Laser frequency stabilization device and method based on atomic receiver and microwave measurement device

Abstract

This invention relates to the field of quantum precision measurement technology, and in particular to a laser frequency stabilization device, method, and microwave measurement device based on an atomic receiver. The laser frequency stabilization device integrates an atomic gas cell and a laser transmission fiber, bonding the atomic gas cell to a glass substrate to form a frequency-stabilized optical path with the laser transmission fiber. This simultaneously locks the laser frequencies of the coupled laser and the probe laser, significantly reducing the size of the frequency-stabilized optical path and greatly improving its stability compared to existing laser frequency stabilization methods. The microwave measurement device employs a handheld U-shaped integrated atomic probe. This U-shaped atomic probe uses a three-port wavelength division multiplexer, eliminating the need for free-space optical path detection. Compared to the original linear atomic probe, this greatly improves the portability of the microwave measurement device.

Description

Technical Field

[0001] This invention relates to the field of quantum precision measurement technology, and in particular to a laser frequency stabilization device, method, and microwave measurement device based on an atomic receiver. Background Technology

[0002] Compared to traditional microwave measurement methods using dipoles, electric field measurements based on Rydberg atoms offer advantages such as self-calibration, traceability to the International System of Units (SI), high sensitivity, and high accuracy, demonstrating significant application potential. In practical measurements, frequency stabilization of the laser is necessary to improve measurement accuracy.

[0003] Commonly used active frequency stabilization methods in existing technologies include frequency modulation spectral stabilization and modulation transfer spectral stabilization. However, the frequency stabilization optical path in existing technologies is often built on an optical platform, which is a free space optical path. Free space optical paths use more optical components, are larger in size, and have complex optical path adjustments, resulting in poor stability of existing laser frequency stabilization methods. Summary of the Invention

[0004] Therefore, it is necessary to provide a laser frequency stabilization device, method, and microwave measurement device based on an atomic receiver to address the above problems. This device integrates the atomic gas cell with the laser transmission fiber and bonds the atomic gas cell to a glass substrate to form a frequency-stabilized optical path. It also achieves laser frequency locking for both the coupled laser source and the probe laser source, greatly reducing the size of the frequency-stabilized optical path. Compared with existing laser frequency stabilization methods, it also greatly improves the stability of the frequency-stabilized optical path.

[0005] In one embodiment, a laser frequency stabilization device based on an atomic receiver includes a probe laser controller, a probe laser, a first photodetector, a first frequency stabilization control circuit, a DC biaser, a second photodetector, a second frequency stabilization control circuit, a coupled laser controller, a coupled laser, and a frequency stabilization optical path. The frequency stabilization optical path is disposed on a glass substrate and includes a probe laser frequency stabilization optical path, a coupled laser frequency stabilization optical path, and an alkali metal atom gas chamber. The probe laser emitted by the probe laser forms a saturated absorption spectrum in the alkali metal atom gas chamber through the probe laser frequency stabilization optical path. The first photodetector collects the optical signal of the probe laser transmitted after forming a saturated absorption spectrum in the alkali metal atom gas chamber, converts it into a first electrical signal, and sends it to the first frequency stabilization control circuit. After analysis by the first frequency stabilization control circuit, a first error feedback is output. The signal is sent to the probe laser controller via the DC bias to achieve frequency control of the probe laser; the coupling laser emitted by the coupling laser and the probe laser emitted by the probe laser generate an electromagnetically induced transparency (EIT) spectrum of Rydberg atoms in the alkali metal atom gas chamber through the coupling laser frequency stabilization optical path; the second photodetector collects the optical signal of the probe laser reflected after the EIT spectrum is formed in the alkali metal atom gas chamber, converts it into a second electrical signal, and sends it to the second frequency stabilization control circuit; the second frequency stabilization control circuit receives the first error feedback signal output by the first frequency stabilization control circuit after analysis, and sends the second error feedback signal output after analyzing and processing the second electrical signal and the first error feedback signal to the coupling laser controller to achieve frequency control of the coupling laser.

[0006] Furthermore, the laser frequency stabilization device further includes a first fiber coupling head, and the probe laser frequency stabilization optical path includes a first single-mode polarization-maintaining fiber pigtail, a first depolarizing beam splitter, a second depolarizing beam splitter, a third depolarizing beam splitter, a first plane mirror, a second plane mirror, a fourth depolarizing beam splitter, a third plane mirror, and a first fiber collimating device group; wherein, the probe laser emitted by the probe laser is coupled into the first single-mode polarization-maintaining fiber pigtail through the first fiber coupling head, and the coupled probe laser is split into two beams by the first depolarizing beam splitter. The probe laser beam in the transmission direction is then split again by the second depolarizing beam splitter and the third depolarizing beam splitter. Two probe laser beams, one transmitted through the third depolarizing beam splitter, are reflected sequentially by the first and second plane mirrors, and then by the fourth depolarizing beam splitter before entering the alkali metal atom gas cell. These beams coincide with the probe laser beam reflected by the third depolarizing beam splitter at a first position within the alkali metal atom gas cell, forming a saturated absorption spectrum. After forming the saturated absorption spectrum, the probe laser beam transmitted through the alkali metal atom gas cell is reflected by the third plane mirror and coupled into the multimode fiber via the first fiber collimating device group. The first photodetector collects the probe laser beam coupled into the multimode fiber and converts the collected optical signal into a first electrical signal, which is then input to the first frequency stabilization control circuit.

[0007] Furthermore, the transmittance to reflectance ratio of the first depolarizing beam splitter is T:R=9:1, the transmittance to reflectance ratio of the second depolarizing beam splitter is T:R=1:1, the transmittance to reflectance ratio of the third depolarizing beam splitter is T:R=9:1, and the transmittance to reflectance ratio of the fourth depolarizing beam splitter is T:R=1:1.

[0008] Furthermore, when the probe laser emitted by the probe laser is split into two by the first depolarization beam splitter, the transmitted probe laser beam is used in the probe laser frequency stabilization optical path, and the reflected probe laser beam is used in the coupled laser frequency stabilization optical path.

[0009] Furthermore, the laser frequency stabilization device also includes a second fiber coupling head, a second single-mode polarization-maintaining fiber pigtail, and a third fiber coupling head. The coupled laser frequency stabilization optical path includes a fourth plane mirror, a short-pass dichroic mirror, a second fiber collimating device group, and a third fiber collimating device group. The coupled laser emitted by the coupled laser is output through an optical fiber and enters the second fiber coupling head, then enters the third fiber coupling head through the second single-mode polarization-maintaining fiber pigtail, and is collimated and output through the second fiber collimating device group. The collimated coupled laser enters the alkali metal atom gas cell through the short-pass dichroic mirror. The probe laser beam reflected by the first depolarizing beam splitter and then by the fourth plane mirror coincides with the coupled laser at a second position in the alkali metal atom gas cell, generating a Rydberg atom formation EIT effect. The probe laser beam is then reflected by the short-pass dichroic mirror and coupled into an optical fiber through the third fiber collimating device group, and connected to the second photodetector. The second photodetector converts the collected probe laser optical signal into a second electrical signal, which is input to the second frequency stabilization control circuit.

