Rubidium atomic clock based on speed grating spectrum and implementation method

Abstract

The embodiment of the invention provides a rubidium atomic clock based on a velocity grating spectrum and an implementation method, and the method comprises the steps: enabling a multi-frequency coherent laser source to emit a laser signal containing the velocity grating spectrum, and dividing the laser signal into two paths through a polarization splitting prism; the reflected light beam enters the laser frequency stabilization module to realize laser frequency stabilization; a transmission light beam enters the rubidium bubble through the lens group to interact with rubidium atoms; the photoelectric tube detects a transition spectral line, converts the transition spectral line from an optical signal into an electric signal and transmits the electric signal to the lock-in amplifier for demodulation; the integral amplification module converts the demodulated direct-current voltage into linear increasing voltage and transmits the linear increasing voltage to the crystal oscillator; the crystal oscillator generates an initial microwave signal and generates a microwave signal corresponding to the 87Rb atom through the frequency synthesizer; and the phase frequency modulation module modulates the microwave signal to obtain an error signal and transmits the error signal to the microwave resonant cavity so as to adjust the electromagnetic field according to the error signal to stably lock the rubidium atomic clock. The method is used for achieving the effect of improving the stability of the rubidium atomic clock system.

Description

Technical Field

[0001] This application relates to the technical field of atomic clocks, and in particular, to a rubidium atomic clock based on velocity grating spectroscopy and an implementation method thereof. Background Art

[0002] The unit of time 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.

[0003] In the prior art, compared with other atomic clocks, rubidium atomic clocks have the advantages of being structurally compact, easy to carry, and easy to engineer, and have been widely used in fields such as communication and navigation. Rubidium atomic clocks are divided into spectral lamp pumped rubidium atomic clocks and laser pumped rubidium atomic clocks.

[0004] However, the optical power density of the spectral lamp is low and the frequency is unstable, and the pumping efficiency is limited, resulting in an atomic utilization rate of only a few thousandths in the physical system, which restricts the further improvement of the stability; while the laser source linewidth of the traditional laser pumped rubidium clock is relatively narrow, which limits the signal-to-noise ratio of the electrical signal to a certain extent, thus restricting the system stability of the rubidium atomic clock. Summary of the Invention

[0005] Embodiments of this application provide a rubidium atomic clock based on velocity grating spectroscopy and an implementation method thereof, so as to achieve the effect of improving the system stability of the rubidium atomic clock.

[0006] In a first aspect, an embodiment of the present application provides a rubidium atomic clock based on a velocity grating spectrum, including: a multi-frequency coherent laser source, a polarization beam splitter prism, a lens group, a rubidium cell, a microwave resonator, a phototube, a lock-in amplifier, an integration amplification module, a crystal oscillator, a frequency synthesizer, a phase-frequency modulation module, and a laser frequency stabilization module; wherein, the multi-frequency coherent laser source is located before the polarization beam splitter prism and is used to transmit a laser signal containing velocity grating spectrum information to the polarization beam splitter prism; the polarization beam splitter prism is adjacent to the lens group and the laser frequency stabilization module and is used to split the laser signal into two paths, namely a transmitted beam and a reflected beam, and the reflected beam is incident on the laser frequency stabilization module for laser frequency stabilization; the lens group is adjacent to the rubidium cell and is used to transmit the transmitted beam into the rubidium cell and interact with rubidium atoms; the microwave resonator surrounds the rubidium cell and is used to provide a stable electromagnetic field for the rubidium cell; the rubidium cell is adjacent to the phototube and is used to ensure that the optical signal emitted from the rubidium cell can be received by the phototube; the output end of the phototube is electrically connected to the input end of the lock-in amplifier, and the phototube is used to detect the transition spectral line and convert the transition spectral line from an optical signal into an electrical signal; the output end of the lock-in amplifier is electrically connected to the integration amplification module and the crystal oscillator in sequence, the lock-in amplifier is used to demodulate the electrical signal output by the phototube and output it to the integration amplification module, and the integration amplification module converts the DC voltage into a linearly increasing voltage and transmits the linearly increasing voltage to the crystal oscillator; the output end of the crystal oscillator is electrically connected to the frequency synthesizer and the phase modulation module in sequence, the crystal oscillator is used to provide an initial microwave signal, and the initial microwave signal generates a microwave signal corresponding to the 87 hyperfine energy level transition frequency of Rb atoms after frequency multiplication processing by the frequency synthesizer, and the microwave signal is modulated by the phase-frequency modulation module to obtain an error signal for feedback control; the phase modulation module is connected to the microwave resonator through a circuit and is used to transmit the error signal to the microwave resonator, and the microwave resonator adjusts the electromagnetic field according to the error signal to stably lock the rubidium atomic clock.

