A laser system and laser generation method applied to a strontium atomic optical clock

Abstract

The application discloses a laser system and a laser generation method applied to a strontium atomic optical clock, and the laser system comprises a plurality of seed lasers, a fiber amplifier, a fiber combiner, a fiber splitter and a nonlinear crystal, wherein the laser output by the second and third outputs of the seed lasers is combined, and after frequency conversion, 813nm laser is output; the laser output by the first output of the seed lasers is combined with the above-mentioned 813nm laser, and after frequency conversion, 461nm laser is output; the laser output by the fourth output of the seed lasers is divided into four beams, one of which is combined with the 813nm laser, after difference frequency conversion, 1397nm laser is output, and after frequency doubling, 698nm laser is output; the other three beams are combined with the laser output by the fifth, sixth and seventh outputs of the seed lasers respectively, and after frequency conversion, 679nm, 689nm and 707nm laser is output respectively. Seven special wavelength fiber seed lights are used in the application, and through the fiber amplifier and nonlinear frequency conversion, various wavelengths of laser required in the operation process of the strontium atomic optical clock are formed.

Description

Technical Field

[0001] This invention relates to the field of optics, and more specifically to a laser system and laser generation method for use in a strontium atomic optical clock. Background Technology

[0002] Atomic optical frequency standards are a research hotspot in the field of precision measurement. Currently, they have surpassed microwave atomic frequency standards in terms of frequency uncertainty and stability, and are expected to become the next-generation time and frequency standard. In the field of optical frequency standards, strontium atomic optical clocks hold an important research position. These neutral atomic optical clocks, based on optical lattice technology, are among the optical clocks with the best stability and uncertainty currently available. Strontium atomic optical clocks are not only valuable in the field of time and frequency metrology but also serve as a cutting-edge platform for precision measurement research. Portable and spatial optical clocks are crucial prerequisites for conducting precision measurement research, greatly expanding its scope. For optical clocks to achieve portability and spatialization, the system needs to be highly integrated, vibration-resistant, and capable of robust and stable operation over extended periods.

[0003] In strontium atomic optical clocks, ultracold atomic samples are prepared using atomic laser cooling and loaded into an optical lattice to confine the atoms, eliminating the Doppler shift and broadening effects caused by atomic motion on the transition spectral lines. Finally, an ultra-narrow linewidth laser is used for clock transition probing. The entire optical clock operation requires six wavelengths of laser light, including a 461nm primary cooling laser, 679nm and 707nm repumped lasers, a 689nm secondary cooling laser, a 698nm clock transition probing laser, and an 813nm optical lattice laser. Each wavelength has specific linewidths, frequencies, and power requirements. Because the lasers are mainly concentrated in short wavelengths with very specific wavelength values, currently reported commonly used strontium atomic optical clock laser systems are implemented using semiconductor laser schemes, including laser systems with multiple external cavity semiconductor lasers. Furthermore, to improve the accuracy of the strontium atomic optical clock, the clock laser requires a 1397nm wavelength laser output that can be stabilized on a latest-generation ultrastable cavity that is only compatible with infrared. Then, a 698nm clock transition interrogation laser is obtained through frequency doubling. The high-power 813nm optical lattice laser is used to reduce ASE noise, requiring a Ti:sapphire laser. Therefore, the entire laser system is very large and highly sensitive to environmental changes such as vibration. The laser is prone to mode jumping, causing loss of lock and making long-term stable operation difficult. Therefore, realizing a vibration-resistant, integrated, miniaturized laser system is a crucial technology for achieving the portability and spatialization of high-precision strontium atomic optical clocks. Summary of the Invention

[0004] The purpose of this invention is to provide a laser system and laser generation method for strontium atomic optical clocks. The fiber laser scheme realizes lasers with seven wavelengths including 461nm, 679nm, 707nm, 689nm, 698nm, 813nm and 1397nm. Each wavelength of laser is a single-frequency narrow linewidth laser with tunable frequency to meet the experimental frequency and power requirements. The whole system has integrated and vibration-resistant features, and can realize the portable function of high-precision strontium atomic optical clocks.

[0005] The purpose of this invention is to provide a fiber laser system to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A laser system for use in a strontium atomic optical clock includes seven seed lasers, comprising multiple seed lasers, an optical fiber amplifier, an optical fiber combiner, an optical fiber splitter, and a nonlinear crystal. The laser beams output from seed lasers two and three are combined and frequency-controlled by nonlinear crystal one to output a laser with a wavelength of 813 nm. The laser beam output from seed laser one and the aforementioned 813 nm laser are combined and frequency-controlled by nonlinear crystal five to output a laser with a wavelength of 461 nm.

