Rubidium atomic clock with auxiliary microwave cavity

Abstract

The rubidium atomic clock comprises an optical unit, a microwave unit and a servo frequency control synthesis unit, the microwave unit comprises a first rubidium bubble, a second rubidium bubble, a microwave antenna, the microwave cavity and the auxiliary cavity, the first rubidium bubble and the microwave antenna are arranged in a cavity body of the microwave cavity, and the second rubidium bubble is arranged in the cavity body of the microwave cavity. The first rubidium bubble is arranged in a cavity body of the auxiliary cavity, the second rubidium bubble is arranged in a cavity body of the auxiliary cavity, the auxiliary cavity and the microwave cavity are integrally processed by adopting the same material, the cavity bodies of the first rubidium bubble and the second rubidium bubble are filled with the same buffer gas and rubidium atoms, and the first rubidium bubble and the second rubidium bubble have the same temperature coefficient. According to the rubidium atomic clock with the auxiliary microwave cavity, laser frequency shift, temperature frequency shift and noise of a detector are greatly reduced, and meanwhile, the contrast ratio of signals of the rubidium atomic clock is improved, so that the medium and long term stability index of the rubidium atomic clock can be improved.

Description

Technical Field

[0001] This invention relates to the field of rubidium atomic clock technology, and more specifically to a rubidium atomic clock with a secondary microwave cavity. Background Technology

[0002] Atomic clocks are a product of the high integration of quantum physics and electronics, and one of the most outstanding achievements of spectroscopy in technological applications. Among them, the rubidium atomic clock, which is the most widely used, has the characteristics of small size, low cost, fast preheating and low power consumption, and is a traditional and practical atomic frequency standard.

[0003] Laser-pumped rubidium atomic clocks use lasers as a light source. Compared with traditional rubidium lamp-pumped atomic clocks, they have improved pumping efficiency. However, even with pulsed light pumping (POP), frequency drift still exists.

[0004] The main performance indicators of a rubidium atomic clock include frequency stability, frequency accuracy, and frequency drift rate. Frequency drift rate is one of the most important indicators, as its quality determines the clock's performance. Drift in a rubidium atomic clock is caused by various factors, the most significant being temperature drift and optical drift. Temperature drift is caused by changes in the operating environment temperature, while optical drift is caused by variations in laser power and frequency.

[0005] The drift rate can generally be improved in the following ways: 1. By simultaneously detecting the light intensity change of the spectral lamp itself and the light intensity change after the cavity system (filter, absorber, etc.), the optical frequency shift is comprehensively processed (202210378895.7 A rubidium atomic clock drift control device and method) to achieve the optimization of optical frequency shift; 2. Optimize the sensitivity of the cavity temperature and lamp temperature (202311407706.5 A method for optimizing the cavity temperature and lamp temperature sensitivity of a rubidium atomic clock), reduce the temperature coefficient of the rubidium atomic clock, and thus optimize the temperature frequency shift of the rubidium clock; 3. Establish a drift rate model based on the frequency drift test data of the rubidium atomic clock, and then optimize the frequency drift rate of the rubidium atomic clock by adjusting the DDS; 4. Collect the frequency difference data of the rubidium atomic clock relative to the reference signal, and adjust the output frequency of the rubidium atomic clock according to the least squares method, the time-frequency difference model and the voltage-frequency fitting relationship (202310864240.5 A method, device, storage medium and terminal for optimizing the drift rate of a rubidium atomic clock); 5. Optimize the optical frequency shift by using an additional acousto-optic modulator to power lock the laser, or using orthogonal polarization detection or differential detection schemes when the rubidium atomic clock is pumped by laser. The methods mentioned above can effectively improve optical frequency shift and temperature frequency shift, but they cannot achieve both simultaneously. The method of optimizing frequency shift by measuring the frequency shift model of the rubidium clock or its deviation relative to the reference frequency and then using feedback control of the crystal oscillator requires a large amount of test data, and the frequency shift model will also have errors as the device ages.