[0007] In a possible implementation manner, the lens group includes a first lens and a second lens; the first lens is used to expand the transmitted beam; the second lens is used to collimate the expanded transmitted beam so that the expanded transmitted beam is collimated and becomes parallel light.

[0008] In a possible implementation manner, the periphery of the microwave resonator further includes a heating and cooling device, a heat preservation device, and a thermistor; wherein, the heating and cooling device and the heat preservation device work together to ensure that the temperature of the rubidium cell is constant; the thermistor is used to measure the operating temperature of the rubidium cell.

[0009] In a possible implementation manner, the velocity grating spectrum information is obtained by multi-frequency modulation of the multi-frequency coherent laser source or by pulse modulation.

[0010] In a possible implementation, the multi-frequency coherent laser source is an external cavity laser, a DFB laser, a DBR laser, or other types of lasers.

[0011] In a possible implementation, the laser frequency stabilization module uses saturated absorption spectroscopy frequency stabilization, modulation transfer spectroscopy frequency stabilization, or compact PDH frequency stabilization.

[0012] In a possible implementation, a half-wave plate is further included; the half-wave plate is placed before the polarization beam splitter prism and is closely adjacent to the multi-frequency coherent laser source and the polarization beam splitter prism, and is used to adjust the intensity of the laser signal.

[0013] In a possible implementation, the rubidium cell is filled with rubidium atoms and an inert gas, and the inert gas serves as a buffer gas.

[0014] In a possible implementation, the initial microwave signal is 5 MHz or 10 MHz; the microwave frequency signal of the 87Rb atomic hyperfine level transition is a 6.8 GHz microwave frequency signal.

[0015] In a second aspect, an implementation method of a rubidium atomic clock based on a velocity grating spectrum provided by an embodiment of the present application is applied to the rubidium atomic clock in the first aspect and various possible implementations of the first aspect, and includes: modulating the multi-frequency coherent laser source to obtain a laser signal containing velocity grating spectrum information, splitting the laser signal into two paths through a polarization beam splitter prism, one path being a reflected beam and the other path being a transmitted beam; the reflected beam enters the laser frequency stabilization module to perform laser frequency stabilization on the multi-frequency coherent laser source; the transmitted beam is expanded and collimated through a lens group and enters the rubidium cell to interact with rubidium atoms, and at the same time, a microwave resonator provides an electromagnetic field to stimulate the rubidium atoms in the rubidium cell to undergo energy level transitions; a phototube detects the transition spectrum line, converts the transition spectrum line from an optical signal into an electrical signal, and transmits the electrical signal to a lock-in amplifier, so that the lock-in amplifier demodulates the electrical signal and outputs it to an integration amplification module; the integration amplification module converts the demodulated DC voltage into a linearly increasing voltage and transmits the linearly increasing voltage to a crystal oscillator; the crystal oscillator generates an initial microwave signal and generates a microwave signal corresponding to the 87 microwave frequency of the 87Rb atomic hyperfine level transition after frequency multiplication processing by a frequency synthesizer; the microwave signal is modulated through a phase frequency modulation module to obtain an error signal for feedback control and the error signal is transmitted to the microwave resonator; the microwave resonator adjusts the electromagnetic field according to the error signal to stably lock the rubidium atomic clock.

[0016] The rubidium atomic clock and implementation method based on velocity grating spectrum provided by the embodiments of the present application use a multi-frequency coherent laser as a laser source. By performing multi-frequency modulation or pulse modulation on the multi-frequency coherent laser source, a laser signal containing velocity grating spectrum is generated, which can interact with rubidium atoms in different velocity groups, enabling more rubidium atoms to participate in the contribution to the electrical signal, thereby significantly improving the system stability of the rubidium atomic clock. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings herein are incorporated into the specification and form a part of the specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0018] Figure 1 is a schematic structural diagram of the rubidium atomic clock based on velocity grating spectrum provided by the embodiments of the present application;

[0019] Figure 2 is a schematic flow diagram of the implementation method of the rubidium atomic clock based on velocity grating spectrum provided by the embodiments of the present application.