[0008] The laser output from seed laser four is split into four beams. One beam is combined with the aforementioned 813nm laser and then frequency-multiplied by a nonlinear crystal to output a 1397nm laser. After being frequency-multiplied by a nonlinear crystal seven times, it outputs a 698nm laser. The other three beams are combined with the lasers output from seed laser five, seed laser six, and seed laser seven, respectively. After being frequency-multiplied by a nonlinear crystal, they output lasers with wavelengths of 679nm, 689nm, and 707nm, respectively.

[0009] In a further embodiment, seed laser one, seed laser five, seed laser six and seed laser seven are all ytterbium-doped fiber lasers, wherein the laser wavelength of seed laser one is 1064nm, the laser wavelength of seed laser five is 1043nm, the laser wavelength of seed laser six is ​​1067nm and the laser wavelength of seed laser seven is 1110nm.

[0010] The second seed laser is an erbium-doped fiber laser with a laser wavelength of 1534 nm.

[0011] Both seed laser three and seed laser four are thulium-doped fiber lasers, with seed laser three having a laser wavelength of 1731 nm and seed laser four having a laser wavelength of 1947 nm.

[0012] In a further embodiment, the output end of seed laser one is connected to a ytterbium-doped fiber amplifier, the output end of seed laser two is connected to an erbium-doped fiber amplifier, the output end of seed laser three is connected to a thulium-doped fiber amplifier one, and the output end of seed laser four is connected to a thulium-doped fiber amplifier two.

[0013] The nonlinear crystal is a PPLN crystal or a PPLN waveguide.

[0014] In a further embodiment, the output ends of the erbium-doped fiber amplifier and the thulium-doped fiber amplifier are connected to the nonlinear crystal via the fiber combiner. The output end of the nonlinear crystal is connected to the fiber splitter, which splits the laser generated by the nonlinear crystal into three outputs. The first output is a direct 813nm laser; the second output, along with the output end of the ytterbium-doped fiber amplifier, is connected to the fiber combiner, which is connected to the nonlinear crystal; and the third output, along with the output end of the thulium-doped fiber amplifier, is connected to the fiber combiner, which is connected to the nonlinear crystal. The fiber combiner is connected to the nonlinear crystal via the nonlinear crystal.

[0015] The output end of the thulium-doped fiber amplifier 2 is connected to fiber optic beam splitter 1. Fiber optic beam splitter 1 splits the laser beam amplified by the thulium-doped fiber amplifier 2 into four outputs. One output is combined with the laser beam split by fiber optic beam splitter 2; the second output and the output end of seed laser 5 are connected to fiber optic beam combiner 2; the third output and the output end of seed laser 6 are connected to fiber optic beam combiner 3; and the fourth output and the output end of seed laser 7 are connected to fiber optic beam combiner 4. The output ends of fiber optic beam combiner 2, fiber optic beam combiner 3, and fiber optic beam combiner 4 are each connected to a nonlinear crystal for laser and frequency conversion.

[0016] Another objective of this invention is to provide a laser generation method for use in a strontium atomic optical clock, comprising the following steps:

[0017] (1) Select the wavelengths of the erbium-doped fiber laser and the thulium-doped fiber laser, perform frequency summation on the lasers emitted by the two lasers, and make the wavelength of the laser generated after frequency summation 813nm.

[0018] (2) The 813nm laser and a ytterbium-doped fiber laser are combined to generate a laser with a wavelength of 461nm.

[0019] (3) The laser with a wavelength of 813nm generated in step (1) and the second thulium-doped fiber laser are frequency-differentially frequency-differentially frequency-differentially frequency-differentially frequency-differentially frequency-differentially-frequency ...

[0020] (4) Frequency doubling of the 1397nm laser produces a laser with a wavelength of 698nm;

[0021] (5) The laser generated by the thulium-doped fiber laser in step (3) is split into four paths by a beam splitter. Three of these paths are combined with three ytterbium-doped fiber lasers that emit lasers of different wavelengths to generate lasers with wavelengths of 679, 689 and 707 nm, respectively.

