Cesium atomic clock

Abstract

The invention discloses a cesium atomic clock which comprises a laser, an optical pumping cesium beam tube, a frequency multiplier circuit, an error detection servo circuit, a frequency stabilization temperature control circuit, a beat frequency locking circuit, an optical comb, a photoelectric detection circuit and a frequency dividing circuit. According to the cesium atomic clock, the pump laser is locked through the hyperfine energy level of cesium atoms, then the laser is used for locking the optical comb, high-stability, low-phase-noise and low-drift microwave signals of all frequency bands are generated through the repetition frequency of the optical comb, and the technical problem that in the prior art, a cesium atomic clock is poor in stability in the middle and short periods is solved.

Description

Technical Field

[0001] The present application relates to the technical field of precision measurement and time frequency standards, and in particular to a cesium atomic clock. Background Art

[0002] In 1950, Ramsey invented the method of separating the resonant cavity, which can provide the extremely narrow resonant linewidth required for the atomic frequency standard. In 1955, Essen and Parry of the National Physical Laboratory of the United Kingdom developed the first practical cesium atomic clock. In 1967, the "second" was defined according to the transition frequency of 9192631770Hz between two hyperfine energy levels in the ground state of the 133Cs atom. The "zero" drift and excellent long-term stability of the cesium atomic clock have made it an indispensable atomic clock for timekeeping and time service. Over the past few decades, magnetically selected, optically pumped and coherent population trapping (CPT) types of cesium atomic clocks have been vigorously developed, expanding the types of cesium atomic clocks and improving some indicators.

[0003] However, the short- and medium-term stability of magnetically selected, optically pumped, and CPT-type cesium atomic clocks is still relatively poor, nearly an order of magnitude worse than that of hydrogen atomic clocks. If the short- and medium-term stability of cesium atomic clocks can be improved while maintaining the low drift advantage of cesium atomic clocks, the application field of cesium atomic clocks will be greatly expanded. Summary of the invention

[0004] The main purpose of the present application is to provide a cesium atomic clock to solve the problem of poor short- to medium-term stability of cesium atomic clocks in the prior art.

[0005] According to one aspect of the present application, a cesium atomic clock is provided, comprising: a laser, an optically pumped cesium beam tube, a frequency doubling circuit, an error detection servo circuit, a frequency stabilization temperature control circuit, a beat frequency locking circuit, an optical comb, a photoelectric detection circuit, and a frequency division circuit, wherein the laser is connected to the optically pumped cesium beam tube, configured to generate an optical signal, and input the generated optical signal into the optically pumped cesium beam tube; the frequency doubling circuit is connected to the optically pumped cesium beam tube, configured to generate a first microwave signal, and input the first microwave signal into a U-shaped microwave cavity of the optically pumped cesium beam tube; the error detection servo circuit is respectively connected to the optically pumped cesium beam tube, the frequency doubling circuit, and the frequency stabilization temperature control circuit; The optical combs are connected to the lasers respectively and are configured to generate a maximum error signal, and divide the maximum error signal into two signals and input them into the frequency doubling circuit and the frequency stabilization temperature control circuit respectively; the optical combs are connected to the lasers respectively and are configured to generate a second microwave signal using the optical signal injected by the laser; the beat frequency locking circuit is connected to the optical combs and is configured to lock the repetition frequency of the optical combs to the output frequency of the laser; the photoelectric detection circuits are connected to the optical combs and the frequency division circuit respectively and are configured to shape the second microwave signal generated by the optical combs and then input it into the frequency division circuit; the frequency division circuit is configured to perform frequency division processing on the second microwave signal and output a second microwave signal of the target frequency.

[0006] Optionally, the error detection servo circuit is configured to detect the error when the wavelength of the optical signal generated by the laser is the same as the wavelength of the cesium atom from the 6P 3 / 2 Energy level to 6S 1 / 2 The maximum error signal is generated when the transition frequencies of the energy levels are exactly the same.

[0007] Optionally, when the two signals enter the dynamic locking state, the output frequency of the laser is locked to the cesium atom from 6P 3 / 2 Energy level to 6S 1 / 2 On the spectrum line of energy level transition, the optical signal generated by the laser is input into the optical comb; the optical comb generates multiple spectral lines with fixed frequency intervals, and when the optical signal input by the laser interacts with one of the multiple spectral lines generated by the optical comb, a beat signal is generated, wherein the frequency of the beat signal is equal to the frequency difference between the two interacting light beams; a beat locking circuit is configured to detect and analyze the beat signal, generate a locking voltage according to the analysis result of the beat signal, and use the locking voltage to control the voltage-controlled components inside the optical comb to lock the repetition frequency of the optical comb to the output frequency of the laser.