[0020] 1 - Multi-frequency coherent laser source; 2 - Polarizing beam splitter prism; 3 - Lens group; 4 - Rubidium cell; 5 - Microwave resonator; 6 - Photoelectric tube; 7 - Lock-in amplifier; 8 - Integral amplification module; 9 - Crystal oscillator; 10 - Frequency synthesizer; 11 - Phase-frequency modulation module; 12 - Laser frequency stabilization 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 drawings and text 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 this application, the solutions of the prior art will be introduced in detail first. The time unit is one of the seven basic units defined in the International System of Units. Atomic clocks are the most fundamental applications for measuring time and frequency standards currently. Countries around the world are committed to developing atomic clocks with higher performance. Rubidium atomic clocks have the advantages of being structurally compact, easy to carry, and easy to engineer compared to other atomic clocks, and have been widely used in fields such as communication and navigation. According to the types of pumping light sources of rubidium atomic clocks, rubidium atomic clocks are divided into spectral lamp pumped rubidium atomic clocks and laser pumped rubidium atomic clocks. The technology of spectral lamp rubidium atomic clocks has been relatively mature, but the light power density of the spectral lamp is low and the frequency is unstable, and the pumping efficiency is limited, resulting in an atomic utilization rate of only a few thousandths in the physical system, restricting the further improvement of stability. By using laser pumping, the pumping laser frequency can be maintained at a high stability by stabilizing the frequency of the laser, and at the same time, the laser has the characteristics of good monochromaticity and high optical power spectral density, which helps to improve the pumping efficiency. The way of laser pumping improves the short-term stability performance of rubidium atomic clocks, but due to the narrow linewidth of the laser source of traditional laser pumped rubidium clocks, the output laser only contains one frequency component, so only zero-velocity atoms can be pumped to the upper energy level to participate in the action of the electrical signal, and most of the rubidium atoms in the rubidium cell are not utilized, so to a certain extent, it limits the signal-to-noise ratio of the electrical signal, thus restricting the system stability of rubidium atomic clocks.

[0025] To address the above technical problems, the inventors thought of using a multi-frequency coherent laser as the laser source, and generating a laser signal containing a velocity grating spectrum by performing multi-frequency modulation or pulse modulation on the multi-frequency coherent laser source, which can interact with rubidium atoms in different velocity groups, enabling more rubidium atoms to participate in the contribution to the electrical signal, thereby significantly improving the system stability of rubidium atomic clocks.

[0026] Reference Figure 1 , Figure 1 is the structural schematic diagram of the rubidium atomic clock based on the velocity grating spectrum provided by the embodiment of this application. As Figure 1 shown, the rubidium atomic clock includes: a multi-frequency coherent laser source (1), a polarization beam splitter prism (2), a lens group (3), a rubidium cell (4), a microwave resonator (5), a phototube (6), a lock-in amplifier (7), an integration and amplification module (8), a crystal oscillator (9), a frequency synthesizer (10), a phase and frequency modulation module (11), and a laser frequency stabilization module (12).

[0027] Among them, the multi-frequency coherent laser source (1) is located before the polarization beam splitter prism (2) and is used to transmit the laser signal containing velocity grating spectrum information to the polarization beam splitter prism (2).

[0028] Among them, the velocity grating spectrum information is obtained by multi-frequency modulation of the multi-frequency coherent laser source (1), or by pulse modulation, or by other means. The multi-frequency coherent laser source (1) is not limited to an external cavity laser, a DFB laser (Distributed Feedback Laser), a DBR laser (Distributed Bragg Reflector Laser), or other types of lasers.

[0029] Specifically, the multi-frequency coherent laser source (1) is in the starting position in the entire optical path of the rubidium atomic clock system. The core function of the multi-frequency coherent laser source (1) is to generate a laser signal containing velocity grating spectrum information. This laser signal has the characteristics of multiple frequencies and coherence, and is transmitted along the optical path to the polarization beam splitter prism (2).

[0030] The polarization beam splitter prism (2) is adjacent to the lens group (3) and the laser frequency stabilization module (12), and is used to divide the laser signal into two paths, namely a transmitted beam and a reflected beam. The reflected beam is incident on the laser frequency stabilization module (12) for laser frequency stabilization.

