Laser frequency stabilization method for three-photon excited Rydberg atom microwave detection system

Abstract

A kind of laser frequency stabilization method of three-photon excitation Rydberg atom microwave detection system, including modulation signal generator, probe laser frequency stabilization unit, decorating laser frequency stabilization unit and coupling laser frequency stabilization unit, modulation signal generator generates modulation signal and acts on probe laser, to generate modulated probe laser;Modulated probe laser frequency is stabilized on the required first order transition frequency of alkali metal atom using probe laser frequency stabilization unit, output after frequency stabilization modulated probe laser and respectively split a part of after frequency stabilization modulated probe laser input to decorating laser frequency stabilization unit, coupling laser frequency stabilization unit, decorating laser is stabilized on the required second order transition frequency of alkali metal atom by decorating laser frequency stabilization unit, and coupling laser is stabilized on the required third order transition frequency of alkali metal atom by coupling laser frequency stabilization unit.The present application uses the spectrum generated by atomic transition as reference, and locks the laser frequency on the required atomic transition.

Description

Technical Field

[0001] This invention belongs to the field of laser frequency stabilization technology, and more specifically, relates to a laser frequency stabilization method for a three-photon excited Rydberg atom microwave detection system. Background Technology

[0002] Rydberg atoms are highly excited-state atoms with very large principal quantum numbers n, and their radiation lifetime is related to n. 3 Proportional to n, electric dipole moment and n 4 Proportional to n, polarizability and n 7 These properties make the Rydberg atom an excellent physical platform for research in fields such as quantum storage, quantum computing, and quantum precision measurement.

[0003] Currently, most Rydberg atom fabrications are achieved through two-photon excitation. Two-photon excitation requires a low-power, weak probe laser and a high-power, strong coupling laser. The probe laser can be generated using existing semiconductor laser technology; however, the coupling laser, whether the 480nm laser required for rubidium atom excitation or the 510nm laser required for cesium atom excitation, currently requires a high-power frequency-doubling crystal. This leads to a significant increase in the overall system size, weight, and power consumption, limiting the overall system integration and making it difficult to meet the requirements of practical engineering applications. Furthermore, the large Doppler residual in two-photon excitation limits further improvements in measurement sensitivity.

[0004] In contrast, the three-photon excitation technique for Rydberg atoms can utilize three infrared wavelengths of semiconductor lasers, significantly reducing system size and power consumption. Furthermore, three-photon excitation can further reduce Doppler residuals, thereby improving system measurement sensitivity. However, currently, the frequency stabilization systems for most three-photon excited Rydberg atom detection experiments are based on ultrastable cavities. The Pound-Drever-Hall (PDH) frequency-locking method based on ultrastable cavities has a high signal-to-noise ratio in phase detection curves and can narrow the laser linewidth. However, this method requires extremely high mechanical and temperature stability and is very sensitive to external environmental disturbances, limiting its application to relatively stable temperature and humidity laboratory environments. This makes it unsuitable for the high integration characteristics of three-photon excitation schemes, restricting the current level of engineering practicality for three-photon excited Rydberg atom microwave detection systems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a laser frequency stabilization method for a three-photon excited Rydberg atom microwave detection system.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: This invention provides a laser frequency stabilization method for a three-photon excited Rydberg atom microwave detector system, comprising: The modulation signal generator produces a first modulation signal that acts on the probe laser generated by the probe laser to produce a modulated probe laser; The frequency of the modulated probe laser is stabilized at the required first-order transition frequency of alkali metal atoms using the probe laser frequency stabilization unit. The frequency stabilized modulated probe laser is output and a portion of the frequency stabilized modulated probe laser is split and input to the decorative laser frequency stabilization unit and the coupled laser frequency stabilization unit. The saturated laser frequency stabilization unit uses the interaction between the saturated laser generated by the saturated laser and the frequency-stabilized modulated probe laser to generate a modulated electromagnetically induced transparent spectral signal. Based on the interaction between the electromagnetically induced transparent spectral signal and the second modulation signal generated by the modulation signal generator, a saturated optical phase-detection feedback signal is generated and applied to the saturated laser to stabilize the frequency of the saturated laser at the required second-order transition frequency of alkali metal atoms. The frequency-stabilized saturated laser is output and a portion of the frequency-stabilized saturated laser is split and input to the coupled laser frequency stabilization unit. The coupling laser frequency stabilization unit uses the coupling laser generated by the coupling laser to interact with the frequency-stabilized modulated probe laser and the frequency-stabilized suffix laser to generate a modulated electromagnetically induced transparency / absorption spectrum signal. Based on the interaction between the electromagnetically induced transparency / absorption spectrum signal and the third modulation signal generated by the modulation signal generator, a coupling optical phase detection feedback signal is generated and applied to the coupling laser to stabilize the frequency of the coupling laser at the required third-order transition frequency of alkali metal atoms, and output the frequency-stabilized coupling laser.

[0007] Furthermore, the frequency-stabilized modulated probe laser, frequency-stabilized styling laser, and frequency-stabilized coupled laser outputs from the probe laser frequency stabilization unit, the styling laser, and the coupled laser are used for three-photon excited Rydberg atom microwave detection experiments.

[0008] Furthermore, a detection laser frequency stabilization unit is provided, comprising a detection laser, a first detection beam splitting unit, a second detection beam splitting unit, a third detection beam splitting unit, a detection beam frequency stabilization optical path unit, a first photodetector, and a detection beam phase detection feedback unit; a modulation signal generator is connected to the detection laser and the detection beam phase detection feedback unit; the detection laser is connected to the first detection beam splitting unit; the two outputs of the first detection beam splitting unit are respectively connected to the detection beam frequency stabilization optical path unit and the second detection beam splitting unit; the detection beam frequency stabilization optical path unit is connected to the first photodetector; the first photodetector is connected to the detection beam phase detection feedback unit; and the detection beam phase detection feedback unit is connected to the detection laser. The probe light frequency stabilization optical path unit includes a second half-wave plate for the probe light, a second polarization beam splitter for the probe light, a first gas chamber filled with alkali metal atoms, a quarter-wave plate for the probe light, and a first reflector for the probe light. The modulated probe laser entering the probe light frequency stabilization optical path unit changes its polarization direction through the second half-wave plate for the probe light. After being reflected by the second polarization beam splitter for the probe light, it enters the first gas chamber filled with alkali metal atoms. After passing through the first gas chamber, it changes its polarization direction again after passing through the quarter-wave plate for the probe light and the first reflector for the probe light. The incident and reflected light are collinear and opposite in direction, interacting with the alkali metal atoms to generate a modulated saturated absorption spectral signal. The saturated absorption spectral signal then enters the first photodetector and is converted into an electrical signal inside it.

[0009] Furthermore, another detection laser frequency stabilization unit is provided, which includes a detection laser, a first detection light beam splitting unit, a second detection light beam splitting unit, a detection light frequency stabilization optical path unit, a first photodetector, and a detection light phase detection feedback unit. The modulation signal generator is connected to the detection light phase detection feedback unit and the detection light frequency stabilization optical path unit. The detection laser is connected to the first detection light beam splitting unit, and the two outputs of the first detection light beam splitting unit are respectively connected to the detection light frequency stabilization optical path unit. The detection light frequency stabilization optical path unit is connected to the first photodetector and the second detection light beam splitting unit. The first photodetector is connected to the detection light phase detection feedback unit, and the detection light phase detection feedback unit is connected to the detection laser. Further, the detection light frequency stabilization optical path unit includes a second detection light reflector, a second detection light half-wave plate, a second detection light polarization beam splitting prism, a third detection light reflector, a first gas chamber filled with alkali metal atoms, an electro-optic modulator, and a fourth detection light reflector. The detector laser, after being reflected by the second detector laser mirror, enters the second half-wave plate of the detector laser, changing its polarization direction. After passing through the second polarization beam-splitting prism of the detector laser, it is split into two beams. One beam is transmitted into the first gas chamber filled with alkali metal atoms, and the other beam is reflected by the third detector laser mirror and enters the electro-optic modulator. The first modulation signal generated by the modulation signal generator acts on the electro-optic modulator to modulate the detector laser input to the electro-optic modulator. The output laser of the electro-optic modulator is reflected by the fourth detector laser mirror and split into two by the first detector laser beam splitter. The modulated detector laser reflected by the first beam splitter re-enters the first gas chamber. In the first gas chamber, the modulated detector laser and the unmodulated detector laser are collinear and opposite in direction and interact with the alkali metal atoms to generate a modulated saturated absorption spectrum signal. The saturated absorption spectrum signal then enters the first photodetector and is converted into an electrical signal inside the first photodetector.