[0010] Furthermore, both the first and second frequency stabilization control circuits incorporate an oscilloscope, a mixer, a low-pass filter, and a proportional-integral-differential (PID) circuit. Specifically, the oscilloscope in the first frequency stabilization control circuit receives and displays the converted first electrical signal; the mixer mixes and demodulates the first electrical signal with the local oscillator signal; the low-pass filter filters the mixed and demodulated signal to obtain a first error signal; and the PID circuit analyzes and processes the first error signal to obtain a first error feedback signal, which is then sent to the probe laser controller to achieve laser frequency stabilization for the probe laser. Similarly, the oscilloscope in the second frequency stabilization control circuit receives and displays the converted second electrical signal; the mixer mixes and demodulates the second electrical signal and the first error signal output from the first frequency stabilization control circuit; the low-pass filter performs high-frequency filtering on the mixed and demodulated signal to obtain a second error signal; and the PID circuit analyzes and processes the second error signal to obtain a second error feedback signal, which is then sent to the coupled laser controller to achieve laser frequency stabilization for the coupled laser.

[0011] In one embodiment, the present invention also provides a laser frequency stabilization method based on an atomic receiver, implemented using the laser frequency stabilization device described in the above embodiments, comprising: S10, control the detector laser to emit a detector laser. The detector laser is split into a first transmitted laser beam and a first reflected laser beam by a first depolarizing beam splitter. The first transmitted laser beam is split into a second transmitted laser beam and a second reflected laser beam again by a second depolarizing beam splitter and a third depolarizing beam splitter. The second transmitted laser beam is split into a second transmitted laser beam and a second reflected laser beam by a first plane mirror and a second plane mirror, and then reflected by a fourth depolarizing beam splitter before entering the alkali metal atom gas cell. It forms a saturated absorption spectrum with the second reflected laser beam in opposite directions and collinear with the second reflected laser beam at a first position in the alkali metal atom gas cell. S20, after the saturated absorption spectrum is formed at the first position of the alkali metal atom gas cell, the transmitted probe laser is reflected by the third plane mirror and coupled into the multimode fiber through the first fiber collimation device group. The probe laser coupled into the multimode fiber is collected and the optical signal of the collected probe laser is converted into a first electrical signal and input to the first frequency stabilization control circuit. S30, the first electrical signal and the local oscillator signal are sequentially mixed, demodulated and filtered to obtain the first error signal, and the laser frequency of the probe laser controller when controlling the probe laser to emit is corrected according to the first error signal. S40, control the coupling laser to emit a coupling laser, the coupling laser sequentially passes through the second fiber collimating device group and the short-pass dichroic mirror to enter the alkali metal atom gas cell, the first reflected laser beam is reflected by the fourth plane mirror to enter the alkali metal atom gas cell and forms an EIT spectrum with the coupling laser at the second position of the alkali metal atom gas cell in opposite directions and collinear. S50, after the EIT spectrum is formed at the second position of the alkali metal atom gas cell, it is reflected by the short-pass dichroic mirror and coupled into the multimode fiber through the third fiber collimating device group. The probe laser coupled into the multimode fiber is collected and the optical signal of the collected probe laser is converted into a second electrical signal and input to the second frequency stabilization control circuit. S60, the first electrical signal and the first error signal are sequentially mixed, demodulated and filtered to obtain the second error signal, and the laser frequency of the coupled laser controller when controlling the coupled laser to emit is corrected according to the second error signal.

[0012] In one embodiment, the present invention also provides a microwave measurement device, including a laser source module, a microwave generation module, a data processing module, and a U-shaped integrated atomic probe; wherein, the probe laser and coupling laser in the laser source module are laser frequency stabilized by the laser frequency stabilization method described in the above embodiment, and are excited by the U-shaped integrated atomic probe to generate Rydberg atoms and electromagnetically induced transparency spectra; the microwave generation module is used to generate a microwave signal to be measured, and radiates the microwave signal to be measured onto the U-shaped integrated atomic probe to cause the electromagnetically induced transparency spectrum to split; the data processing module is used to acquire electrical signals, and calculate the microwave electric field intensity by analyzing the splitting frequency spacing of the electromagnetically induced transparency spectrum; the electrical signals are obtained jointly by the laser source module, the microwave generation module, and the U-shaped integrated atomic probe.

[0013] Furthermore, the laser source module includes a probe laser, a fourth fiber coupler, a third single-mode polarization-maintaining fiber pigtail, a coupling laser, a wavelength division multiplexer, a coupling light input fiber, a probe light output fiber, and a fifth fiber coupler; the microwave generation module includes a microwave source and a horn antenna; the U-shaped integrated atomic probe integrates a fourth fiber collimating device group, a Dowell prism, a short-pass triangular prism, a second alkali metal atom gas cell, and a fifth fiber collimating device group; the data processing module includes a third photodetector and a digital oscilloscope; wherein, the microwave source generates a microwave signal to be measured, which is radiated to the U-shaped integrated atomic probe through the horn antenna; the probe laser generated by the probe laser is polarized through a free-space optical path and then coupled through the fourth fiber coupler into the third single-mode polarization-maintaining fiber pigtail and the fourth fiber collimating device group for collimated output. The collimated probe laser enters the Dowell prism and then flows in the opposite direction through the short-pass triangular prism into the alkali metal atom gas chamber. The coupled laser generated by the coupled laser is coupled into the wavelength division multiplexer via the free-space optical route through the fifth fiber coupler, and then parallel collimated and output through the fifth fiber collimating device group into the alkali metal atom gas chamber, where it interacts with the probe laser to generate the Rydberg atomic EIT spectrum. The microwave signal to be measured causes the electromagnetically induced transparency spectrum to split, and the probe light from the alkali metal atom gas chamber is coupled into the fifth fiber collimating device group. The signal is then collected by the third photodetector through the wavelength division multiplexer and the probe light output fiber. The third photodetector converts the collected probe laser optical signal into a third electrical signal. The digital oscilloscope analyzes the splitting frequency spacing of the electromagnetically induced transparency spectrum by analyzing the collected electrical signal to calculate the microwave electric field intensity.

