Rubidium atomic clock based on velocity grating spectrum and its implementation method

Abstract

This application provides a rubidium atomic clock based on a velocity grating spectrum and its implementation method. The method includes: a multi-frequency coherent laser source emitting a laser signal containing a velocity grating spectrum, which is split into two paths by a polarization beam splitter; the reflected beam is injected into a laser frequency stabilization module to achieve laser frequency stabilization; the transmitted beam is injected into a rubidium bulb through a lens group to interact with rubidium atoms; a phototube detects transition spectral lines, converts the transition spectral lines from optical signals to electrical signals, and transmits them to a lock-in amplifier for demodulation; an integral amplification module converts the demodulated DC voltage into a linearly increasing voltage and transmits it to a crystal oscillator; the crystal oscillator generates an initial microwave signal and generates a frequency synthesizer. 87 The microwave signal corresponding to the Rb atom; the phase-frequency modulation module modulates the microwave signal to obtain an error signal, which is then transmitted to the microwave resonant cavity to adjust the electromagnetic field according to the error signal, thereby stabilizing and locking the rubidium atomic clock. This method is used to improve the stability of the rubidium atomic clock system.

Description

Technical Field

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

[0002] The atomic clock is one of the seven base units defined by the International System of Units (SI). It is the fundamental application of the current standard for measuring time and frequency, and countries around the world are working to develop higher-performance atomic clocks.

[0003] In existing technologies, rubidium atomic clocks have advantages over other atomic clocks, such as compact structure, portability, and ease of engineering, and have been widely used in communication, navigation, and other fields. Rubidium atomic clocks are divided into spectral lamp-pumped rubidium atomic clocks and laser-pumped rubidium atomic clocks.

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

[0005] This application provides a rubidium atomic clock based on velocity grating spectrum and its implementation method, which can improve the stability of the rubidium atomic clock system.

[0006] In a first aspect, embodiments of this application provide a rubidium atomic clock based on a velocity grating spectrum, comprising: a multi-frequency coherent laser source, a polarizing beam splitter, a lens group, a rubidium bulb, a microwave resonant cavity, a phototube, a lock-in amplifier, an integrating 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 polarizing beam splitter and is used to transmit the laser signal containing velocity grating spectrum information to the polarizing beam splitter; the polarizing beam splitter 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 being injected into the laser frequency stabilization module for laser frequency stabilization; the lens group is adjacent to the rubidium bulb and is used to inject the transmitted beam into the rubidium bulb and interact with the rubidium atoms; the microwave resonant cavity surrounds the rubidium bulb and is used to provide rubidium... The bulb provides a stable electromagnetic field; the rubidium bulb is adjacent to the phototube to ensure that the light signal emitted from the rubidium bulb can be received by the phototube; the output of the phototube is electrically connected to the input of the lock-in amplifier. The phototube is used to detect transition lines and convert the transition lines from optical signals to electrical signals; the output of the lock-in amplifier is electrically connected in sequence to the integrating amplifier module and the crystal oscillator. The lock-in amplifier is used to demodulate the electrical signal output by the phototube and output it to the integrating amplifier module. The integrating amplifier module converts the DC voltage into a linearly increased voltage and transmits the linearly increased voltage to the crystal oscillator; the output of the crystal oscillator is electrically connected in sequence to the frequency synthesizer and the phase modulation module. The crystal oscillator is used to provide the initial microwave signal. The initial microwave signal is frequency multiplied by the frequency synthesizer to generate the corresponding phase modulation module. 87 The microwave signal of the hyperfine energy level transition frequency of Rb atoms is modulated by a phase frequency modulation module to obtain an error signal for feedback control. The phase modulation module is connected to the microwave resonant cavity through a line to transmit the error signal to the microwave resonant cavity. The microwave resonant cavity adjusts the electromagnetic field according to the error signal to stabilize and lock the rubidium atomic clock.

[0007] In one possible implementation, 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 it becomes parallel light.

[0008] In one possible implementation, the microwave resonant cavity periphery also 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 bulb is constant; the thermistor is used to measure the operating temperature of the rubidium bulb.

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

[0010] In one 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 one possible implementation, the laser frequency stabilization module employs saturated absorption spectrum stabilization, modulation transfer spectrum stabilization, or compact PDH stabilization.

[0012] In one possible implementation, a half-wave plate is also included; the half-wave plate is placed in front of the polarizing beam splitter and closely adjacent to the multi-frequency coherent laser source and the polarizing beam splitter, for adjusting the intensity of the laser signal.