[0010] Furthermore, the embellished laser frequency stabilization unit includes an embellished laser, a first embellished light beam splitting unit, a second embellished light beam splitting unit, an embellished light frequency stabilization optical path unit, a second photodetector, and an embellished light phase detection feedback unit; the modulation signal generator is connected to the embellished light phase detection feedback unit; the embellished laser is connected to the first embellished light beam splitting unit, the first embellished light beam splitting unit is connected to the second embellished light beam splitting unit and the embellished light frequency stabilization optical path unit, the embellished light frequency stabilization optical path unit is connected to the second photodetector, the second photodetector is connected to the embellished light phase detection feedback unit, the embellished light phase detection feedback unit is connected to the embellished laser, and the frequency-stabilized modulated detection laser is input to the embellished light frequency stabilization optical path unit.

[0011] Furthermore, the coupled laser frequency stabilization unit includes a coupled laser, a coupled light first beam splitting unit, a coupled light frequency stabilization optical path unit, a third photodetector, and a coupled light phase detection feedback unit; the modulation signal generator is connected to the coupled light phase detection feedback unit, the coupled laser is connected to the coupled light first beam splitting unit, the coupled light first beam splitting unit is connected to the coupled light frequency stabilization optical path unit, the coupled light frequency stabilization optical path unit is connected to the third photodetector, the third photodetector is connected to the coupled light phase detection feedback unit, the coupled light phase detection feedback unit is connected to the coupled laser, and the frequency-stabilized modulated probe laser and the frequency-stabilized suffix laser are input to the coupled light frequency stabilization optical path unit.

[0012] Furthermore, the embellished optical frequency stabilization optical path unit includes a second gas chamber filled with alkali metal atoms. The embellished laser enters the second gas chamber, and after frequency stabilization, the modulated probe laser and the embellished laser enter the second gas chamber in opposite directions along the same line. They interact in the second gas chamber to generate a modulated electromagnetically induced transparent spectral signal. The coupled light frequency stabilization optical path unit includes a third gas chamber filled with alkali metal atoms. The coupled laser enters the third gas chamber. After frequency stabilization, the styling laser and the coupled laser enter the third gas chamber in the same direction and along the same line. After frequency stabilization, the modulated probe laser and the styling laser and the coupled laser enter the third gas chamber in opposite directions and along the same line. They interact in the third gas chamber to generate a modulated electromagnetically induced transparent / absorption spectral signal.

[0013] Furthermore, the probe light phase detection feedback unit, the embellishment light phase detection feedback unit, and the coupling light phase detection feedback unit have the same structure, all including a phase shifter, a mixer, a low-pass filter, and a feedback unit. The input electrical signal enters the mixer through one port, and the modulation signal generated by the modulation signal generator enters the mixer through the other port after passing through the phase shifter. Adjusting the phase shift of the phase shifter can change the amplitude of the down-converted signal. The down-converted signal output by the mixer is filtered by the low-pass filter and then enters the feedback unit to output the phase detection feedback signal.

[0014] The beneficial effects that this invention can produce are as follows: This invention provides a laser frequency stabilization method for a three-photon excited Rydberg atom microwave detection system, comprising: a probe laser, a dummy laser, a coupling laser, a laser beam splitting unit, a frequency stabilization optical path unit, a photodetector, a phase detection feedback unit, and a modulation signal generator. The probe laser, dummy laser, and coupling laser respectively generate a probe laser, a dummy laser, and a coupling laser near the desired frequency. Subsequently, the three laser beams are split into their respective laser beam splitting units, with one beam used for detection experiments and the other one or more beams used for laser frequency stabilization. The split probe laser, dummy laser, and coupling laser then enter their respective frequency stabilization optical path units to generate a frequency-stabilized spectral signal modulated by a modulation signal generator. This signal is converted into an electrical signal by the photodetector and then enters its respective phase detection feedback unit. Within the phase detection feedback units corresponding to the probe laser, dummy laser, and coupling laser, the modulation signal generated by the modulation signal generator interacts with the electrical signal converted by the photodetector, generating a feedback signal for laser frequency stabilization and acting on the corresponding laser.

[0015] This invention utilizes the spectrum generated by atomic transitions as a reference to lock the laser frequency at the desired atomic transition. Since the atomic transition frequency is unaffected by external environmental interference, the reference spectrum frequency stabilization method is beneficial for improving the miniaturization and engineering practicality of three-photon excited Rydberg atom microwave detection systems. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structural principle of the laser frequency stabilization device (laser internal modulation frequency stabilization) of a three-photon excited Rydberg atom microwave detection system in one embodiment; Figure 2 This is a schematic diagram of the structural principle of the laser frequency stabilization device (laser external modulation frequency stabilization) of a three-photon excited Rydberg atom microwave detection system in one embodiment; Figure 3 This is a schematic diagram of a specific embodiment of the laser frequency stabilization device (laser internal modulation frequency stabilization) of a three-photon excited Rydberg atom microwave detection system; Figure 4 This is a schematic diagram of a specific embodiment of the laser frequency stabilization device (external laser modulation frequency stabilization) of a three-photon excited Rydberg atom microwave detector system; Numbering on the map: 11. Detecting the laser; 111. Detecting the laser output from the laser; 12. First beam splitter unit for probe light; 121. First modulated probe laser; 122. Second modulated probe laser; 123. First half-wave plate for probe light; 124. First polarizing beam splitter prism for probe light; 13. Second beam splitter unit for probe light; 131. Third modulated probe laser; 132. Fourth modulated probe laser; 133. Third half-wave plate for probe light; 134. Third polarization beam splitter prism for probe light; 14. Third beam splitter unit for probe light; 141. Fifth modulated probe laser; 142. Sixth modulated probe laser; 143. Fourth half-wave plate for probe light; 144. Fourth polarization beam splitter prism for probe light; 15. Probe light frequency stabilization optical path unit; 151. Saturated absorption spectral signal; 152. Seventh modulated probe laser; 153. Probe light second half-wave plate; 154. Probe light second polarization beam splitter prism; 155. First gas cell; 156. Probe light quarter-wave plate; 157. Probe light first reflector; 158. Probe light second reflector; 159. Probe light third reflector; 1510. Electro-optic modulator; 1511. Electro-optic modulator output laser; 1512. Probe light fourth reflector; 1513. Probe light first beam splitter; 1514. Eighth modulated probe laser; 16. First photodetector; 161. First electrical signal; 17. Detection optical phase detection feedback unit; 171. Detection optical phase detection feedback signal; 172. First phase shifter; 173. First mixer; 174. First low-pass filter; 175. First feedback unit; 21. Decorative laser; 211. Decorative laser; 22. First beam splitter unit for embellished light; 221. First embellished laser beam; 222. Second embellished laser beam; 223. First half-wave plate for embellished light; 224. First polarizing beam splitter prism for embellished light; 23. Second beam splitter unit for embellished light; 231. Third embellished laser; 232. Fourth embellished laser; 233. Second half-wave plate for embellished light; 234. Second polarizing beam splitter prism for embellished light; 24. Decorative optical frequency-stabilized optical path unit; 241. Modulation of electromagnetically induced transparent spectral signal; 242. First dichroic mirror; 243. Second gas cell; 25. Second photodetector; 251. Second electrical signal; 26. Decorative optical phase-detection feedback unit; 261. Decorative optical phase-detection feedback signal; 262. Second phase shifter; 263. Second mixer; 264. Second low-pass filter; 265. Second feedback unit; 31. Coupled laser; 311. Coupled laser; 32. First beam splitter unit for coupled light; 321. First coupled laser beam; 322. Second coupled laser beam; 323. First half-wave plate for coupled light; 324. First polarization beam splitter prism for coupled light; 33. Coupled light frequency stabilization optical path unit; 331. Modulation of electromagnetically induced transparent / absorption spectral signal; 332. Decorative light first reflector; 333. Decorative light third reflector; 334. Decorative light second reflector; 335. Second dichroic mirror; 336. Third dichroic mirror; 337. Third gas cell; 34. Third photodetector; 341. Third electrical signal; 35. Coupled optical phase detection feedback unit; 351. Coupled optical phase detection feedback signal; 352. Third phase shifter; 353. Third mixer; 354. Third low-pass filter; 355. Third feedback unit; 41. Modulation signal generator; 411. First modulation signal; 412. Second modulation signal; 413. Third modulation signal; 414. Fourth modulation signal. Detailed Implementation

[0018] 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 a part of the embodiments of the present invention, and not all of the 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.

