Chip-based atomic clock based on velocity grating spectrum and its implementation method

Abstract

This application provides a chip atomic clock based on velocity grating spectrum and its implementation method. It includes: a multi-frequency coherent laser source, a quarter-wave plate, an atomic gas cell, a photodetector, a bandpass filter, a microwave modulation / demodulation module, a crystal oscillator, a phase-locked loop (PLL) module, a bias-tee module, a DC modulation / demodulation module, and a servo control module. The multi-frequency coherent laser source is sequentially connected to the quarter-wave plate, the atomic gas cell, the photodetector, and the bandpass filter. The first output terminal of the bandpass filter is sequentially connected to the microwave modulation / demodulation module, the crystal oscillator, and the PLL module. Simultaneously, the microwave modulation / demodulation module is connected to the PLL module. The second output terminal of the bandpass filter is sequentially connected to the DC modulation / demodulation module and the servo control module. The bias-tee module is connected to the servo control module and the PLL module, and feeds back the coupled signal to the multi-frequency coherent laser source to complete the clock locking. This atomic clock is used to improve the spectral signal-to-noise ratio.

Description

Technical Field

[0001] This application relates to the field of optical frequency standard technology, and in particular to a chip atomic clock based on velocity grating spectrum and its implementation method. Background Technology

[0002] Compared with traditional atomic clocks, chip atomic clocks have the advantages of small size, low power consumption, and low cost, which can reduce the cost of use while ensuring certain performance and expand the application fields of atomic clocks.

[0003] In existing technologies, chip atomic clocks all use vertical cavity surface-emitting lasers (VCSELs) as laser sources. However, the laser output by VCSELs is a single-mode laser. Since atoms have different velocity groups in the gas chamber after being heated, only zero-velocity atoms contribute to the detection spectral lines, while most other principles are ineffective, which to some extent limits the spectral line signal-to-noise ratio. Summary of the Invention

[0004] This application provides a chip atomic clock based on velocity grating spectrum and its implementation method. By interacting with atoms through lasers containing velocity grating spectrum information, atoms of different velocity groups can participate in the spectral line contribution, thereby improving the spectral line signal-to-noise ratio.

[0005] In a first aspect, embodiments of this application provide a chip atomic clock based on velocity grating spectrum, comprising: a multi-frequency coherent laser source, a quarter-wave plate, an atomic gas cell, a photodetector, a bandpass filter, a microwave modulation and demodulation module, a crystal oscillator, a phase-locked loop module, a bias-tee module, a DC modulation and demodulation module, and a servo control module; wherein, the output end of the multi-frequency coherent laser source is aligned with the quarter-wave plate for directly transmitting the generated laser signal containing velocity grating spectrum information to the quarter-wave plate; the quarter-wave plate is closely adjacent to the atomic gas cell for allowing the laser signal to enter the atomic gas cell and fully interact with the atoms in the atomic gas cell; the atomic gas cell and the photodetector are arranged sequentially, with the atomic gas cell located before the photodetector to ensure that the optical signal emitted from the atomic gas cell can be received by the photodetector; the output end of the photodetector is directly connected to the input end of the bandpass filter for converting the optical signal into a composite electrical signal and transmitting the composite electrical signal to the bandpass filter; the first output end of the bandpass filter is connected to the input end of the microwave modulation and demodulation module, and the second output end of the bandpass filter is connected to... A DC modulation and demodulation module is connected to separate the composite electrical signal into two superimposed signals in the time domain, including a DC signal and a microwave signal. The DC modulation and demodulation module is connected to a servo control module to generate a DC error signal for feedback control based on the DC signal. This DC error signal is input to the servo control module to generate a current signal for locking the multi-frequency coherent laser source. The first output of the microwave modulation and demodulation module is connected to a crystal oscillator and a phase-locked loop (PLL) module in sequence. The second output of the microwave modulation and demodulation module is connected to the PLL module to modulate and demodulate the microwave signal to obtain a microwave error signal. This signal, after passing through the crystal oscillator and the PLL module, completes the phase locking between the microwave frequency and the crystal oscillator frequency. The DC port of the bias-tee module is connected to the output of the servo control module, the RF port of the bias-tee module is connected to the output of the PLL module, and the common port of the bias-tee module is connected to the incident end of the multi-frequency coherent laser source. This port couples the current signal and the microwave signal and feeds them back to the multi-frequency coherent laser source to complete the overall clock locking of the chip atomic clock based on the velocity grating spectrum.