[0031] Among them, the laser frequency stabilization module (12) adopts saturated absorption spectrum frequency stabilization, or modulation transfer spectrum frequency stabilization, or compact PDH frequency stabilization (Pound-Drever-Hall frequency stabilization), or other laser frequency stabilization schemes.

[0032] Specifically, after receiving the laser signal from the multi-frequency coherent laser source (1), the polarization beam splitter prism (2) divides the laser signal into two paths, namely a transmitted beam and a reflected beam, according to its own optical characteristics. At the same time, the reflected beam will be incident on the laser frequency stabilization module (12), and the laser frequency stabilization module (12) performs laser frequency stabilization operations on the reflected beam to ensure the frequency stability of the reflected light beam.

[0033] Among them, the reflected beam is incident on the laser frequency stabilization module (12) by a spatial light method using a mirror behind, or is coupled into an optical fiber and then transmitted to the laser frequency stabilization module (12).

[0034] The lens group (3) is adjacent to the rubidium cell (4) and is used to inject the transmitted beam into the rubidium cell (4) and interact with rubidium atoms.

[0035] Among them, the rubidium cell (4) is filled with rubidium atoms and an inert gas, and the inert gas serves as a buffer gas.

[0036] Among them, the inert gas is neon or argon, or other gases.

[0037] In this embodiment, the lens group (3) includes a first lens and a second lens. The first lens is used to expand the transmitted beam, and the second lens is used to collimate the expanded transmitted beam so that the expanded transmitted beam is collimated and becomes parallel light.

[0038] Specifically, the lens group (3) performs operations such as expanding and collimating the transmitted beam transmitted from the polarization beam splitter prism (2), so that the transmitted beam can enter the rubidium cell (4) with a preset beam quality and size. When the transmitted beam enters the rubidium cell (4), it will interact with the rubidium atoms in the rubidium cell (4). Through the interaction between the transmitted beam and the rubidium atoms, the energy level transition of the rubidium atoms is excited, thereby generating a signal related to the atomic energy level.

[0039] The microwave resonator (5) surrounds the rubidium cell (4) and is used to provide a stable electromagnetic field for the rubidium cell (4).

[0040] Specifically, the microwave resonator (5) can generate an electromagnetic field with a specific frequency and intensity, so that the rubidium atoms in the rubidium cell (4) are in a stable electromagnetic environment, promoting the rubidium atoms to undergo energy level transitions according to specific laws, thereby ensuring that the entire rubidium atomic clock system can operate stably and accurately. By precisely controlling the electromagnetic field parameters of the microwave resonator (5), precise adjustment and locking of the frequency of the rubidium atomic clock can be achieved.

[0041] The rubidium cell (4) is adjacent to the phototube (6) and is used to ensure that the optical signal emitted from the rubidium cell (4) can be received by the phototube (6).

[0042] Specifically, when the transmitted beam interacts with the rubidium atoms in the rubidium cell (4), an optical signal carrying information about the energy level transition of the rubidium atoms is generated. The rubidium cell (4) is adjacent to the phototube (6) to ensure that the optical signal emitted from the rubidium cell (4) can be efficiently received by the phototube (6). The phototube (6) is used as a detector of the optical signal, and its core function is to detect the transition spectrum line of the rubidium atoms and convert the received optical signal into an electrical signal, which contains the frequency information of the energy level transition of the rubidium atoms.

[0043] The output end of the phototube (6) is electrically connected to the input end of the lock-in amplifier (7). The phototube (6) is used to detect the transition spectrum line and convert the transition spectrum line from an optical signal into an electrical signal.

[0044] Specifically, after the phototube (6) converts the detected rubidium atomic transition spectral line from an optical signal into an electrical signal, it transmits the electrical signal to the phase-locked amplifier (7). The phase-locked amplifier (7) plays a role in demodulating the electrical signal in the system. Since the electrical signal may contain various noises and interferences, the phase-locked amplifier (7) can use its own phase-locking technology to extract useful frequency information from the complex signal and perform demodulation processing on the electrical signal. The demodulated signal can more accurately reflect the energy level transition frequency of rubidium atoms.