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

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

[0015] Secondly, embodiments of this application provide a method for implementing a rubidium atomic clock based on a velocity grating spectrum, applicable to the rubidium atomic clock in the first aspect and various possible embodiments of the first aspect, comprising: modulating a multi-frequency coherent laser source to obtain a laser signal containing velocity grating spectrum information; splitting the laser signal into two paths, one a reflected beam and the other a transmitted beam, by a polarizing beam splitter; the reflected beam is injected into a laser frequency stabilization module to stabilize the multi-frequency coherent laser source; the transmitted beam is expanded and collimated by a lens group and injected into a rubidium bulb to interact with rubidium atoms, while a microwave resonant cavity provides an electromagnetic field to excite rubidium atoms in the rubidium bulb to undergo energy level transitions; a phototube detects the transition spectrum lines and converts the transition spectrum lines from optical signals to electrical signals, and transmits the electrical signals to a lock-in amplifier so that the lock-in amplifier demodulates the electrical signals and outputs them to an integrating amplifier module; the integrating amplifier 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 corresponding frequency multiplier after frequency multiplication by a frequency synthesizer. 87 The microwave signal is the hyperfine energy level transition frequency of Rb atoms; the microwave signal is modulated by a phase frequency modulation module to obtain an error signal for feedback control, and the error signal is transmitted to the microwave resonant cavity; the microwave resonant cavity adjusts the electromagnetic field according to the error signal to stabilize and lock the rubidium atomic clock.

[0016] The rubidium atomic clock and its implementation method based on velocity grating spectrum provided in this application utilize 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 a velocity grating spectrum is generated. This signal can interact with rubidium atoms of different velocity groups, allowing more rubidium atoms to participate in the contribution to the electrical signal, thereby significantly improving the system stability of the rubidium atomic clock. Attached Figure Description

[0017] 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.

[0018] Figure 1 A schematic diagram of the structure of a rubidium atomic clock based on a velocity grating spectrum provided in this application embodiment;

[0019] Figure 2 This is a flowchart illustrating the implementation method of a rubidium atomic clock based on a velocity grating spectrum provided in an embodiment of this application.

[0020] 1-Multi-frequency coherent laser source; 2-Polarizing beam splitter prism; 3-Lens group; 4-Russian bulb; 5-Microwave resonant cavity; 6-Phototube; 7-Lock-in amplifier; 8-Integrating amplifier module; 9-Crystal oscillator; 10-Frequency synthesizer; 11-Phase frequency modulation module; 12-Laser frequency stabilization 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 technology 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 most fundamental application for measuring time and frequency standards. Countries around the world are committed to developing higher-performance atomic clocks. Compared with other atomic clocks, rubidium atomic clocks have advantages such as compact structure, portability, and ease of engineering, and have been widely used in communication, navigation, and other fields. Based on the type of pump light source, rubidium atomic clocks are divided into spectral lamp-pumped rubidium atomic clocks and laser-pumped rubidium atomic clocks. Spectral lamp rubidium atomic clock technology is relatively mature, but the low power density and unstable frequency of the spectral lamp limit the pumping efficiency, resulting in an atomic utilization rate of only a few thousandths of a percent, which restricts further improvement in stability. Laser pumping, on the other hand, can stabilize the frequency of the pump laser by stabilizing the laser, thus maintaining a high degree of stability. Furthermore, lasers have characteristics such as good monochromaticity and high power spectral density, which help improve pumping efficiency. Laser pumping improves the short-term stability of rubidium atomic clocks. However, because traditional laser-pumped rubidium clocks have narrow laser source linewidths and the output laser contains only one frequency component, only zero-velocity atoms can be pumped to the upper energy level to participate in the electrical signal. Most of the rubidium atoms in the rubidium bulb are not utilized, which limits the signal-to-noise ratio of the electrical signal to a certain extent, thus limiting the system stability of the rubidium atomic clock.

[0025] To address the aforementioned technical problems, the inventors conceived of using multi-frequency coherent lasers as the laser source. By performing multi-frequency modulation or pulse modulation on the multi-frequency coherent laser source, a laser signal containing a velocity grating spectrum is generated. This signal can interact with rubidium atoms of different velocity groups, allowing more rubidium atoms to participate in the contribution to the electrical signal, thereby significantly improving the system stability of the rubidium atomic clock.