[0006] In one possible implementation, the atoms in the atomic gas chamber are rubidium atoms, cesium atoms, or other alkali metal atoms.

[0007] In one possible implementation, the periphery of the atomic gas chamber includes a heating device, a heat preservation device, and a thermistor; wherein the heating device and the heat preservation device work together to ensure that the temperature inside the atomic gas chamber is constant; and the thermistor is used to measure the operating temperature of the atomic gas chamber.

[0008] In one possible implementation, an attenuator is also included; the attenuator is placed between the quarter-wave plate and the atomic gas cell to adjust the intensity of the laser signal.

[0009] In one possible implementation, a shielding cover is also included; the shielding cover is disposed outside the atomic gas chamber.

[0010] In one possible implementation, the multi-frequency coherent laser source is obtained by multi-frequency modulation of the laser source or by pulse modulation, and the laser output by the multi-frequency coherent laser source contains velocity grating spectrum information.

[0011] In one possible implementation, the multi-frequency coherent laser source is an external cavity laser, a distributed feedback laser, or a distributed Bragg reflector laser.

[0012] In one possible implementation, a packaging shell is also included; the packaging shell is installed outside the chip atomic clock, covering the chip atomic clock, and is used for magnetic shielding of the chip atomic clock.

[0013] In one possible implementation, the encapsulation housing is made of permalloy material.

[0014] Secondly, embodiments of this application provide a method for implementing a chip atomic clock based on a velocity grating spectrum, applicable to the first aspect and various possible implementations thereof, including: a multi-frequency coherent laser source generating a laser signal containing velocity grating spectrum information; the laser signal being incident on an atomic gas cell through a quarter-wave plate and interacting fully with the atoms in the atomic gas cell; a photodetector receiving the optical signal emitted from the atomic gas cell, converting the optical signal into a composite electrical signal, and transmitting the composite electrical signal to a bandpass filter; the bandpass filter separating the composite electrical signal into two superimposed signals in the time domain, namely a DC signal and a microwave signal; and a DC modulation and demodulation module generating a DC error signal for feedback control based on the DC signal, and transmitting the DC error signal to a servo control module. The system comprises the following modules: a servo control module generates a current signal to drive the multi-frequency coherent laser source and achieve multi-frequency coherent laser source locking based on the DC error signal; a microwave modulation and demodulation module modulates and demodulates the microwave signal to obtain a microwave error signal, which is then transmitted to the crystal oscillator; a phase-locked loop module adjusts the output microwave frequency based on the frequency of the crystal oscillator and the microwave error signal sent by the microwave modulation and demodulation module, thereby achieving phase locking between the microwave frequency and the frequency of the crystal oscillator; and a bias-tee module couples the current signal and the microwave frequency, and uses the coupled composite signal to achieve feedback control of the multi-frequency coherent laser source, realizing current locking and microwave locking of the multi-frequency coherent laser source, and thus completing the overall clock locking of the chip atomic clock based on velocity grating spectrum.

[0015] The chip atomic clock and its implementation method based on velocity grating spectrum provided in this application use a multi-frequency coherent laser source as the laser source of the chip atomic clock. The laser output contains velocity grating spectrum information and can interact with atoms of different velocity groups in the atomic gas cell, so that more atoms will participate in the contribution to the spectral lines. This can improve the spectral line signal-to-noise ratio by a near order of magnitude, thereby improving the stability of the chip atomic clock by a near order of magnitude. Attached Figure Description

[0016] 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.