[0019] This invention provides a laser frequency stabilization method for a three-photon excited Rydberg atom microwave detector system, comprising: The modulation signal generator produces a first modulation signal that acts on the probe laser generated by the probe laser to produce a modulated probe laser; The frequency of the modulated probe laser is stabilized at the required first-order transition frequency of alkali metal atoms using the probe laser frequency stabilization unit. The frequency stabilized modulated probe laser is output and a portion of the frequency stabilized modulated probe laser is split and input to the decorative laser frequency stabilization unit and the coupled laser frequency stabilization unit. The saturated laser frequency stabilization unit uses the interaction between the saturated laser generated by the saturated laser and the frequency-stabilized modulated probe laser to generate a modulated electromagnetically induced transparent spectrum signal. The electrical signal converted from the electromagnetically induced transparent spectrum signal interacts with the second modulation signal generated by the modulation signal generator to generate a saturated optical phase-discrimination feedback signal. The saturated optical phase-discrimination feedback signal acts on the saturated laser to stabilize the frequency of the saturated laser at the required second-order transition frequency of alkali metal atoms. The frequency-stabilized saturated laser is output and a portion of the frequency-stabilized saturated laser is split and input to the coupled laser frequency stabilization unit. A coupled laser frequency stabilization unit is used to generate a modulated electromagnetically induced transparency / absorption spectral signal by interacting the coupled laser generated by the coupled laser with a frequency-stabilized modulated probe laser and a frequency-stabilized suffix laser. The converted electrical signal from the electromagnetically induced transparency / absorption spectral signal interacts with a third modulation signal generated by a modulation signal generator to generate a coupled optical phase-discrimination feedback signal. This feedback signal acts on the coupled laser, stabilizing its frequency at the desired alkali metal atom third-order transition frequency, and outputting the frequency-stabilized coupled laser. The modulation signals generated by the modulation signal generator are identical across all channels.

[0020] Reference Figure 1 , Figure 1 This is a schematic diagram of the structure and principle of the laser frequency stabilization device (laser internal modulation frequency stabilization) of a three-photon excited Rydberg atom microwave detection system in one embodiment. It includes a modulation signal generator, a detection laser frequency stabilization unit, a decorative laser frequency stabilization unit, and a coupling laser frequency stabilization unit. The modulation signal generator 41 generates four identical modulation signals.

[0021] The probe laser frequency stabilization unit includes a probe laser 11, a probe light first beam splitting unit 12, a probe light second beam splitting unit 13, a probe light third beam splitting unit 14, a probe light frequency stabilization optical path unit 15, a first photodetector 16, and a probe light phase detection feedback unit 17. The modulation signal generator 41 is connected to the probe laser 11 and the probe light phase detection feedback unit 17. The probe laser 11 is connected to the probe light first beam splitting unit 12. The two output terminals of the probe light first beam splitting unit 12 are respectively connected to the probe light frequency stabilization optical path unit 15 and the probe light second beam splitting unit 13. The probe light frequency stabilization optical path unit 15 is connected to the first photodetector 16. The first photodetector 16 is connected to the probe light phase detection feedback unit 17, and the probe light phase detection feedback unit 17 is connected to the probe laser 11.

[0022] The embellished laser frequency stabilization unit includes an embellished laser 21, an embellished light first beam splitting unit 22, an embellished light second beam splitting unit 23, an embellished light frequency stabilization optical path unit 24, a second photodetector 25, and an embellished light phase detection feedback unit 26. The modulation signal generator 41 is connected to the embellished light phase detection feedback unit 26; the embellished laser 21 is connected to the embellished light first beam splitting unit 22, the embellished light first beam splitting unit 22 is connected to the embellished light second beam splitting unit 23 and the embellished light frequency stabilization optical path unit 24, the embellished light frequency stabilization optical path unit 24 is connected to the second photodetector 25, the second photodetector 25 is connected to the embellished light phase detection feedback unit 26, and the embellished light phase detection feedback unit 26 is connected to the embellished laser 21. After frequency stabilization, the modulated detection laser is input to the embellished light frequency stabilization optical path unit 24.

[0023] The coupled laser frequency stabilization unit includes a coupled laser 31, a coupled light first beam splitting unit 32, a coupled light frequency stabilization optical path unit 33, a third photodetector 34, and a coupled light phase detection feedback unit 35. The modulation signal generator 41 is connected to the coupled light phase detection feedback unit 35. The coupled laser 31 is connected to the coupled light first beam splitting unit 32. The coupled light first beam splitting unit 32 is connected to the coupled light frequency stabilization optical path unit 33. The coupled light frequency stabilization optical path unit 33 is connected to the third photodetector 34. The third photodetector 34 is connected to the coupled light phase detection feedback unit 35. The coupled light phase detection feedback unit 35 is connected to the coupled laser 31. The frequency-stabilized modulated probe laser and the frequency-stabilized suffix laser are input to the coupled light frequency stabilization optical path unit 33.

[0024] The modulation signal generator 41 generates a first modulation signal 411, which acts on the probe laser 11. The probe laser output 111 is a modulated probe laser. After the probe laser output 111 passes through the first probe light beam splitting unit 12, one of the laser beams split by the first probe light beam splitting unit 12 (i.e., the first modulated probe laser 121) enters the probe light frequency stabilization optical path unit 15. A modulated saturated absorption spectrum signal 151 is generated inside the probe light frequency stabilization optical path unit 15. The saturated absorption spectrum signal 151 then enters the first photodetector 16 and is converted. Instead of an electrical signal, the first electrical signal 161 output by the first photodetector 16 is input to the probe light phase detection feedback unit 17. Inside the probe light phase detection feedback unit 17, it interacts with the second modulation signal 412 generated by the modulation signal generator 41 to generate the probe light phase detection feedback signal 171. The probe light phase detection feedback signal 171 acts on the current or piezoelectric ceramic port of the probe laser 11 to stabilize the frequency of the probe laser 11 at the required first-order transition frequency of alkali metal atoms. The probe laser output laser 111 is the frequency-stabilized modulated probe laser. After frequency stabilization, the modulated probe laser is split by a laser beam-splitting unit consisting of a first probe beam splitting unit 12, a second probe beam splitting unit 13, and a third probe beam splitting unit 14. One beam from the first probe beam splitting unit 12 (i.e., the first modulated probe laser 121) enters the probe beam frequency stabilization optical path unit 15. The other beam from the first probe beam splitting unit 12 (i.e., the second modulated probe laser 122) enters the second probe beam splitting unit 13 for further splitting. One beam from the second probe beam splitting unit 13 (i.e., the third modulated probe laser 122) is then split again. The modulated probe laser 131 enters the embellishment laser frequency stabilization optical path unit 24 of the embellishment laser frequency stabilization unit. The other laser beam split from the second probe beam splitting unit 13 (i.e., the fourth modulated probe laser 132) enters the third probe beam splitting unit 14 and is split again. One of the laser beams split from the third probe beam splitting unit 14 (i.e., the fifth modulated probe laser 141) enters the coupling laser frequency stabilization optical path unit 33 of the coupling laser frequency stabilization unit. The other laser beam split from the third probe beam splitting unit 14 (i.e., the sixth modulated probe laser 142) serves as the output beam of the probe laser frequency stabilization unit.

[0025] The embellished laser 21 generates an embellished laser 211. The embellished laser 211 is split by the first embellished light beam splitting unit 22. One of the lasers split by the first embellished light beam splitting unit 22 (i.e., the first embellished laser 221) enters the embellished light frequency stabilization optical path unit 24. Inside the embellished light frequency stabilization optical path unit 24, the frequency stabilized modulated probe laser interacts with the embellished laser to generate a modulated electromagnetically induced transparent spectral signal 241. The modulated electromagnetically induced transparent spectral signal 241 enters the second photodetector 25 and is converted into an electrical signal. The second electrical signal 251 output by the second photodetector 25 enters the embellished light phase detection feedback unit 26. Inside the embellished light phase detection feedback unit 26, it interacts with the third modulation signal 413 generated by the modulation signal generator 41 to generate the embellished light phase detection feedback signal 261. The phase detection feedback signal 261 of the embellishment light acts on the current or piezoelectric ceramic port of the embellishment laser 21, stabilizing the laser frequency at the required second-order transition frequency of alkali metal atoms, and outputting the frequency-stabilized embellishment laser 211. The frequency-stabilized embellishment laser 211 is split by the first beam splitting unit 22 of the embellishment light. One of the lasers split by the first beam splitting unit 22 (i.e., the first embellishment laser 221) enters the frequency stabilization optical path unit 24 of the embellishment light. Another laser split by the first beam splitting unit 22 (i.e., the second embellishment laser 222) is split again by the second beam splitting unit 23 of the embellishment light. One of the lasers split by the second beam splitting unit 23 (i.e., the third embellishment laser 231) enters the frequency stabilization optical path unit 33 of the coupling laser frequency stabilization unit. The other laser split by the second beam splitting unit 23 (i.e., the fourth embellishment laser 232) serves as the output beam of the frequency stabilization unit of the embellishment laser.