[0014] Furthermore, the wavelength division multiplexer includes three ports: the first port is connected to the fifth fiber coupler, the other 8° second port with a pigtail ferrule is connected to the fourth fiber collimating device group to output the coupled laser to the alkali metal atom gas cell, and the third port is connected to the photodetector to output the detection laser after the EIT effect is formed in the alkali metal atom gas cell.

[0015] The beneficial technical effects of this invention are as follows: 1. This invention achieves frequency locking of the probe laser and the coupling laser through internal modulation, without the need for additional optical devices such as electro-optic modulators. It can simultaneously achieve frequency stabilization and locking of two lasers by relying on a single alkali metal atom gas cell and circuit.

[0016] 2. This invention eliminates the need for external modulation of the probe light field. It employs a homogeneous all-glass and fiber optic bonding technology, with all optical components fixed and non-adjustable. The probe laser can be directly connected to the frequency-stabilized optical path via fiber optics, significantly reducing the optical path size and improving its stability and convenience. The frequency-stabilized optical path based on the all-glass bonding scheme not only meets the requirements of integration and miniaturization but also enhances the stability and anti-interference capabilities of the optical system.

[0017] 3. This invention integrates the optical and detection components into a single unit, developing a U-shaped all-fiber atomic probe. This reduces the optical path volume and improves the overall portability and stability of the Rydberg atomic detection device. Furthermore, the handheld U-shaped integrated atomic probe utilizes a three-port wavelength division multiplexing device, eliminating the need for the probe light to return to the free-space optical path for detection. This significantly enhances the device's portability. With a protective case, it allows for handheld measurements, facilitating outdoor microwave electric field detection. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Furthermore, the accompanying drawings are not drawn to a 1:1 scale, and the relative dimensions of the various components are shown in the drawings only as examples and not necessarily to actual scale.

[0021] Figure 1 A schematic diagram of a laser frequency stabilization device based on an atomic receiver provided in an embodiment of the present invention; Figure 2 A schematic flowchart of a laser frequency stabilization method based on an atomic receiver provided in an embodiment of the present invention; Figure 3 A schematic diagram of a microwave measuring device provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the U-shaped integrated atomic probe and housing assembly provided in an embodiment of the present invention; Figure 5 A schematic diagram of the U-shaped integrated atomic probe protective shell design provided in an embodiment of the present invention.

[0022] Explanation of reference numerals in the attached figures: Figure 1 Components: 1. Detector laser controller; 2. Detector laser; 3. First fiber optic coupler; 4. First single-mode polarization-maintaining fiber optic pigtail; 5. First GRIN lens; 6. First glass sleeve; 7. First depolarization beam splitter; 8. Second depolarization beam splitter; 9. Third depolarization beam splitter; 10. First plane mirror; 11. Second plane mirror; 12. Fourth depolarization beam splitter; 13. First alkali metal atom gas cell; 14. Third plane mirror; 15. First fiber collimating device group; 16. First photodetector; 17. First frequency stabilization control circuit; 18. DC biaser; 19. Fourth plane mirror; 20. Short-pass dichroic mirror; 21. Second fiber collimating device group; 22. Third fiber collimating device group; 23. Second frequency stabilization control circuit; 24. Coupled laser controller; 25. Coupled laser; 26. Second fiber optic coupler; 27. Second single-mode polarization-maintaining fiber optic pigtail; 28. Third fiber optic coupler; 29. ​​Base plate; 30. Frequency stabilization optical path; 31.

[0023] Figure 3 The following components are included: 2. Detector laser; 32. Fourth fiber optic coupler; 33. Fourth fiber optic collimating device group (composed of third single-mode polarization-maintaining fiber optic pigtail 33, second small glass sleeve 34, first large glass sleeve 35, and second GRIN lens 36); 37. Dowell prism; 38. Short-pass triangular prism; 39. Second alkali metal atom gas chamber; 40. Fifth fiber optic collimating device group (composed of fiber optic pigtail ferrule, third GRIN lens, third small glass sleeve, and second large glass sleeve); 41. Wavelength division multiplexer (WDM); 42. Coupler input fiber; 43. Detector output fiber; 44. Fifth fiber optic coupler; 26. Coupler laser; 45. Third photodetector; 46. Oscilloscope; 47. Microwave source; 48. Horn antenna.

[0024] Figure 4 : Main supporting shell 51, upper fixed shell 52, lower supporting shell 53, outer handle 54. Detailed Implementation

[0025] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0026] This invention proposes a laser frequency stabilization device, method, and microwave measurement device based on an atomic receiver. The laser frequency stabilization device integrates an atomic gas cell with a laser transmission fiber, bonding the atomic gas cell to a glass substrate to form a frequency-stabilized optical path. This simultaneously achieves laser frequency locking for both the coupled and probe laser sources, significantly reducing the size of the frequency-stabilized optical path and greatly improving its stability compared to existing laser frequency stabilization methods. The microwave measurement device employs a handheld U-shaped integrated atomic probe. This U-shaped atomic probe uses a three-port wavelength division multiplexer, eliminating the need for free-space optical path detection. Compared to the original linear atomic probe, this greatly improves the portability of the microwave measurement device.

[0027] The following description is based on specific embodiments: See Figure 1 , Figure 1This diagram illustrates the overall structure of a laser frequency stabilization device based on an atomic receiver according to an embodiment of the present invention. It includes a probe laser controller 1, a probe laser 2, a first photodetector 16, a first frequency stabilization control circuit 17, a DC bias circuit 18, a second photodetector 23, a second frequency stabilization control circuit 24, a coupling laser controller 25, a coupling laser 26, and a frequency stabilization optical path 31. The frequency stabilization optical path 31 is mounted on a base plate 30 and includes a probe laser frequency stabilization optical path, a coupling laser frequency stabilization optical path, and an alkali metal atom gas chamber 13. The probe laser emitted by the probe laser 2 forms a saturated absorption spectrum within the alkali metal atom gas chamber 13 through the probe laser frequency stabilization optical path. The first photodetector 16 collects the optical signal of the probe light transmitted after forming a saturated absorption spectrum within the alkali metal atom gas chamber 13, converts it into a first electrical signal, and sends it to the first frequency stabilization control circuit 17. The first error feedback signal output after analysis by circuit 17 is sent to the probe laser controller 1 via the DC bias 18 to achieve frequency control of the probe laser 2. The probe laser emitted by the probe laser 2 and the coupling laser emitted by the coupling laser 26 generate an electromagnetically induced transparency (EIT) spectrum of Rydberg atoms in the alkali metal atom gas cell 13 through the coupling laser frequency stabilization optical path. The second photodetector 23 collects the optical signal of the probe light reflected after the EIT spectrum is formed in the alkali metal atom gas cell 13, converts it into a second electrical signal, and sends it to the second frequency stabilization control circuit 24. The second frequency stabilization control circuit 24 receives the first error feedback signal output after analysis by the first frequency stabilization control circuit 17, and processes the second electrical signal and the first error feedback signal to obtain a second error feedback signal, which is sent to the coupling laser controller 25 to achieve frequency control of the coupling laser 26.