[0022] In a further embodiment, the formula for the sum-frequency conversion of the laser beams from the ytterbium-doped fiber laser and the thulium-doped fiber laser is as follows:

[0023]

[0024] In the formula, λ Y This indicates the laser wavelength and λ emitted by the ytterbium-doped fiber laser. T The wavelength of the laser emitted by the thulium-doped fiber laser is indicated by 'i', where 'i' represents the number.

[0025] In a further step, the laser wavelength of the erbium-doped fiber laser in step (1) is 1534 nm and the laser wavelength of the thulium-doped fiber laser is 1731 nm.

[0026] In step (2), the wavelength of the ytterbium-doped fiber laser is 1064 nm.

[0027] In step (3), the laser wavelength of the second thulium-doped fiber laser is 1947 nm.

[0028] In step (5), the laser wavelengths of the three ytterbium-doped fiber lasers emitting different wavelengths are 1043 nm, 1067 nm, and 1110 nm, respectively.

[0029] In a further embodiment, the sum frequency, doubling frequency, and difference frequency all employ nonlinear devices to expand the range of laser wavelengths by utilizing nonlinear processes to change the frequency. The nonlinear devices are PPLN crystals or PPLN waveguides.

[0030] The preferred embodiment is that in steps (1) and (2), PPLN crystals and frequency-generated lasers with wavelengths of 813nm and 461nm are used.

[0031] In step (5), the thulium-doped fiber laser II and the three ytterbium-doped fiber lasers that emit lasers of different wavelengths are frequency-sum ...

[0032] In a further embodiment, the ytterbium-doped fiber laser, the erbium-doped fiber laser, and the thulium-doped fiber laser are all narrow-linewidth single-frequency fiber lasers, with linewidths less than 99 kHz, and they have frequency tuning mechanisms.

[0033] This application uses a fiber laser system to realize lasers with seven wavelengths including 461nm, 679nm, 707nm, 689nm, 698nm, 813nm and 1397nm. Each wavelength of laser is a single-frequency narrow linewidth laser with tunable frequency, which meets the experimental frequency and power requirements. The system is integrated and vibration-resistant, and can realize the portable function of a high-precision strontium atomic optical clock.

[0034] The fiber laser system described in this application can be applied to strontium atomic optical clocks. It utilizes a fiber laser scheme to realize all the wavelengths of laser light required for strontium atomic optical clocks, meeting the requirements for high-precision atomic preparation and trapping in terms of frequency, power, and ASE noise. This application uses seven wavelengths of fiber seed light, which can be designed to be multiplexed to generate multiple lasers of different wavelengths. Through fiber amplifiers and nonlinear frequency changes, the various wavelengths of laser light required for the operation of strontium atomic optical clocks are ultimately formed.

[0035] The laser system in this application has extremely high integration, and the optical fiber itself has no spatial optical path, which makes the system have better vibration resistance. This plays a great role in realizing the portability of high-precision strontium atomic optical clocks and can promote the field application research of optical clocks. Attached Figure Description

[0036] Figure 1 This is a schematic diagram illustrating the principle of the present invention.

[0037] In the diagram, 1-Seed laser one; 2-Seed laser two; 3-Seed laser three; 4-Seed laser four; 5-Seed laser five; 6-Seed laser six; 7-Seed laser seven; 8-Ytterbium-doped fiber amplifier; 9-Er-doped fiber amplifier; 10-Thulium-doped fiber amplifier one; 11-Thulium-doped fiber amplifier two; 12-Fiber optic bundle splitter one; 13-Fiber optic bundle combiner one; 14-Nonlinear crystal one; 15-Fiber optic bundle combiner two; 16-Fiber optic bundle combiner three; 17-Fiber optic bundle combiner four; 18-Fiber optic bundle splitter two; 19-Nonlinear crystal two; 20-Nonlinear crystal three; 21-Nonlinear crystal four; 22-Fiber optic bundle combiner five; 23-Fiber optic bundle combiner six; 24-Nonlinear crystal five; 25-Nonlinear crystal six; 26-Nonlinear crystal seven. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1:

[0040] A laser system for use in a strontium atomic optical clock, in this embodiment specifically includes seven seed lasers, four fiber amplifiers, six fiber combiners, two fiber splitters, and seven nonlinear crystals. The laser beams output from seed laser 2 and seed laser 3 are combined and frequency-controlled by nonlinear crystal 14 to output a laser with a wavelength of 813 nm. The laser beam output from seed laser 1 and the aforementioned 813 nm laser are combined and frequency-controlled by nonlinear crystal 54 to output a laser with a wavelength of 416 nm.