[0017] Figure 1 A schematic diagram of the structure of a chip atomic clock based on velocity grating spectrum provided in this application embodiment;

[0018] Figure 2 This is a flowchart illustrating the implementation method of a chip atomic clock based on velocity grating spectrum provided in an embodiment of this application.

[0019] Figure label:

[0020] 1-Multi-frequency coherent laser source; 2-Quarter-wave plate; 3-Atomic gas cell; 4-Photodetector; 5-Bandpass filter; 6-Microwave modulation and demodulation module; 7-Crystal oscillator; 8-Phase-locked loop module; 9-Bbias-tee module; 10-DC modulation and demodulation module; 11-Servo control module.

[0021] 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

[0022] 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.

[0023] The technical solution of this application and how it solves the above-mentioned technical problems will be described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0024] To clearly understand the technical solution of this application, the existing technical solutions will first be described in detail. The unit of time is one of the seven base units defined by the International System of Units (SI), and the atomic clock is currently the fundamental application for measuring time and frequency standards. Countries around the world are committed to developing atomic clocks with higher performance. Currently, the world's highest-performing atomic clock is the optical lattice type, originating from China, with a frequency uncertainty reaching 10-1. -18 While atomic clocks are large-scale, their bulky size and inaccessibility prevent them from being used in many applications. Therefore, miniaturized, low-power atomic clocks have become another important direction in the development of atomic clock technology, with chip-based atomic clocks being the most typical example. Compared to traditional atomic clocks, chip-based atomic clocks have advantages such as small size, low power consumption, and low cost, reducing operating costs while maintaining certain performance and expanding the application areas of atomic clocks. Currently, chip-based atomic clocks on the market all use vertical-cavity surface-emitting lasers (VCSELs) as their laser source. These lasers have relatively weak output power, only a few hundred microwatts, and the output laser is single-mode, meaning it contains only one mode and a single wavelength. Because atoms exist in different velocity groups within the gas chamber after heating, only zero-velocity atoms contribute to the detection spectral lines; the vast majority of other atoms are inactive, thus limiting the spectral signal-to-noise ratio to some extent.

[0025] To address the aforementioned technical problems, the inventors conceived of using a velocity grating spectrum as a laser source. The laser signal, containing multiple frequency components, can interact with atoms of different velocity groups, and more atoms will participate in contributing to the spectral lines. This can improve the spectral line signal-to-noise ratio by a near-order-of-magnitude, thereby improving the stability of the chip atomic clock by a near-order-of-magnitude.

[0026] refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a chip atomic clock based on a velocity grating spectrum, provided as an embodiment of this application. Figure 1 As shown, the chip atomic clock includes: a multi-frequency coherent laser source (1), a quarter-wave plate (2), an atomic gas cell (3), a photodetector (4), a bandpass filter (5), a microwave modulation and demodulation module (6), a crystal oscillator (7), a phase-locked loop module (8), a bias-tee module (9), a DC modulation and demodulation module (10), and a servo control module (11).

[0027] The output end of the multi-frequency coherent laser source (1) is aligned with the incident end of the quarter-wave plate (2) to directly transmit the generated laser signal containing velocity grating spectrum information to the quarter-wave plate (2).

[0028] Among them, the multi-frequency coherent laser source (1) provides the initial laser signal containing velocity grating spectrum information for the entire chip atomic clock. The quarter-wave plate (2), as an optical element, plays a role in changing the polarization state of the laser signal from the multi-frequency coherent laser source (2).

[0029] In this embodiment, the multi-frequency coherent laser source (1) and the quarter-wave plate (2) are spatially adjacent and optically connected. The multi-frequency coherent laser source (1) is aligned with the quarter-wave plate (2) so that the laser signal generated by the laser source, which contains velocity grating spectrum information, can be directly transmitted to the quarter-wave plate with minimal optical loss and scattering.

[0030] In this embodiment, different types of multi-frequency coherent laser sources may emit divergent or collimated light. Therefore, a beam expander and a collimating lens may be included between the multi-frequency coherent laser source (1) and the quarter-wave plate (2) to shape the laser and ensure that the laser interacts fully with the atoms in the atomic gas chamber.