[0028] Optionally, the probe laser controller 1 is a narrow-linewidth semiconductor laser controller, the probe laser 2 is a narrow-linewidth semiconductor laser, and the probe laser emitted by the narrow-linewidth semiconductor laser has a wavelength of 852 nm; the coupling laser controller 25 is a single-frequency fiber laser controller, the coupling laser 26 is a single-frequency fiber laser, and the coupling laser emitted by the single-frequency fiber laser has a wavelength of 509 nm. Understandably, the narrow-linewidth semiconductor laser controller provides adjustable drive current and control for the narrow-linewidth semiconductor laser; more preferably, the base plate 30 is a glass base plate, and the frequency-stabilized optical path 31 is bonded to the glass base plate. In this embodiment, the glass base plate is preferably made of K9 glass, with a volume of 150 mm * 150 mm * 7 mm, and several holes are drilled in it to fix the frequency-stabilized optical path.

[0029] Specifically, the laser frequency stabilization device further includes a first fiber coupling head 3, and the probe laser frequency stabilization optical path includes a first single-mode polarization-maintaining fiber pigtail 4, a first GRIN lens 5, a first glass sleeve 6, a first depolarizing beam splitter 7, a second depolarizing beam splitter 8, a third depolarizing beam splitter 9, a first plane mirror 10, a second plane mirror 11, a fourth depolarizing beam splitter 12, a third plane mirror 14, and a first fiber collimating device group 15; wherein, the probe laser emitted by the probe laser 2 is coupled into the first single-mode polarization-maintaining fiber pigtail 4 through the first fiber coupling head 3, and the coupled probe laser is split into two beams by the first depolarizing beam splitter 7, wherein the probe laser beam in the transmission direction then passes sequentially through the second depolarizing beam splitter 8 and the third depolarizing beam splitter 9. Mirror 9 splits the probe laser beam in the transmission direction into two beams again. The probe laser beam in the secondary transmission direction is reflected sequentially by the first plane mirror 10 and the second plane mirror 11, and then reflected by the fourth depolarizing beam splitter 12 into the alkali metal atom gas cell 13. It coincides with the weak probe laser beam reflected by the depolarizing beam splitter 9 at the first position of the alkali metal atom gas cell 13 to form a saturated absorption spectrum. After the saturated absorption spectrum is formed, the probe laser beam transmitted through the alkali metal atom gas cell 13 is reflected by the third plane mirror 14 and coupled into the multimode fiber through the first fiber collimating device group 15. The photodetector 16 collects the probe laser coupled into the multimode fiber and converts the collected probe laser optical signal into a first electrical signal, which is input to the first frequency stabilization control circuit 17.

[0030] In one embodiment, a first glass sleeve 6 is further disposed between the first single-mode polarization-maintaining fiber pigtail 4 and the first depolarizing beam splitter 7. A first GRIN lens 5 is disposed within the first glass sleeve 6, and the ferrule of the first single-mode polarization-maintaining fiber pigtail 4 is encased within the first glass sleeve 6. The standard wavelength of the first GRIN lens 5 is 780 nm, and its 8° plane can be parallel to the 8° plane of the ferrule of the first single-mode polarization-maintaining fiber pigtail 4, allowing the probe laser to be collimated and emitted horizontally. By changing the distance between the two, the spot size of the probe laser emitted by the probe laser 2 can be changed. In this embodiment, the ferrule of the first single-mode polarization-maintaining fiber pigtail 4 and the first GRIN lens 5 are fixedly connected using optical adhesive.

[0031] Specifically, in this embodiment, the first depolarization beam splitter 7 has a transmittance to reflectance ratio T:R=9:1, splitting the 852nm probe laser in two. The probe laser beam in the transmission direction passes through the second depolarization beam splitter 8 with a transmittance to reflectance ratio T:R=1:1. The probe laser beam reflected by the second depolarization beam splitter 8 reaches the third depolarization beam splitter 9 with a transmittance to reflectance ratio T:R=9:1. The third depolarization beam splitter 9 splits the probe laser beam reflected by the second depolarization beam splitter 8 in two again. The strong probe laser beam transmitted through the third depolarization beam splitter 9 serves as a strong pump light, reflected sequentially by the first plane mirror 10 and the second plane mirror 11, and then reflected by the fourth depolarization beam splitter 12 with a transmittance to reflectance ratio T:R=1:1. The probe laser beam enters the alkali metal atom gas chamber 13 and interacts with the weak probe laser beam reflected by the third depolarizing beam splitter 9 within the alkali metal atom gas chamber 13. By adjusting the two plane mirrors 10 and 11, the two probe laser beams are made to coincide at a first position in the alkali metal atom gas chamber 13, forming a saturated absorption spectrum. After forming the saturated absorption spectrum, the probe laser beam transmitted through the alkali metal atom gas chamber 13 is reflected by the third plane mirror 14 and coupled into the 852nm multimode fiber through the first fiber collimation device group 15. The first photodetector 16 collects the probe laser beam coupled into the multimode fiber and converts the collected probe laser light signal into a first electrical signal, which is input to the first frequency stabilization control circuit 17. It can be understood that in this embodiment, when the probe laser beam emitted by the probe laser 2 is split into two by the first depolarizing beam splitter 7, the transmitted probe laser beam is used for the 852nm probe laser frequency stabilization optical path, and the reflected probe laser beam is used for the 509nm coupled laser frequency stabilization optical path. Furthermore, the first planar reflector 10 and the second planar reflector 11 are used to adjust the frequency-stabilized optical path of the probe laser, so as to achieve the alignment of the two laser beams with internal modulation and frequency stabilization of the probe laser.

[0032] Furthermore, in this embodiment, the first fiber collimation device group 15 is composed of a 780nm GRIN lens, a fiber optic pigtail ferrule, and large and small glass sleeves fixed together with optical adhesive, and is used to collimate and emit the collected optical signal. The first frequency stabilization control circuit 17 has a built-in oscilloscope, mixer, low-pass filter, proportional-integral-differential circuit, and waveform generator. The first frequency stabilization control circuit 17 performs frequency mixing, demodulation, filtering, and other analysis processing on the converted electrical signal and the internal local oscillation signal through the mixer, low-pass filter, proportional-integral-differential circuit, and waveform generator to obtain a first error feedback signal, which is sent to the DC bias unit 18. The DC bias unit 18 is used to DC bias the obtained first error feedback signal and then feed it back to the probe laser controller 1 to control the probe laser frequency. Specifically, the frequency mixing, demodulation, filtering, and other methods are existing technologies and will not be described in detail in this invention.