[0041] The laser output from seed laser 4 is split into four beams. One beam is combined with the aforementioned 813nm laser and then frequency-differentiated by nonlinear crystal 6 25 to output a 1397nm laser. After frequency-doubled by nonlinear crystal 7 26, it outputs a 698nm laser. The other three beams are combined with the lasers output from seed laser 5, seed laser 6, and seed laser 7, respectively. After frequency-doubled by nonlinear crystals, they output lasers with wavelengths of 679nm, 689nm, and 707nm, respectively.

[0042] The wavelengths that fiber lasers can produce are mainly related to the doping material of their active fiber. Currently, the wavelength range that commercial fiber lasers can produce includes:

[0043] Ytterbium-doped fiber laser λ Y =1018nm~1156nm,

[0044] erbium-doped fiber laser λ E =1530nm~1596nm,

[0045] Thulium-doped fiber laser λ T =1730nm~2050nm.

[0046] From a wavelength range perspective, existing doped fiber lasers cannot directly generate the laser wavelengths used in strontium atomic optical clocks. Therefore, nonlinear devices are needed to extend the wavelength range by utilizing nonlinear processes to change the frequency. These nonlinear frequency changes include harmonics, sum frequencies, and difference frequencies.

[0047] By using ytterbium-doped fiber lasers and thulium-doped fiber lasers for laser frequency modulation, laser wavelengths covering the range of 641 nm to 739 nm can be generated. Therefore, lasers with wavelengths of λ can be used. Y1 / Y2 / Y3 Three ytterbium-doped fiber lasers were respectively coupled to a wavelength of λ. T1 / T2 / T3 Three thulium-doped fiber lasers and their frequencies can generate λ. 1 / 2 / 3 =Laser with three wavelengths: 679nm, 689nm, and 707nm. And using an erbium-doped fiber laser with a wavelength of λ... E and a thulium-doped fiber laser with a wavelength of λ T4By performing frequency summation, laser wavelengths covering the range of 812nm to 879nm can be generated, and theoretically, 813nm wavelength lasers can be produced. Therefore, by selecting erbium-doped fiber lasers and thulium-doped fiber lasers of suitable wavelengths, such as erbium-doped fiber lasers with a wavelength of 1534nm and thulium-doped fiber lasers with a wavelength of 1731nm, and performing frequency summation on these two lasers, a laser wavelength of 813nm will be generated.

[0048] In this embodiment, seed laser one, seed laser five, seed laser six and seed laser seven are all ytterbium-doped fiber lasers, wherein the laser wavelength of seed laser one is 1064nm, the laser wavelength of seed laser five is 1043nm, the laser wavelength of seed laser six is ​​1067nm and the laser wavelength of seed laser seven is 1110nm.

[0049] Seed laser 2 is an erbium-doped fiber laser with a laser wavelength of 1534nm; seed laser 3 and seed laser 4 are both thulium-doped fiber lasers, with seed laser 3 having a laser wavelength of 1731nm and seed laser 4 having a laser wavelength of 1947nm.

[0050] In a further embodiment, the output end of seed laser one is connected to a ytterbium-doped fiber amplifier, the output end of seed laser two is connected to an erbium-doped fiber amplifier, the output end of seed laser three is connected to a thulium-doped fiber amplifier one, and the output end of seed laser four is connected to a thulium-doped fiber amplifier two.

[0051] The nonlinear crystal is either a PPLN crystal or a PPLN waveguide. In practice, the PPLN crystal or PPLN waveguide is selected based on the power required for the final laser. For example, the 461nm and 813nm lasers in a strontium atomic clock require watt-level power, so a PPLN crystal is chosen as the nonlinear device; while the 679 / 689 / 707nm lasers require tens to hundreds of milliwatts of power, so a PPLN waveguide is chosen as the nonlinear device.

[0052] Specifically, such as Figure 1 As shown, a laser system for a strontium atomic clock has seven types of fiber seed light generated by seven seed lasers. Among them, seed laser 1 is a ytterbium-doped fiber laser that generates fiber seed light with a wavelength of 1064nm. It is a single-frequency narrow linewidth output, and its wavelength can be tuned by the temperature in the ytterbium-doped fiber laser and the piezoelectric ceramic (PZT) set in it. Then, the power is amplified to more than 3W by the ytterbium-doped fiber amplifier 8.

