Chip atomic clock based on speed grating spectrum and implementation method

Abstract

The embodiment of the invention provides a chip atomic clock based on a speed grating spectrum and an implementation method. Comprising a multi-frequency coherent laser source, a quarter-wave plate, an atomic gas chamber, a photoelectric detector, a band-pass filter, a microwave modulation and demodulation module, a crystal oscillator, a phase-locked loop module, a bias-tree module, a DC modulation and demodulation module and a servo control module. The multi-frequency coherent laser source is sequentially connected with the quarter-wave plate, the atomic gas chamber, the photoelectric detector and the band-pass filter, the first output end of the band-pass filter is sequentially connected with the microwave modulation and demodulation module, the crystal oscillator and the phase-locked loop module, and meanwhile the microwave modulation and demodulation module is connected with the phase-locked loop module. And the second output end of the band-pass filter is connected with the DC modulation-demodulation module and the servo control module in sequence. And the bias-tree module is connected with the servo control module and the phase-locked loop module and feeds back a coupled signal to the multi-frequency coherent laser source so as to complete whole clock locking. The atomic clock is used for achieving the effect of improving the spectral line signal-to-noise ratio.

Description

Technical Field

[0001] The present application relates to the technical field of optical frequency standards, and particularly to a chip atomic clock based on velocity grating spectrum and an implementation method thereof. Background Art

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

[0003] In the prior art, vertical cavity surface emitting lasers are used as laser sources for chip atomic clocks. However, the laser output by a vertical cavity surface emitting laser is single-mode laser. Since atoms have different velocity groups in the gas chamber after heating, only zero-velocity atoms contribute to the detection spectral line, and most of the other principles do not work, which limits the signal-to-noise ratio of the spectral line to a certain extent. Summary of the Invention

[0004] The embodiments of the present application provide a chip atomic clock based on velocity grating spectrum and an implementation method thereof. By making the laser containing velocity grating spectrum information interact with atoms, atoms in different velocity groups can all participate in the spectral line contribution, thereby achieving the effect of improving the signal-to-noise ratio of the spectral line.

[0005] In a first aspect, an embodiment of the present application provides a chip atomic clock based on a velocity grating spectrum, including: a multi-frequency coherent laser source, a quarter-wave plate, an atomic cell, a photodetector, a band-pass 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, and is used 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 cell, and is used to enable the laser signal to enter the atomic cell and fully interact with the atoms in the atomic cell; the atomic cell and the photodetector are arranged in sequence, and the atomic cell is located in front of the photodetector, and is used to ensure that the optical signal emitted from the atomic cell can be received by the photodetector; the output end of the photodetector is directly connected to the input end of the band-pass filter, and is used to convert the optical signal into a composite electrical signal and transmit the composite electrical signal to the band-pass filter; the first output end of the band-pass filter is connected to the input end of the microwave modulation and demodulation module, and the second output end of the band-pass filter is connected to the DC modulation and demodulation module, and 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 according to the DC signal, and the DC error signal is input into the servo control module to generate a current signal for locking the multi-frequency coherent laser source; the first output end of the microwave modulation and demodulation module is sequentially connected to the crystal oscillator and the phase-locked loop module, and the second output end of the microwave modulation and demodulation module is connected to the phase-locked loop module, and is used to modulate and demodulate the microwave signal to obtain a microwave error signal, and after passing through the crystal oscillator and the phase-locked loop module, the phase locking of the microwave frequency and the crystal oscillator frequency is completed; the DC port of the bias-tee module is connected to the output end of the servo control module, the RF port of the bias-tee module is connected to the output end of the phase-locked loop module, and the common port of the bias-tee module is connected to the input end of the multi-frequency coherent laser source, and is used to couple the current signal and the microwave signal and feedback them 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 a possible implementation manner, the atoms in the atomic cell are rubidium atoms, cesium atoms, or other alkali metal atoms.

[0007] In a possible implementation manner, the periphery of the atomic cell includes a heating device, a heat preservation device, and a thermistor; wherein the heating device and the heat preservation device act together to ensure the temperature in the atomic cell is constant; the thermistor is used to measure the working temperature of the atomic cell.

