output requirements (e.g., location) and output requirements. Figure 1 As shown, it converts the incident Gaussian beam into a circular flat-topped spot with a diameter of approximately 4 mm, achieving a homogenization efficiency of 85% and an intensity uniformity within ±3%. The homogenized pump light L4 ultimately enters the atomic physics module through optical window 20.

[0047] The frequency-stabilized light L2 is split into pump light L5 and probe light L6 by the third polarization beam splitter 8. Pump light L5 passes through an electro-optic modulator 9 and is phase-modulated by a radio frequency signal (typically in the MHz range) from the automatic frequency stabilization control module 17. The modulated pump light L5 and the unmodulated probe light L6 are incident collinearly into a dedicated atomic gas chamber 10 at a small angle of about 3°. Both interact with atoms in the gas chamber, producing a modulation transfer effect.

[0048] The probe light L6 emitted from the atomic gas chamber 10 carries sideband information generated by modulation transfer. This information is received by a high-speed photodetector 11 and converted into an electrical signal. This signal is then sent to the automatic frequency stabilization control module 17. The frequency stabilization control module 17 first amplifies the signal and filters out the DC component. Then, it sends the signal along with the original modulation signal (after phase adjustment by an adjustable phase shifter) to a double-balanced mixer for mixing. The mixer output passes through a low-pass filter to obtain a dispersive error signal corresponding to the center of the atomic absorption line. This error signal is input to a PID (proportional-integral-derivative) controller. The output of the PID controller is ultimately fed back to the laser system drive module 16. By fine-tuning the drive current of the laser 1, the laser frequency is precisely locked onto the atomic hyperfine level transition line, completing closed-loop frequency stabilization control.

[0049] Figures 4-6 This is a screenshot of the automatic spectral line locking process of an 852nm laser monitored by an oscilloscope, based on Example 1. Figure 4 The image shows the spectral lines and error signal status of the laser after power-on. The blue line marked with number 2 on the left side of the oscilloscope is the frequency-stabilized probe light L6 signal, and the purple line marked with number 3 is the error signal demodulated by the automatic frequency stabilization control module. Figure 5 To capture a screenshot of the oscilloscope after locking, the program automatically performs a series of control and algorithm locking operations, including parameter configuration, phase identification, and spectral line locking. The voltage level of the lock point marker line is 1.14V. To check if the locking position is accurate, Figure 6 To determine the signal status after unlocking, the marker line position corresponds to the cesium atom F=4→F′=5 cyclic transition line, with a voltage level of 1.18V, which is basically the same as the voltage level of the locked position, indicating that the automatic locking position is accurate.

[0050] According to the oscilloscope, the power-on time was 9:55:22. Figure 4 The time after locking was 9:58:40. Figure 5 That is, the laser completes the locking time in 3 minutes and 18 seconds.

[0051] Example 2

[0052] like Figure 2 As shown, this embodiment 2 provides an optically pumped cesium atomic clock, which includes all the laser systems described in embodiment 1, and further integrates an atomic physics module.

[0053] The atomic physics module mainly includes an atomic gas chamber filled with high-purity atoms (not shown separately in the figure, located inside the module), a magnetic shielding and coil system that generates a static magnetic field, and a microwave cavity and detection system for detecting atomic states (all controlled by the atomic physics drive module 18).

[0054] During operation, a homogenized, flat-topped pump beam L4, generated by a laser, is injected through optical window 19 into the atomic gas chamber of the atomic physics module. The uniform light intensity distribution ensures that all atoms passing through the laser region experience almost the same optical field, greatly suppressing the optical frequency shift effect caused by the intensity gradient. The pump beam prepares the atoms to specific ground state energy levels. Subsequently, the transition probabilities of the atoms are detected by the combined action of the probe beam L3 and the microwave field, thus obtaining the error signal of the atomic clock. This error signal is used to lock the microwave frequency generated by the crystal oscillator, ultimately outputting a highly stable second pulse signal and a standard frequency signal.

[0055] In an improved embodiment of Example 2, the laser system described in Example 1 is applied to a rubidium atomic clock.

[0056] In another improved embodiment of Example 2, the laser system described in Example 1 is applied to a hydrogen atomic clock.

[0057] In another improved embodiment of Example 2, the laser system described in Example 1 is applied to a strontium atomic clock.

[0058] Because of the use of the laser of the present invention, the systematic errors (especially optical frequency shift) introduced by the pumping process are minimized, thereby significantly improving the frequency stability and accuracy of the atomic clocks achieved in this embodiment 2 and its improved embodiments compared with conventional designs.

[0059] Example 3

[0060] This embodiment 3 provides a method for eliminating atomic clock optical frequency shift based on the laser implemented in embodiment 1 above. The method mainly includes the following steps:

[0061] S1: Laser Generation and Preliminary Processing: Controlling the DFB semiconductor laser 1 to generate 852nm laser light. After collimation by collimating lens 2, isolation by isolator 3, and beam expansion by beam expansion module 4, the light is split by PBS 5 into the main optical path L1 and the frequency-stabilized optical path L2.

[0062] S2: Pump light homogenization: The main optical path L1 is split into one path by PBS 6, and then frequency-shifted by AOM 7. It is then pre-shaped by shaping module 12. The most critical step is to convert the beam from Gaussian distribution to a flat-top distribution with light intensity uniformity better than ±3% by diffraction homogenizer 13, and then perform dynamic beam correction by wavefront sensor and spatial light modulator to generate homogenized pump light L4.

[0063] S3: Modulation-Transfer Stabilization: The frequency-stabilized optical path L2 is split into pump light L5 and probe light L6 via PBS 8. The pump light L5 is phase-modulated using EOM 9. The modulated pump light L5 and probe light L6 are then incident collinearly into the atomic gas cell 10, where they undergo nonlinear interaction.