[0026] The coupled laser 311 generated by the coupled laser 31 enters the coupled laser frequency stabilization optical path unit 33 after passing through the first coupled laser beam splitting unit 32. Inside the coupled laser frequency stabilization optical path unit 33, the frequency-stabilized modulated probe laser and the frequency-stabilized styling laser from the probe laser frequency stabilization unit and the styling laser frequency stabilization unit interact with the coupled laser to generate a modulated electromagnetically induced transparency / absorption spectrum signal 331. The modulated electromagnetically induced transparency / absorption spectrum signal 331 enters the third photodetector 34 and is converted into an electrical signal. The third electrical signal 341 output by the third photodetector 34 enters the coupled laser phase detection feedback unit 35. Inside the coupled laser phase detection feedback unit 35, it interacts with the fourth modulation signal 414 generated by the modulation signal generator 41 to generate a coupled laser phase detection feedback signal 351. The coupled laser phase detection feedback signal 351 acts on the current or piezoelectric ceramic port of the coupled laser 31 to stabilize the frequency of the coupled laser at the required third-order transition frequency of alkali metal atoms, and outputs the frequency-stabilized coupled laser.

[0027] The frequency-stabilized modulated probe laser, frequency-stabilized styling laser, and frequency-stabilized coupled laser outputs from the probe laser frequency stabilization unit, the styling laser, and the coupling laser are used for three-photon excited Rydberg atom microwave detection experiments.

[0028] Reference Figure 2 , Figure 2 This is a schematic diagram of the structure and principle of a laser frequency stabilization device (external laser modulation frequency stabilization) for a three-photon excited Rydberg atom microwave detection system in one embodiment. It includes a modulation signal generator, a detection laser frequency stabilization unit, a decorative laser frequency stabilization unit, and a coupling laser frequency stabilization unit. The modulation signal generator 41 generates four identical modulation signals.

[0029] The probe laser frequency stabilization unit includes a probe laser 11, a probe light first beam splitting unit 12, a probe light second beam splitting unit 13, a probe light frequency stabilization optical path unit 15, a first photodetector 16, and a probe light phase detection feedback unit 17. The modulation signal generator 41 is connected to the probe light phase detection feedback unit 17 and the probe light frequency stabilization optical path unit 15. The probe laser 11 is connected to the probe light first beam splitting unit 12. One output terminal of the probe light first beam splitting unit 12 is connected to the probe light frequency stabilization optical path unit 15. The probe light frequency stabilization optical path unit 15 is connected to the first photodetector 16 and the probe light second beam splitting unit 13. The first photodetector 16 is connected to the probe light phase detection feedback unit 17. The probe light phase detection feedback unit 17 is connected to the probe laser 11.

[0030] The probe laser output 111 passes through the probe light first beam splitting unit 12 and enters the probe light frequency stabilization optical path unit 15. Inside the probe light frequency stabilization optical path unit 15, the probe laser interacts with the first modulation signal 411 generated by the modulation signal generator 41 to generate a modulated saturated absorption spectrum signal 151. The saturated absorption spectrum signal 151 then enters the first photodetector 16 and is converted into an electrical signal. The first electrical signal 161 output by the first photodetector 16 enters the probe light phase detection feedback unit 17. Inside the probe light phase detection feedback unit 17, it interacts with the second modulation signal 412 generated by the modulation signal generator 41 to generate a probe light phase detection feedback signal 171. The probe light phase detection feedback signal 171 acts on the current or piezoelectric ceramic port of the probe laser 11 to stabilize the frequency of the probe laser 11 at the required first-order transition frequency of alkali metal atoms. At this time, the probe laser output 111 is the frequency-stabilized modulated probe laser. After frequency stabilization, one beam of the modulated probe laser (i.e., the first modulated probe laser 121) is split by the first probe beam splitting unit 12 and enters the probe beam frequency stabilization optical path unit 15. The other beam (i.e., the second modulated probe laser 122) is split by the first probe beam splitting unit 12 and serves as the output beam of the probe laser frequency stabilization unit. A portion of the frequency stabilized modulated probe laser in the probe beam frequency stabilization optical path unit 15 is split by the second probe beam splitting unit 13 and enters the embellishment laser frequency stabilization optical path unit 24 in the embellishment laser frequency stabilization unit. The other beam (i.e., the fourth modulated probe laser 132) is split by the second probe beam splitting unit 13 and enters the coupling laser frequency stabilization optical path unit 33 in the coupling laser frequency stabilization unit.

[0031] The embellished laser 21 generates an embellished laser 211. The embellished laser 211 is split by the first embellished light beam splitting unit 22. One of the lasers split by the first embellished light beam splitting unit 221 (i.e., the first embellished laser 221) enters the embellished light frequency stabilization optical path unit 24. Inside the embellished light frequency stabilization optical path unit 24, the third modulated probe laser 131 interacts with the first embellished laser 221 to generate a modulated electromagnetically induced transparent spectral signal 241. The modulated electromagnetically induced transparent spectral signal 241 enters the second photodetector 25 and is converted into an electrical signal. The second electrical signal 251 output by the second photodetector 25 enters the embellished light phase detection feedback unit 26. Inside the embellished light phase detection feedback unit 26, it interacts with the third modulation signal 413 generated by the modulation signal generator 41 to generate the embellished light phase detection feedback signal 261. The phase detection feedback signal 261 of the embellishment light acts on the current or piezoelectric ceramic port of the embellishment laser 21, stabilizing the laser frequency at the required second-order transition frequency of alkali metal atoms, and outputting the frequency-stabilized embellishment laser 211. The frequency-stabilized embellishment laser 211 is split by the first beam splitting unit 22 of the embellishment light. One of the lasers split by the first beam splitting unit 22 (i.e., the first embellishment laser 221) enters the frequency stabilization optical path unit 24 of the embellishment light. Another laser split by the first beam splitting unit 22 (i.e., the second embellishment laser 222) is split again by the second beam splitting unit 23 of the embellishment light. One of the lasers split by the second beam splitting unit 23 (i.e., the third embellishment laser 231) enters the frequency stabilization optical path unit 33 of the coupling laser frequency stabilization unit. The other laser split by the second beam splitting unit 23 (i.e., the fourth embellishment laser 232) serves as the output beam of the frequency stabilization unit of the embellishment laser.

[0032] The coupled laser 311 generated by the coupled laser 31 enters the coupled laser frequency stabilization optical path unit 33 after passing through the first coupled laser beam splitting unit 32. Inside the coupled laser frequency stabilization optical path unit 33, the frequency-stabilized modulated probe laser and the frequency-stabilized styling laser from the probe laser frequency stabilization unit and the styling laser frequency stabilization unit interact with the coupled laser to generate a modulated electromagnetically induced transparency / absorption spectrum signal 331. The modulated electromagnetically induced transparency / absorption spectrum signal 331 enters the third photodetector 34 and is converted into an electrical signal. The third electrical signal 341 output by the third photodetector enters the coupled laser phase detection feedback unit 35. Inside the coupled laser phase detection feedback unit 35, it interacts with the fourth modulation signal 414 generated by the modulation signal generator 41 to generate a coupled laser phase detection feedback signal 351. The coupled laser phase detection feedback signal 351 acts on the current or piezoelectric ceramic port of the coupled laser 31 to stabilize the frequency of the coupled laser at the required third-order transition frequency of alkali metal atoms, and outputs the frequency-stabilized coupled laser.

[0033] The frequency-stabilized modulated probe laser, frequency-stabilized styling laser, and frequency-stabilized coupled laser outputs from the probe laser frequency stabilization unit, the styling laser, and the coupling laser are used for three-photon excited Rydberg atom microwave detection experiments.

[0034] Reference Figure 3 , Figure 3 This is a schematic diagram of a specific embodiment of the laser frequency stabilization device (laser internal modulation frequency stabilization) of a three-photon excited Rydberg atom microwave detection system, including a modulation signal generator 41, a detection laser frequency stabilization unit, a decorative laser frequency stabilization unit, and a coupling laser frequency stabilization unit, wherein the modulation signal generator 41 generates four identical modulation signals.

[0035] The detection laser frequency stabilization unit includes a detection laser 11, a first detection beam splitting unit 12, a second detection beam splitting unit 13, a third detection beam splitting unit 14, a detection beam frequency stabilization optical path unit 15, a first photodetector 16, and a detection beam phase detection feedback unit 17. The embellished laser frequency stabilization unit includes an embellished laser 21, an embellished light first beam splitting unit 22, an embellished light second beam splitting unit 23, an embellished light frequency stabilization optical path unit 24, a second photodetector 25, and an embellished light phase detection feedback unit 26. The coupled laser frequency stabilization unit includes a coupled laser 31, a coupled light first beam splitting unit 32, a coupled light frequency stabilization optical path unit 33, a third photodetector 34, and a coupled light phase detection feedback unit 35.