[0008] Optionally, the photoelectric detection circuit is further configured to detect the repetition frequency of the optical comb, and select the nonlinear harmonic order of the repetition frequency according to the frequency size requirement of the final output microwave signal.

[0009] Optionally, the optically pumped cesium beam tube is configured to determine the frequency of the first microwave signal by detecting the interaction between the first microwave signal and cesium atoms in the U-shaped microwave cavity to provide a time reference.

[0010] Optionally, the optically pumped cesium beam tube is a cesium beam tube having a pump and a detector with the same light source structure.

[0011] Optionally, the frequency of the first microwave signal is 9.19 GHz, wherein the frequency doubling circuit generates the first microwave signal in one of the following ways: using a crystal oscillator of a preset frequency to generate a crystal oscillator signal of a preset frequency, and multiplying the crystal oscillator signal to a first microwave signal of 9.19 GHz; or using a 9.19 GHz dielectric oscillator and a crystal oscillator to lock the first microwave signal.

[0012] Optionally, the laser is a 852.1 nm semiconductor laser.

[0013] In this application, a new type of cesium atomic clock is proposed, which uses the hyperfine energy level of cesium atoms to lock the pump laser, and then uses the laser to lock the optical comb, and uses the repetition frequency of the optical comb to generate microwave signals of various frequency bands with high stability, low phase noise and low drift. It can improve the medium- and short-term stability of the output frequency under the condition of ensuring the low drift of the cesium atomic clock, and can generate microwave signals of various frequencies, which is convenient for users to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0015] Figure 1 It is a schematic diagram of the structure of a cesium atomic clock according to an embodiment of the present application. DETAILED DESCRIPTION

[0016] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0017] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0018] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0019] In order to better understand the embodiments of the present application, the technical terms involved in the embodiments of the present application are explained as follows:

[0020] Cesium atomic clock: is a very accurate time measurement device that uses the natural vibration frequency of cesium-133 atoms to define the time unit "second". According to the International System of Units, since 1967, the "second" has been defined as 9,192,631,770 times the period of electromagnetic radiation between two hyperfine energy levels of the ground state of cesium-133 atoms. This means that cesium atomic clocks can provide extremely stable and accurate time standards.

[0021] In the related art, the medium- and short-term stability of magnetically selected, optically pumped and CPT-type cesium atomic clocks is still relatively poor, which is nearly an order of magnitude worse than the medium- and short-term stability of hydrogen atomic clocks. In order to solve this problem, the embodiments of the present application provide relevant solutions, which are described in detail below.

[0022] Figure 1 is a schematic diagram of the structure of a cesium atomic clock according to an embodiment of the present application, such as Figure 1 As shown, the cesium atomic clock includes: a laser 1, an optically pumped cesium beam tube 2, a frequency doubling circuit 3, an error detection servo circuit 4, a frequency stabilization temperature control circuit 5, a beat frequency locking circuit 6, an optical comb 7, a photoelectric detection circuit 8 and a frequency division circuit 9, wherein:

[0023] The laser 1 is connected to the optically pumped cesium beam tube 2 , and is configured to generate an optical signal and input the generated optical signal into the optically pumped cesium beam tube 2 .

[0024] A laser is a device that can generate a highly concentrated, monochromatic, and coherent light beam. When using a cesium atomic clock, the optical signal generated by the laser 1 is first injected into the optical pumping cesium beam tube 2.

[0025] According to an optional embodiment of the present application, the laser 1 is a 852.1 nm semiconductor laser.

[0026] The laser 1 preferably uses a 852.1nm semiconductor laser as the pump and detection light source in the optically pumped cesium beam tube 2, based on the specific optical transition characteristics of cesium atoms and the performance advantages of semiconductor lasers. The following are the reasons for selecting a 852.1nm semiconductor laser:

[0027] 1) The D2 line transition of cesium-133 atoms occurs at 6S 1 / 2 To 6P 3 / 2 The corresponding wavelength is 852.1nm. This transition is a very strong optical transition and is very suitable for optical pumping and detection.

[0028] 2) The 852.1nm light is a perfect match to the D2 line transition of cesium atoms, enabling efficient excitation and detection.