[0033] Specifically, the laser frequency stabilization device further includes a second fiber coupler 27, a second single-mode polarization-maintaining fiber pigtail 28, and a third fiber coupler 29. The coupled laser frequency stabilization optical path includes a fourth plane mirror 19, a short-pass dichroic mirror 20, a second fiber collimating device group 21, and a third fiber collimating device group 22. The coupled laser output from the coupled laser 26 enters the second fiber coupler 27 via an optical fiber output, then enters the third fiber coupler 29 via the second single-mode polarization-maintaining fiber pigtail 28, and is then collimated and output via the second fiber collimating device group 21. The collimated coupled laser then passes through the short-pass dichroic mirror 29. The dichroic mirror 20 enters the alkali metal atom gas chamber 13. The probe laser beam reflected by the first depolarizing beam splitter 7 and then by the fourth plane mirror 19 coincides with the coupled laser at the second position of the alkali metal atom gas chamber 13, generating a Rydberg atom-forming electromagnetically induced transparent (EIT) effect. The probe laser beam is then reflected by the short-pass dichroic mirror 20 and coupled into the optical fiber by the third fiber collimating device group 22, and connected to the second photodetector 23. The second photodetector 23 converts the collected probe laser optical signal into a second electrical signal, which is input to the second frequency stabilization control circuit 24. In this embodiment, the probe laser signal emitted by the probe laser 2, reflected by the first depolarizing beam splitter 7 and then by the fourth plane mirror 19, reaches the second position of the alkali metal atom gas chamber 13. It interacts with the coupled laser to generate an EIT effect, is then reflected by the short-pass dichroic mirror 20, and coupled into the third fiber collimating device group 22. In this embodiment, the short-pass dichroic mirror 20 is a dichroic mirror with a reflection of 509nm and a transmission of 852nm.

[0034] Furthermore, in this embodiment, the second frequency stabilization control circuit 24 also incorporates an oscilloscope, a mixer, a low-pass filter, a proportional-integral-differential circuit, and a waveform generator. The second frequency stabilization control circuit 24 uses the mixer, low-pass filter, proportional-integral-differential circuit, and waveform generator to perform mixing, demodulation, filtering, and other analysis processing on the converted second electrical signal and the first error feedback signal to obtain the second error feedback signal. Specifically, when the second electrical signal is input to the second frequency stabilization control circuit 24, the EIT transmission peak can be observed when viewing the second electrical signal (AC signal) on the oscilloscope of the second frequency stabilization control circuit 24. The second electrical signal and the first error feedback signal with modulation information output from the first frequency stabilization control circuit 17 are input together into the second frequency stabilization control circuit 24. The second electrical signal and the received first error feedback signal are input to the mixer for mixing and demodulation, and then high-frequency filtering is performed by the low-pass filter to obtain the second error feedback signal. This signal is then output by the proportional-integral-differential circuit and fed back to the coupled laser controller 25, achieving frequency stabilization correction for the coupled laser frequency.

[0035] The laser frequency stabilization device based on an atomic receiver provided in this embodiment integrates an alkali metal atomic gas chamber with a laser transmission optical fiber. The alkali metal atomic gas chamber is bonded to a glass substrate and forms a frequency stabilization optical path with the laser transmission module. At the same time, it achieves laser frequency locking for both the coupled laser source and the probe laser source, greatly reducing the size of the frequency stabilization optical path. Compared with the existing laser frequency stabilization methods, it also greatly improves the stability of the frequency stabilization optical path.

[0036] In one embodiment, based on the laser frequency stabilization device based on the atomic receiver provided above, see [reference needed]. Figure 2 The present invention also provides a laser frequency stabilization method based on an atomic receiver, comprising: S10, control the detector laser to emit a detector laser. The detector laser is split into a first transmitted laser beam and a first reflected laser beam by a first depolarizing beam splitter. The first transmitted laser beam is split into a second transmitted laser beam and a second reflected laser beam again by a second depolarizing beam splitter and a third depolarizing beam splitter. The second transmitted laser beam is split into a second transmitted laser beam and a second reflected laser beam by a first plane mirror and a second plane mirror, and then reflected by a fourth depolarizing beam splitter before entering the alkali metal atom gas cell. It forms a saturated absorption spectrum with the second reflected laser beam in opposite directions and collinear with the second reflected laser beam at a first position in the alkali metal atom gas cell. S20, after the saturated absorption spectrum is formed at the first position of the alkali metal atom gas cell, the transmitted probe laser is reflected by the third plane mirror and coupled into the multimode fiber through the first fiber collimation device group. The probe laser coupled into the multimode fiber is collected and the optical signal of the collected probe laser is converted into a first electrical signal and input to the first frequency stabilization control circuit. S30, the first electrical signal and the local oscillator signal are sequentially mixed, demodulated and filtered to obtain the first error signal, and the laser frequency of the probe laser controller when controlling the probe laser to emit is corrected according to the first error signal. S40, control the coupling laser to emit a coupling laser, the coupling laser sequentially passes through the second fiber collimating device group and the short-pass dichroic mirror to enter the alkali metal atom gas cell, the first reflected laser beam is reflected by the fourth plane mirror to enter the alkali metal atom gas cell and forms an EIT spectrum with the coupling laser at the second position of the alkali metal atom gas cell in opposite directions and collinear. S50, after the EIT spectrum is formed at the second position of the alkali metal atom gas cell, it is reflected by the short-pass dichroic mirror and coupled into the multimode fiber through the third fiber collimating device group. The probe laser coupled into the multimode fiber is collected and the optical signal of the collected probe laser is converted into a second electrical signal and input to the second frequency stabilization control circuit. S60, the first electrical signal and the first error signal are sequentially mixed, demodulated and filtered to obtain the second error signal, and the laser frequency of the coupled laser controller when controlling the coupled laser to emit is corrected according to the second error signal.