[0026] refer to Figure 1 , Figure 1 A schematic diagram of the structure of a rubidium atomic clock based on a velocity grating spectrum provided in an embodiment of this application. Figure 1 As shown, the rubidium atomic clock includes: a multi-frequency coherent laser source (1), a polarization beam splitter (2), a lens group (3), a rubidium bulb (4), a microwave resonant cavity (5), a phototube (6), a lock-in amplifier (7), an integral amplifier module (8), a crystal oscillator (9), a frequency synthesizer (10), a phase frequency modulation module (11), and a laser frequency stabilization module (12).

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

[0028] 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 external cavity lasers, DFB lasers (Distributed Feedback Lasers), DBR lasers (Distributed Bragg Reflector Lasers), or other types of lasers.

[0029] Specifically, the multi-frequency coherent laser source (1) is located at the beginning of the optical path of the entire 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 multi-frequency and coherent characteristics and is transmitted along the optical path to the polarization beam splitter (2).

[0030] The polarizing beam splitter (2) is adjacent to the lens group (3) and the laser frequency stabilization module (12) and is used to split the laser signal into two paths, namely the transmitted beam and the reflected beam. The reflected beam enters 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, modulation transfer spectrum frequency stabilization, 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 polarizing beam splitter (2) splits the laser signal into two paths, namely the transmitted beam and the reflected beam, according to its own optical characteristics. At the same time, the reflected beam enters the laser frequency stabilization module (12), and the laser frequency stabilization module (12) performs laser frequency stabilization operation on the reflected beam to ensure the frequency stability of the reflected beam.

[0033] The reflected beam is either transmitted to the laser frequency stabilization module (12) via a reflector after passing through a spatial light or via a coupled optical fiber.

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

[0035] The rubidium bubble (4) is filled with rubidium atoms and an inert gas, which serves as a buffer gas.

[0036] 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 becomes parallel light.

[0038] Specifically, the lens group (3) performs operations such as beam expansion and collimation on the transmitted beam from the polarizing beam splitter (2), enabling the transmitted beam to enter the rubidium bulb (4) with a preset beam quality and size. When the transmitted beam enters the rubidium bulb (4), it interacts with the rubidium atoms inside the rubidium bulb (4). Through the interaction between the transmitted beam and the rubidium atoms, energy level transitions of the rubidium atoms are excited, thereby generating signals related to the atomic energy levels.

[0039] A microwave resonant cavity (5) surrounds the rubidium bulb (4) to provide a stable electromagnetic field for the rubidium bulb (4).

[0040] Specifically, the microwave resonant cavity (5) can generate an electromagnetic field of a specific frequency and intensity, so that the rubidium atoms in the rubidium bulb (4) are in a stable electromagnetic environment, promoting the energy level transition of the rubidium atoms according to a specific law, thereby ensuring that the entire rubidium atomic clock system can operate stably and accurately. By precisely controlling the electromagnetic field parameters of the microwave resonant cavity (5), the frequency of the rubidium atomic clock can be precisely adjusted and locked.

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

[0042] Specifically, when the transmitted light beam interacts with the rubidium atoms inside the rubidium bulb (4), it generates an optical signal carrying information about the energy level transitions of the rubidium atoms. The rubidium bulb (4) is adjacent to the phototube (6), ensuring that the optical signal emitted from the rubidium bulb (4) can be efficiently received by the phototube (6). As a detector of the optical signal, the phototube (6) has the core function of detecting the transition spectral lines of the rubidium atoms and converting the received optical signal into an electrical signal, which contains the frequency information of the energy level transitions of the rubidium atoms.

[0043] The output terminal of the phototube (6) is electrically connected to the input terminal of the lock-in amplifier (7). The phototube (6) is used to detect transition spectral lines and convert the transition spectral lines from optical signals to electrical signals.

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

[0045] The output of the lock-in amplifier (7) is electrically connected to the integrating amplifier module (8) and the crystal oscillator (9) in sequence. The lock-in amplifier (7) is used to demodulate the electrical signal output by the phototube and output it to the integrating amplifier module (8). The integrating amplifier 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 receiving the linearly increased voltage from the integrating amplifier module (8), the crystal oscillator (9) generates an initial microwave signal based on the voltage signal.

[0047] The output 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 the initial microwave signal. The initial microwave signal is multiplied by the frequency synthesizer (10) to generate the corresponding phase modulation module. 87 The microwave signal of the hyperfine energy level transition frequency of Rb atom is obtained by modulating the microwave signal through the phase frequency modulation module (11) to obtain the error signal used for feedback control.