[0029] Semiconductor lasers have the following advantages:

[0030] Compactness: Semiconductor lasers are small in size and light in weight, making them suitable for integration into precision instruments.

[0031] High stability: Modern semiconductor lasers have good frequency stability and power stability, suitable for long-term operation.

[0032] Tuning range: Many semiconductor lasers can be tuned via temperature or current to fine-tune their output frequency to precisely match the transition frequency of cesium atoms.

[0033] Low power consumption: Compared with other types of lasers, semiconductor lasers generally have lower power consumption, making them suitable for portable and low-power applications.

[0034] The frequency doubling circuit 3 is connected to the optically pumped cesium beam tube 2 , and is configured to generate a first microwave signal and input the first microwave signal into the U-shaped microwave cavity of the optically pumped cesium beam tube 2 .

[0035] The frequency doubling circuit 3 is used in the cesium atomic clock system to generate a 9.19 GHz microwave signal (ie, the first microwave signal mentioned above), which is then fed into the U-shaped microwave cavity in the optically pumped cesium beam tube 2 to interact with the hyperfine energy levels of cesium atoms.

[0036] The frequency multiplication circuit 3 converts a lower frequency input signal into a higher frequency output signal by using a frequency multiplier. For example, if the input signal is 4.595 GHz, then a 9.19 GHz output signal can be obtained by doubling the frequency. The frequency 9.19 is selected because it corresponds to the transition frequency between the ground state hyperfine energy levels of the cesium-133 atom.

[0037] As an optional embodiment of the present application, the optically pumped cesium beam tube 2 is configured to determine the frequency of the first microwave signal by detecting the interaction between the first microwave signal and cesium atoms in the U-shaped microwave cavity to provide a time reference.

[0038] There is a U-shaped microwave cavity in the optically pumped cesium beam tube 2 for providing a uniform and stable electromagnetic field environment. This electromagnetic field interacts with the cesium atoms passing through the cesium beam tube.

[0039] When a 9.19 GHz microwave signal passes through the U-shaped microwave cavity, if its frequency is exactly equal to the transition frequency between the hyperfine energy levels of cesium atoms, the cesium atoms will absorb the microwave energy and transition from one energy level to another. This absorption phenomenon can be measured by detecting the state change of cesium atoms.

[0040] The 9.19 GHz microwave signal generated by the frequency doubling circuit 3 is fed into the U-shaped cavity in the optically pumped cesium beam tube 2, and interacts with the hyperfine energy levels of cesium atoms. By detecting this interaction, the microwave frequency can be accurately determined and its long-term stability can be maintained through a feedback control mechanism. This process is one of the core technologies for achieving high-precision time measurement of cesium atomic clocks. In this way, cesium atomic clocks can provide extremely stable and accurate time references, which are widely used in scientific research, navigation and positioning systems, communications and other fields.

[0041] According to an optional embodiment of the present application, the optically pumped cesium beam tube 2 is a cesium beam tube having a same light source structure for pumping and detecting.

[0042] When designing and selecting optically pumped cesium beam tubes, using the same light source structure for pumping and detection can reduce system complexity, reduce hardware costs, and simplify system integration. At the same time, it reduces the need for synchronization and calibration between different light sources and improves system reliability and stability.

[0043] According to another optional embodiment of the present application, the frequency of the first microwave signal is 9.19 GHz, wherein the frequency multiplication circuit 3 generates the first microwave signal in one of the following ways: using a crystal oscillator of a preset frequency to generate a crystal oscillator signal of a preset frequency, and multiplying the crystal oscillator signal to a first microwave signal of 9.19 GHz; or using a 9.19 GHz dielectric oscillator and a crystal oscillator to lock the first microwave signal.

[0044] The frequency multiplication circuit 3 can generate a 9.19 GHz microwave signal in a variety of ways. In the embodiments of the present application, the following two methods for generating a 9.19 GHz microwave signal are provided:

[0045] Method 1: Use a high-stability 10MHz quartz crystal oscillator as a reference source. Quartz crystal oscillators have very high frequency stability and low phase noise. Use a series of frequency multipliers (such as doublers, quadruplers, etc.) to gradually multiply the 10MHz signal to 9.19GHz. For example, you can first multiply 10MHz to 20MHz, then to 40MHz, and so on, until you reach 9.19GHz.

