High-stability frequency control light path device and method for rubidium fountain atomic clock

Abstract

The invention provides a rubidium fountain atomic clock high-stability frequency control light path device and a rubidium fountain atomic clock high-stability frequency control light path method. The rubidium fountain atomic clock high-stability frequency control light path device comprises a main laser part and a re-pumping light part, upper cooling light, lower cooling light and detection light are formed through the main laser part; re-pumping light is formed through the re-pumping light part; the main laser part specifically comprises an ECDL external cavity laser, a 1 / 2 wave plate, a PBS prism, a mechanical switch 3, a reflector, an AOM acoustic optical modulator, a lens, a 1 / 4 wave plate and an optical fiber coupler. The re-pumping light part specifically comprises a DFB laser, a fourth AOM acousto-optic modulator 55, a seventh reflector 56, an eighth reflector 57 and an eighth optical fiber coupler 58, and high-stability laser frequency locking and frequency shifting are achieved through the devices.

Description

Technical Field

[0001] This invention relates to the field of cold atom frequency standard technology, and in particular to a rubidium fountain atomic clock high-stability frequency control optical path device and method. Background Technology

[0002] The rubidium fountain clock is a time-frequency metrology instrument with ultra-high frequency stability and reproducibility. Through laser cooling and trapping technology, room-temperature atoms in a vacuum environment can be cooled to a few μK, forming a cold atom cloud. This cold atom cloud is then projected upwards using a moving optical gel. During this process, the atom cloud is prepared onto a single state of clock transition. Under gravity, the atom cloud interacts twice with the same excitation microwave field during its ascent and descent, achieving Ramsey interference. By detecting the transition probability signal of the falling atom cloud after interference, the error signal of the excitation microwave field frequency relative to the hyperfine transition frequency of the atomic ground state is obtained, thereby locking the microwave source frequency to the atomic transition frequency.

[0003] In a rubidium fountain clock, the laser is used for the manipulation and detection of atoms. The optical path device is used for laser beam splitting, frequency modulation, and polarization control, meeting the laser frequency, amplitude, polarization, and timing control requirements for laser cooling in the fountain clock. Instability in laser frequency and power can cause fluctuations in the number of cold atoms, thus affecting the hyperfine transitions and the stability of the number of cold atoms during laser cooling. To improve the stability of the laser frequency, a suitable frequency-locking design is needed to lock and shift the laser frequency. After frequency locking and shifting, the laser needs to undergo further frequency shifting to form cooling light, detection light, and re-pump light.

[0004] The laser used in rubidium fountain atomic clocks requires high stability, narrow linewidth, and high power, while the frequency control optical path needs to have the ability to rapidly modulate the laser frequency. Selecting a suitable laser type and rationally designing the frequency locking and shifting mechanisms are crucial to meeting the requirements of the rubidium fountain clock in terms of laser frequency stability, power stability, and linewidth. The frequency control optical path needs to be designed with appropriate frequency locking and shifting based on the laser characteristics to achieve frequency locking and rapid modulation of the laser frequency and power, respectively. Traditional rubidium fountain atomic clocks primarily use a saturated absorption spectrum frequency locking scheme in the laser frequency locking optical path. This scheme suffers from problems such as insufficient laser power and frequency stability, insufficient power, and insufficient linewidth; the frequency control optical path also exhibits poor stability.

[0005] Therefore, how to achieve highly stable laser frequency locking and frequency shifting has become one of the existing technical problems that urgently need to be solved. Summary of the Invention

[0006] This invention provides a rubidium fountain atomic clock high-stability frequency control optical path device and method for achieving highly stable laser frequency locking and frequency shifting.

[0007] In a first aspect, a high-stability frequency control optical path device for a rubidium fountain atomic clock is provided, comprising: a main laser section and a re-pumping light section; the main laser section generates an upper cooling light, a lower cooling light, and a probe light; and the re-pumping light section generates a re-pumping light.

[0008] The main laser component specifically includes: an ECDL external cavity laser, a half-wave plate, a PBS prism, a mechanical switch 3, a mirror, an AOM acousto-optic modulator, a lens, a quarter-wave plate, and an optical fiber coupler.

[0009] The specific device for the re-pumped optical section includes: a DFB laser, a fourth AOM acousto-optic modulator 55, a seventh reflector 56, an eighth reflector 57, and an eighth fiber coupler 58.