[0008] In a possible implementation manner, an attenuation sheet is further included; the attenuation sheet is placed between the quarter-wave plate and the atomic cell and is used to adjust the intensity of the laser signal.

[0009] In a possible implementation, it further includes a shielding cover; the shielding cover is arranged outside the atomic gas cell.

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

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

[0012] In a possible implementation, it further includes a packaging shell; the packaging shell is installed outside the chip atomic clock and covers the chip atomic clock for magnetic shielding of the chip atomic clock.

[0013] In a possible implementation, the packaging shell uses permalloy material.

[0014] In a second aspect, an implementation method of a chip atomic clock based on velocity grating spectrum provided by an embodiment of the present application is applied to the first aspect above and various possible implementations of the first aspect, and includes: a multi-frequency coherent laser source generates a laser signal containing velocity grating spectrum information; the laser signal enters the atomic gas cell through a quarter-wave plate and fully interacts with the atoms in the atomic gas cell; a photodetector receives the optical signal exiting from the atomic gas cell, converts the optical signal into a composite electrical signal, and transmits the composite electrical signal to a band-pass filter; the band-pass filter separates the composite electrical signal into two superimposed signals in the time domain, namely a DC signal and a microwave signal; a DC modulation and demodulation module generates a DC error signal for feedback control according to the DC signal and transmits the DC error signal to a servo control module; the servo control module generates a current signal for driving the multi-frequency coherent laser source to achieve locking of the multi-frequency coherent laser source according to the DC error signal; a microwave modulation and demodulation module modulates and demodulates the microwave signal to obtain a microwave error signal and transmits the microwave error signal to a crystal oscillator; a 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, so that the microwave frequency is phase-locked with the frequency of the crystal oscillator; a 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, realizes current locking and microwave locking of the multi-frequency coherent laser source, and further completes overall clock locking of the chip atomic clock based on velocity grating spectrum.

[0015] The chip atomic clock based on the velocity grating spectrum and the implementation method provided by the embodiments of the present application use a multi-frequency coherent laser source as the laser source of the chip atomic clock. The output laser contains velocity grating spectrum information and can interact with atoms in different velocity groups in the atomic gas cell, enabling more atoms to participate in the contribution to the spectral line, which can nearly exponentially improve the signal-to-noise ratio of the spectral line, thereby nearly exponentially improving the stability of the chip atomic clock. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings herein are incorporated into the specification and form a part of this specification, showing embodiments consistent with the present application and, together with the specification, are used to explain the principles of the present application.

[0017] Figure 1 is a schematic structural diagram of the chip atomic clock based on the velocity grating spectrum provided by the embodiments of the present application;

[0018] Figure 2 is a schematic flow diagram of the implementation method of the chip atomic clock based on the velocity grating spectrum provided by the embodiments of the present application.

[0019] Reference Numerals:

[0020] 1 - multi-frequency coherent laser source; 2 - quarter-wave plate; 3 - atomic gas cell; 4 - photodetector; 5 - band-pass filter; 6 - microwave modulation and demodulation module; 7 - crystal oscillator; 8 - phase-locked loop module; 9 - bias-tee module; 10 - DC modulation and demodulation module; 11 - servo control module.

[0021] Through the above accompanying drawings, specific embodiments of the present application have been shown, and there will be more detailed descriptions hereinafter. These accompanying drawings and textual descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Here, the exemplary embodiments will be described in detail, and the examples are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0023] The technical solutions of the present application and how the technical solutions of the present application solve the above technical problems will be described in detail below with specific embodiments. These several specific embodiments below can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below with reference to the accompanying drawings.