[0036] Specifically, the modulation signal generator 41 generates a first modulation signal 411, which acts on the current or piezoelectric ceramic port of the probe laser 11, thereby making the probe laser output laser 111 a modulated probe laser. The modulated probe laser is split into two paths by the probe light first beam splitting unit 12, which consists of the probe light first half-wave plate 123 and the probe light first polarization beam splitter prism 124: a first modulated probe laser 121 and a second modulated probe laser 122. The first modulated probe laser 121 enters the probe light frequency stabilization optical path unit 15, and the second modulated probe laser 122 enters the probe light second beam splitting unit 13. Further, the probe light frequency stabilization optical path unit 15 includes a probe light second half-wave plate 153, a probe light second polarization beam splitter prism 154, a first gas cell 155 filled with alkali metal atoms, a probe light quarter-wave plate 156, and a probe light first reflector 157. Rotating the probe light first half-wave plate 123 can change the power ratio of the first modulated probe laser 121 and the second modulated probe laser 122. After the first modulated probe laser 121 enters the probe light frequency stabilization optical path unit 15, it generates a modulated saturated absorption spectrum signal 151 within it. Specifically, the first modulated probe laser 121 changes its polarization direction through the second half-wave plate 153 of the probe light, and after being reflected by the second polarization beam splitter prism 154 of the probe light, it enters the first gas chamber 155 filled with alkali metal atoms. After passing through the first gas chamber 155 filled with alkali metal atoms, it changes its polarization direction again after passing through the quarter-wave plate 156 of the probe light and the first reflector 157 of the probe light, and re-enters the first gas chamber 155 filled with alkali metal atoms. The incident and reflected light are collinear and opposite in direction, interacting with the alkali metal atoms to generate the modulated saturated absorption spectrum signal 151. The saturated absorption spectrum signal 151 then enters the first photodetector 16 and is converted into a first electrical signal 161 within it. The first electrical signal 161 output by the first photodetector 16 enters the probe light phase detection feedback unit 17. The probe light phase detection feedback unit 17 includes a first phase shifter 172, a first mixer 173, a first low-pass filter 174, and a first feedback unit 175. The first electrical signal 161 output from the first photodetector 16 enters one port of the first mixer 173 in the probe light phase detection feedback unit 17. The second modulation signal 412 generated by the modulation signal generator 41 passes through the first phase shifter 172 and enters the other port of the first mixer 173 for down-conversion. Adjusting the phase shift of the first phase shifter 172 can change the amplitude of the down-converted signal. The down-converted signal after mixing is filtered by the first low-pass filter 174 and then enters the first feedback unit 175, generating the probe light phase detection feedback signal 171. The probe light phase detection feedback signal 171 acts on the current or piezoelectric ceramic port of the probe laser 11, stabilizing the frequency of the probe laser 11 at the required first-order transition frequency of alkali metal atoms. At this time, the output laser 111 of the probe laser is the frequency-stabilized modulated probe laser.

[0037] The frequency-stabilized modulated probe laser is split into two paths by a first probe beam splitting unit 12, consisting of a first half-wave plate 123 and a first polarization beam splitter prism 124: a first modulated probe laser 121 and a second modulated probe laser 122. The first modulated probe laser 121 enters a probe beam frequency stabilization optical path unit 15, while the second modulated probe laser 122 enters a second probe beam splitting unit 13, consisting of a third half-wave plate 133 and a third polarization beam splitter prism 134. The second probe beam splitting unit 13 splits the incident frequency-stabilized modulated probe laser into two paths: a third modulated probe laser 131 and a fourth modulated probe laser 132. The fourth modulated probe laser 132 serves as the output beam of the probe laser frequency stabilization unit and is used in three-photon excited Rydberg atom microwave detection experiments. Furthermore, rotating the third half-wave plate 133 can change the power ratio between the third modulated probe laser 131 and the fourth modulated probe laser 132. The third modulated probe laser 131 enters the third probe beam splitting unit 14, which consists of the fourth half-wave plate 143 and the fourth polarization beam splitter prism 144, and is split into two beams: the fifth modulated probe laser 141 and the sixth modulated probe laser 142. The fifth modulated probe laser 141 enters the embellishment light frequency stabilization optical path unit 24, and the sixth modulated probe laser 142 enters the coupling light frequency stabilization optical path unit 33. Furthermore, rotating the fourth half-wave plate 143 can change the power ratio of the fifth modulated probe laser 141 and the sixth modulated probe laser 142.

[0038] Specifically, the embellished laser 21 generates an embellished laser 211. The embellished laser 211 is split into a first embellished laser 221 and a second embellished laser 222 by a first embellished light beam splitting unit 222, which consists of an embellished light first half-wave plate 223 and an embellished light first polarizing beam splitting prism 224. The first embellished laser 221 enters an embellished light frequency stabilization optical path unit 24, and the second embellished laser 222 enters an embellished light second beam splitting unit 23. Further, rotating the embellished light first half-wave plate 223 can change the power ratio of the first embellished laser 221 and the second embellished laser 222. Inside the embellished light frequency stabilization optical path unit 24, the first embellished laser 221 is reflected by a first dichroic mirror 242 and enters a second gas chamber 243 filled with alkali metal atoms. The fifth modulated probe laser 141 and the embellishment laser reflected by the first dichroic mirror 242 are collinear and enter the second gas chamber 243 in opposite directions, generating a modulated electromagnetically induced transparent spectral signal 241. After being transmitted through the first dichroic mirror 242, this signal enters the second photodetector 25 and is converted into an electrical signal. The second electrical signal 251 output by the second photodetector 25 enters the embellishment optical phase detection feedback unit 26. The embellishment optical phase detection feedback unit 26 includes a second phase shifter 262, a second mixer 263, a second low-pass filter 264, and a second feedback unit 265. The second electrical signal 251 output by the second photodetector 25 enters one port of the second mixer 263 in the embellishment optical phase detection feedback unit 26. The third modulated signal 413 generated by the modulation signal generator 41 passes through the second phase shifter 262 and enters the other port of the second mixer 263 for down-conversion. Adjusting the phase shift of the second phase shifter 262 can change the amplitude of the down-converted signal. The down-converted signal after mixing is filtered by the second low-pass filter 264 and then enters the second feedback unit 265, generating the embellished optical phase detection feedback signal 261. The embellished optical phase detection feedback signal 261 acts on the current or piezoelectric ceramic port of the embellished laser 21, stabilizing the frequency of the embellished laser 21 at the required second-order transition frequency of alkali metal atoms. After the stabilized frequency of the stabilized laser 21 output from the stabilized laser 21, it is split into a first stabilized laser 221 and a second stabilized laser 222 by a first stabilized beam splitting unit 222 composed of a first half-wave plate 223 and a first polarization beam splitting prism 224. The first stabilized laser 221 enters the stabilized frequency optical path unit 24, and the second stabilized laser 222 enters the second stabilized beam splitting unit 23 composed of a second half-wave plate 233 and a second polarization beam splitting prism 234, and is split into two paths again: a third stabilized laser 231 and a fourth stabilized laser 232. The third stabilized laser 231 enters the coupling light stabilized frequency optical path unit 33, and the fourth stabilized laser 232 serves as the output beam of the stabilized frequency optical path unit 24, used for the three-photon excited Rydberg atom microwave detection experiment. Furthermore, rotating the second half-wave plate 233 of the decorative light can change the power ratio of the third decorative laser 231 and the fourth decorative laser 232.

[0039] Specifically, the coupling laser 31 generates a coupling laser 311. The coupling laser 311 is split into two paths by a first coupling beam splitting unit 32, composed of a first half-wave plate 323 and a first polarizing beam splitter prism 324: a first coupling laser 321 and a second coupling laser 322. The first coupling laser 321 enters the coupling beam frequency stabilization optical path unit 33. Further, rotating the first half-wave plate 323 can change the power ratio of the first coupling laser 321 and the second coupling laser 322. Inside the coupling beam frequency stabilization optical path unit 33, the first coupling laser 321, after reflection by a second dichroic mirror 335 and transmission by a third dichroic mirror 336, enters a third gas chamber 337 filled with alkali metal atoms. The third adorned laser 231, after reflection by an adorned light first reflector 332, an adorned light second reflector 334, and a third dichroic mirror 336, enters the third gas chamber 337 collinearly and in the same direction as the first coupling laser 321. The sixth modulated probe laser 142, after being reflected by the second reflector 158, enters the third gas chamber 337 collinearly and in opposite directions with the third embellishment laser 231 and the first coupling laser 321, generating a modulated electromagnetically induced transparency / absorption spectral signal 331. This signal 331 is transmitted through the third dichroic mirror 336 and the second dichroic mirror 335 before entering the third photodetector 34 and being converted into an electrical signal. The third electrical signal 341 output from the third photodetector 34 enters the coupled light phase-detection feedback unit 35. The coupled light phase-detection feedback unit 35 includes a third phase shifter 352, a third mixer 353, a third low-pass filter 354, and a third feedback unit 355. The third electrical signal 341 output from the third photodetector 34 enters one port of the third mixer 353 in the coupled light phase-detection feedback unit 35. The fourth modulated signal 414 generated by the modulation signal generator 41 passes through the third phase shifter 352 and enters the other port of the third mixer 353 for down-conversion. Adjusting the phase shift of the third phase shifter 352 can change the amplitude of the down-converted signal. The down-converted signal after mixing is filtered by the third low-pass filter 354 and then enters the third feedback unit 355, generating a coupled optical phase detection feedback signal 351. The coupled optical phase detection feedback signal 351 acts on the current or piezoelectric ceramic port of the coupled laser 31, stabilizing the frequency of the coupled laser at the desired alkali metal atom third-order transition frequency. The coupled laser 31 outputs a frequency-stabilized coupled laser 311. The frequency-stabilized coupled laser 311 is split into two paths by the first beam splitting unit 32, which is composed of the first half-wave plate 323 and the first polarization beam splitting prism 324 of the coupled light. The first coupled laser 321 and the second coupled laser 322 are both frequency-stabilized coupled lasers. The first coupled laser 321 enters the frequency stabilization optical path unit 33 of the coupled light, and the second coupled laser 322 is used as the output laser of the frequency stabilization unit of the coupled laser for the three-photon excited Rydberg atom microwave detection experiment.