[0010] In one embodiment, the ECDL external cavity laser splits into two beams. One beam is sequentially guided into the frequency-shifting optical path and the MTS frequency-locking optical path for frequency locking, while the other beam is shaped and output through a single-mode polarization-maintaining fiber to form the main laser.

[0011] In one embodiment, the main laser beam passes through a first half-wave plate 1 and a first PBS2, and then through a mechanical switch 3 to split into cooling light and probe light.

[0012] In one embodiment, the cooling light is split into transmitted upper cooling light and reflected lower cooling light by the third half-wave plate 6 and the third PBS7.

[0013] In one embodiment, the upper cooling light sequentially passes through a first reflecting mirror 8, a fourth half-wave plate 9, a fourth PBS 10, a first AOM 11, a first lens 12, a second reflecting mirror 13, a first lens 12, and a first AOM 11. Its -1st order diffracted light, after reflection by the fourth PBS 10, is then split after passing through a fifth half-wave plate 14 and a fifth PBS 15. The transmitted light from the fifth PBS 15 is then polarized by a sixth half-wave plate 16 and a first quarter-wave plate 17 before being coupled to a first fiber coupler 18. The first upper cooling light is formed by passing through the seventh half-wave plate 19 and the sixth half-wave plate 20. The reflected light from the sixth half-wave plate 20 is then split by passing through the polarization adjustment of the eighth half-wave plate 21 and the second half-wave plate 22 in sequence, and then coupled to the second fiber coupler 23 to form the second upper cooling light. The transmitted light from the sixth half-wave plate 20 is then coupled to the third fiber coupler 27 after passing through the polarization adjustment of the third mirror 24, the ninth half-wave plate 25 and the third half-wave plate 26 in sequence, and then formed the third upper cooling light.

[0014] In one embodiment, the downcooling light sequentially passes through the 10th half-wave plate 28, the 7th PBS 29, the 2nd AOM 30, the 2nd lens 31, the 4th mirror 32, the 2nd lens 31, and the 2nd AOM 30. Its -1st order diffracted light, after reflection by the 7th PBS 29, is then split after passing through the 11th half-wave plate 33 and the 8th PBS 34. The transmitted light from the 8th PBS 34 is then polarized by the 12th half-wave plate 35 and the 4th quarter-wave plate 36 before being coupled to the 4th fiber coupler 37, forming... The first lower cooling light; the reflected light from the eighth PBS34 is then split after passing through the thirteenth half-wave plate 38 and the ninth PBS39. The reflected light from the ninth PBS39 is then coupled to the fifth fiber coupler 42 after being polarized by the fourteenth half-wave plate 40 and the fifth quarter-wave plate 41, forming the second lower cooling light; the transmitted light from the ninth PBS39 is coupled to the sixth fiber coupler 46 after being polarized by the fifth mirror 43, the fifteenth half-wave plate 44 and the sixth quarter-wave plate 45, forming the third lower cooling light.

[0015] In one embodiment, the probe light passes through the sixteenth half-wave plate 47 and the tenth PBS 48, and then sequentially passes through the third AOM 49, the third lens 50, the sixth reflector 51, the third lens 50, and the third AOM 49. Its -1st order diffracted light is reflected by the tenth PBS 48, and then sequentially passes through the seventeenth half-wave plate 52 and the seventh half-wave plate 53 for polarization adjustment. Finally, it is coupled into the seventh fiber coupler 54 to form the probe light output.

[0016] In one embodiment, the DFB laser splits into two beams. One beam is guided into the SAS frequency-locking optical path for frequency locking, and the other beam is output to the fourth AOM 55 for diffraction. The -1st order diffracted light after passing through the fourth AOM 55 passes through the seventh mirror 56 and the eighth mirror 57 in sequence, and is then coupled into the single-mode polarization-maintaining fiber by the eighth fiber coupler 58 to form the re-pumped light output.

[0017] In one embodiment, the mechanical switch is used for timing control of rubidium atom cooling.

[0018] Secondly, a method for controlling the high-stability frequency of a rubidium fountain atomic clock is provided, the method being applied to the aforementioned system, including:

[0019] use 87 One of the frequency-sensitive spectral lines of the Rb D2 line is used as a reference spectral line. The laser frequency is locked using the MTS modulation transfer spectroscopy method and the SAS saturated absorption spectroscopy method.