[0024] To clearly understand the technical solution of the present application, the solutions of the prior art will be introduced in detail first. The time unit is one of the seven basic units defined by the International System of Units. Atomic clocks are the basic applications for measuring time and frequency standards currently. Countries around the world are committed to developing atomic clocks with higher performance. Currently, the atomic clock with the highest global indicators is the optical lattice atomic clock from China, and its frequency uncertainty has reached 10 -18 orders of magnitude. However, due to its large volume and non-portability, it cannot be used in many application scenarios. Therefore, miniaturized and low-power atomic clocks have become another important direction in the development of atomic clock technology. Chip atomic clocks are the most typical representatives of miniaturized atomic clocks. Compared with traditional atomic clocks, chip atomic clocks have the advantages of small size, low power consumption, and low cost. They can reduce the usage cost while ensuring certain performance, and expand the application fields of atomic clocks. Currently, all chip atomic clocks on the market use vertical-cavity surface-emitting lasers as the laser source. The laser output by this type of laser has a relatively weak power, only a few hundred microwatts, and the output laser is single-mode laser, that is, it only contains a single-wavelength laser of a single mode. Since atoms have different velocity groups in the gas chamber after being heated, but only atoms with zero velocity contribute to the detection spectral line, and the vast majority of the remaining atoms do not play a role, to a certain extent, it limits the signal-to-noise ratio of the spectral line.

[0025] To address the above technical problems, the inventor thought of using a velocity grating spectrum as the laser source. The laser signal containing multiple frequency components can interact with atoms in different velocity groups, and more atoms will participate in the contribution to the spectral line. In this way, the signal-to-noise ratio of the spectral line can be increased by nearly an order of magnitude, thereby enabling the stability of the chip atomic clock to be improved by nearly an order of magnitude.

[0026] Reference Figure 1 , Figure 1 is the structural schematic diagram of the chip atomic clock based on the velocity grating spectrum provided by the embodiment of the present application. As Figure 1 shown, the chip atomic clock includes: a multi-frequency coherent laser source (1), a quarter-wave plate (2), an atomic gas chamber (3), a photodetector (4), a band-pass 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] Among them, the output end of the multi-frequency coherent laser source (1) is aligned with the input end of the quarter-wave plate (2), and is used 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 an initial laser signal containing velocity grating spectrum information for the entire chip atomic clock. The quarter-wave plate (2), as an optical element, changes 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 adjacent in spatial position and optically connected. The multi-frequency coherent laser source (1) is aligned with the quarter-wave plate (2) so that the laser signal containing velocity grating spectrum information generated by the laser source can be directly transmitted to the quarter-wave plate with minimal optical loss and scattering.

[0030] In this embodiment, the light emitted by different types of multi-frequency coherent laser sources may be divergent light or collimated light. Therefore, between the multi-frequency coherent laser source (1) and the quarter-wave plate (2), there may be included an expansion lens, a collimation lens, etc., for shaping the laser to ensure that the laser interacts fully with the atoms in the atomic gas cell.

[0031] Specifically, an optical bracket or a 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 or a distributed feedback laser or a distributed Bragg reflector laser.

[0033] Among them, by adding a feedback element in the resonator of the laser, the external cavity laser can effectively control the frequency and linewidth of the laser. The characteristic of this kind of laser is that the frequency stability of the output laser is high and the linewidth is narrow, which is very beneficial for the chip atomic clock application scenario that requires high-precision frequency output.

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

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

[0036] In this embodiment, the quarter-wave plate (2) is closely adjacent to the atomic gas cell (3) in space, and the quarter-wave plate (2) is aligned with the atomic gas cell (3).

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

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

[0039] The periphery of the atomic gas cell includes a heating device, a heat insulation device, and a thermistor. The heating device and the heat insulation device work together to ensure a constant temperature inside the atomic gas cell. The thermistor is used to measure the operating temperature of the atomic gas cell.

[0040] Among them, the main function of the heating device is to provide heat to the atomic gas cell to reach and maintain the set operating temperature.

[0041] Among them, the thermistor is a resistance element sensitive to temperature changes, and its resistance value changes with temperature. In the atomic gas cell system, the thermistor is placed at a position where it can accurately sense the temperature of the atomic gas cell, usually close to the outer wall of the atomic gas cell or embedded in the outer shell of the atomic gas cell. By measuring the change in the resistance value of the thermistor, the temperature information of the atomic gas cell can be obtained.

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

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

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

[0045] Specifically, after the photodetector (4) converts the received optical signal into a composite electrical signal, it transmits the composite electrical signal to the band - pass filter (5) through a connection line. The composite electrical signal contains electrical signals of multiple frequency components, and these signals carry information about the interaction between light and atoms in the atomic gas cell. The band - pass filter (5) then screens and filters the received composite electrical signal according to its preset frequency range.