[0046] Each frequency multiplication will introduce a certain amount of power loss and phase noise, so appropriate amplification and filtering are required at each step to maintain signal quality. In the frequency multiplication process, a phase locked loop (PLL) is usually used to ensure the frequency stability and phase consistency of the output signal. PLL compares the phase difference between the output signal and the reference signal and adjusts the frequency of the multiplier to maintain the stability of the output signal.

[0047] Method 2: Use a dielectric oscillator (such as a dielectric resonator oscillator or a dielectric cavity oscillator) that works directly at 9.19 GHz. Dielectric oscillators have high Q values ​​and good frequency stability, but their long-term stability may not be as good as that of quartz crystal oscillators. Therefore, the output of the 9.19 GHz dielectric oscillator is compared with the output of a 10 MHz quartz crystal oscillator, and frequency locking is achieved through a phase-locked loop (PLL).

[0048] The error detection servo circuit 4 is connected to the optically pumped cesium beam tube 2, the frequency doubling circuit 3 and the frequency stabilization temperature control circuit 5 respectively, and is configured to generate a maximum error signal and divide the maximum error signal into two signals which are input into the frequency doubling circuit 3 and the frequency stabilization temperature control circuit 5 respectively.

[0049] According to an optional embodiment of the present application, the error detection servo circuit 4 is configured to detect the wavelength of the optical signal generated by the laser 1 and the wavelength of the cesium atom from 6P 3 / 2 Energy level to 6S 1 / 2 The maximum error signal is generated when the transition frequencies of the energy levels are exactly the same.

[0050] When the wavelength of the optical signal generated by laser 1 is close to the cesium atom hyperfine level 6P 3 / 2 To 6S 1 / 2 When the fine energy levels are completely consistent, the maximum error signal can be obtained in the error detection servo circuit 4. The signal is divided into two paths. One path is input into the frequency multiplication circuit 3 to control the crystal oscillator in the frequency multiplication circuit 3 to improve the stability of the output microwave; the other path is input into the frequency stabilization temperature control circuit 5 to control the temperature of the laser and the wavelength of the generated signal.

[0051] When the wavelength of laser 1 matches the wavelength of the cesium atoms from 6P 3 / 2 Energy level to 6S 1 / 2When the transition frequencies between energy levels match, the maximum error signal can be obtained in the error detection servo circuit 4. This is because the laser and the cesium atom have the best resonance absorption at this time, making the system response most sensitive. Through such a feedback mechanism, it can be ensured that the laser frequency is stable near the target value for a long time, which is crucial for the cesium atomic clock to maintain high-precision time measurement.

[0052] The optical combs 7 are respectively connected to the lasers 1 and are configured to generate a second microwave signal using the optical signal injected by the lasers 1 .

[0053] An optical frequency comb (or light comb for short) is a special laser source that can generate a series of equally spaced discrete frequency lines that cover a wide spectral range.

[0054] The beat frequency locking circuit 6 is connected to the optical comb 7 and is configured to lock the repetition frequency of the optical comb 7 to the output frequency of the laser 1 .

[0055] According to an optional embodiment of the present application, when the two signals of the error detection servo circuit 4 enter the dynamic locking state, the output frequency of the laser 1 is locked to the cesium atom from 6P 3 / 2 Energy level to 6S 1 / 2 On the spectrum line of energy level transition, the optical signal generated by the laser 1 is input into the optical comb 7; the optical comb 7 generates multiple spectral lines with fixed frequency intervals, and when the optical signal input by the laser 1 interacts with one of the multiple spectral lines generated by the optical comb 7, a beat signal is generated, wherein the frequency of the beat signal is equal to the frequency difference between the two interacting light beams; the beat locking circuit 6 is configured to detect and analyze the beat signal, generate a locking voltage according to the analysis result of the beat signal, and use the locking voltage to control the voltage-controlled components inside the optical comb 7, so as to lock the repetition frequency of the optical comb 7 to the output frequency of the laser 1.

[0056] In this embodiment, a scheme for improving the stability of the optical comb is provided by locking the frequency of the laser 1 to the cesium atom 6P 3 / 2 Energy level to 6S 1 / 2 The energy level transition spectrum is obtained by using the beat frequency signal between the laser and the optical comb 7 to further stabilize the optical comb. This process specifically includes the following steps:

[0057] 1) First, the output frequency of laser 1 is precisely locked to the cesium atom 6P 3 / 2 Energy level to 6S 1 / 2 This locking process is usually achieved through saturation absorption spectroscopy or other high-precision frequency locking methods, ensuring that the frequency of the laser is extremely stable and accurate.