[0031] Specifically, an optical support or fine-tuning device can be used to ensure that the central axis of the laser beam coincides with the central axis of the quarter-wave plate, so as to ensure that the laser signal passes through the quarter-wave plate completely.

[0032] The multi-frequency coherent laser source (1) is an external cavity laser, a distributed feedback laser, or a distributed Bragg reflection laser.

[0033] External cavity lasers, by adding feedback elements within the laser's resonant cavity, can effectively control the laser's frequency and linewidth. These lasers are characterized by high frequency stability and narrow linewidth, making them highly advantageous for applications requiring high-precision frequency output, such as atomic clocks for chips.

[0034] The velocity grating spectrum is obtained by multi-frequency modulation of a multi-frequency correlated laser source or by pulse modulation.

[0035] The quarter-wave plate (2) is closely adjacent to the atomic gas chamber (3) and is used to allow the laser signal to enter the atomic gas chamber (3) and interact fully with the atoms in the atomic gas chamber (3).

[0036] In this embodiment, the quarter-wave plate (2) and the atomic gas chamber (3) are spatially close to each other, and the quarter-wave plate (2) is aligned with the atomic gas chamber (3).

[0037] Specifically, the laser beam, after its polarization state is changed by a quarter-wave plate (2), enters the atomic gas chamber (3) directly along a precise optical path. After entering the atomic gas chamber, the laser interacts with the atoms.

[0038] The atoms in the atomic gas chamber are rubidium atoms, cesium atoms, or other alkali metal atoms.

[0039] The atomic gas chamber is surrounded by a heating device, a heat preservation device, and a thermistor. The heating and heat preservation devices work together to maintain a constant temperature inside the atomic gas chamber. The thermistor is used to measure the operating temperature of the atomic gas chamber.

[0040] The main function of the heating device is to provide heat to the atomic gas chamber in order to reach and maintain the set operating temperature.

[0041] A thermistor is a resistive element that is sensitive to temperature changes; its resistance changes with temperature. In an atomic chamber system, the thermistor is placed in a location that accurately senses the temperature of the atomic chamber, typically close to the outer wall of the chamber or embedded within its outer shell. By measuring the change in the thermistor's resistance, the temperature information of the atomic chamber can be obtained.

[0042] The atomic gas chamber (3) and the photodetector (4) are arranged in sequence. The atomic gas chamber (3) is located in front of the photodetector (4) to ensure that the light signal emitted from the atomic gas chamber (3) can be received by the photodetector (4).

[0043] Specifically, the light signal after the interaction between the atoms and the laser in the atomic gas chamber (3) is transmitted to the photodetector (4) along a specific optical path. The photodetector (4) converts the received light signal into an electrical signal, thereby outputting the result of the interaction between the light and the atoms in the atomic gas chamber (3) in the form of an electrical signal.

[0044] The output of the photodetector (4) is directly connected to the input of the bandpass filter (5) to convert the optical signal into a composite electrical signal and transmit the composite electrical signal to the bandpass filter (5).

[0045] Specifically, the photodetector (4) converts the received optical signal into a composite electrical signal, and then transmits the composite electrical signal to the bandpass filter (5) through a connecting line. The composite electrical signal contains electrical signals with multiple frequency components, which carry information about the interaction between light and atoms in the atomic gas chamber. The bandpass filter (5) then filters the received composite electrical signal according to its preset frequency range.

[0046] The bandpass filter (5) is used to separate the composite electrical signal into two superimposed signals in the time domain, including a DC signal and a microwave signal. Its first output terminal is connected to the input terminal of the microwave modulation and demodulation module (6), and the second output terminal of the bandpass filter (5) is connected to the DC modulation and demodulation module (10).

[0047] Specifically, the bandpass filter (5) effectively separates the composite electrical signal transmitted from the photodetector (4). Based on the filter circuit and specific frequency response characteristics, it can decompose the DC signal and microwave signal that are superimposed in the time domain from the composite electrical signal.