[0040] Reference Figure 4 , Figure 4 This is a schematic diagram of a specific embodiment of the laser frequency stabilization device (external laser modulation frequency stabilization) of a three-photon excited Rydberg atom microwave detection system, including a modulation signal generator 41, a detection laser frequency stabilization unit, a decorative laser frequency stabilization unit, and a coupling laser frequency stabilization unit, wherein the modulation signal generator 41 generates four identical modulation signals.

[0041] The detection laser frequency stabilization unit includes a detection laser 11, a first detection beam splitting unit 12, a second detection beam splitting unit 13, a detection beam frequency stabilization optical path unit 15, a first photodetector 16, and a detection beam phase detection feedback unit 17. The embellished laser frequency stabilization unit includes an embellished laser 21, an embellished light first beam splitting unit 22, an embellished light second beam splitting unit 23, an embellished light frequency stabilization optical path unit 24, a second photodetector 25, and an embellished light phase detection feedback unit 26. The coupled laser frequency stabilization unit includes a coupled laser 31, a coupled light first beam splitting unit 32, a coupled light frequency stabilization optical path unit 33, a third photodetector 34, and a coupled light phase detection feedback unit 35.

[0042] The probe laser frequency stabilization unit includes a probe laser 11, a probe light first beam splitting unit 12, a probe light second beam splitting unit 13, a probe light frequency stabilization optical path unit 15, a first photodetector 16, and a probe light phase detection feedback unit 17. Specifically, the probe laser 11 generates a probe laser output laser 111. The probe laser output laser 111 is split into a first modulated probe laser 121 and a second modulated probe laser 122 by the probe light first beam splitting unit 122, which consists of a probe light first half-wave plate 123 and a probe light first polarization beam splitting prism 124. The first modulated probe laser 121 enters the probe light frequency stabilization optical path unit 15. Further, rotating the probe light first half-wave plate 123 can change the power ratio of the first modulated probe laser 121 and the second modulated probe laser 122.

[0043] The probe light frequency stabilization optical path unit 15 includes a probe light second reflector 158, a probe light second half-wave plate 153, a probe light second polarization beam splitter prism 154, a probe light third reflector 159, a first gas chamber 155 filled with alkali metal atoms, an electro-optic modulator 1510, a probe light fourth reflector 1512, and a probe light first beam splitter 1513. The probe laser input to the probe light frequency stabilization optical path unit 15 is reflected by the probe light second reflector 158 and enters the probe light second half-wave plate 153 to change its polarization direction. After passing through the probe light second polarization beam splitter prism 154, it is split into two beams. One beam is transmitted into the first gas chamber 155 filled with alkali metal atoms, and the other beam is reflected by the probe light third reflector 159 and enters the electro-optic modulator 1510. The first modulation signal 411 generated by the modulation signal generator 41 acts on the electro-optic modulator 1510. The probe laser input to the electro-optic modulator 1510 is modulated. The output laser 1511 of the electro-optic modulator is reflected by the fourth reflector 1512 of the probe light and then split into two paths by the first beam splitter 1513 of the probe light. The seventh modulated probe laser 152 is transmitted through the first beam splitter 1513 of the probe light, and the eighth modulated probe laser 1514 is reflected by the first beam splitter 1513 of the probe light. The eighth modulated probe laser 1514 reflected by the first beam splitter 1513 of the probe light re-enters the first gas chamber 155. In the first gas chamber 155, the modulated probe laser and the unmodulated probe laser are collinear and opposite in direction and interact with alkali metal atoms to generate a modulated saturated absorption spectrum signal 151. The saturated absorption spectrum signal 151 then enters the first photodetector 16 and is converted into an electrical signal inside the first photodetector 16.

[0044] The first electrical signal 161 output by the first photodetector 16 enters the detection light phase-detection feedback unit 17. The detection light phase-detection feedback unit 17 includes a first phase shifter 172, a first mixer 173, a first low-pass filter 174, and a first feedback unit 175. The first electrical signal 161 output by the first photodetector enters one port of the first mixer 173 in the detection light phase-detection feedback unit 17. The second modulation signal 412 generated by the modulation signal generator 41 passes through the first phase shifter 172 and enters the other port of the first mixer 173 for down-conversion. Adjusting the phase shift of the first phase shifter 172 can change the amplitude of the down-converted signal. The down-converted signal after mixing is filtered by the first low-pass filter 174 and enters the first feedback unit 175, generating the detection light phase-detection feedback signal 171. The detection light phase-detection feedback signal 171 acts on the current or piezoelectric ceramic port of the detection laser 11, stabilizing the detection laser frequency at the required first-order transition frequency of alkali metal atoms. At this time, the laser 111 output by the probe laser is a frequency-stabilized modulated probe laser, which is split into two frequency-stabilized modulated probe lasers (the first modulated probe laser 121 and the second modulated probe laser 122) by the first probe beam splitting unit 12. The first modulated probe laser 121 enters the probe beam frequency stabilization optical path unit 15, and the second modulated probe laser 122 serves as the output beam of the probe laser frequency stabilization unit for the three-photon excited Rydberg atom microwave detection experiment. Specifically, the seventh modulated probe laser 152 transmitted through the first beam splitter 1513 in the probe light frequency stabilization optical path unit 15 is a frequency-stabilized modulated probe laser. This seventh modulated probe laser 152 is split into two paths by the second beam splitter 13, which consists of the third half-wave plate 133 and the third polarization beam splitter prism 134: the third modulated probe laser 131 and the fourth modulated probe laser 132. The third modulated probe laser 131 is input to the embellishment light frequency stabilization optical path unit 24 in the embellishment laser frequency stabilization unit, and the fourth modulated probe laser 132 is input to the coupling light frequency stabilization optical path unit 33 in the coupling laser frequency stabilization unit. Furthermore, rotating the third half-wave plate 133 can change the power ratio between the third modulated probe laser 131 and the fourth modulated probe laser 132.

[0045] Specifically, the embellished laser 21 generates an embellished laser 211. The embellished laser 211 is split into a first embellished laser 221 and a second embellished laser 222 by a first embellished light beam splitting unit 222, which consists of an embellished light first half-wave plate 223 and an embellished light first polarizing beam splitting prism 224. The first embellished laser 221 enters an embellished light frequency stabilization optical path unit 24, and the second embellished laser 222 enters an embellished light second beam splitting unit 23. Further, rotating the embellished light first half-wave plate 223 can change the power ratio of the first embellished laser 221 and the second embellished laser 222. Inside the embellished light frequency stabilization optical path unit 24, the first embellished laser 221 is reflected by a first dichroic mirror 242 and enters a second gas chamber 243 filled with alkali metal atoms. The third-path modulation probe laser 131 and the decorative laser reflected by the first dichroic mirror 242 are collinear and enter the second gas chamber 243 in opposite directions, generating a modulated electromagnetically induced transparent spectral signal 241. After being transmitted through the first dichroic mirror 242, this signal enters the second photodetector 25 and is converted into an electrical signal. The second electrical signal 251 output by the second photodetector 25 enters the decorative optical phase detection feedback unit 26. The decorative optical phase detection feedback unit 26 includes a second phase shifter 262, a second mixer 263, a second low-pass filter 264, and a second feedback unit 265. The second electrical signal 251 output by the second photodetector 25 enters one port of the second mixer 263 in the decorative optical phase detection feedback unit 26. The third-path modulation signal 413 generated by the modulation signal generator 41 passes through the second phase shifter 262 and enters the other port of the second mixer 263 for down-conversion. Adjusting the phase shift of the second phase shifter 262 can change the amplitude of the down-converted signal. The down-converted signal after mixing is filtered by the second low-pass filter 264 and then enters the second feedback unit 265, generating the embellished optical phase detection feedback signal 261. The embellished optical phase detection feedback signal 261 acts on the current or piezoelectric ceramic port of the embellished laser 21, stabilizing the frequency of the embellished laser 21 at the required second-order transition frequency of alkali metal atoms. After the stabilized output of the stabilized laser 21, the stabilized laser beam is split into a first stabilized laser beam 221 and a second stabilized laser beam 222 by a first stabilized beam splitting unit 222, which consists of a first half-wave plate 223 and a first polarization beam splitting prism 224. The first stabilized laser beam 221 enters the stabilized beam frequency-stabilized optical path unit 24, and the second stabilized laser beam 222 enters the second stabilized beam splitting unit 23, which consists of a second half-wave plate 233 and a second polarization beam splitting prism 234, and is split into two beams again: a third stabilized laser beam 231 and a fourth stabilized laser beam 232. The third stabilized laser beam 231 enters the coupling beam frequency-stabilized optical path unit 33, and the fourth stabilized laser beam 232 serves as the output beam of the stabilized beam frequency-stabilized optical path unit 24, and is used for the three-photon excited Rydberg atom microwave detection experiment. Furthermore, rotating the second half-wave plate 233 of the decorative light can change the power ratio of the third decorative laser 231 and the fourth decorative laser 232.