[0058] 2) Another optical signal output by laser 1 is input into optical comb 7, which generates a series of equally spaced discrete frequency lines covering a wide spectral range. The stability of the optical comb is crucial for many applications, such as precision measurement, spectroscopy, and time and frequency standards.

[0059] Since the optical comb 7 generates a series of spectral lines with fixed frequency intervals, when the monochromatic light of the laser 1 interacts with a spectral line in the optical comb 7, a beat signal is generated, and the frequency of the beat signal is equal to the frequency difference between the two beams of light.

[0060] 3) The beat frequency locking circuit 6 is used to detect and process the beat frequency signal. By analyzing the beat frequency signal, information about the frequency deviation of the optical comb 7 relative to the laser 1 can be obtained. Based on the analysis result of the beat frequency signal, the beat frequency locking circuit 6 generates a control voltage, which is used to adjust the voltage-controlled element (such as a voltage-controlled oscillator or a voltage-controlled phase modulator) inside the optical comb 7 to adjust the repetition rate or carrier envelope offset frequency of the optical comb 7, thereby locking it to the output frequency of the laser 1.

[0061] In this way, not only can the optical comb 7 keep its own frequency interval very stable, but the absolute frequency of the entire system is also significantly improved. This is because the laser 1 has been precisely locked to a hyperfine energy level transition of the cesium atom, which makes the frequency reference point of the optical comb 7 extremely stable.

[0062] In summary, by using the laser 1 with a known stable frequency as a reference and combining it with the beat frequency locking technology, the frequency stability of the optical comb 7 can be greatly improved, which is of great significance for achieving high-precision time frequency measurement and other precision optical applications.

[0063] The photoelectric detection circuit 8 is connected to the optical comb 7 and the frequency division circuit 9 respectively, and is configured to shape the second microwave signal generated by the optical comb 7 and then input it into the frequency division circuit 9.

[0064] As an optional embodiment of the present application, the photoelectric detection circuit 8 is further configured to detect the repetition frequency of the optical comb 7 and select the nonlinear harmonic order of the repetition frequency according to the frequency size requirement of the final output microwave signal.

[0065] The repetition frequency of the optical comb refers to the interval between adjacent frequency lines generated by the optical comb. The photoelectric detection circuit 8 is used to detect the repetition frequency of the optical comb 7, and according to the size of the final microwave output signal, determine the number of nonlinear harmonics of the selected repetition frequency, and filter and shape it; then input it to the frequency division circuit 9.

[0066] In some applications, the fundamental frequency (i.e., repetition frequency) of the optical comb may not be sufficient to meet the needs. In this case, nonlinear elements (such as frequency multipliers or mixers) can be used to generate higher harmonics of the optical comb repetition frequency. For example, if a higher frequency microwave signal is required, the repetition frequency of the optical comb can be multiplied by an integer multiple through a frequency multiplier to obtain the required high-frequency signal.

[0067] Select the appropriate nonlinear harmonic order based on the final microwave output signal size requirements. This usually involves evaluating different harmonic orders to determine which harmonic provides the best signal quality and stability. Selection criteria may include output power, phase noise, frequency stability, etc.

[0068] The selected nonlinear harmonic signal is then filtered through a bandpass filter to remove other unnecessary frequency components and retain only the target frequency. The filtered signal may also need further shaping to obtain ideal waveform characteristics, such as a sine wave or other specifically shaped waveform.

[0069] After the above series of processing, a stable and high-quality microwave signal (ie, the above second microwave signal) is finally obtained, which can be used in various applications, such as time and frequency standards, precision measurement, communication systems, etc.

[0070] The frequency dividing circuit 9 is configured to perform frequency division processing on the second microwave signal and output a second microwave signal of a target frequency.

[0071] The frequency division circuit 9 is a key component for generating a microwave signal of a specific frequency in the optical comb system, and it generates the required low-frequency microwave signal by dividing the high-frequency signal (such as the repetition frequency of the optical comb or its higher harmonics).

[0072] The frequency division circuit 9 provides a stable and accurate microwave source for various applications by dividing the high-frequency microwave signal into the required low-frequency signal. This technology is widely used in the fields of time and frequency standards, communication systems, and precision measurements. By flexibly selecting the frequency division ratio, microwave signals of different frequencies can be generated according to specific needs, thereby meeting the requirements of different application scenarios.