[0048] The initial microwave signal is usually a commonly used standard frequency, such as 5MHz or 10MHz. 87 The microwave frequency signal for the hyperfine level transition of Rb atoms 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 function of the frequency synthesizer (10) is to perform frequency multiplication on the initial microwave signal, and through a series of frequency synthesis techniques, raise the frequency of the initial microwave signal to the corresponding frequency. 87 The microwave signal required for the hyperfine level transition frequency of Rb atoms. This microwave signal has a precise frequency value that meets the requirements for rubidium atom energy level transitions in the rubidium atomic clock system. Then, this microwave frequency signal is transmitted to a phase modulation module, which modulates the microwave frequency signal to generate an error signal for feedback control.

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

[0051] Specifically, the phase modulation module transmits the error signal obtained after modulation processing to the microwave resonant cavity (5) through the line. After receiving the error signal, the microwave resonant cavity (5) adjusts the electromagnetic field it generates according to the error signal. If the error signal indicates that the current frequency of the system deviates from the target frequency, the microwave resonant cavity (5) will correspondingly change the frequency, intensity and other parameters of the electromagnetic field, so that the transition frequency of the rubidium atom energy level in the rubidium bulb (4) changes, thereby bringing the frequency of the entire rubidium atomic clock system closer to the target frequency, and finally achieving 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 multi-frequency coherent laser as a laser source, and by performing multi-frequency modulation or pulse modulation on the multi-frequency coherent laser source to generate a laser signal containing a velocity grating spectrum, it can interact with rubidium atoms of different velocity groups, so that more rubidium atoms participate in the contribution to the electrical signal, thereby greatly improving the system stability of the rubidium atomic clock.

[0053] Based on this embodiment, the microwave resonant cavity (5) is further surrounded by a heating and cooling device, a heat preservation device, and a thermistor. The heating and cooling device and the heat preservation device work together to ensure that the temperature of the rubidium bulb (4) is constant, and the thermistor is used to measure the operating temperature of the rubidium bulb (4).

[0054] In summary, because the energy level characteristics of rubidium atoms are extremely sensitive to temperature, temperature fluctuations directly affect the transition frequency of rubidium atoms. The heating and cooling devices work in tandem with the insulation devices to ensure a constant temperature of the rubidium bulb, keeping the rubidium atoms in a stable energy level state. This guarantees the stability and accuracy of the rubidium atomic clock's output frequency, reduces frequency drift errors caused by temperature changes, and thus improves the timing accuracy of the entire system.

[0055] Based on this embodiment, the rubidium atomic clock also includes a half-wave plate, which is placed in front of the polarizing beam splitter (2) and closely adjacent to the multi-frequency coherent laser source (1) and the polarizing beam splitter (2) to adjust the intensity of the laser signal.

[0056] In summary, different experimental stages or measurement requirements may necessitate different laser intensity levels during rubidium atomic clock operation. A half-wave plate can be rotated to alter the polarization state of the laser, thereby adjusting the laser signal intensity.

[0057] Figure 2This is a flowchart illustrating the implementation method of a rubidium atomic clock based on a velocity grating spectrum provided in an embodiment of this application. Figure 2 As shown, the implementation method of this rubidium atomic clock includes:

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

[0059] S202: The reflected beam enters 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 by the lens group and enters the rubidium bulb to interact with rubidium atoms. At the same time, the microwave resonant cavity provides an electromagnetic field to excite the rubidium atoms in the rubidium bulb to undergo energy level transitions.

[0061] S204: The phototube detects the transition spectrum line and converts the transition spectrum line from an optical signal to an electrical signal. The electrical signal is then transmitted to the lock-in amplifier, which demodulates the electrical signal and outputs it to the integrating amplifier module.

[0062] S205: The integrating amplifier module converts the demodulated DC voltage into a linearly increased voltage and transmits the linearly increased voltage to the crystal oscillator.

[0063] S206: The crystal oscillator generates the initial microwave signal, which is then multiplied by the frequency synthesizer to generate the corresponding signal. 87 Microwave signals of the hyperfine energy level transition frequency of Rb atoms.

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

[0065] S208: The microwave resonant cavity adjusts the electromagnetic field according to the error signal to stabilize and lock the rubidium atomic clock.

[0066] In summary, by using a multi-frequency coherent laser source to output laser light containing velocity grating spectrum information as the pump laser, the single-frequency component laser source used in traditional laser-pumped rubidium clocks is replaced, thus realizing a rubidium atomic clock based on the velocity grating spectrum. The embodiments of this application generate laser signals containing velocity grating spectra by multi-frequency modulation or pulse modulation of the multi-frequency coherent laser source. These signals can interact with rubidium atoms of different velocity groups, allowing more rubidium atoms to contribute to the electrical signal. This significantly improves the signal-to-noise ratio, resulting in a near-order-of-magnitude improvement in the system stability of the rubidium atomic clock.