[0006] Therefore, providing a rubidium atomic clock that can effectively reduce both optical and temperature frequency shifts has become an urgent problem to be solved. Summary of the Invention

[0007] To address the aforementioned problems in the prior art, this invention provides a rubidium atomic clock with a secondary microwave cavity. The technical problem to be solved by this invention is achieved through the following technical solution: This invention provides a rubidium atomic clock with a secondary microwave cavity. The rubidium atomic clock includes an optical unit, a microwave unit, and a servo-controlled frequency synthesis unit. The microwave unit includes a first rubidium bulb, a second rubidium bulb, a microwave antenna, a microwave cavity, and a secondary cavity. The first rubidium bulb and the microwave antenna are disposed within the microwave cavity, and the second rubidium bulb is disposed within the secondary cavity. Both the first and second rubidium bulb cavities are filled with the same buffer gas and rubidium atoms, and the first and second rubidium bulbs have the same temperature coefficient. The optical unit is used to provide a first frequency-stabilized laser and a second frequency-stabilized laser; The microwave cavity is used to receive the first frequency-stabilized laser incident from the optical unit. The first frequency-stabilized laser and the microwave signal interact simultaneously with the rubidium atoms in the first rubidium bulb to obtain the first laser carrying rubidium atom information. The secondary cavity is used to receive the second frequency-stabilized laser incident from the optical unit. The second frequency-stabilized laser interacts with rubidium atoms in the second rubidium bulb to obtain a second laser carrying rubidium atom information. The servo frequency control synthesis unit is used to obtain a stable microwave signal based on the first detection signal corresponding to the first laser and the second detection signal corresponding to the second laser, and feed the microwave signal into the microwave cavity.

[0008] In one embodiment of the present invention, the optical unit includes: Laser, used to provide laser light after shaping and isolation; A beam splitter is used to split the shaped and isolated laser into a first split laser and a second split laser, wherein the light intensity of the first split laser is less than the light intensity of the second split laser. A saturated absorption spectroscopy module is used to process the first split laser beam through a saturated absorption spectroscopy to obtain saturated absorbed laser light, and the saturated absorbed laser light is detected to obtain a spectral modulation signal. The laser frequency locking module is used to perform beat frequency processing on the spectral modulation signal and the modulation signal applied to the laser to obtain an error signal, and feed the error signal back to the laser to achieve laser frequency locking; A beam splitter is used to split the second beam laser into the first frequency-stabilized laser and the second frequency-stabilized laser, with the first frequency-stabilized laser entering the microwave cavity; A total reflection mirror is used to reflect the second frequency-stabilized laser into the sub-cavity. In one embodiment of the present invention, the servo frequency synthesis unit includes: The signal acquisition module is used to calculate the rubidium atomic clock signal based on the first detection signal corresponding to the first laser and the second detection signal corresponding to the second laser; A servo loop is used to obtain a feedback voltage signal based on the rubidium atomic clock signal; A voltage-controlled crystal oscillator is used to receive the feedback voltage signal and output a radio frequency signal at a fixed frequency. A frequency synthesizer is used to take a fixed-frequency radio frequency signal as a local reference frequency to obtain a microwave signal, and feed the microwave signal into the microwave cavity. In one embodiment of the present invention, the signal acquisition module includes: A first detector is used to detect the first laser and obtain the first detection signal; The second detector is used to detect the second laser and obtain the second detection signal; A signal acquisition processor is used to obtain the rubidium atomic clock signal based on the first detection signal and the second detection signal. In one embodiment of the present invention, the calculation formula for the rubidium atomic clock signal is as follows: P0 = P1 - mP2 Wherein, P0 is the rubidium atomic clock signal, P1 is the first detection signal, P2 is the second detection signal, and m is a multiple. In one embodiment of the present invention, the microwave cavity and the sub-cavity are made of the same material. In one embodiment of the present invention, the outer shells of the first rubidium bulb and the outer shells of the second rubidium bulb are made of the same material. In one embodiment of the present invention, the volume of the microwave cavity is larger than the volume of the sub-cavity, and the volume of the first rubidium bulb is larger than the volume of the second rubidium bulb. In one embodiment of the present invention, the rubidium atomic clock further includes: A C-field coil is arranged around the microwave cavity and the sub-cavity; The magnetic shielding and heating structure includes a microwave cavity, a sub-cavity, and a C-field coil, all of which are housed within the cavity of the magnetic shielding and heating structure. In one embodiment of the present invention, the magnetic shielding and heating structure includes a first magnetic shielding cylinder, a first heating and heat preservation layer, a second magnetic shielding cylinder, a second heating and heat preservation layer, and a third magnetic shielding cylinder arranged sequentially from the inside to the outside.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, the microwave cavity of a traditional rubidium atomic clock is modified into a microwave cavity with a secondary cavity. This secondary cavity has an additional secondary cavity outside the traditional microwave cavity. The main microwave cavity receives a microwave signal, while the secondary cavity does not. Both cavities contain rubidium bulbs. Laser light passing through the rubidium bulb in the secondary cavity is used as the reference light, and laser light passing through the rubidium bulb in the main microwave cavity is used as the signal light. The rubidium atomic clock signal is obtained by subtracting the reference light from the signal light. This significantly reduces the impact of temperature drift, laser power, and frequency fluctuations on the long-term stability of the rubidium atomic clock. Furthermore, the subtraction of the two beams greatly improves the contrast of the rubidium atomic clock signal, which is beneficial for improving the short-term stability of the rubidium atomic clock.