[0048] The DC modulation and demodulation module (10) is connected to the servo control module (11) and is used to generate a DC error signal for feedback control based on the DC signal. The DC error signal is input to the servo control module (11) to generate a current signal to achieve multi-frequency coherent laser source locking.

[0049] Specifically, the DC modulation and demodulation module (10) generates a DC error signal for feedback control based on the DC signal. This DC error signal includes information for precise adjustment of the multi-frequency coherent laser source (1). After receiving the DC error signal, the servo control module (11) analyzes and processes the signal according to its internally preset control logic and corresponding circuit mechanism. It can convert the DC error signal into a suitable current signal to complete the locking of the multi-frequency coherent laser source (1).

[0050] The first output terminal of the microwave modulation and demodulation module (6) is connected to the crystal oscillator (7) and the phase-locked loop module (8) in sequence. The second output terminal of the microwave modulation and demodulation module (6) is connected to the phase-locked loop module (8) to modulate and demodulate the microwave signal to obtain the microwave error signal. After passing through the crystal oscillator (7) and the phase-locked loop module (8), the phase lock between the microwave frequency and the crystal oscillator frequency is completed.

[0051] Specifically, after receiving the microwave signal separated from the bandpass filter, the microwave modulation and demodulation module (6) performs fine processing on the microwave signal according to a specific algorithm and processing logic to obtain a microwave error signal containing control information. After the microwave error signal is input, it will affect the output frequency of the crystal oscillator (7), causing it to make corresponding frequency fine adjustments according to the specific situation of the error signal. The phase-locked loop module (8) uses the signal information of different dimensions from the first and second output terminals of the microwave modulation and demodulation module (6) to obtain the phase relationship between the current microwave frequency and the crystal oscillator frequency, and then through dynamic adjustment, gradually achieves phase locking between the microwave frequency and the crystal oscillator frequency.

[0052] The DC port of the bias-tee module (9) is connected to the output of the servo control module (11), the RF port of the bias-tee module (9) is connected to the output of the phase-locked loop module (8), and the output port of the bias-tee module (9) is connected to the incident end of the multi-frequency coherent laser source (1). This is used to couple the locked current signal and the locked microwave signal and then feed them back to the multi-frequency coherent laser source (1) to complete the whole clock locking of the chip atomic clock based on the velocity grating spectrum.

[0053] Specifically, the bias-tee module (9) couples the current signal received from the DC port for laser locking with the microwave signal received from the RF port for locking, and then feeds it back to the multi-frequency coherent laser source (1) through the output port, thereby completing the whole clock locking of the chip atomic clock based on the velocity grating spectrum.

[0054] In this embodiment, the bandpass filter (5), DC modulation and demodulation module (10), servo control module (11), microwave modulation and demodulation module (6), crystal oscillator (7), phase-locked loop module (8) and bias-tee module can be discrete components or integrated components.

[0055] As can be seen from the above embodiments, by using a multi-frequency coherent laser source as the laser source of the chip atomic clock, the output laser contains velocity grating spectrum information. In the atomic gas cell, it can interact with atoms of different velocity groups, so that more atoms will participate in the contribution to the spectral lines, which can improve the spectral line signal-to-noise ratio by a near order of magnitude, thereby improving the stability of the chip atomic clock by a near order of magnitude.

[0056] In another embodiment of this application, the chip atomic clock further includes an attenuator. The attenuator is placed between the exit end of the quarter-wave plate and the incident window of the atomic gas cell to adjust the intensity of the laser signal.

[0057] In this embodiment, the attenuator is placed in the optical path after the quarter-wave plate and before the atomic gas cell. This allows for direct adjustment of the laser intensity after its polarization state is altered by the quarter-wave plate, ensuring that the laser intensity entering the atomic gas cell reaches its optimal state.

[0058] Continue to refer Figure 1 The chip-based atomic clock also includes a shield. The shield is located outside the atomic gas chamber.

[0059] The chip-based atomic clock also includes a packaging shell. The packaging shell is installed outside the chip-based atomic clock, covering it and providing magnetic shielding.