[0045] The output end of the phase-locked amplifier (7) is electrically connected to the integration amplification module (8) and the crystal oscillator (9) in sequence. The phase-locked amplifier (7) is used to demodulate the electrical signal output by the phototube and output it to the integration amplification module (8). The integration amplification module (8) converts the DC voltage into a linearly increasing voltage and transmits the linearly increasing voltage to the crystal oscillator (9).

[0046] Specifically, after the crystal oscillator (9) receives the linearly increasing voltage from the integration amplification module (8), it generates an initial microwave signal according to the voltage signal.

[0047] The output end of the crystal oscillator (9) is electrically connected to the frequency synthesizer (10) and the phase modulation module (11) in sequence. The crystal oscillator (9) is used to provide an initial microwave signal. After the initial microwave signal is frequency-multiplied by the frequency synthesizer (10), a microwave signal corresponding to 87 the Rb atomic hyperfine energy level transition frequency is generated. The microwave signal is modulated by the phase-frequency modulation module (11) to obtain an error signal for feedback control.

[0048] Among them, the initial microwave signal is usually a common standard frequency, which is 5 MHz or 10 MHz. 87 The microwave frequency signal of the Rb atomic hyperfine energy level transition is a 6.8 GHz microwave frequency signal.

[0049] Specifically, the initial microwave signal generated by the crystal oscillator (9) is first transmitted to the frequency synthesizer (10). The role of the frequency synthesizer (10) is to perform frequency multiplication on the initial microwave signal. Through a series of frequency synthesis technologies, the frequency of the initial microwave signal is increased to the microwave signal required for the 87 Rb atomic hyperfine energy level transition. This microwave signal has an accurate frequency value and can meet the requirements of the rubidium atom energy level transition in the rubidium atomic clock system. Then, this microwave frequency signal will be transmitted to the phase modulation module, and the phase modulation module modulates the microwave frequency signal to generate an error signal for feedback control.

[0050] The phase modulation module (11) is connected to the microwave resonator (5) via a line and is used to transmit the error signal to the microwave resonator (5). The microwave resonator (5) adjusts the electromagnetic field according to the error signal to stably lock the rubidium atomic clock.

[0051] Specifically, the phase modulation module transmits the error signal obtained after modulation processing to the microwave resonator (5) via a line. After receiving the error signal, the microwave resonator (5) adjusts the electromagnetic field generated by itself according to the error signal. If the error signal indicates that the current frequency of the system deviates from the target frequency, the microwave resonator (5) will correspondingly change parameters such as the frequency and intensity of the electromagnetic field, causing the transition frequency of the rubidium atoms in the rubidium cell (4) to change, so that the frequency of the entire rubidium atomic clock system approaches the target frequency, and finally realizes the stable locking of the rubidium atomic clock, ensuring that the rubidium atomic clock can operate accurately and stably.

[0052] As can be seen from the above embodiments, by using a multi-frequency coherent laser as the laser source and generating a laser signal containing a velocity grating spectrum through multi-frequency modulation or pulse modulation of the multi-frequency coherent laser source, it can interact with rubidium atoms in different velocity groups, enabling more rubidium atoms to participate in the contribution to the electrical signal, thereby greatly improving the system stability of the rubidium atomic clock.

[0053] On the basis of this embodiment, the periphery of the microwave resonator (5) further includes a heating and cooling device, a heat preservation device, and a thermistor. Among them, the heating and cooling device and the heat preservation device work together to ensure that the temperature of the rubidium cell (4) is constant, and the thermistor is used to measure the operating temperature of the rubidium cell (4).

[0054] In summary, due to the extremely sensitive energy level characteristics of rubidium atoms to temperature, temperature fluctuations will directly affect the transition frequency of rubidium atoms. The heating and cooling device and the heat preservation device work together to ensure that the temperature of the rubidium cell is constant, enabling the rubidium atoms to always be in a stable energy level state, ensuring the stability and accuracy of the output frequency of the rubidium atomic clock, reducing the frequency drift error caused by temperature changes, and thus improving the timing accuracy of the entire system.

[0055] On the basis of this embodiment, the rubidium atomic clock further includes a half-wave plate, which is placed before the polarization beam splitter prism (2) and is closely adjacent to the multi-frequency coherent laser source (1) and the polarization beam splitter prism (2), and is used to adjust the intensity of the laser signal.