[0010] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of a microwave cavity with a secondary cavity provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a rubidium atomic clock with a secondary cavity microwave cavity provided in an embodiment of the present invention.

[0012] in: Microwave cavity-1, first rubidium bulb-2, secondary cavity-3, second rubidium bulb-4, microwave antenna-5, C-field coil-6, light-transmitting structure of magnetic shielding heating structure-7, first magnetic shielding cylinder-8, first heating and heat preservation layer-9, second magnetic shielding cylinder-10, second heating and heat preservation layer-11, third magnetic shielding cylinder-12, laser-13, beam splitter-14, saturated absorption spectroscopy module-15, laser frequency locking module-16, beam splitter-17, total reflection mirror-18, first detector-19, second detector-20, signal acquisition processor-21, servo loop-22, voltage-controlled crystal oscillator-23, frequency synthesizer-24. Detailed Implementation

[0013] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description of a rubidium atomic clock with a secondary cavity microwave cavity according to the present invention is provided in conjunction with the accompanying drawings and specific embodiments.

[0014] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0015] Example 1 Please see Figure 1 , Figure 1 This is a schematic diagram of a microwave cavity with a secondary cavity provided by an embodiment of the present invention. The embodiment of the present invention provides a rubidium atomic clock with a secondary cavity microwave cavity. The rubidium atomic clock includes an optical unit, a microwave unit, and a servo-controlled frequency synthesis unit. The microwave unit includes a first rubidium bulb 2, a second rubidium bulb 4, a microwave antenna 5, a microwave cavity 1, and a secondary cavity 3. The first rubidium bulb 2 and the microwave antenna 5 are disposed within the microwave cavity 1, and the second rubidium bulb 4 is disposed within the secondary cavity 3. Both the microwave cavity 1 and the secondary cavity 3 are filled with the same buffer gas and rubidium atoms, and the first rubidium bulb 2 and the second rubidium bulb 4 have the same temperature coefficient. Optical unit for providing first and second frequency-stabilized lasers; Microwave cavity 1 is used to receive the first frequency-stabilized laser incident from the optical unit. The first frequency-stabilized laser and the microwave signal interact with the rubidium atoms in the first rubidium bulb 2 simultaneously to obtain the first laser carrying the information of the rubidium atoms. Sub-cavity 3 is used to receive the second frequency-stabilized laser incident from the optical unit. The second frequency-stabilized laser interacts with the rubidium atoms in the second rubidium bulb 4 to obtain a second laser carrying rubidium atom information. The first frequency-stabilized laser and the second frequency-stabilized laser come from the same laser, and the light intensity of the first frequency-stabilized laser is greater than that of the second frequency-stabilized laser. The servo frequency control synthesis unit is used to obtain a stable microwave signal based on the first detection signal corresponding to the first laser and the second detection signal corresponding to the second laser, and feed the microwave signal into the microwave cavity 1.