[0046] Specifically, the coupling laser 31 generates a coupling laser 311. The coupling laser 311 is split into two paths by a first coupling beam splitting unit 32, composed of a first half-wave plate 323 and a first polarizing beam splitter prism 324: a first coupling laser 321 and a second coupling laser 322. The first coupling laser 321 enters the coupling beam frequency stabilization optical path unit 33. Further, rotating the first half-wave plate 323 can change the power ratio of the first coupling laser 321 and the second coupling laser 322. Inside the coupling beam frequency stabilization optical path unit 33, the first coupling laser 321, after reflection by a second dichroic mirror 335 and transmission by a third dichroic mirror 336, enters a third gas chamber 337 filled with alkali metal atoms. The third adorned laser 231, after reflection by an adorned light first reflector 332, an adorned light second reflector 334, and a third dichroic mirror 336, enters the third gas chamber 337 collinearly and in the same direction as the first coupling laser 321. The fourth modulated probe laser 132, after being reflected by the third reflector 333, enters the third gas chamber 337 collinearly and in opposite directions with the third adorned laser 231 and the first coupled laser 321, generating a modulated electromagnetically induced transparency / absorption spectral signal 331. This signal 331 is transmitted through the third dichroic mirror 336 and the second dichroic mirror 335 before entering the third photodetector 34 and being converted into an electrical signal. The third electrical signal 341 output from the third photodetector enters the coupled light phase-detection feedback unit 35. The coupled light phase-detection feedback unit 35 includes a third phase shifter 352, a third mixer 353, a third low-pass filter 354, and a third feedback unit 355. The third electrical signal 341 output from the third photodetector enters one port of the third mixer 353 in the coupled light phase-detection feedback unit 35. The fourth modulated signal 414 generated by the modulation signal generator 41 passes through the third phase shifter 352 and enters the other port of the third mixer 353 for down-conversion. Adjusting the phase shift of the third phase shifter 352 can change the amplitude of the down-converted signal. The down-converted signal after mixing is filtered by the third low-pass filter 354 and then enters the third feedback unit 355, generating a coupled optical phase detection feedback signal 351. The coupled optical phase detection feedback signal 351 acts on the current or piezoelectric ceramic port of the coupled laser 31, stabilizing the frequency of the coupled laser at the desired alkali metal atom third-order transition frequency. The coupled laser 31 outputs a frequency-stabilized coupled laser 311. The frequency-stabilized coupled laser 311 is split into two paths by the first beam splitting unit 32, which is composed of the first half-wave plate 323 and the first polarization beam splitting prism 324 of the coupled light. The first coupled laser 321 and the second coupled laser 322 are both frequency-stabilized coupled lasers. The first coupled laser 321 enters the frequency stabilization optical path unit 33 of the coupled light, and the second coupled laser 322 is used as the output laser of the frequency stabilization unit of the coupled laser for the three-photon excited Rydberg atom microwave detection experiment.

[0047] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A laser frequency stabilization method for a three-photon excited Rydberg atom microwave detector system, characterized in that, include: The modulation signal generator generates a first modulation signal that acts on the probe laser generated by the probe laser to produce a modulated probe laser; The frequency of the modulated probe laser is stabilized at the required first-order transition frequency of alkali metal atoms using the probe laser frequency stabilization unit. The frequency stabilized modulated probe laser is output and a portion of the frequency stabilized modulated probe laser is split and input to the decorative laser frequency stabilization unit and the coupled laser frequency stabilization unit. The saturated laser frequency stabilization unit uses the interaction between the saturated laser generated by the saturated laser and the frequency-stabilized modulated probe laser to generate a modulated electromagnetically induced transparent spectral signal. Based on the interaction between the electromagnetically induced transparent spectral signal and the second modulation signal generated by the modulation signal generator, a saturated optical phase-detection feedback signal is generated and applied to the saturated laser to stabilize the frequency of the saturated laser at the required second-order transition frequency of alkali metal atoms. The frequency-stabilized saturated laser is output and a portion of the frequency-stabilized saturated laser is split and input to the coupled laser frequency stabilization unit. The coupling laser frequency stabilization unit uses the coupling laser generated by the coupling laser to interact with the frequency-stabilized modulated probe laser and the frequency-stabilized suffix laser to generate a modulated electromagnetically induced transparency / absorption spectrum signal. Based on the interaction between the electromagnetically induced transparency / absorption spectrum signal and the third modulation signal generated by the modulation signal generator, a coupling optical phase detection feedback signal is generated and applied to the coupling laser to stabilize the frequency of the coupling laser at the required third-order transition frequency of alkali metal atoms, and output the frequency-stabilized coupling laser.

2. The laser frequency stabilization method for the three-photon excited Rydberg atom microwave detection system according to claim 1, characterized in that, The frequency-stabilized modulated probe laser, frequency-stabilized styling laser, and frequency-stabilized coupled laser outputs from the probe laser frequency stabilization unit, the styling laser, and the coupling laser are used for three-photon excited Rydberg atom microwave detection experiments.

3. The laser frequency stabilization method for the three-photon excited Rydberg atom microwave detection system according to claim 1, characterized in that, The detection laser frequency stabilization unit includes a detection laser, a first detection beam splitting unit, a second detection beam splitting unit, a third detection beam splitting unit, a detection beam frequency stabilization optical path unit, a first photodetector, and a detection beam phase detection feedback unit; The modulation signal generator is connected to the probe laser and the probe light phase detection feedback unit. The probe laser is connected to the probe light first beam splitting unit. The two outputs of the probe light first beam splitting unit are respectively connected to the probe light frequency stabilization optical path unit and the probe light second beam splitting unit. The probe light frequency stabilization optical path unit is connected to the first photodetector. The first photodetector is connected to the probe light phase detection feedback unit. The probe light phase detection feedback unit is connected to the probe laser. The modulated probe laser generated by the probe laser enters the probe light frequency stabilization optical path unit after passing through the first probe light beam splitting unit. Inside the probe light frequency stabilization optical path unit, a modulated saturated absorption spectrum signal is generated. The saturated absorption spectrum signal then enters the first photodetector and is converted into an electrical signal, which is then input to the probe light phase detection feedback unit. Inside the probe light phase detection feedback unit, it interacts with the second modulation signal generated by the modulation signal generator to generate a probe light phase detection feedback signal. The probe light phase detection feedback signal acts on the current or piezoelectric ceramic port of the probe laser, stabilizing the probe laser frequency at the required first-order transition frequency of alkali metal atoms. The probe laser then outputs the frequency-stabilized modulated probe laser. After frequency stabilization, the modulated probe laser is split sequentially by the first probe beam splitting unit, the second probe beam splitting unit, and the third probe beam splitting unit. A portion of the modulated probe laser beam is then input to the decorative laser frequency stabilization unit and the coupling laser frequency stabilization unit, while the remaining modulated probe laser beam serves as the output beam of the probe laser frequency stabilization unit.

4. The laser frequency stabilization method for the three-photon excited Rydberg atom microwave detection system according to claim 3, characterized in that, The probe light frequency stabilization optical path unit includes a probe light second half-wave plate, a probe light second polarization beam splitter prism, a first gas chamber filled with alkali metal atoms, a probe light quarter-wave plate, and a probe light first reflector. The modulated probe laser entering the probe light frequency stabilization optical path unit changes its polarization direction through the probe light second half-wave plate, and after being reflected by the probe light second polarization beam splitter prism, it enters the first gas chamber. After passing through the first gas chamber, it changes its polarization direction again after passing through the probe light quarter-wave plate and the probe light first reflector. The incident and reflected light are collinear and opposite in direction, interacting with the alkali metal atoms to generate a modulated saturated absorption spectrum signal. The saturated absorption spectrum signal then enters the first photodetector and is converted into an electrical signal inside it.