[0020] The external cavity laser and the frequency control optical path are shifted by a frequency modulation device. After the external cavity laser is frequency shifted, it is amplified by a TA and shaped by a single-mode polarization-maintaining fiber to output the main laser. The main laser is split in the frequency control optical path and formed into cooling light and probe light through different frequency shifting processes. The output light of the DFB laser is formed into re-pump light in the frequency control optical path through a certain frequency shifting process.

[0021] This invention provides a high-stability frequency control optical path device and method for a rubidium fountain atomic clock. The device includes a main laser section and a re-pumping light section. The main laser section forms an upper cooling light, a lower cooling light, and a probe light. The re-pumping light section forms a re-pumping light. The main laser section specifically includes an ECDL external cavity laser, a half-wave plate, a PBS prism, a mechanical switch 3, a mirror, an AOM acousto-optic modulator, a lens, a quarter-wave plate, and an optical fiber coupler. The re-pumping light section specifically includes a DFB laser, a fourth AOM acousto-optic modulator 55, a seventh mirror 56, an eighth mirror 57, and an eighth optical fiber coupler 58. Through the above device, high-stability laser frequency locking and frequency shifting are achieved.

[0022] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and accompanying drawings. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0024] Figure 1 This is a schematic diagram of a high-stability frequency control optical path device for a rubidium fountain atomic clock according to an embodiment of the present invention.

[0025] 1. First half-wave plate, 2. First PBS, 3. Mechanical switch, 4. Second half-wave plate, 5. Second PBS, 6. Third half-wave plate, 7. Third PBS, 8. First mirror, 9. Fourth half-wave plate, 10. Fourth PBS, 11. First AOM, 12. First lens, 13. Second mirror, 14. Fifth half-wave plate, 15. Fifth PBS, 16. Sixth half-wave plate, 17. First quarter-wave plate, 18. First fiber coupler, 19. Seventh half-wave plate, 20. Sixth PBS, 21. Eighth half-wave plate, 22. Second quarter-wave plate, 23. Second fiber coupler, 24. Third mirror, 25. Ninth half-wave plate, 26. Third quarter-wave plate, 27. Third fiber coupler, 28. Tenth half-wave plate, 29. Seventh PBS, 30. Second AOM 31 Second lens, 32 Fourth mirror, 33 Eleventh half-wave plate, 34 Eighth PBS, 35 Twelfth half-wave plate, 36 Fourth quarter-wave plate, 37 Fourth fiber coupler, 38 Thirteenth half-wave plate, 39 Ninth PBS, 40 Fourteenth half-wave plate, 41 Fifth quarter-wave plate, 42 Fifth fiber coupler, 43 Fifth mirror, 44 Fifteenth half-wave plate, 45 Sixth quarter-wave plate, 46 Sixth fiber coupler, 47 Sixteenth half-wave plate, 48 Tenth PBS, 49 Third AOM, 50 Third lens, 51 Sixth mirror, 52 Seventeenth half-wave plate, 53 Seventh quarter-wave plate, 54 Seventh fiber coupler, 55 Fourth AOM, 56 Seventh mirror, 57 Eighth mirror, 58 Eighth fiber coupler;

[0026] Figure 2 This is a schematic diagram of a frequency-locking and frequency-shifting energy level scheme according to an embodiment of the present invention. Detailed Implementation

[0027] To achieve highly stable laser frequency locking and frequency shifting, a rubidium fountain atomic clock high-stability frequency control optical path device and method are provided.

[0028] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention. Furthermore, the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0029] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of the embodiments of the present invention 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 described herein can be implemented in a sequence other than that illustrated or described herein.

[0030] like Figure 1As shown, the embodiment provides a high-stability frequency control optical path device for a rubidium fountain atomic clock, including: a main laser section and a re-pumping light section; the main laser section forms an upper cooling light, a lower cooling light, and a probe light; the re-pumping light section forms a re-pumping light.

[0031] The main laser component specifically includes: an ECDL external cavity laser, a half-wave plate, a PBS prism, a mechanical switch 3, a mirror, an AOM acousto-optic modulator, a lens, a quarter-wave plate, and an optical fiber coupler.