[0060] The encapsulation shell is made of permalloy. As can be seen from the above embodiments, by applying magnetic shielding to both the atomic cell and the entire clock of the chip atomic clock, the influence of the ambient magnetic field on the signal is reduced, thereby improving the stability of the atomic clock system.

[0061] refer to Figure 2 , Figure 2 This is a flowchart illustrating the implementation method of a chip atomic clock based on velocity grating spectrum provided in an embodiment of this application. Figure 2 As shown, the method includes:

[0062] S201: A multi-frequency coherent laser source generates a laser signal containing velocity grating spectrum information.

[0063] S202: The laser signal is injected into the atomic gas cell through a quarter-wave plate and interacts fully with the atoms in the atomic gas cell.

[0064] S203: The photodetector receives the optical signal emitted from the atomic gas cell, converts the optical signal into a composite electrical signal, and transmits the composite electrical signal to the bandpass filter.

[0065] S204: The bandpass filter separates a composite electrical signal into two superimposed signals in the time domain, including a DC signal and a microwave signal.

[0066] S205: The DC modulation and demodulation module generates a DC error signal for feedback control based on the DC signal and transmits the DC error signal to the servo control module.

[0067] S206: The servo control module generates a current signal based on the DC error signal to drive the multi-frequency coherent laser source and achieve multi-frequency coherent laser source locking.

[0068] S207: The microwave modulation and demodulation module modulates and demodulates the microwave signal to obtain a microwave error signal, and then transmits the microwave error signal to the crystal oscillator.

[0069] S208: The phase-locked loop module adjusts the output microwave frequency based on the frequency of the crystal oscillator and the microwave error signal sent by the microwave modulation and demodulation module, thereby completing microwave frequency locking.

[0070] S209: The bias-tee module couples the current signal and the microwave frequency, and realizes the feedback control of the multi-frequency coherent laser source through the coupled composite signal, thereby achieving current locking and microwave locking of the multi-frequency coherent laser source, and finally completing the whole clock locking of the chip atomic clock based on the velocity grating spectrum.

[0071] As can be seen from the above embodiments, by using a multi-frequency coherent laser source as the laser source of the chip atomic clock, the output laser contains velocity grating spectrum information. In the atomic gas cell, it can interact with atoms of different velocity groups, so that more atoms will participate in the contribution to the spectral lines, which can improve the spectral line signal-to-noise ratio by a near order of magnitude, thereby improving the stability of the chip atomic clock by a near order of magnitude.

[0072] In the above embodiments, the descriptions of each embodiment have their own emphasis. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of 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.

[0073] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present application that follow the general principles of the present application and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0074] It should be understood that the present application is not limited to the exact structure described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A chip atomic clock based on velocity grating spectrum, characterized in that, include: Multi-frequency coherent laser source, quarter-wave plate, atomic gas cell, photodetector, bandpass filter, microwave modulation and demodulation module, crystal oscillator, phase-locked loop module, bias-tee module, DC modulation and demodulation module and servo control module; The output end of the multi-frequency coherent laser source is aligned with the quarter-wave plate to directly transmit the generated laser signal containing velocity grating spectrum information to the quarter-wave plate. The quarter-wave plate is closely adjacent to the atomic gas cell, which allows the laser signal to enter the atomic gas cell and interact fully with the atoms in the atomic gas cell. The atomic gas chamber and the photodetector are arranged in sequence, with the atomic gas chamber located in front of the photodetector to ensure that the light signal emitted from the atomic gas chamber can be received by the photodetector. The output terminal of the photodetector is directly connected to the input terminal of the bandpass filter, which is used to convert the optical signal into a composite electrical signal and transmit the composite electrical signal to the bandpass filter. The first output terminal of the bandpass filter is connected to the input terminal of the microwave modulation and demodulation module, and the second output terminal of the bandpass filter is connected to the DC modulation and demodulation module, which is used to separate the composite electrical signal into two superimposed signals in the time domain, including a DC signal and a microwave signal. The DC modulation and demodulation module is connected to the servo control module and is used to generate a DC error signal for feedback control based on the DC signal. The DC error signal is input to the servo control module to generate a current signal for locking the multi-frequency coherent laser source. The first output terminal of the microwave modulation and demodulation module is connected to the crystal oscillator and the phase-locked loop module in sequence, and the second output terminal of the microwave modulation and demodulation module is connected to the phase-locked loop module. It is used to modulate and demodulate the microwave signal to obtain a microwave error signal. After passing through the crystal oscillator and the phase-locked loop module, the phase lock between the microwave frequency and the crystal oscillator frequency is completed. The DC port of the bias-tee module is connected to the output of the servo control module, the RF port of the bias-tee module is connected to the output of the phase-locked loop module, and the common port of the bias-tee module is connected to the incident end of the multi-frequency coherent laser source. This is used to couple the current signal and the microwave signal and then feed them back to the multi-frequency coherent laser source to complete the whole-clock locking of the chip atomic clock based on the velocity grating spectrum.