[0016] Specifically, a first rubidium bulb 2 is disposed within the cavity of microwave cavity 1, and the first rubidium bulb 2 is disposed along the path of the first frequency-stabilized laser, so that the first frequency-stabilized laser can pass through the first rubidium bulb 2. The microwave antenna 5 is disposed on the inner wall of the cavity of microwave cavity 1. A second rubidium bulb 4 is disposed within the cavity of sub-cavity 3, and the second rubidium bulb 4 is disposed along the path of the second frequency-stabilized laser, so that the second frequency-stabilized laser can pass through the first rubidium bulb 2. The first rubidium bulb 2 and the second rubidium bulb 4 are both filled with the same buffer gas and rubidium atoms. An optical unit provides a first frequency-stabilized laser with relatively high intensity and a second frequency-stabilized laser with relatively low intensity from the same laser beam to the microwave unit. The first frequency-stabilized laser enters the microwave cavity 1 through a light-transmitting structure 7 on the microwave cavity 1. Simultaneously, the microwave antenna 5 continuously provides microwave signals. Under the influence of the microwave signals, the first frequency-stabilized laser passes through the first rubidium bulb 2, becoming the first laser carrying rubidium atomic clock information. The second frequency-stabilized laser enters the cavity 3 through the light-transmitting structure 7 on the secondary cavity 3, passes through the second rubidium bulb 4, and becomes the second laser carrying rubidium atomic clock information. The first frequency-stabilized laser carrying rubidium atomic clock information... A first laser beam passes through the light-transmitting structure of microwave cavity 1, and a second laser beam carrying rubidium atom information passes through the light-transmitting structure of sub-cavity 3. Both enter the servo-controlled frequency synthesis unit simultaneously. The first laser beam strikes the first detector 19 to obtain a first detection signal, and the second laser beam strikes the second detector 20 to obtain a second detection signal. Both the first and second detection signals simultaneously enter the signal acquisition processor 21 to calculate a feedback signal. The feedback signal controls the voltage-controlled crystal oscillator 23 via the servo loop 22. This voltage-controlled crystal oscillator also serves as the local oscillator of the frequency synthesizer 24. The frequency synthesizer 24 outputs microwaves that are fed into the microwave antenna 5 of microwave cavity 1. Simultaneously, the stabilized radio frequency signal within the frequency synthesizer is also provided to the user. The microwave cavity with sub-cavity in this embodiment of the invention is shown below. Figure 1 The first rubidium bulb 2 in microwave cavity 1 and the second rubidium bulb 4 in sub-cavity 3 have the same temperature coefficient; the first rubidium bulb 2 and the second rubidium bulb 4 are placed in the same physical system and have the same temperature environment; as time goes by, the first rubidium bulb 2 and the second rubidium bulb 4 face the same aging of the temperature control system, and the changes in gas pressure and rubidium atom density in the rubidium bulb have the same trend.

[0017] Optionally, the microwave cavity 1 and the sub-cavity 3 are made of the same material, which can be oxygen-free copper, aluminum, microcrystalline glass coating or other non-magnetic materials. In order to reduce the temperature coefficient of the microwave cavity and the sub-cavity, oxygen-free copper is preferred.