[0064] S4: Error Signal Generation and Locking: The emitted light L6 carrying atomic absorption information is detected by PD 11 and converted into an electrical signal. In the automatic frequency stabilization control module 17, this signal is amplified, mixed with the phase-shifted original modulation signal, filtered, and demodulated to obtain a dispersion-type error signal. The error signal is processed by a PID controller, and the output control quantity is fed back to the drive current of laser 1 to precisely lock its frequency on the atomic transition line.

[0065] In an improved embodiment of Example 3, step S5 is further included: atomic clock signal generation: the frequency-stabilized and homogenized pump light L4 and probe light L3 are injected into the main atomic gas cell of the atomic physics module to perform optical pumping and microwave transition detection of atoms, and finally output a highly stable atomic clock signal.

[0066] In another improved embodiment of Example 3, the method is applied to a cesium atomic clock.

[0067] In another improved embodiment of Example 3, the method is applied to a rubidium atomic clock.

[0068] In another improved embodiment of Example 3, the method is applied to a hydrogen atomic clock.

[0069] In another improved embodiment of Example 3, the method is applied to a strontium atomic clock.

[0070] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

[0071] In the above embodiments 1-3, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments. The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification.

[0072] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0073] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A laser based on diffraction homogenization and closed-loop frequency stabilization control, characterized in that, include: A laser source (1) is used to generate laser light of a specific wavelength; The optical path optimization module is used to collimate, expand, split, and shape the laser output from the laser source (1); Automatic frequency stabilization electronic control module (17) is used to receive feedback signals and generate control commands to stabilize the laser frequency; The optical path optimization module further includes a diffraction homogenizer (13), which is located after the shaping module (12) in the optical path and is used to homogenize the Gaussian distributed beam into a flat-top distributed beam with a light intensity uniformity better than ±5%.

2. The laser according to claim 1, characterized in that, The diffraction homogenizer (13) is a homogenizer designed based on the principle of micro-optical diffraction, with a homogenization efficiency of not less than 80% and an output light spot with a circular flat-top distribution.

3. The laser according to claim 1 or 2, characterized in that, The optical path optimization module further includes an optical path dynamic correction unit, which includes: A wavefront sensor (14) is used to monitor the wavefront distortion of the output beam of the diffraction homogenizer (13) in real time; A spatial light modulator (15) is disposed in the optical path after the diffraction homogenizer (13) and is used to dynamically phase modulate the homogenized beam according to the monitoring signal of the wavefront sensor (14) to compensate for optical distortion caused by environmental disturbance and maintain the distribution quality of the flat-top beam.

4. The laser according to claim 1 or 2, characterized in that, The laser source (1) is a distributed feedback semiconductor laser with a center wavelength corresponding to an atomic transition line and an output power adjustable in the range of 10-50mW.

5. The laser according to claim 4, characterized in that, The atom is a rubidium atom, a hydrogen atom, a strontium atom, or a cesium atom.

6. The laser according to claim 1, characterized in that, The automatic frequency stabilization electronic control module (17) achieves closed-loop control based on modulation transfer spectroscopy technology, including: The photoelectric receiving section is used to convert optical signals into electrical signals and amplify them; The modulation and demodulation section is used to generate a modulation signal and to mix and demodulate the electrical signal to extract the error signal; The PID control section is used to generate control commands based on the error signal and to adjust the driving current and / or temperature of the laser source (1) in response to feedback.

7. A light-pumped atomic clock, characterized in that, It includes a laser based on diffraction homogenization and closed-loop frequency stabilization control as described in any one of claims 1 to 6, and an atomic physics module; the homogenized pump light (L4) and probe light (L3) generated by the laser are guided into the atomic physics module to interact with atoms.

8. A method for eliminating optical frequency shift in atomic clocks, characterized in that, Applied to the optically pumped atomic clock as described in claim 7, the method comprises: Laser generation steps: A laser corresponding to an atomic line transition is generated by a laser source (1); Optical path optimization steps: collimation, beam expansion, beam splitting, and shaping of the generated laser; Beam homogenization step: The shaped pump laser beam with Gaussian distribution is converted into a flat-top distribution beam with uniform light intensity using a diffraction homogenizer (13). Frequency stabilization control steps: A portion of the laser is separated as a frequency stabilization optical path, which interacts with atoms to generate quantum reference spectral lines. Error signals are detected and generated by modulation transfer spectroscopy technology, and feedback control is used to control the driving current and / or temperature of the laser source (1) to achieve closed-loop locking of the laser frequency. Atomic clock operation steps: The homogenized flat-top distributed pump light (L4) and probe light (L3) are irradiated onto the atomic gas cell to complete the pumping and detection of atoms and output a stable clock signal.

9. The method according to claim 8, characterized in that, In the beam homogenization step, the diffraction homogenizer (13) optimizes the intensity uniformity of the beam to ≤±3%.

10. The method according to claim 8, characterized in that, The frequency stabilization control steps specifically include: Modulation steps: Phase modulation of the pump light (L5) in the frequency-stabilized optical path is performed using an electro-optic modulator (9); Interaction step: The modulated pump light (L5) and the probe light (L6) are incident collinearly into the atomic gas cell (10) at a small angle; Signal demodulation steps: The photodetector (11) receives the modulated and transferred probe light signal, converts it into an electrical signal, and extracts the dispersion error signal after amplification, mixing, and low-pass filtering; Feedback execution steps: The error signal is input into the PID controller, and its output is fed back to the drive current of the laser source (1) to complete the frequency-locked closed-loop control.

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