[0046] The band - pass 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 end is connected to the input end of the microwave modulation and demodulation module (6), and the second output end of the band - pass filter (5) is connected to the DC modulation and demodulation module (10).

[0047] Specifically, the band-pass filter (5) effectively separates the composite electrical signal transmitted from the photodetector (4). According to the filtering circuit and specific frequency response characteristics, it can decompose the direct current signal and microwave signal that are superimposed on each other 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 according to the DC signal. The DC error signal is input into the servo control module (11) to generate a current signal for realizing the locking of the multi-frequency coherent laser source.

[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 precisely adjusting 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 the pre-set control logic and corresponding circuit mechanism inside it. It can convert the DC error signal into an appropriate 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 sequentially connected to the crystal oscillator (7) and the phase-locked loop module (8), and the second output terminal of the microwave modulation and demodulation module (6) is connected to the phase-locked loop module (8). It is used to modulate and demodulate the microwave signal to obtain a microwave error signal, and through the crystal oscillator (7) and the phase-locked loop module (8), the phase locking between the microwave frequency and the crystal oscillator frequency is completed.

[0051] Specifically, after receiving the microwave signal separated by the band-pass filter, the microwave modulation and demodulation module (6) finely processes the microwave signal according to a specific algorithm and processing logic, thereby obtaining 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), making it perform corresponding frequency fine-tuning according to the specific situation of the error signal. The phase-locked loop module (8) uses the signal information of different dimensions transmitted from the first output terminal and the second output terminal 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, makes the microwave frequency gradually achieve phase locking with the crystal oscillator frequency.

[0052] The DC port of the bias-tee module (9) is connected to the output terminal of the servo control module (11), the RF port of the bias-tee module (9) is connected to the output terminal 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). It is used to couple the locked current signal and the locked microwave signal and then feedback them to the multi-frequency coherent laser source (1) to complete the overall clock locking of the chip atomic clock based on the velocity grating spectrum.

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

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

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

[0056] In another embodiment of the present application, the chip atomic clock further includes an attenuation sheet. The attenuation sheet is placed between the output end of the quarter-wave plate and the incident window of the atomic gas cell for adjusting the intensity of the laser signal.

[0057] In this embodiment, the attenuation sheet is placed in the optical path after the quarter-wave plate and before the atomic gas cell. Thus, after the laser changes its polarization state through the quarter-wave plate, its intensity can be directly adjusted to make the intensity of the laser entering the atomic gas cell reach the optimal state.

[0058] Continue to refer to Figure 1 , the chip atomic clock further includes a shielding cover. The shielding cover is arranged outside the atomic gas cell.

[0059] The chip atomic clock further includes a packaging shell. The packaging shell is installed outside the chip atomic clock to cover the chip atomic clock for magnetic shielding treatment of the chip atomic clock.

[0060] The packaging shell uses permalloy material. As can be seen from the above embodiments, by performing magnetic shielding treatment on both the atomic gas cell and the overall clock of the chip atomic clock, the influence of the environmental magnetic field on the signal can be reduced, and the stability index of the atomic clock system can be improved.

[0061] Refer to Figure 2 , Figure 2 is a schematic flow chart of the implementation method of the chip atomic clock based on the velocity grating spectrum provided by the embodiments of the present application. As Figure 2 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 enters the atomic gas cell through a quarter-wave plate and interacts fully with the atoms in the atomic gas cell.

[0064] S203: A photodetector receives the optical signal exiting the atomic gas cell, converts the optical signal into a composite electrical signal, and transmits the composite electrical signal to a band-pass filter.

[0065] S204: The band-pass filter separates the 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 that drives the multi-frequency coherent laser source to achieve locking of the multi-frequency coherent laser source based on the DC error signal.

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

[0069] S208: 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 to complete microwave frequency locking.

[0070] S209: 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, achieving current locking and microwave locking of the multi-frequency coherent laser source, and then completing the overall 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 and can interact with atoms in different velocity groups in the atomic gas cell, enabling more atoms to participate in the contribution to the spectral line, which can nearly order-of-magnitude improve the signal-to-noise ratio of the spectral line, thereby nearly order-of-magnitude improving the stability of the chip atomic clock.