[0018] Optionally, the volume of microwave cavity 1 is larger than the volume of sub-cavity 3, and the volume of first rubidium bulb 2 is larger than the volume of second rubidium bulb 4.

[0019] Furthermore, the microwave cavity 1 and the sub-cavity 3 can be formed in one piece. The microwave cavity 1 is in the TE011 or TE111 mode. The external shape of the microwave cavity 1 and the sub-cavity 3 is cuboid. The cavity shape of the microwave cavity 1 and the sub-cavity 3 is cylindrical. The sub-cavity 3 is used to place the second rubidium bulb 4 as a reference. Therefore, under the premise of meeting the application requirements, the volume of the sub-cavity 3 can be made as small as possible.

[0020] Optionally, the first rubidium bulb 2 and the second rubidium bulb 4 are made of the same material. The outer shell of the first rubidium bulb 2 and the second rubidium bulb 4 is, for example, glass or quartz.

[0021] Optionally, the first rubidium bubble 2 and the second rubidium bubble 4 are cylindrical in shape.

[0022] For example, in the TE011 mode, the microwave cavity 1 has a cavity diameter of 26 mm and a length of 33 mm, the first rubidium bulb 2 has a diameter of 30 mm and a length of 25 mm; the sub-cavity 3 has a cavity diameter of 8 mm to 20 mm and a length of 33 mm, and the corresponding second rubidium bulb 4 has a diameter of 8 mm to 20 mm and a length of 25 mm. If necessary, those skilled in the art can also design the sub-cavity into other shapes according to requirements, and appropriately adjust the internal dimensions of the sub-cavity, while correspondingly changing the dimensions of the second rubidium bulb 4.

[0023] Optionally, the rubidium atom is rubidium-87.

[0024] Optionally, the buffer gas is a mixture of argon and nitrogen.

[0025] Optionally, the light-transmitting structure of microwave cavity 1 and the light-transmitting structure of sub-cavity 3 can be light-transmitting holes, or the light-transmitting holes can be sealed with lenses with high transmittance coatings or quartz.

[0026] In one specific embodiment, please refer to Figure 1 Rubidium atomic clocks also include: C-field coil 6 is arranged around microwave cavity 1 and sub-cavity 3; The magnetic shielding and heating structure includes microwave cavity 1, sub-cavity 3, and C-field coil 6, all housed within the cavity of the magnetic shielding and heating structure.

[0027] Specifically, a transparent structure corresponding to the transparent structure 7 of the microwave cavity 1 is provided on the magnetic shielding and heating structure, thereby allowing the transparent structure 7 of the first frequency-stabilized laser to enter the microwave cavity 1, and the first laser carrying rubidium atomic clock information to enter the servo frequency control synthesis unit through the transparent structure of the magnetic shielding and heating structure; a transparent structure corresponding to the transparent structure 7 of the sub-cavity 3 is also provided on the magnetic shielding and heating structure, thereby allowing the transparent structure 7 of the second frequency-stabilized laser to enter the sub-cavity 3, and the second laser carrying rubidium atomic information to enter the servo frequency control synthesis unit through the transparent structure of the magnetic shielding and heating structure.

[0028] Optionally, the magnetic shielding and heating structure can be cylindrical, and the outermost magnetic shielding can also be cuboid.

[0029] Optionally, the light-transmitting structure 7 of the magnetic shielding and heating structure can be a light-transmitting hole. For heat preservation, a lens with high transmittance coating or quartz can be used to seal the light-transmitting hole.

[0030] Further, please see Figure 1 The magnetic shielding and heating structure includes a first magnetic shielding cylinder 8, a first heating and insulation layer 9, a second magnetic shielding cylinder 10, a second heating and insulation layer 11, and a third magnetic shielding cylinder 12 arranged sequentially from the inside to the outside.