[0032] The specific device for the re-pumped optical section includes: a DFB laser, a fourth AOM acousto-optic modulator 55, a seventh reflector 56, an eighth reflector 57, and an eighth fiber coupler 58.

[0033] In one embodiment, the ECDL external cavity laser splits into two beams. One beam is sequentially guided into the frequency-shifting optical path and the MTS frequency-locking optical path for frequency locking, while the other beam is shaped and output through a single-mode polarization-maintaining fiber to form the main laser.

[0034] In one embodiment, the main laser beam passes through a first half-wave plate 1 and a first PBS 2, and then through a mechanical switch 3 to split into cooling light and probe light. The mechanical switch is used for timing control of rubidium atom cooling.

[0035] In one embodiment, the cooling light is split into transmitted upper cooling light and reflected lower cooling light by the third half-wave plate 6 and the third PBS7.

[0036] In one embodiment, the upper cooling light sequentially passes through a first reflecting mirror 8, a fourth half-wave plate 9, a fourth PBS 10, a first AOM 11, a first lens 12, a second reflecting mirror 13, a first lens 12, and a first AOM 11. Its -1st order diffracted light, after reflection by the fourth PBS 10, is then split after passing through a fifth half-wave plate 14 and a fifth PBS 15. The transmitted light from the fifth PBS 15 is then polarized by a sixth half-wave plate 16 and a first quarter-wave plate 17 before being coupled to a first fiber coupler 18. The first upper cooling light is formed by passing through the seventh half-wave plate 19 and the sixth half-wave plate 20. The reflected light from the sixth half-wave plate 20 is then split by passing through the polarization adjustment of the eighth half-wave plate 21 and the second half-wave plate 22 in sequence, and then coupled to the second fiber coupler 23 to form the second upper cooling light. The transmitted light from the sixth half-wave plate 20 is then coupled to the third fiber coupler 27 after passing through the polarization adjustment of the third mirror 24, the ninth half-wave plate 25 and the third half-wave plate 26 in sequence, and then formed the third upper cooling light.

[0037] In one embodiment, the downcooling light sequentially passes through the 10th half-wave plate 28, the 7th PBS 29, the 2nd AOM 30, the 2nd lens 31, the 4th mirror 32, the 2nd lens 31, and the 2nd AOM 30. Its -1st order diffracted light, after reflection by the 7th PBS 29, is then split after passing through the 11th half-wave plate 33 and the 8th PBS 34. The transmitted light from the 8th PBS 34 is then polarized by the 12th half-wave plate 35 and the 4th quarter-wave plate 36 before being coupled to the 4th fiber coupler 37, forming... The first lower cooling light; the reflected light from the eighth PBS34 is then split after passing through the thirteenth half-wave plate 38 and the ninth PBS39. The reflected light from the ninth PBS39 is then coupled to the fifth fiber coupler 42 after being polarized by the fourteenth half-wave plate 40 and the fifth quarter-wave plate 41, forming the second lower cooling light; the transmitted light from the ninth PBS39 is coupled to the sixth fiber coupler 46 after being polarized by the fifth mirror 43, the fifteenth half-wave plate 44 and the sixth quarter-wave plate 45, forming the third lower cooling light.

[0038] In one embodiment, the probe light passes through the sixteenth half-wave plate 47 and the tenth PBS 48, and then sequentially passes through the third AOM 49, the third lens 50, the sixth reflector 51, the third lens 50, and the third AOM 49. Its -1st order diffracted light is reflected by the tenth PBS 48, and then sequentially passes through the seventeenth half-wave plate 52 and the seventh half-wave plate 53 for polarization adjustment. Finally, it is coupled into the seventh fiber coupler 54 to form the probe light output.

[0039] In one embodiment, the DFB laser splits into two beams. One beam is guided into the SAS frequency-locking optical path for frequency locking, and the other beam is output to the fourth AOM 55 for diffraction. The -1st order diffracted light after passing through the fourth AOM 55 passes through the seventh mirror 56 and the eighth mirror 57 in sequence, and is then coupled into the single-mode polarization-maintaining fiber by the eighth fiber coupler 58 to form the re-pumped light output.

[0040] The output light in the frequency-controlled optical path device is introduced into the MOT cavity or the detection area through single-mode polarization-maintaining fiber, fiber beam splitter, and fiber coupler, respectively. Compared with traditional optical devices, fiber optic devices can freely control the light transmission path, reducing the complexity of the optical system and thus improving the overall stability of the fountain clock.