[0037] In this embodiment of the invention, the frequency locking of the narrow-linewidth semiconductor laser 2 is specifically performed using an internal modulation method. Internal modulation spectral stabilization primarily utilizes the laser beam passing through a gas cell containing alkali metal atoms. The saturated absorption of the laser by the atoms within the alkali metal atom gas cell generates an absorption peak. When the laser frequency matches the atomic transition frequency, the absorption reaches its maximum, forming a characteristic peak. By detecting the position of the characteristic peak, the laser frequency can be precisely controlled, stabilizing it at a specific atomic transition frequency. Therefore, when the narrow-linewidth semiconductor laser 2 emits a probe laser, it obtains a probe laser signal whose laser frequency can be precisely controlled through the probe laser frequency stabilization optical path. This probe laser signal is converted into an electrical signal by a first photodetector and then observed on an oscilloscope within the first frequency stabilization control circuit. The first electrical signal, after saturated absorption spectrum conversion, is combined with the local oscillator signal and fed into a mixer for mixing and demodulation to obtain the initial error signal. This initial error signal is then filtered by an internal low-pass filter to obtain a clearer first error signal. This signal is then analyzed by the proportional-integral-differential circuit of the high-performance servo controller to obtain the first error feedback signal, which is fed back to the narrow-linewidth semiconductor laser controller 1. In this way, the frequency of the narrow-linewidth semiconductor laser is corrected, ultimately achieving frequency stabilization. At this point, the modulation signal input to the narrow-linewidth semiconductor laser controller 1 is the corrected first error feedback signal.

[0038] The frequency locking of the single-frequency laser source 26 is specifically as follows: The frequency locking of the single-frequency fiber laser 26 mainly utilizes the Rydberg electromagnetic induced transparency effect to lock the frequency of the laser excited to the Rydberg state transition frequency. The probe laser output from the narrow-linewidth semiconductor laser 2 already carries a modulation signal. Then, the modulated probe laser and the coupled laser, after forming the EIT effect in the alkali metal atom gas cell, are further mixed and demodulated with the first error signal generated in the first frequency stabilization control circuit 17 in the second frequency stabilization control circuit 24. After passing through a low-pass filter to filter the high-frequency signal to obtain a second error signal, the second error signal is transmitted to the built-in high-performance servo controller proportional-integral-differential circuit to obtain a second error feedback signal. The second error feedback signal is then fed back to the coupled laser controller 25. In this way, the single-frequency fiber laser 26 is controlled to achieve frequency stabilization.

[0039] In one embodiment, after using the above-described laser frequency stabilization device and method to achieve frequency control of the probe laser and the coupling laser, please refer to... Figure 2The present invention also provides a microwave measurement device, including a laser source module, a microwave generation module, a data processing module, and a U-shaped integrated atomic probe. The probe laser and coupling laser in the laser source module are frequency stabilized by the frequency stabilization method described in the above embodiments, and Rydberg atoms and electromagnetically induced transparency spectrum are generated by the U-shaped integrated atomic probe. The microwave generation module is used to generate the microwave signal to be measured and radiates the microwave signal to be measured onto the U-shaped integrated atomic probe, causing the electromagnetically induced transparency spectrum to split. The data processing module is used to collect electrical signals and calculate the microwave electric field intensity by analyzing the splitting frequency spacing of the electromagnetically induced transparency spectrum. The electrical signals are obtained jointly by the laser source module, the microwave generation module, and the U-shaped integrated atomic probe.

[0040] Specifically, in this embodiment, the laser source module includes a probe laser 2, a fourth fiber optic coupler 32, a third single-mode polarization-maintaining fiber optic pigtail 33, a coupling laser 26, a wavelength division multiplexer (WDM) 41, a coupling light input fiber 42, a probe light output fiber 43, and a fifth fiber optic coupler 44; the microwave generation module includes a microwave source 47 and a horn antenna 48; the U-shaped integrated atomic probe integrates a fourth fiber optic collimating device group composed of a second small glass sleeve 34, a first large glass sleeve 35, and a second GRIN lens 36, a Dowell prism 37, a short-pass triangular prism 38, a second alkali metal atomic gas cell 39, and a fifth fiber optic collimating device group 40 composed of a fiber optic pigtail ferrule, a third GRIN lens, a third small glass sleeve, and a second large glass sleeve; the data processing module includes a third photodetector 45 and a digital oscilloscope 46. Understandably, in this embodiment, the Dowell prism 37 is used to change the propagation direction of the 852 beam, and the short-pass triangular prism 38 is a right-angle prism used for beam combining and splitting (its inclined surface is coated with a microwave anti-reflection film with high reflection of 852 and high transmission of 509).

[0041] Understandably, in this embodiment, further reference is made to... Figure 2Microwave source 47 generates the microwave signal to be tested, which is connected to horn antenna 48 via BNC cable. The horn antenna 48 radiates the microwave signal to be tested to the U-shaped integrated atomic probe. The probe laser generated by probe laser 2 is polarized through free space optical path and then coupled into third single-mode polarization-maintaining fiber pigtail 33 through fourth fiber coupler 32. The probe laser is collimated and output by adjusting the 8° plane of the ferrule of the third single-mode polarization-maintaining fiber pigtail to be parallel to the 8° plane of the second GRIN lens 36. The ferrule of the third single-mode polarization-maintaining fiber pigtail and the second GRIN lens 36 are fixed together in the second small glass sleeve 34 with ultraviolet optical adhesive. The small glass sleeve 34 is then fixed in the first large glass sleeve 35 with ultraviolet optical adhesive and then connected and fixed to the Daowei prism 37. The collimated probe laser enters the Daowei prism 37 and enters the alkali metal atom gas chamber 39 in reverse through the short-pass triangular prism 38. The coupled laser generated by coupling laser 26 is coupled into wavelength division multiplexer (WDM) through free space optical path via fifth fiber coupler 44. The WDM (Wavelength Division Multiplexing) 12, collimated by aligning the 8° plane of the fiber optic pigtail with the 8° plane of the third GRIN lens, enters the alkali metal atom gas cell 39. By adjusting the positions of the probe laser and the coupling laser, the two beams are made to coincide within the alkali metal atom gas cell. The two beams interact with the atoms, exciting them to the Rydberg state and generating an electromagnetically induced transparency effect. The microwave signal to be measured causes the electromagnetically induced transparency spectrum to split, generating an EIT spectrum. The coupling laser from the alkali metal atom gas cell 39 is emitted through the short-pass triangular prism 38 and coupled into the fifth fiber collimating device group 40 via the probe light from the alkali metal atom gas cell 39. After passing through the wavelength division multiplexer (WDM) 41, the probe light output fiber 43 is collected by the third photodetector 45. The third photodetector 45 converts the collected probe light optical signal into an electrical signal, which is transmitted to the digital oscilloscope 46 for observation. The splitting frequency spacing of the electromagnetically induced transparency spectrum is analyzed by the collected electrical signal, and the microwave electric field intensity is calculated. The specific method for calculating microwave electric field intensity is existing technology and will not be described in detail in this embodiment.