[0072] In the above embodiments, the descriptions of the various embodiments have their own emphases. For parts not detailed in a certain embodiment, reference may be made to the relevant descriptions of other embodiments. The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification.

[0073] Those skilled in the art will readily conceive of other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any variations, uses, or adaptations of the present application, which follow the general principles of the present application and include known common general knowledge or conventional technical means in the technical field not disclosed in the present application. The specification and embodiments are only regarded as exemplary, and the true scope and spirit of the present application are pointed out by the following claims.

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

Claims

1. A chip atomic clock based on velocity grating spectroscopy, characterized in that Comprising: A multi-frequency coherent laser source, a quarter-wave plate, an atomic gas cell, a photodetector, a band-pass 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, and is used to directly transmit the laser signal containing the velocity grating spectrum information generated to the quarter-wave plate; The quarter-wave plate is closely adjacent to the atomic gas cell, and is used to enable 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 in sequence, and the atomic gas cell is located in front of the photodetector, and is used 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 band-pass filter, and is used to convert the optical signal into a composite electrical signal and transmit the composite electrical signal to the band-pass filter; The first output end of the band-pass filter is connected to the input end of the microwave modulation and demodulation module, and the second output end of the band-pass filter is connected to the DC modulation and demodulation module, and 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 according to the DC signal, and the DC error signal is input to the servo control module to generate a current signal for realizing the locking of the multi-frequency coherent laser source; The first output end of the microwave modulation and demodulation module is sequentially connected to the crystal oscillator and the phase-locked loop module, and the second output end of the microwave modulation and demodulation module is connected to the phase-locked loop module, and is used to modulate and demodulate the microwave signal to obtain a microwave error signal, and through the crystal oscillator and the phase-locked loop module, complete the phase locking of the microwave frequency and the crystal oscillator frequency; The DC port of the bias-tee module is connected to the output end of the servo control module, the RF port of the bias-tee module is connected to the output end of the phase-locked loop module, and the common port of the bias-tee module is connected to the input end of the multi-frequency coherent laser source, and is used to couple the current signal and the microwave signal and feedback them to the multi-frequency coherent laser source to complete the overall 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 cell are rubidium atoms or cesium atoms or other alkali metal atoms.

3. The chip atomic clock according to claim 2, wherein The periphery of the atomic gas cell includes a heating device, a heat preservation device, and a thermistor; Wherein the heating device and the heat preservation device act together to ensure that the temperature in the atomic gas cell is constant; The thermistor is used to measure the working temperature of the atomic gas cell.

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

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

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

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

8. The chip atomic clock according to claim 1, characterized in that, It further includes a packaging housing; The packaging housing is installed outside the chip atomic clock and covers the chip atomic clock for magnetic shielding of the chip atomic clock.

9. The chip atomic clock according to claim 8, wherein The packaging housing uses permalloy material.

10. A method for implementing a chip atomic clock based on a velocity grating spectrum, characterized in that, Applied to the chip atomic clock according to any one of claims 1 to 9, it includes: The multi-frequency coherent laser source generates a laser signal containing velocity grating spectrum information; The laser signal enters the atomic gas cell through the quarter-wave plate and interacts fully with the atoms in the atomic gas cell; The photodetector receives the optical signal exiting from the atomic gas cell, converts the optical signal into a composite electrical signal, and transmits the composite electrical signal to the band-pass filter; The band-pass filter separates two superimposed signals in the time domain from the composite electrical signal, namely a DC signal and a microwave signal; The DC modulation and demodulation module generates a DC error signal for feedback control according to the DC signal and transmits the DC error signal to the servo control module; The servo control module generates a current signal for driving the multi-frequency coherent laser source to achieve locking of the multi-frequency coherent laser source according to the DC error signal; The microwave modulation and demodulation module modulates and demodulates the microwave signal to obtain a microwave error signal and 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 to complete 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, realizes current locking and microwave locking of the multi-frequency coherent laser source, and further completes the overall clock locking of the chip atomic clock based on the velocity grating spectrum.

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