2. The chip atomic clock according to claim 1, characterized in that, The atoms in the atomic gas chamber are rubidium atoms, cesium atoms, or other alkali metal atoms.

3. The chip atomic clock according to claim 2, characterized in that, The periphery of the atomic gas chamber includes a heating device, a heat preservation device, and a thermistor; The heating device and the heat preservation device work together to ensure that the temperature inside the atomic gas chamber remains constant; The thermistor is used to measure the operating temperature of the atomic gas chamber.

4. The chip atomic clock according to claim 1, characterized in that, It also includes attenuation plates; The attenuator is placed between the quarter-wave plate and the atomic gas cell to adjust the intensity of the laser signal.

5. The chip atomic clock according to claim 1, characterized in that, It also includes a shielding cover; The shielding cover is located outside the atomic gas chamber.

6. The chip atomic clock according to claim 1, characterized in that, The multi-frequency coherent laser source is obtained by multi-frequency modulation of the laser source or by pulse modulation, and the laser output by the multi-frequency coherent laser source contains velocity grating spectrum information.

7. The chip atomic clock according to claim 1, characterized in that, The multi-frequency coherent laser source is an external cavity laser, a distributed feedback laser, or a distributed Bragg reflection laser.

8. The chip atomic clock according to claim 1, characterized in that, It also includes the packaging shell; The encapsulation shell is installed outside the chip atomic clock, covering the chip atomic clock, and is used to perform magnetic shielding treatment on the chip atomic clock.

9. The chip atomic clock according to claim 8, characterized in that, The encapsulation shell is made of permalloy.

10. A method for implementing a chip atomic clock based on velocity grating spectrum, characterized in that, Applied to the chip atomic clock as described in any one of claims 1 to 9, comprising: The multi-frequency coherent laser source generates a laser signal containing velocity grating spectrum information; The laser signal is injected into the atomic gas chamber through the quarter-wave plate and interacts fully with the atoms in the atomic gas chamber; The photodetector receives the optical signal emitted from the atomic gas cell, converts the optical signal into a composite electrical signal, and transmits the composite electrical signal to the bandpass filter; The bandpass filter separates the composite electrical signal into two superimposed signals in the time domain, namely a DC signal and a microwave signal. The DC modulation and demodulation module generates a DC error signal for feedback control based on the DC signal, and transmits the DC error signal to the servo control module. The servo control module generates a current signal to drive the multi-frequency coherent laser source and achieve multi-frequency coherent laser source locking based on the DC error signal; The microwave modulation and demodulation module modulates and demodulates the microwave signal to obtain a microwave error signal, and then transmits the microwave error signal to the crystal oscillator. The phase-locked loop module adjusts the output microwave frequency according to the frequency of the crystal oscillator and the microwave error signal sent by the microwave modulation and demodulation module, thereby completing microwave frequency locking. The bias-tee module couples the current signal and the microwave frequency, and realizes feedback control of the multi-frequency coherent laser source through the coupled composite signal, thereby achieving current locking and microwave locking of the multi-frequency coherent laser source, and finally completing the whole clock locking of the chip atomic clock based on velocity grating spectrum.

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