[0042] Furthermore, the wavelength division multiplexer 41, which transmits coupled laser light and collects probe laser light via a fiber optic pigtail, includes three ports. The first port connects to the fifth fiber optic coupler 44 to transmit a 509nm coupled laser light. The second port, with a fiber optic pigtail and an 8° angle, is collimated parallel to the 8° plane of the third GRIN lens (coupled light graded refractive index lens) to output the coupled laser light to the alkali metal atom gas cell 39. The third port connects to the photodetector 45 to output the probe laser light after the EIT effect is formed in the alkali metal atom gas cell 39. Understandably, the parallel collimation of the second port with the fiber optic pigtail to the 8° plane of the third GRIN lens (coupled light graded refractive index lens) also allows as much probe laser light as possible to enter the port with the fiber optic pigtail of the wavelength division multiplexer 41 and be collected by the third photodetector 45.

[0043] See Figure 3 A schematic diagram of the assembly of the U-shaped integrated atomic probe in this embodiment is provided, including a main supporting shell 51, an upper fixed shell 52, a lower supporting shell 53, and an outer handle 54; see reference. Figure 4 Further schematic diagrams of the components of the handheld protective shell are provided. The main support shell 51 supports the alkali metal atom gas chamber, bearing the main force, and has a window for the chamber to receive microwave signals. The main support shell 51 has several protrusions. The upper fixed shell 52 has several through holes for fixing to the main support shell 51, and has a window at the same position as the main support shell for transmitting the microwave signals received by the alkali metal atom gas chamber. The lower support shell 53 has a recessed groove on its inner side for transmitting laser fiber. The laser fiber is wound and fixed internally by a protective sleeve to prevent pulling on the fiber during microwave measurement from affecting the measurement accuracy of the microwave electric field. The lower end of the outer handle of the lower support shell 53 has external threads, and the lower end of the inner side of the outer handle 54 has internal threads. The lower support shell 53 and the outer handle 54 are fixed together by the matching internal and external threads. Optionally, the U-shaped integrated probe is made of nylon PA12 material to achieve interference-free measurement of the microwave electric field under test.

[0044] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0045] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A laser frequency stabilization device based on an atomic receiver, characterized in that, The system includes a probe laser controller, a probe laser, a first photodetector, a first frequency stabilization control circuit, a DC bias, a second photodetector, a second frequency stabilization control circuit, a coupled laser controller, a coupled laser, and a frequency stabilization optical path. The frequency stabilization optical path is mounted on a glass substrate and includes a probe laser frequency stabilization optical path, a coupled laser frequency stabilization optical path, and an alkali metal atom gas chamber. The probe laser emitted by the probe laser forms a saturated absorption spectrum in the alkali metal atom gas chamber through the probe laser frequency stabilization optical path. The first photodetector collects the optical signal of the probe laser transmitted after forming a saturated absorption spectrum in the alkali metal atom gas chamber, converts it into a first electrical signal, and sends it to the first frequency stabilization control circuit. After analysis by the first frequency stabilization control circuit, a first error feedback signal is output and transmitted through the DC bias. The frequency of the probe laser is controlled by the probe laser controller. The coupling laser emitted by the coupling laser and the probe laser emitted by the probe laser are transmitted through the coupling laser frequency stabilization optical path to generate an electromagnetically induced transparency (EIT) spectrum of Rydberg atoms in the alkali metal atom gas chamber. The second photodetector collects the optical signal of the probe laser reflected after the EIT spectrum is formed in the alkali metal atom gas chamber, converts it into a second electrical signal, and sends it to the second frequency stabilization control circuit. The second frequency stabilization control circuit receives the first error feedback signal output by the first frequency stabilization control circuit after analysis, and sends the second error feedback signal output by analyzing and processing the second electrical signal and the first error feedback signal to the coupling laser controller to control the frequency of the coupling laser.

2. The laser frequency stabilization device according to claim 1, characterized in that, The laser frequency stabilization device further includes a first fiber optic coupler. The probe laser frequency stabilization optical path includes a first single-mode polarization-maintaining fiber pigtail, a first depolarization beam splitter, a second depolarization beam splitter, a third depolarization beam splitter, a first plane mirror, a second plane mirror, a fourth depolarization beam splitter, a third plane mirror, and a first fiber collimating device group. The probe laser emitted by the probe laser is coupled into the first single-mode polarization-maintaining fiber pigtail through the first fiber optic coupler. The coupled probe laser is split into two beams by the first depolarization beam splitter. The probe laser beam in the transmission direction is then split into two beams again by the second and third depolarization beam splitters. The probe laser beam transmitted through the third depolarizing beam splitter is reflected sequentially by the first plane mirror and the second plane mirror, and then reflected by the fourth depolarizing beam splitter into the alkali metal atom gas cell. It coincides with the probe laser beam reflected by the third depolarizing beam splitter at the first position in the alkali metal atom gas cell, forming a saturated absorption spectrum. After forming the saturated absorption spectrum, the probe laser transmitted through the alkali metal atom gas cell is reflected by the third plane mirror and coupled into the multimode fiber through the first fiber collimating device group. The first photodetector collects the probe laser coupled into the multimode fiber and converts the collected probe laser optical signal into a first electrical signal, which is input to the first frequency stabilization control circuit.

3. The laser frequency stabilization device according to claim 2, characterized in that, The first depolarizing beam splitter has a transmittance to reflectance ratio T:R=9:1, the second depolarizing beam splitter has a transmittance to reflectance ratio T:R=1:1, the third depolarizing beam splitter has a transmittance to reflectance ratio T:R=9:1, and the fourth depolarizing beam splitter has a transmittance to reflectance ratio T:R=1:

1.

4. The laser frequency stabilization device according to claim 3, characterized in that, When the probe laser emitted by the probe laser is split into two by the first depolarizing beam splitter, the transmitted probe laser beam is used in the probe laser frequency stabilization optical path, and the reflected probe laser beam is used in the coupled laser frequency stabilization optical path.

5. The laser frequency stabilization device according to claim 1, characterized in that, The laser frequency stabilization device further includes a second fiber coupler, a second single-mode polarization-maintaining fiber pigtail, and a third fiber coupler. The coupled laser frequency stabilization optical path includes a fourth plane mirror, a short-pass dichroic mirror, a second fiber collimating device group, and a third fiber collimating device group. The coupled laser emitted by the coupled laser enters the second fiber coupler, passes through the second single-mode polarization-maintaining fiber pigtail, enters the third fiber coupler, and is then collimated and output by the second fiber collimating device group. The collimated coupled laser enters the alkali metal atom gas cell through the short-pass dichroic mirror. The probe laser beam reflected by the first depolarizing beam splitter and then by the fourth plane mirror coincides with the coupled laser at a second position in the alkali metal atom gas cell, generating a Rydberg atom formation EIT effect. The probe laser beam is then reflected by the short-pass dichroic mirror and coupled into the optical fiber by the third fiber collimating device group, and connected to the second photodetector. The second photodetector converts the collected probe laser optical signal into a second electrical signal, which is input to the second frequency stabilization control circuit.