[0041] An embodiment provides a high-stability frequency control optical path device for a rubidium fountain atomic clock, including a laser section and a re-pumping light section; the main laser section forms an upper cooling light, a lower cooling light, and a probe light; the re-pumping light section forms a re-pumping light; the main laser section specifically includes: an ECDL external cavity laser, a half-wave plate, a PBS prism, a mechanical switch 3, a mirror, an AOM acousto-optic modulator, a lens, a quarter-wave plate, and an optical fiber coupler; the re-pumping light section specifically includes: a DFB laser, a fourth AOM acousto-optic modulator 55, a seventh mirror 56, an eighth mirror 57, and an eighth optical fiber coupler 58.

[0042] Based on the same technical concept, this application also provides a method for controlling the optical path of a rubidium fountain atomic clock with high stability. Since the method is applied to the above-mentioned device, the implementation of the method can refer to the implementation of the device, and repeated details will not be described again.

[0043] An embodiment provides a method for controlling the optical path of a rubidium fountain atomic clock with high stability, including:

[0044] use 87 One of the frequency-sensitive spectral lines of the Rb D2 line is used as a reference spectral line. The laser frequency is locked using the MTS modulation transfer spectroscopy method and the SAS saturated absorption spectroscopy method.

[0045] The external cavity laser and the frequency control optical path are shifted by a frequency modulation device. After the external cavity laser is frequency shifted, it is amplified by a TA and shaped by a single-mode polarization-maintaining fiber to output the main laser. The main laser is split in the frequency control optical path and formed into cooling light and probe light through different frequency shifting processes. The output light of the DFB laser is formed into re-pump light in the frequency control optical path through a certain frequency shifting process.

[0046] To make it easier to understand, a specific example is given below:

[0047] A method for high-stability frequency control optical path of a rubidium fountain atomic clock is provided, including a high-stability frequency locking and frequency shifting energy level scheme, as well as a corresponding frequency control optical path device and method.

[0048] This frequency-locked energy level scheme specifically refers to the selection of... 87 One of the Rb D2 lines, which is sensitive to frequency fluctuations, is used as a reference line to lock the laser frequency according to a certain frequency stabilization method.

[0049] Preferably, this energy level scheme employs two types of lasers, which minimizes the number of laser sources and simplifies the laser frequency shifting process. Preferably, an external cavity laser (ECDL), serving as the laser source for atomic cooling and detection, features high coherence, narrow bandwidth, and a wide wavelength tuning range, improving the cooling effect of the cooling light and the detection efficiency of the probe light. Preferably, a distributed feedback Bragg (DFB) laser, serving as the laser source for re-pumping light, features ultra-narrow linewidth and high side-mode suppression ratio, ensuring highly stable re-pumping light frequency that can be precisely matched to the specific energy level transition frequencies of rubidium atoms.

[0050] Preferably, the reference spectral line of the ECDL laser is 87 The Rb D2 line F=2→F'=3. This spectral line is very sensitive to frequency fluctuations, which can effectively improve the frequency locking accuracy of external cavity semiconductor lasers, while reducing the linewidth of the output laser and improving power stability.

[0051] Preferably, the reference spectral line of the DFB laser is the cross peak of the D2 line F=1→F'=1 and 2.

[0052] Preferably, the frequency stabilization method for ECDL lasers is the modulation transfer spectrum (MTS) method, which has a very flat zero background signal, a large error signal slope, good frequency stabilization effect, and small frequency line drift.

[0053] Preferably, the frequency stabilization method for DFB lasers is the saturated absorption spectroscopy (SAS) method, which can effectively suppress Doppler broadening with simple equipment and low cost, while taking into account frequency stabilization accuracy and environmental adaptability.

[0054] This frequency shifting scheme specifically refers to the use of frequency modulation devices to shift the laser frequency of the external cavity laser and the frequency control optical path. After frequency shifting, the external cavity laser is amplified by a TA (Transient Amplifier) ​​and shaped by a single-mode polarization-maintaining fiber before outputting the main laser beam. This beam is then split in the frequency control optical path, forming cooling and probe beams through different frequency shifting processes. The output light of the DFB laser is transformed into re-pump light through a specific frequency shifting process in the frequency control optical path.