[0031] In one specific embodiment, please refer to Figure 2 The optical unit includes: Laser 13 is used to provide laser light after shaping and isolation; Beam splitter 14 is used to split the shaped and isolated laser into a first split laser and a second split laser, wherein the light intensity of the first split laser is less than the light intensity of the second split laser. The saturated absorption spectroscopy module 15 is used to pass the first split laser beam through saturated absorption spectroscopy processing to obtain saturated absorbed laser, and the saturated absorbed laser is detected to obtain a spectral modulation signal. The laser frequency locking module 16 is used to perform beat frequency processing on the spectral modulation signal and the modulation signal applied to the laser 13 to obtain an error signal, and feed the error signal back to the laser 13 to achieve laser frequency locking. The beam splitter 17 is used to split the second beam laser into a first frequency-stabilized laser and a second frequency-stabilized laser, with the first frequency-stabilized laser entering the microwave cavity 1. Total reflection mirror 18 is used to reflect the second frequency-stabilized laser into the sub-cavity 3.

[0032] Specifically, the laser 13 outputs a shaped and isolated laser beam, which is then split into a first beam with relatively weak intensity and a second beam with relatively strong intensity by a beam splitter 14. The first beam enters the saturated absorption spectral module 15, and after processing by the saturated absorption spectral structure in the saturated absorption spectral module 15, a saturated absorbed laser beam is output. The saturated absorbed laser beam is then detected by the detector in the saturated absorption spectral module 15 to obtain a spectral modulation signal. The spectral modulation signal is transmitted to the laser frequency locking module 16. The laser frequency locking module 16 performs beat frequency processing on the spectral modulation signal and the modulation signal applied to the laser 13 to generate an error signal. The laser frequency locking module 16 feeds back the error signal to the laser control section of the laser 13 to achieve laser frequency locking. Meanwhile, the second laser beam is split again by the beam splitter prism 17 into a first frequency-stabilized laser with relatively strong light intensity and a second frequency-stabilized laser with relatively weak light intensity. The relatively strong first frequency-stabilized laser is directly incident on the first rubidium bulb 2 in the microwave cavity 1, while the relatively weak second frequency-stabilized laser is reflected by the total reflection mirror 18 into the second rubidium bulb 4 in the sub-cavity 3.

[0033] Alternatively, laser 13 may be a 780nm or 795nm semiconductor laser.

[0034] Optionally, the angle of the total reflection mirror 18 is 45°.

[0035] In one specific embodiment, please refer to Figure 2 The servo frequency control synthesis unit includes: The signal acquisition module is used to obtain the rubidium atomic clock signal based on the first detection signal corresponding to the first laser and the second detection signal corresponding to the second laser. Servo loop 22 is used to obtain a feedback voltage signal based on the rubidium atomic clock signal; The voltage-controlled crystal oscillator 23 is used to receive feedback voltage signals in order to output crystal oscillator signals of a fixed frequency. The frequency synthesizer 24 is used to take the fixed-frequency crystal oscillator signal as the local reference frequency to obtain the microwave signal, and feed the microwave signal into the microwave antenna 5 of the microwave cavity 1.

[0036] Specifically, in the signal acquisition module, the first detection signal of the first detector 19 and the second detection signal of the second detector 20 are first acquired, and then the rubidium atomic clock signal is calculated from the first and second detection signals. The signal acquisition module then transmits the rubidium atomic clock signal to the servo loop 22, which obtains a feedback voltage signal through proportional-integral-differential conversion. This feedback voltage signal is applied to the voltage-controlled port of the voltage-controlled crystal oscillator 23, and the output RF frequency of the voltage-controlled crystal oscillator 23 is finely adjusted in real time. Using the output RF frequency of the voltage-controlled crystal oscillator 23 as the local reference frequency, the frequency synthesizer 24 synthesizes the local reference frequency to the microwave frequency (approximately 6.8 GHz) required for rubidium atom transitions through a series of frequency multiplication, division, and mixing operations. This microwave signal is then fed into the microwave antenna 5 of the microwave cavity 1. This microwave signal and the first laser simultaneously interact with the rubidium atoms in the rubidium bulb 2, completing closed-loop control. Simultaneously, the frequency synthesizer 24 can also provide a stable RF signal to the user.