6. The laser frequency stabilization device according to any one of claims 1-5, characterized in that, Both the first and second frequency stabilization control circuits incorporate an oscilloscope, a mixer, a low-pass filter, and a proportional-integral-differential (PID) circuit. Specifically, the oscilloscope in the first frequency stabilization control circuit receives and displays the converted first electrical signal; the mixer mixes and demodulates the first electrical signal with a local oscillator signal; the low-pass filter filters the mixed and demodulated signal to obtain a first error signal; and the PID circuit analyzes and processes the first error signal to obtain a first error feedback signal, which is then sent to the probe laser controller to achieve laser frequency stabilization for the probe laser. Similarly, the oscilloscope in the second frequency stabilization control circuit receives and displays the converted second electrical signal; the mixer mixes and demodulates the second electrical signal and the first error signal output from the first frequency stabilization control circuit; the low-pass filter performs high-frequency filtering on the mixed and demodulated signal to obtain a second error signal; and the PID circuit analyzes and processes the second error signal to obtain a second error feedback signal, which is then sent to the coupled laser controller to achieve laser frequency stabilization for the coupled laser.

7. A laser frequency stabilization method based on an atomic receiver, implemented using the laser frequency stabilization device according to any one of claims 1-6, comprising: S10, control the detector laser to emit a detector laser. The detector laser is split into a first transmitted laser beam and a first reflected laser beam by a first depolarizing beam splitter. The first transmitted laser beam is split into a second transmitted laser beam and a second reflected laser beam again by a second depolarizing beam splitter and a third depolarizing beam splitter. The second transmitted laser beam is split into a second transmitted laser beam and a second reflected laser beam by a first plane mirror and a second plane mirror, and then reflected by a fourth depolarizing beam splitter before entering the alkali metal atom gas cell. It forms a saturated absorption spectrum with the second reflected laser beam in opposite directions and collinear with the second reflected laser beam at a first position in the alkali metal atom gas cell. S20, after the saturated absorption spectrum is formed at the first position of the alkali metal atom gas cell, the transmitted probe laser is reflected by the third plane mirror and coupled into the multimode fiber through the first fiber collimation device group. The probe laser coupled into the multimode fiber is collected and the optical signal of the collected probe laser is converted into a first electrical signal and input to the first frequency stabilization control circuit. S30, the first electrical signal and the local oscillator signal are sequentially mixed, demodulated and filtered to obtain the first error signal, and the laser frequency of the probe laser controller when controlling the probe laser to emit is corrected according to the first error signal. S40, control the coupling laser to emit a coupling laser, the coupling laser sequentially passes through the second fiber collimating device group and the short-pass dichroic mirror to enter the alkali metal atom gas cell, the first reflected laser beam is reflected by the fourth plane mirror to enter the alkali metal atom gas cell and forms an EIT spectrum with the coupling laser at the second position of the alkali metal atom gas cell in opposite directions and collinear. S50, after the EIT spectrum is formed at the second position of the alkali metal atom gas cell, it is reflected by the short-pass dichroic mirror and coupled into the multimode fiber through the third fiber collimating device group. The probe laser coupled into the multimode fiber is collected and the optical signal of the collected probe laser is converted into a second electrical signal and input to the second frequency stabilization control circuit. S60, the first electrical signal and the first error signal are sequentially mixed, demodulated and filtered to obtain the second error signal, and the laser frequency of the coupled laser controller when controlling the coupled laser to emit is corrected according to the second error signal.

8. A microwave measuring device, characterized in that, The system includes a laser source module, a microwave generator module, a data processing module, and a U-shaped integrated atomic probe. The laser source module uses a probe laser and a coupling laser for laser frequency stabilization using the laser frequency stabilization method described in claim 7, and generates Rydberg atoms and an electromagnetically induced transparency spectrum through the U-shaped integrated atomic probe. The microwave generator module generates a microwave signal to be measured, which is then radiated onto the U-shaped integrated atomic probe, causing the electromagnetically induced transparency spectrum to split. The data processing module acquires electrical signals and calculates the microwave electric field strength by analyzing the splitting frequency interval of the electromagnetically induced transparency spectrum. The electrical signals are obtained jointly by the laser source module, the microwave generator module, and the U-shaped integrated atomic probe.

9. The microwave measuring device according to claim 8, characterized in that, The laser source module includes a probe laser, a fourth fiber coupler, a third single-mode polarization-maintaining fiber pigtail, a coupling laser, a wavelength division multiplexer, a coupling light input fiber, a probe light output fiber, and a fifth fiber coupler. The microwave generation module includes a microwave source and a horn antenna. The U-shaped integrated atomic probe integrates a fourth fiber collimating device group, a Dowell prism, a short-pass triangular prism, a second alkali metal atom gas cell, and a fifth fiber collimating device group. The data processing module includes a third photodetector and a digital oscilloscope. The microwave source generates a microwave signal to be measured, which is radiated to the U-shaped integrated atomic probe via the horn antenna. The probe laser generated by the probe laser is coupled through the fourth fiber coupler into the third single-mode polarization-maintaining fiber pigtail and the fourth fiber collimating device group for collimation output. The collimated probe laser output... Light enters the Dowell prism and then flows backward through the short-pass triangular prism into the alkali metal atom gas chamber. The coupled laser generated by the coupled laser is coupled into the wavelength division multiplexer via the free-space optical route through the fifth fiber coupler, and then parallel-collimated by the fifth fiber collimating device group before entering the alkali metal atom gas chamber to interact with the probe laser and generate the Rydberg atom EIT spectrum. The microwave signal to be measured causes the electromagnetically induced transparency spectrum to split. The probe light from the alkali metal atom gas chamber is coupled into the fifth fiber collimating device group, and then collected by the third photodetector through the wavelength division multiplexer and the probe light output fiber. The third photodetector converts the collected probe laser optical signal into a third electrical signal. The digital oscilloscope analyzes the splitting frequency spacing of the electromagnetically induced transparency spectrum by analyzing the collected electrical signal to calculate the microwave electric field intensity.

10. The microwave measuring device according to claim 9, characterized in that, The wavelength division multiplexer includes three ports. The first port is connected to the fifth fiber coupler, and the second port with a pigtail ferrule is connected to the fourth fiber collimating device group to output the coupled laser to the alkali metal atom gas cell. The third port is connected to the photodetector to output the detection laser after the EIT effect is formed in the alkali metal atom gas cell.

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