[0053] Seed laser 2 is an erbium-doped fiber laser, generating 1534nm fiber seed light, which is amplified to over 10W by erbium-doped fiber amplifier 9; Seed laser 3 is a thulium-doped fiber laser, generating 1731nm fiber seed light, which is amplified to over 10W by thulium-doped fiber amplifier 10; The amplified lasers from these two sources are then passed through fiber combiner 13 and nonlinear crystal 14 (a PPLN crystal) to generate approximately 3W of 813nm laser light; After passing through fiber splitter 18, the laser light is split into three paths, one of which is a direct output of 1W; the second path, with a 1W laser light and a 3W 1064nm laser light, is frequency-multiplied by nonlinear crystal 5 (a PPLN crystal) 24 to generate 500mW of 461nm laser light; The third path, with approximately 1W laser light and a 1947nm laser light, is frequency-multiplied by nonlinear crystal 6 25 to generate 1397nm laser light.

[0054] The 1947nm fiber seed light is amplified to over 2W by a thulium-doped fiber amplifier 11, and then split into four paths by a fiber splitter 12: the first path is combined with approximately 0.2W of 1043nm laser light through a nonlinear crystal 2 (PPLN waveguide) 19 to generate 679nm laser light; the second path is combined with approximately 0.5W of 1067nm laser light through a nonlinear crystal 3 (PPLN waveguide) 20 to generate 689nm laser light; the third path is combined with approximately 0.2W of 1110nm fiber laser light through a nonlinear crystal 4 (PPLN waveguide) 21 to generate 707nm laser light; the fourth path, approximately 300mW, is combined with 1.5W of 813nm laser light through a fiber splitter 6 23, and then through a nonlinear crystal 6 (PPLN difference frequency waveguide) 25 to generate approximately 300mW of 1397nm laser light, which is then passed through a nonlinear crystal 6 (PPLN frequency doubling waveguide) 26 to generate 698nm interrogation laser light.

[0055] Example 2:

[0056] A laser generation method for use in a strontium atomic optical clock includes the following steps:

[0057] (1) Select the wavelengths of the erbium-doped fiber laser and the thulium-doped fiber laser, perform frequency summation on the lasers emitted by the two lasers, and make the wavelength of the laser generated after frequency summation 813nm.

[0058] (2) The 813nm laser and a ytterbium-doped fiber laser are combined to generate a laser with a wavelength of 461nm.

[0059] (3) The laser with a wavelength of 813nm generated in step (1) and the second thulium-doped fiber laser are frequency-differentially frequency-differentially frequency-differentially frequency-differentially frequency-differentially frequency-differentially-frequency ...

[0060] (4) Frequency doubling of the 1397nm laser produces a laser with a wavelength of 698nm;

[0061] (5) The laser generated by the thulium-doped fiber laser in step (3) is split into four paths by a beam splitter. Three of these paths are combined with three ytterbium-doped fiber lasers that emit lasers of different wavelengths to generate lasers with wavelengths of 679, 689 and 707 nm, respectively.

[0062] In a further scheme, the formula for the sum-frequency of the laser beams from ytterbium-doped fiber lasers and thulium-doped fiber lasers is:

[0063]

[0064] In the formula, λ Y This indicates the laser wavelength and λ emitted by the ytterbium-doped fiber laser. T The wavelength of the laser emitted by the thulium-doped fiber laser is represented by , and i represents the quantity.

[0065] According to the above formula, using a wavelength of λ Y1 / Y2 / Y3 Three ytterbium-doped fiber lasers were respectively coupled to a wavelength of λ. T1 / T2 / T3 Three thulium-doped fiber lasers and frequency converters generate λ. 1 / 2 / 3 = Lasers with three wavelengths: 679nm, 689nm, and 707nm.

[0066] We used an erbium-doped fiber laser with a wavelength of λ E and a thulium-doped fiber laser with a wavelength of λ T4 By performing frequency matching, a laser wavelength range covering 812nm to 879nm can be generated. After adjustment, if the laser wavelength of the erbium-doped fiber laser is selected as 1534nm and the laser wavelength of the thulium-doped fiber laser is selected as 1731nm, then an 813nm wavelength laser will be generated.