[0067] 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.

[0068] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0069] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A rubidium atomic clock based on velocity grating spectrum, characterized in that, include: Multi-frequency coherent laser source, polarization beam splitter, lens group, rubidium bulb, microwave resonant cavity, phototube, lock-in amplifier, integrating amplifier module, crystal oscillator, frequency synthesizer, phase-frequency modulation module and laser frequency stabilization module; The multi-frequency coherent laser source is located in front of the polarization beam splitter and is used to transmit the laser signal containing velocity grating spectrum information to the polarization beam splitter. The polarizing beam splitter 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 enters the laser frequency stabilization module for laser frequency stabilization. The lens group is adjacent to the rubidium bulb and is used to direct the transmitted light beam into the rubidium bulb and interact with the rubidium atoms; The microwave resonant cavity surrounds the rubidium bulb and is used to provide a stable electromagnetic field for the rubidium bulb; The rubidium bulb is adjacent to the phototube, which is used to ensure that the light signal emitted from the rubidium bulb can be received by the phototube; The output terminal of the phototube is electrically connected to the input terminal of the lock-in amplifier. The phototube is used to detect transition spectral lines and convert the transition spectral lines from optical signals to electrical signals. The output terminal of the lock-in amplifier is electrically connected in sequence to the integrating amplifier module and the crystal oscillator. The lock-in amplifier is used to demodulate the electrical signal output by the phototube and output it to the integrating amplifier module. The integrating amplifier module converts the DC voltage into a linearly increased voltage and transmits the linearly increased voltage to the crystal oscillator. The output of the crystal oscillator is electrically connected in sequence to the frequency synthesizer and the phase-frequency modulation module. The crystal oscillator is used to provide an initial microwave signal, which is then multiplied by the frequency synthesizer to generate a corresponding frequency modulation module. 87 The microwave signal of the hyperfine energy level transition frequency of Rb atoms is obtained by the phase frequency modulation module to obtain an error signal for feedback control. The phase-frequency modulation module is connected to the microwave resonant cavity via a line and is used to transmit the error signal to the microwave resonant cavity. The microwave resonant cavity adjusts the electromagnetic field according to the error signal to stabilize and lock the rubidium atomic clock.

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

3. The rubidium atomic clock according to claim 1, characterized in that, The microwave resonant cavity also includes a heating and cooling device, a heat preservation device, and a thermistor. The heating and cooling device and the heat preservation device work together to ensure that the temperature of the rubidium bulb remains constant; The thermistor is used to measure the operating temperature of the rubidium bulb.

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, a DFB laser, or a DBR laser.

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

7. The rubidium atomic clock according to claim 1, characterized in that, It also includes half-wave plates; The half-wave plate is placed in front of the polarizing beam splitter and is closely adjacent to the multi-frequency coherent laser source and the polarizing beam splitter 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 bubble is filled with rubidium atoms and an inert gas, which serves as a buffer gas.

9. The rubidium atomic clock according to claim 1, characterized in that, The initial microwave signal is 5MHz or 10MHz; the microwave frequency signal for the hyperfine level transition of the 87Rb atom is a 6.8GHz 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 as described in any one of claims 1 to 9, comprising: The multi-frequency coherent laser source is modulated to obtain a laser signal containing velocity grating spectrum information. The laser signal is then split into two paths by the polarization beam splitter: one is a reflected beam and the other is 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 light beam is expanded and collimated by the lens group and enters the rubidium bulb to interact with the rubidium atoms. At the same time, the microwave resonant cavity provides an electromagnetic field to excite the rubidium atoms in the rubidium bulb to undergo energy level transitions. The phototube detects the transition spectral line and converts the transition spectral line from an optical signal to an electrical signal. The electrical signal is then transmitted to the lock-in amplifier, which demodulates the electrical signal and outputs it to the integrating amplifier module. The integral amplifier module converts the demodulated DC voltage into the linearly increased voltage, and transmits the linearly increased voltage to the crystal oscillator; The crystal oscillator generates the initial microwave signal, and after frequency multiplication by the frequency synthesizer, a corresponding signal is generated. 87 Microwave signal of the hyperfine energy level transition frequency of Rb atoms; The microwave signal is modulated by the phase-frequency modulation module to obtain an error signal for feedback control, and the error signal is transmitted to the microwave resonant cavity. The microwave resonant cavity adjusts the electromagnetic field according to the error signal to stabilize and lock the rubidium atomic clock.

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