[0056] In summary, when the rubidium atomic clock is working, different experimental stages or measurement requirements may have different requirements for the laser intensity. The half-wave plate can change the polarization state of the laser by rotation, thereby adjusting the intensity of the laser signal.

[0057] Figure 2Schematic flow chart of the implementation method of a rubidium atomic clock based on a velocity grating spectrum provided by an embodiment of the present application, as Figure 2 shown, the implementation method of the rubidium atomic clock includes:

[0058] S201: Modulate a multi-frequency coherent laser source to obtain a laser signal containing velocity grating spectrum information, and divide the laser signal into two paths through a polarization beam splitter prism, one path is the reflected beam and the other path is the transmitted beam.

[0059] S202: The reflected beam is incident on the laser frequency stabilization module to stabilize the frequency of the multi-frequency coherent laser source.

[0060] S203: The transmitted beam is expanded and collimated through a lens group and is incident on the rubidium cell to interact with rubidium atoms. At the same time, a microwave resonator provides an electromagnetic field to stimulate the energy level transition of rubidium atoms in the rubidium cell.

[0061] S204: A phototube detects the transition spectral line, converts the transition spectral line from an optical signal into an electrical signal, and transmits the electrical signal to a lock-in amplifier, so that the lock-in amplifier demodulates the electrical signal and outputs it to an integration and amplification module.

[0062] S205: The integration and amplification module converts the demodulated DC voltage into a linearly increasing voltage and transmits the linearly increasing voltage to a crystal oscillator.

[0063] S206: The crystal oscillator generates an initial microwave signal, and generates a microwave signal corresponding to the 87 hyperfine energy level transition frequency of Rb atoms after frequency doubling processing by a frequency synthesizer.

[0064] S207: The microwave signal is modulated through a phase-frequency modulation module to obtain an error signal for feedback control, and the error signal is transmitted to the microwave resonator.

[0065] S208: The microwave resonator adjusts the electromagnetic field according to the error signal to stably lock the rubidium atomic clock.

[0066] In summary, it can be seen that by using the laser output from the multi-frequency coherent laser source containing velocity grating spectrum information as the pumping laser, which replaces the single-frequency component laser source used in traditional laser-pumped rubidium clocks, a rubidium atomic clock based on a velocity grating spectrum is realized. In the embodiment of the present application, a laser signal containing a velocity grating spectrum is generated by performing multi-frequency modulation or pulse modulation on the multi-frequency coherent laser source, which can interact with rubidium atoms in different velocity groups, enabling more rubidium atoms to participate in the contribution to the electrical signal, doubling the signal-to-noise ratio of the signal, and thus achieving a nearly order-of-magnitude improvement in the system stability of the rubidium atomic clock.

[0067] In the above embodiments, the descriptions of the various embodiments each have their own emphasis. 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.

[0068] 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 knowledge or conventional technical means in the technical field not disclosed in the present application. The specification and the embodiments are only regarded as exemplary, and the true scope and spirit of the present application are pointed out by the following claims.

[0069] It should be understood that the present application is not limited to the exact structures described above 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 rubidium atomic clock based on a velocity grating spectrum, characterized in that, Comprising: A multi-frequency coherent laser source, a polarization beam splitter prism, a lens group, a rubidium cell, a microwave resonator, a phototube, a lock-in amplifier, an integration amplifier module, a crystal oscillator, a frequency synthesizer, a phase-frequency modulation module, and a laser frequency stabilization module; Wherein, the multi-frequency coherent laser source is located before the polarization beam splitter prism and is used to transmit a laser signal containing velocity grating spectrum information to the polarization beam splitter prism; The polarization beam splitter prism is adjacent to the lens group and the laser frequency stabilization module and is used to split the laser signal into two paths, namely a transmitted beam and a reflected beam. The reflected beam is incident on the laser frequency stabilization module for laser frequency stabilization; The lens group is adjacent to the rubidium cell and is used to transmit the transmitted beam into the rubidium cell and interact with rubidium atoms; The microwave resonator surrounds the rubidium cell and is used to provide a stable electromagnetic field for the rubidium cell; The rubidium cell is adjacent to the phototube and is used to ensure that the optical signal emitted from the rubidium cell can be received by the phototube; The output end of the phototube is electrically connected to the input end of the lock-in amplifier. The phototube is used to detect the transition spectral line and convert the transition spectral line from an optical signal into an electrical signal; The output end of the lock-in amplifier is electrically connected to the integration amplifier module and the crystal oscillator in sequence. The lock-in amplifier is used to demodulate the electrical signal output by the phototube and output it to the integration amplifier module. The integration amplifier module converts a DC voltage into a linearly increasing voltage and transmits the linearly increasing voltage to the crystal oscillator; The output end of the crystal oscillator is electrically connected to the frequency synthesizer and the phase modulation module in sequence. The crystal oscillator is used to provide an initial microwave signal, and after frequency multiplication processing by the frequency synthesizer, the initial microwave signal generates a microwave signal corresponding to 87 the microwave signal of the Rb atomic hyperfine level transition frequency. After being modulated by the phase-frequency modulation module, the microwave signal obtains an error signal for feedback control; The phase modulation module is connected to the microwave resonator through a circuit and is used to transmit the error signal to the microwave resonator. The microwave resonator adjusts the electromagnetic field according to the error signal to stably lock the rubidium atomic clock.