[0055] Specifically, a frequency-controlled optical path device refers to an optical path that performs frequency shifting and timing control on cooling light, probe light, and re-pump light.

[0056] Preferably, the frequency modulation device is an acousto-optic modulator (AOM).

[0057] Preferably, the laser frequency of the external cavity laser has a frequency offset of -237.8MHz. After frequency shifting, the laser frequency is stabilized, and then amplified by a TA (transformer amplification) and output through a single-mode polarization-maintaining fiber, which is called the main laser.

[0058] Preferably, the frequency control optical path shifts the main laser frequency by a certain amount, with the offset being slightly less than 237.8MHz, causing the red line to detune at the D2 line F=2→F'=3, forming cooling light. After certain timing control, laser cooling of rubidium atoms is achieved.

[0059] Preferably, the frequency control optical path shifts the main laser frequency by 237.8MHz, resonating at the D2 line F=2→F'=3 to form a probe light, and then, after certain timing control, realizes the detection of cold atoms.

[0060] Preferably, the frequency control optical path shifts the output light of the DFB laser by 78.47MHz to resonate at the D2 line F=1→F'=2, forming re-pump light. After certain timing control, the re-pumping of cold atoms is realized.

[0061] The present invention proposes a high-stability frequency control optical path device and method for a rubidium fountain atomic clock. The key feature is the energy level scheme for frequency locking of the main laser source, which employs a modulation transfer spectrum (MTS) frequency stabilization method to lock the energy level at the specified energy level. 87 The Rb D2 line transitions from F=2 to F'=3. Utilizing the high sensitivity of this transition line to environmental factors, the stability of ECDL frequency locking can be effectively improved. Simultaneously, minimizing the optical path length and the number of components used in the frequency-shifting optical path, as well as the use of fiber optic devices, can significantly reduce the complexity of the optical system, thereby improving the overall stability of the rubidium fountain clock.

[0062] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0063] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A high-stability frequency control optical path device for a rubidium fountain atomic clock, characterized in that, It comprises: a main laser part and a repumping light part; upper cooling light, lower cooling light and probe light are formed by the main laser part; repumping light is formed by the repumping light part; the main laser part comprises: an ECDL external cavity laser, a 1 / 2 wave plate, a PBS prism, a mechanical switch (3), a mirror, an AOM acousto-optic modulator, a lens, a 1 / 4 wave plate, a fiber coupler; the repumping light part comprises: a DFB laser, a fourth AOM acousto-optic modulator (55), a seventh mirror (56), an eighth mirror (57), an eighth fiber coupler (58).

2. The rubidium fountain atomic clock high stability frequency control optical path device of claim 1, wherein, The ECDL external cavity laser splits into two beams, one of which is introduced into the frequency shift light path and the MTS frequency locking light path in turn for frequency locking, and the other of which is output after shaping through a single-mode polarization maintaining optical fiber to form the main laser.

3. The rubidium fountain atomic clock high stability frequency control optical path device of claim 2, wherein, The main laser passes through the first 1 / 2 wave plate (1) and the first PBS (2), and then passes through a mechanical switch (3), and is split into cooling light and probe light.

4. The rubidium fountain atomic clock high stability frequency control optical path device of claim 3, wherein, The cooling light is split into transmitted upper cooling light and reflected lower cooling light by the third 1 / 2 wave plate (6) and the third PBS (7).

5. The rubidium fountain atomic clock high stability frequency control optical path device of claim 4, wherein, The upper cooling light passes through the first mirror (8), the fourth 1 / 2 wave plate (9), the fourth PBS (10), the first AOM (11), the first lens (12), the second mirror (13), the first lens (12), and the first AOM (11) in turn, and the -1 order diffracted light passes through the reflection of the fourth PBS (10) and then is split after passing through the fifth 1 / 2 wave plate (14) and the fifth PBS (15), the transmitted light of the fifth PBS (15) passes through the polarization adjustment of the sixth 1 / 2 wave plate (16) and the first 1 / 4 wave plate (17) in turn, and is coupled to the first fiber coupler (18) to form the first upper cooling light; the reflected light of the fifth PBS (15) is split after passing through the seventh 1 / 2 wave plate (19) and the sixth PBS (20), the reflected light of the sixth PBS (20) passes through the polarization adjustment of the eighth 1 / 2 wave plate (21) and the second 1 / 4 wave plate (22) in turn, and is coupled to the second fiber coupler (23) to form the second upper cooling light; the transmitted light of the sixth PBS (20) passes through the polarization adjustment of the third mirror (24), the ninth 1 / 2 wave plate (25) and the third 1 / 4 wave plate (26) in turn, and is coupled to the third fiber coupler (27) to form the third upper cooling light.