[0067] After generating an 813nm wavelength laser, this laser can be combined with a ytterbium-doped fiber laser to generate a 461nm laser. The wavelength λ of the ytterbium-doped fiber laser can then be calculated using the formula. Y4 The value of λ Y4 =1065nm, specifically as follows:

[0068]

[0069] Furthermore, with the availability of 813nm wavelength lasers, this wavelength laser can be used in conjunction with a thulium-doped fiber laser to generate 1397nm lasers through difference frequency modulation.

[0070]

[0071] λ T4 =1945nm

[0072] The laser wavelength of the second thulium-doped fiber laser is 1945nm, and then a 698nm laser is generated through a frequency doubling process.

[0073] λ T4 The thulium-doped fiber laser beam is split into four paths by a beam splitter, which can also be used to generate lasers with three wavelengths of 679 / 689 / 707nm. This simplifies the number of lasers required; only four ytterbium-doped fiber lasers, one thulium-doped fiber laser, and two thulium-doped fiber lasers are needed. T1 / T2 / T3 =λ T4 =1945nm, then λ Y1 =1043nm, λ Y2 =1067nm, λ Y1 =1110nm. That is, the laser wavelengths of the three ytterbium-doped fiber lasers emitting laser light of different wavelengths are 1043nm, 1067nm, and 1110nm, respectively.

[0074] In a further embodiment, the sum frequency, doubling frequency, and difference frequency all employ nonlinear devices to expand the range of laser wavelengths by utilizing nonlinear processes to change the frequency. The nonlinear devices are PPLN crystals or PPLN waveguides.

[0075] Since the 461nm and 813nm lasers in the strontium atomic optical clock require watt-level power, the fiber laser used for sum-frequency generation is used as the seed light. After being amplified by an amplifier, a nonlinear device is used, and the nonlinear device is selected as a PPLN crystal. Therefore, in steps (1) and (2), the wavelengths of 813nm and 461nm lasers generated by sum-frequency generation are both PPLN crystals.

[0076] The 679 / 689 / 707nm lasers require tens to hundreds of milliwatts of power, and the nonlinear devices use PPLN waveguides. Therefore, in step (5), the second thulium-doped fiber laser and the three ytterbium-doped fiber lasers that emit lasers of different wavelengths use PPLN waveguides for summation.

[0077] A further approach involves using narrow-linewidth single-frequency lasers for the strontium atomic optical clock, which require continuous output and tunable frequency. Therefore, the fiber lasers used are all narrow-linewidth single-frequency fiber lasers with linewidths in the tens of kHz range or below, and they also require a frequency tuning mechanism.

[0078] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0079] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A laser system for use in a strontium atomic optical clock, comprising multiple seed lasers, an optical fiber amplifier, an optical fiber combiner, an optical fiber splitter, and a nonlinear crystal, characterized in that: There are seven seed lasers. The laser beams output from seed laser two and seed laser three are combined and frequency-controlled by nonlinear crystal one to output a laser with a wavelength of 813nm. The laser beam output from seed laser one and the aforementioned 813nm laser are combined and frequency-controlled by nonlinear crystal five to output a laser with a wavelength of 461nm. The laser output from seed laser four is split into four beams. One beam is combined with the aforementioned 813nm laser and then frequency-multiplied by a nonlinear crystal to output a 1397nm laser. After being frequency-multiplied by a nonlinear crystal seven times, it outputs a 698nm laser. The other three beams are combined with the lasers output from seed laser five, seed laser six, and seed laser seven, respectively. After being frequency-multiplied by a nonlinear crystal, they output lasers with wavelengths of 679nm, 689nm, and 707nm, respectively.

2. The laser system according to claim 1, characterized in that: Seed laser 1, seed laser 5, seed laser 6 and seed laser 7 are all ytterbium-doped fiber lasers, wherein the laser wavelength of seed laser 1 is 1064nm, the laser wavelength of seed laser 5 is 1043nm, the laser wavelength of seed laser 6 is 1067nm and the laser wavelength of seed laser 7 is 1110nm. The second seed laser is an erbium-doped fiber laser with a laser wavelength of 1534 nm. Both seed laser three and seed laser four are thulium-doped fiber lasers, with seed laser three having a laser wavelength of 1731 nm and seed laser four having a laser wavelength of 1947 nm.