[0073] The cesium atomic clock proposed in this application has the advantages of small drift, extremely high stability, and extremely low phase noise, and can output multiple frequencies to meet user needs. It has great application prospects in the fields of metrology, basic research, aerospace, etc.

[0074] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0075] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0076] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A cesium atomic clock, characterized in that: include: A laser (1), an optically pumped cesium beam tube (2), a frequency doubling circuit (3), an error detection servo circuit (4), a frequency stabilization temperature control circuit (5), a beat frequency locking circuit (6), an optical comb (7), a photoelectric detection circuit (8) and a frequency division circuit (9), wherein: The laser (1) is connected to the optically pumped cesium beam tube (2), and is configured to generate an optical signal and input the generated optical signal into the optically pumped cesium beam tube (2); The frequency doubling circuit (3) is connected to the optically pumped cesium beam tube (2), and is configured to generate a first microwave signal and input the first microwave signal into the U-shaped microwave cavity of the optically pumped cesium beam tube (2); The error detection servo circuit (4) is respectively connected to the optically pumped cesium beam tube (2), the frequency doubling circuit (3) and the frequency stabilization temperature control circuit (5), and is configured to generate a maximum error signal, and divide the maximum error signal into two signals, which are respectively input into the frequency doubling circuit (3) and the frequency stabilization temperature control circuit (5); The optical combs (7) are respectively connected to the lasers (1) and are configured to generate a second microwave signal using the optical signal injected by the lasers (1); The beat frequency locking circuit (6) is connected to the optical comb (7) and is configured to lock the repetition frequency of the optical comb (7) to the output frequency of the laser (1); The photoelectric detection circuit (8) is connected to the optical comb (7) and the frequency division circuit (9) respectively, and is configured to shape the second microwave signal generated by the optical comb (7) and then input it into the frequency division circuit (9); The frequency division circuit (9) is configured to perform frequency division processing on the second microwave signal and output the second microwave signal of a target frequency.

2. The cesium atomic clock according to claim 1, characterized in that: The error detection servo circuit (4) is configured to detect the error when the wavelength of the optical signal generated by the laser (1) is the same as the wavelength of the cesium atom from 6P 3 / 2 Energy level to 6S 1 / 2 When the transition frequencies of the energy levels are completely consistent, the maximum error signal is generated.

3. The cesium atomic clock according to claim 1, characterized in that: When the two signals enter the dynamic locking state, the output frequency of the laser (1) is locked to the frequency of the cesium atom from 6P 3 / 2 Energy level to 6S 1 / 2 On the spectrum line of energy level transition, the optical signal generated by the laser (1) is input into the optical comb (7); The optical comb (7) generates a plurality of spectral lines with fixed frequency intervals, and when the optical signal input by the laser (1) interacts with one of the plurality of spectral lines generated by the optical comb (7), a beat signal is generated, wherein the frequency of the beat signal is equal to the frequency difference between the two interacting light beams; The beat frequency locking circuit (6) is configured to detect and analyze the beat frequency signal, generate a locking voltage according to the analysis result of the beat frequency signal, and use the locking voltage to control the voltage-controlled components inside the optical comb (7) so as to lock the repetition frequency of the optical comb (7) to the output frequency of the laser (1).

4. The cesium atomic clock according to claim 1, characterized in that: The photoelectric detection circuit (8) is also configured to detect the repetition frequency of the optical comb (7), and select the nonlinear harmonic order of the repetition frequency according to the frequency magnitude requirement of the microwave signal finally outputted.

5. The cesium atomic clock according to claim 1, characterized in that: The optically pumped cesium beam tube (2) is configured to determine the frequency of the first microwave signal by detecting the interaction between the first microwave signal and cesium atoms in the U-shaped microwave cavity, so as to provide a time reference.

6. The cesium atomic clock according to claim 1 or 5, characterized in that: The optically pumped cesium beam tube (2) is a cesium beam tube with the same light source structure for pumping and detecting.

7. The cesium atomic clock according to claim 1, characterized in that: The frequency of the first microwave signal is 9.19 GHz, wherein the frequency multiplication circuit (3) generates the first microwave signal in one of the following ways: Using a crystal oscillator with a preset frequency to generate a crystal oscillator signal with the preset frequency, and multiplying the crystal oscillator signal to the first microwave signal of 9.19 GHz; The first microwave signal is generated by locking a 9.19 GHz dielectric oscillator with a crystal oscillator.

8. The cesium atomic clock according to claim 1, characterized in that: The laser (1) is a 852.1 nm semiconductor laser.

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