2. The rubidium atomic clock according to claim 1, wherein The lens group includes a first lens and a second lens; The first lens is used to expand the transmitted beam; The second lens is used to collimate the expanded transmitted beam so that the expanded transmitted beam becomes parallel light.

3. The rubidium atomic clock according to claim 1, characterized in that, The periphery of the microwave resonator further includes a heating and cooling device, a heat insulation device, and a thermistor; Wherein, the heating and cooling device and the heat insulation device work together to ensure that the temperature of the rubidium cell is constant; The thermistor is used to measure the operating temperature of the rubidium cell.

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

5. The rubidium atomic clock according to claim 4, characterized in that, The multi-frequency coherent laser source is an external cavity laser or a DFB laser or a DBR laser or other types of lasers.

6. The rubidium atomic clock according to claim 1, characterized in that, The laser frequency stabilization module adopts saturated absorption spectrum frequency stabilization or modulation transfer spectrum frequency stabilization or compact PDH frequency stabilization.

7. The rubidium atomic clock according to claim 1, characterized in that, Also includes a half-wave plate; The half-wave plate is placed before the polarization beam splitter prism and is closely adjacent to the multi-frequency coherent laser source and the polarization beam splitter prism, and is used to adjust the intensity of the laser signal.

8. The rubidium atomic clock according to any one of claims 1 to 7, characterized in that, The rubidium cell is filled with rubidium atoms and an inert gas, and the inert gas serves as a buffer gas.

9. The rubidium atomic clock according to claim 1, wherein The initial microwave signal is 5 MHz or 10 MHz; the microwave frequency signal for the hyperfine level transition of 87Rb atoms is a 6.8 GHz microwave frequency signal.

10. A method for implementing a rubidium atomic clock based on a velocity grating spectrum, characterized in that, Applied to the rubidium atomic clock according to any one of claims 1 to 9, comprising: Modulating the multi-frequency coherent laser source to obtain the laser signal containing velocity grating spectrum information, and splitting the laser signal into two paths through the polarization beam splitter prism, one path is the reflected beam and the other path is the transmitted beam; The reflected beam is incident on the laser frequency stabilization module to perform laser frequency stabilization on the multi-frequency coherent laser source; The transmitted beam is expanded and collimated through the lens group and is incident on the rubidium cell to interact with the rubidium atoms. At the same time, the microwave resonator provides an electromagnetic field to stimulate the rubidium atoms in the rubidium cell to undergo energy level transitions; The phototube detects the transition spectral line, converts the transition spectral line from an optical signal into an electrical signal, and transmits the electrical signal to the lock-in amplifier, so that the lock-in amplifier demodulates the electrical signal and outputs it to the integration and amplification module; The integration and amplification module converts the demodulated DC voltage into the linearly increasing voltage and transmits the linearly increasing voltage to the crystal oscillator; The crystal oscillator generates the initial microwave signal, and after frequency multiplication processing by the frequency synthesizer, generates a corresponding 87 microwave signal at the hyperfine level transition frequency of Rb atoms; The microwave signal is modulated through the phase-frequency modulation module to obtain an error signal for feedback control, and the error signal is transmitted to the microwave resonator; The microwave resonator adjusts the electromagnetic field according to the error signal to stably lock the rubidium atomic clock.

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