[0037] Further, please see Figure 2 The signal acquisition module includes: The first detector 19 is used to detect the first laser and obtain the first detection signal; The second detector 20 is used to detect the second laser and obtain the second detection signal; The signal acquisition processor 21 is used to obtain the rubidium atomic clock signal based on the first detection signal and the second detection signal.

[0038] Specifically, the first detector 19 and the second detector 20 are used to detect the laser light passing through the first rubidium bulb 2 in the microwave cavity 1 and the laser light passing through the second rubidium bulb 4 in the sub-cavity 3, respectively; the signal acquisition processor 21 is used to acquire the detection signals output by the first detector 19 and the second detector 20, and obtain the rubidium atomic clock signal based on the first detection signal and the second detection signal.

[0039] Optionally, the formula for calculating the rubidium atomic clock signal is: P0 = P1 - mP2 Wherein, P0 is the rubidium atomic clock signal, P1 is the first detection signal, P2 is the second detection signal, and m is a multiple, with the value of m ranging from 10 to 15.

[0040] The rubidium atomic clock of this invention utilizes a microwave cavity with a secondary cavity. By subtracting the first detection signal corresponding to the first laser obtained from the first rubidium bulb in the microwave cavity from the second detection signal corresponding to the second laser obtained from the second reference rubidium bulb (second rubidium bulb) in the secondary cavity (m times the value of the first laser), the influence of rubidium bulb temperature drift on the long-term stability of the rubidium atomic frequency standard can be reduced. Simultaneously, since the detection laser and the reference laser originate from the same light source, subtracting them can significantly reduce the influence of laser power and frequency fluctuations on the long-term stability of the rubidium atomic frequency standard. Furthermore, because the contrast of the rubidium atomic clock signal is only 30%-50%, subtracting the two beams can greatly improve the contrast of the rubidium atomic clock signal, which is also beneficial for improving the short-term stability of the rubidium atomic clock.

[0041] Therefore, the rubidium atomic clock of this invention can effectively reduce the limitations imposed by rubidium absorber temperature fluctuations, laser power, and frequency fluctuations on the long-term frequency stability of the rubidium atomic clock. Compared with traditional rubidium atomic clocks, it can simultaneously reduce temperature frequency shift and optical frequency shift by one to two orders of magnitude, and the long-term stability is expected to improve by one to two orders of magnitude.

[0042] It should be noted that the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. The embodiments described in the above exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the present invention.

[0043] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0044] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings and the disclosure in carrying out the claimed invention. In the description of the invention, the word "comprising" does not exclude other components or steps, "a" or "an" does not exclude a plurality, and "a plurality" means two or more, unless otherwise explicitly specified. Furthermore, while different embodiments may describe certain measures, this does not mean that these measures cannot be combined to produce good results.

[0045] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A rubidium atomic clock with a secondary microwave cavity, characterized in that, The rubidium atomic clock includes an optical unit, a microwave unit, and a servo-controlled frequency synthesis unit. The microwave unit includes a first rubidium bulb, a second rubidium bulb, a microwave antenna, a microwave cavity, and a sub-cavity. The first rubidium bulb and the microwave antenna are disposed within the microwave cavity, and the second rubidium bulb is disposed within the sub-cavity. Both the first and second rubidium bulbs are filled with the same buffer gas and rubidium atoms, and both have the same temperature coefficient. The optical unit is used to provide a first frequency-stabilized laser and a second frequency-stabilized laser; The microwave cavity is used to receive the first frequency-stabilized laser incident from the optical unit. The first frequency-stabilized laser and the microwave signal interact simultaneously with the rubidium atoms in the first rubidium bulb to obtain the first laser carrying rubidium atom information. The secondary cavity is used to receive the second frequency-stabilized laser incident from the optical unit. The second frequency-stabilized laser interacts with rubidium atoms in the second rubidium bulb to obtain a second laser carrying rubidium atom information. The servo frequency control synthesis unit is used to obtain a stable microwave signal based on the first detection signal corresponding to the first laser and the second detection signal corresponding to the second laser, and feed the microwave signal into the microwave cavity.