5. The laser frequency stabilization method for the three-photon excited Rydberg atom microwave detection system according to claim 1, characterized in that, The detection laser frequency stabilization unit includes a detection laser, a first detection beam splitting unit, a second detection beam splitting unit, a detection beam frequency stabilization optical path unit, a first photodetector, and a detection beam phase detection feedback unit; The modulation signal generator is connected to the probe light phase detection feedback unit and the probe light frequency stabilization optical path unit. The probe laser is connected to the probe light first beam splitting unit. The two outputs of the probe light first beam splitting unit are respectively connected to the probe light frequency stabilization optical path unit. The probe light frequency stabilization optical path unit is connected to the first photodetector and the probe light second beam splitting unit. The first photodetector is connected to the probe light phase detection feedback unit. The probe light phase detection feedback unit is connected to the probe laser. The probe laser generates a probe laser, which enters the probe light frequency stabilization optical path unit after passing through the first probe light beam splitting unit. Inside the probe light frequency stabilization optical path unit, the probe laser interacts with the first modulation signal generated by the modulation signal generator to generate a modulated saturated absorption spectrum signal. The saturated absorption spectrum signal then enters the first photodetector and is converted into an electrical signal before entering the probe light phase detection feedback unit. Inside the probe light phase detection feedback unit, it interacts with the second modulation signal generated by the modulation signal generator to generate a probe light phase detection feedback signal. The probe light phase detection feedback signal acts on the current or piezoelectric ceramic port of the probe laser to stabilize the probe laser frequency at the required first-order transition frequency of alkali metal atoms. After the frequency stabilization of the probe laser output, a portion of the modulated probe laser is split by the first probe beam splitting unit and enters the probe beam frequency stabilization optical path unit. The remaining frequency stabilized modulated probe laser is used as the output beam of the probe laser frequency stabilization unit. A portion of the frequency stabilized modulated probe laser in the probe beam frequency stabilization optical path unit is split by the second probe beam splitting unit and then input to the embellishment laser frequency stabilization unit and the coupling laser frequency stabilization unit, respectively.

6. The laser frequency stabilization method for a three-photon excited Rydberg atom microwave detection system according to claim 5, characterized in that, The probe light frequency stabilization optical path unit includes a second probe light reflector, a second probe light half-wave plate, a second probe light polarization beam splitter prism, a third probe light reflector, a first gas chamber filled with alkali metal atoms, an electro-optic modulator, a fourth probe light reflector, and a first probe light beam splitter. The probe laser input to the probe light frequency stabilization optical path unit is reflected by the second probe light reflector and then enters the second probe light half-wave plate to change its polarization direction. After passing through the second probe light polarization beam splitter prism, it is split into two beams. One beam is transmitted into the first gas chamber filled with alkali metal atoms, and the other beam is reflected by the third probe light reflector and then enters the electro-optic modulator. The first modulation signal generated by the modulation signal generator modulates the probe laser input to the electro-optic modulator. The output laser of the electro-optic modulator is reflected by the fourth reflector of the probe laser and then split into two paths by the first beam splitter of the probe laser. The modulated probe laser reflected by the first beam splitter re-enters the first gas chamber. In the first gas chamber, the modulated probe laser and the unmodulated probe laser are collinear and opposite in direction and interact with alkali metal atoms to generate a modulated saturated absorption spectrum signal. The saturated absorption spectrum signal then enters the first photodetector and is converted into an electrical signal inside the first photodetector.

7. The laser frequency stabilization method for a three-photon excited Rydberg atom microwave detector system according to any one of claims 3 to 6, characterized in that, The embellished laser frequency stabilization unit includes an embellished laser, a first embellished light beam splitting unit, a second embellished light beam splitting unit, an embellished light frequency stabilization optical path unit, a second photodetector, and an embellished light phase detection feedback unit; The modulation signal generator is connected to the embellishment light phase detection feedback unit; the embellishment laser is connected to the embellishment light first beam splitting unit, the embellishment light first beam splitting unit is connected to the embellishment light second beam splitting unit and the embellishment light frequency stabilization optical path unit, the embellishment light frequency stabilization optical path unit is connected to the second photodetector, the second photodetector is connected to the embellishment light phase detection feedback unit, the embellishment light phase detection feedback unit is connected to the embellishment laser, and the frequency-stabilized modulated detection laser is input to the embellishment light frequency stabilization optical path unit; A adorned laser generates adorned laser light, which enters the adorned laser frequency stabilization optical path unit after passing through the first adorned laser beam splitting unit. Inside the adorned laser frequency stabilization optical path unit, the frequency-stabilized modulated probe laser interacts with the adorned laser to generate a modulated electromagnetically induced transparent spectral signal. This modulated electromagnetically induced transparent spectral signal enters the second photodetector, is converted into an electrical signal, and then enters the adorned laser phase-discrimination feedback unit. Inside the phase-discrimination feedback unit, it interacts with the third modulation signal generated by the modulation signal generator to generate a phase-discrimination feedback signal. This feedback signal acts on the current or piezoelectric ceramic port of the adorned laser, stabilizing the laser frequency at the desired second-order transition frequency of alkali metal atoms, and outputting the frequency-stabilized adorned laser light. A portion of the frequency-stabilized adorned laser light is split by the second adorned laser beam splitting unit and enters the coupled laser frequency stabilization unit, while the remaining frequency-stabilized adorned laser light serves as the output beam of the adorned laser frequency stabilization unit.

8. The laser frequency stabilization method for the three-photon excited Rydberg atom microwave detection system according to claim 7, characterized in that, The coupled laser frequency stabilization unit includes a coupled laser, a first coupled light beam splitting unit, a coupled light frequency stabilization optical path unit, a third photodetector, and a coupled light phase detection feedback unit. The modulation signal generator is connected to the coupled light phase detection feedback unit, the coupled laser is connected to the coupled light first beam splitting unit, the coupled light first beam splitting unit is connected to the coupled light frequency stabilization optical path unit, the coupled light frequency stabilization optical path unit is connected to the third photodetector, the third photodetector is connected to the coupled light phase detection feedback unit, the coupled light phase detection feedback unit is connected to the coupled laser, and the frequency-stabilized modulated probe laser and the frequency-stabilized suffix laser are input to the coupled light frequency stabilization optical path unit. The coupled laser generated by the coupled laser enters the coupled laser frequency stabilization optical path unit after passing through the first coupled laser beam splitting unit. Inside the coupled laser frequency stabilization optical path unit, the frequency-stabilized modulated probe laser and the frequency-stabilized suffix laser interact with the coupled laser to generate a modulated electromagnetically induced transparency / absorption spectral signal. The modulated electromagnetically induced transparency / absorption spectral signal enters the third photodetector and is converted into an electrical signal, which then enters the coupled laser phase detection feedback unit. Inside the coupled laser phase detection feedback unit, the signal interacts with the fourth modulation signal generated by the modulation signal generator to generate a coupled laser phase detection feedback signal. The coupled laser phase detection feedback signal acts on the current or piezoelectric ceramic port of the coupled laser, stabilizing the frequency of the coupled laser at the required alkali metal atom third-order transition frequency, and outputting the frequency-stabilized coupled laser.

9. The laser frequency stabilization method for the three-photon excited Rydberg atom microwave detection system according to claim 8, characterized in that, The embellished optical frequency stabilization optical path unit includes a second gas chamber filled with alkali metal atoms. The embellished laser enters the second gas chamber, and after frequency stabilization, the modulated probe laser and the embellished laser enter the second gas chamber in opposite directions along the same line. They interact in the second gas chamber to generate a modulated electromagnetically induced transparent spectral signal. The coupled light frequency stabilization optical path unit includes a third gas chamber filled with alkali metal atoms. The coupled laser enters the third gas chamber. After frequency stabilization, the styling laser and the coupled laser enter the third gas chamber in the same direction and along the same line. After frequency stabilization, the modulated probe laser and the styling laser and the coupled laser enter the third gas chamber in opposite directions and along the same line. They interact in the third gas chamber to generate a modulated electromagnetically induced transparent / absorption spectral signal.

10. The laser frequency stabilization method for a three-photon excited Rydberg atom microwave detection system according to any one of claims 1 to 6, characterized in that, The detector phase-detection feedback unit, the embellished phase-detection feedback unit, and the coupled phase-detection feedback unit have the same structure, all including a phase shifter, a mixer, a low-pass filter, and a feedback unit. The input electrical signal enters the mixer through one port. The modulation signal generated by the modulation signal generator enters the mixer through the other port after passing through the phase shifter. Adjusting the phase shift of the phase shifter can change the amplitude of the down-converted signal. The down-converted signal output by the mixer is filtered by the low-pass filter and then enters the feedback unit to output the phase-detection feedback signal.

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