6. The rubidium fountain atomic clock high stability frequency control optical path device of claim 5, wherein, The lower cooling light passes through the tenth 1 / 2 wave plate (28), the seventh PBS (29), the second AOM (30), the second lens (31), the fourth mirror (32), the second lens (31), the second AOM (30) in turn, the -1 order diffracted light passes through the reflection of the seventh PBS (29) and is split after passing through the eleventh 1 / 2 wave plate (33) and the eighth PBS (34), the transmission light of the eighth PBS (34) passes through the polarization adjustment of the twelfth 1 / 2 wave plate (35) and the fourth 1 / 4 wave plate (36) in turn and is coupled into the fourth fiber coupler (37) to form the first lower cooling light; the reflection light of the eighth PBS (34) passes through the thirteenth 1 / 2 wave plate (38) and the ninth PBS (39) and is split, the reflection light of the ninth PBS (39) passes through the polarization adjustment of the fourteenth 1 / 2 wave plate (40) and the fifth 1 / 4 wave plate (41) in turn and is coupled into the fifth fiber coupler (42) to form the second lower cooling light; the transmission light of the ninth PBS (39) passes through the polarization adjustment of the fifth mirror (43), the fifteenth 1 / 2 wave plate (44) and the sixth 1 / 4 wave plate (45) in turn and is coupled into the sixth fiber coupler (46) to form the third lower cooling light.

7. The rubidium fountain atomic clock high stability frequency control optical path device of claim 6, wherein, The probe light passes through the sixteenth 1 / 2 wave plate (47) and the tenth PBS (48) and passes through the third AOM (49), the third lens (50), the sixth mirror (51), the third lens (50), the third AOM (49) in turn, the -1 order diffracted light passes through the reflection of the tenth PBS (48) and is split, then passes through the polarization adjustment of the seventeenth 1 / 2 wave plate (52) and the seventh 1 / 4 wave plate (53) in turn and is finally coupled into the seventh fiber coupler (54) to form the probe light output.

8. The rubidium fountain atomic clock high stability frequency control optical path device of claim 7, wherein, The DFB laser splits two beams of light, one of which is introduced into the SAS frequency locking light path for frequency locking, and the other of which is output to the fourth AOM (55) for diffraction, the -1 order diffracted light after the fourth AOM (55) passes through the seventh mirror (56) and the eighth mirror (57) in turn and is coupled into the single-mode polarization maintaining fiber by the eighth fiber coupler (58) to form the re-pumping light output.

9. The rubidium fountain atomic clock high stability frequency control optical path device of claim 8, wherein, The mechanical switch is used for timing control of rubidium atom cooling.

10. A high stability frequency control optical path method for a rubidium fountain atomic clock, the method being applied to the device of 1-9, characterized in that, The application relates to a frequency locking device for a rubidium atom cooling system. Adopting 87 The frequency of the laser is locked by MTS modulation transfer spectroscopy and SAS saturated absorption spectroscopy, taking one of the two D2 lines sensitive to frequency fluctuation as reference line. The frequency of the external cavity laser is shifted by a frequency modulation device and a frequency control light path; the external cavity laser shifts the frequency and outputs main laser after TA amplification and single-mode polarization maintaining fiber shaping, the main laser is split in the frequency control light path, cooling light and probe light are formed by different frequency shifting processes; the output light of the DFB laser is subjected to a certain frequency shifting process in the frequency control light path to form re-pumping light. The mechanical switch is used for timing control of rubidium atom cooling. The application relates to a frequency locking device for a rubidium atom cooling system. The frequency of the external cavity laser is shifted by a frequency modulation device and a frequency control light path; the external cavity laser shifts the frequency and outputs main laser after TA amplification and single-mode polarization maintaining fiber shaping, the main laser is split in the frequency control light path, cooling light and probe light are formed by different frequency shifting processes; the output light of the DFB laser is subjected to a certain frequency shifting process in the frequency control light path to form re-pumping light.

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