3. The laser system according to claim 1, characterized in that: The output end of the seed laser one is connected to a ytterbium-doped fiber amplifier, the output end of the seed laser two is connected to an erbium-doped fiber amplifier, the output end of the seed laser three is connected to a thulium-doped fiber amplifier one, and the output end of the seed laser four is connected to a thulium-doped fiber amplifier two. The nonlinear crystal is a PPLN crystal or a PPLN waveguide.

4. The laser system according to claim 3, characterized in that: The output ends of the erbium-doped fiber amplifier and the thulium-doped fiber amplifier are connected to the nonlinear crystal 1 via fiber combiner 1. The output end of the nonlinear crystal 1 is connected to the fiber splitter 2, which splits the laser generated by the nonlinear crystal 1 into three outputs. The first output is a direct 813nm laser. The second output, along with the output end of the ytterbium-doped fiber amplifier, is connected to the fiber combiner 5, which is connected to the nonlinear crystal 5. The third output, along with the output end of the thulium-doped fiber amplifier 2, is connected to the fiber combiner 6, which is connected to the nonlinear crystal 7 via the nonlinear crystal 6. The output end of the thulium-doped fiber amplifier 2 is connected to the fiber beam splitter 1. The fiber beam splitter 1 splits the laser beam amplified by the thulium-doped fiber amplifier 2 into four outputs, one of which is combined with the laser beam split by the fiber beam splitter 2. The output of the second laser and the output of the seed laser five are connected together to the second fiber combiner; the output of the third laser and the output of the seed laser six are connected together to the third fiber combiner; and the output of the fourth laser and the output of the seed laser seven are connected together to the fourth fiber combiner. The outputs of the second, third, and fourth fiber combiners are each connected to a nonlinear crystal for laser and frequency conversion.

5. A laser generation method for use in a strontium atomic optical clock, characterized in that: Includes the following steps: (1) Select the wavelengths of the erbium-doped fiber laser and the thulium-doped fiber laser, perform frequency summation on the lasers emitted by the two lasers, and make the wavelength of the laser generated after frequency summation 813nm. (2) The 813nm laser and a ytterbium-doped fiber laser are combined to generate a laser with a wavelength of 461nm. (3) The laser with a wavelength of 813nm generated in step (1) and the second thulium-doped fiber laser are frequency-differentially frequency-differentially frequency-differentially frequency-differentially frequency-differentially frequency-differentially-frequency ... (4) Frequency doubling of the 1397nm laser produces a laser with a wavelength of 698nm; (5) The laser generated by the thulium-doped fiber laser in step (3) is split into four paths by a beam splitter. Three of these paths are combined with three ytterbium-doped fiber lasers that emit lasers of different wavelengths to generate lasers with wavelengths of 679, 689 and 707 nm, respectively.

6. The laser generation method according to claim 5, characterized in that: The formulas for summing the frequencies of the ytterbium-doped fiber laser and the thulium-doped fiber laser are as follows: In the formula, λ Y This indicates the laser wavelength and λ emitted by the ytterbium-doped fiber laser. T The wavelength of the laser emitted by the thulium-doped fiber laser is indicated by 'i', where 'i' represents the number.

7. The laser generation method according to claim 6, characterized in that: In step (1), the laser wavelength of the erbium-doped fiber laser is 1534 nm and the laser wavelength of the thulium-doped fiber laser is 1731 nm. In step (2), the wavelength of the ytterbium-doped fiber laser is 1064 nm. In step (3), the laser wavelength of the second thulium-doped fiber laser is 1947 nm. In step (5), the laser wavelengths of the three ytterbium-doped fiber lasers emitting different wavelengths are 1043 nm, 1067 nm, and 1110 nm, respectively.

8. The laser generation method according to claim 5, characterized in that: The sum, doubling, and difference frequencies all employ nonlinear devices to extend the range of laser wavelengths by utilizing nonlinear processes to change the frequency. The nonlinear devices are PPLN crystals or PPLN waveguides.

9. The laser generation method according to claim 8, characterized in that: In steps (1) and (2), PPLN crystals and frequency-generated lasers with wavelengths of 813nm and 461nm are used. In step (5), the thulium-doped fiber laser II and the three ytterbium-doped fiber lasers that emit lasers of different wavelengths are frequency-sum ...

10. The laser generation method according to claim 5, characterized in that: The ytterbium-doped fiber laser, erbium-doped fiber laser, and thulium-doped fiber laser are all narrow-linewidth single-frequency fiber lasers, with linewidths less than 99 kHz and frequency tuning mechanisms.

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