2. The rubidium atomic clock according to claim 1, characterized in that, The optical unit includes: Laser, used to provide laser light after shaping and isolation; A beam splitter is used to split the shaped and isolated laser into a first split laser and a second split laser, wherein the light intensity of the first split laser is less than the light intensity of the second split laser. A saturated absorption spectroscopy module is used to process the first split laser beam through a saturated absorption spectroscopy to obtain saturated absorbed laser light, and the saturated absorbed laser light is detected to obtain a spectral modulation signal. The laser frequency locking module is used to perform beat frequency processing on the spectral modulation signal and the modulation signal applied to the laser to obtain an error signal, and feed the error signal back to the laser to achieve laser frequency locking; A beam splitter is used to split the second beam laser into the first frequency-stabilized laser and the second frequency-stabilized laser, with the first frequency-stabilized laser entering the microwave cavity; A total reflection mirror is used to reflect the second frequency-stabilized laser into the sub-cavity.

3. The rubidium atomic clock according to claim 1, characterized in that, The servo frequency control synthesis unit includes: The signal acquisition module is used to obtain the rubidium atomic clock signal based on the first detection signal corresponding to the first laser and the second detection signal corresponding to the second laser; A servo loop is used to obtain a feedback voltage signal based on the rubidium atomic clock signal; A voltage-controlled crystal oscillator is used to receive the feedback voltage signal and output a radio frequency signal at a fixed frequency. A frequency synthesizer is used to take a fixed-frequency radio frequency signal as a local reference frequency to obtain a microwave signal, and feed the microwave signal into the microwave cavity.

4. The rubidium atomic clock according to claim 3, characterized in that, The signal acquisition module includes: A first detector is used to detect the first laser and obtain the first detection signal; The second detector is used to detect the second laser and obtain the second detection signal; A signal acquisition processor is used to obtain the rubidium atomic clock signal based on the first detection signal and the second detection signal.

5. The rubidium atomic clock according to claim 4, characterized in that, The formula for calculating the rubidium atomic clock signal is as follows: P0 = P1 - mP2 Wherein, P0 is the rubidium atomic clock signal, P1 is the first detection signal, P2 is the second detection signal, and m is a multiple.

6. The rubidium atomic clock according to claim 1, characterized in that, The microwave cavity and the sub-cavity are made of the same material.

7. The rubidium atomic clock according to claim 1, characterized in that, The outer shells of the first rubidium bulb and the second rubidium bulb are made of the same material.

8. The rubidium atomic clock according to claim 1, characterized in that, The volume of the microwave cavity is larger than the volume of the sub-cavity, and the volume of the first rubidium bulb is larger than the volume of the second rubidium bulb.

9. The rubidium atomic clock according to claim 1, characterized in that, The rubidium atomic clock also includes: A C-field coil is arranged around the microwave cavity and the sub-cavity; The magnetic shielding and heating structure includes a microwave cavity, a sub-cavity, and a C-field coil, all of which are housed within the cavity of the magnetic shielding and heating structure.

10. The rubidium atomic clock according to claim 9, characterized in that, The magnetic shielding and heating structure includes a first magnetic shielding cylinder, a first heating and insulation layer, a second magnetic shielding cylinder, a second heating and insulation layer, and a third magnetic shielding cylinder arranged sequentially from the inside to the outside.

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