Method and device for calibrating spectrum frequencies of atoms and molecules

Abstract

The invention provides a method and device for calibrating atomic and molecular spectral frequencies, and relates to the technical field of quantum precision measurement, and the method comprises the steps: obtaining a free spectral path of an ultra-stable optical reference cavity; synchronously acquiring an atomic molecule spectral signal and a transmission signal of the ultra-stable optical reference cavity; wherein the atomic molecule spectral signal and the transmission signal are respectively generated by laser output by the same single-frequency laser after beam splitting; and performing frequency calibration on the atomic molecular spectral signal based on the free spectral path. The method has the advantages of high precision, high stability, relatively simple system and controllable cost.

Description

Technical Field

[0001] This invention relates to the field of quantum precision measurement technology, and in particular to a method and apparatus for calibrating the spectral frequencies of atoms and molecules. Background Technology

[0002] Measuring the frequency spacing of atomic and molecular spectral transition peaks is a core technology in the field of quantum precision measurement. Essentially, it involves analyzing the frequency distribution of transmission spectra formed by the interaction of atoms and molecules with light to infer the energy level spacing, thereby revealing the energy level structure and dynamic processes of microscopic matter. This technology is widely used in quantum metrology, quantum sensing, and quantum computing, and its accuracy directly determines the reliability of measurements such as material composition analysis and atomic clock calibration.

[0003] In existing technologies, the main methods for measuring the frequency spacing of atomic and molecular spectral transition peaks are as follows: First, using an electro-optic modulator (EOM) or an acousto-optic modulator (AOM) to modulate the phase or frequency of a laser, enabling the spectrum to simultaneously generate sideband reference peaks of known frequencies, thus achieving spectral frequency spacing measurement; this method has a relatively simple overall setup. Second, using a commercially available Fabry-Perot etalon (FP etalon) to measure the spectral frequency spacing. Third, using an optical frequency comb to achieve spectral frequency measurement. However, these methods have many shortcomings. For example, the spectral linewidths of atomic and molecular spectral transition peaks are often on the order of MHz, and the spectral linewidths of known frequency reference peaks generated by electro-optic modulators (EOM) or acousto-optic modulators (AOM) are also often on the order of MHz, insufficient to meet the accuracy requirements of spectral frequency calibration. Although commercially available Fabry-Perot etalons can provide frequency references, their cavity length cannot be precisely measured, and they lack high-precision temperature and vacuum control measures, resulting in significant frequency drift. While optical frequency combs can provide equally spaced, low-noise frequency references, they suffer from drawbacks such as system complexity, large size, high cost, and weak anti-interference capability. In summary, the methods described above for measuring the frequency spacing of transition peaks in atomic and molecular spectra cannot provide a high-precision and cost-effective measurement solution, thus limiting the application of atomic and molecular spectroscopy. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method and apparatus for calibrating the spectral frequencies of atoms and molecules, which can simultaneously have the advantages of high precision, high stability, relatively simple system and controllable cost.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: In a first aspect, a method for calibrating atomic and molecular spectral frequencies, the method comprising: Obtain the free spectral path of the ultrastable optical reference cavity; Simultaneously acquire atomic and molecular spectral signals and transmission signals from an ultrastable optical reference cavity; wherein, the atomic and molecular spectral signals and the transmission signals are generated separately by the laser beam output from the same single-frequency laser after beam splitting; Frequency calibration of atomic and molecular spectral signals is performed based on the free spectral path.

[0006] In a second aspect, an apparatus for calibrating atomic and molecular spectral frequencies, for implementing the aforementioned method for calibrating atomic and molecular spectral frequencies, the apparatus comprising: A free spectral path measurement system for measuring the free spectral path of an ultrastable optical reference cavity; A single-frequency laser source, used to generate tunable single-frequency laser light; A beam splitter, connected to a single-frequency laser source, is used to split the single-frequency laser beam into a spectrum generation beam and a reference beam. The spectrum generation module is located in the optical path of the spectrum generation beam and is used to enable the spectrum generation beam to interact with atoms or molecules to generate atomic and molecular spectral signals. The first detection device is used to receive and convert atomic and molecular spectral signals into a first electrical signal; The second detection device is used to receive the transmission signal of the reference beam after passing through the ultra-stable optical reference cavity and convert it into a second electrical signal. A synchronous acquisition device, electrically connected to the first detection device and the second detection device, is used to synchronously acquire the first electrical signal and the second electrical signal; and The calibration processing unit, connected to the synchronous acquisition device and the free path measurement system, is used to perform frequency calibration on the atomic and molecular spectral signals acquired by the synchronous acquisition device based on the free path measured by the free path measurement system.

[0007] The above-described solution of the present invention has at least the following beneficial effects: The ultra-stable optical reference cavity provides a frequency reference for atomic or molecular spectral frequency calibration by offering high stability and high precision (linewidth <10kHz) optical resonant frequencies. By using dual lasers to lock adjacent transmission peaks of the ultra-stable optical reference cavity to measure the free spectral path, compared with the optical frequency comb (OFC) calibration method, it has advantages such as system simplicity, low cost, and strong environmental adaptability, providing a cost-effective solution for precise atomic and molecular spectral frequency calibration. Attached Figure Description

[0008] Figure 1 The cavity structure is for an ultra-stable optical reference cavity.

[0009] Figure 2 This is a schematic diagram of the longitudinal mode of the FP resonant cavity of the present invention.

[0010] Figure 3This is a schematic diagram of the ultra-stable optical reference cavity FSR measurement device of the present invention.

[0011] Figure 4 This is a schematic diagram of the free spectral path measurement of the ultrastable optical cavity of the present invention.

[0012] Figure 5 For application to cesium atom nD J A schematic diagram of cesium atom energy levels, illustrating a specific example of Rydberg state fine structure splitting measurement.

[0013] Figure 6 This is a schematic diagram of the detection optical frequency stabilization module.

[0014] Figure 7 The present invention provides an application to cesium atom nD J The result of fine structure measurement.

[0015] Figure 8 This is a schematic diagram of the device provided by the present invention for frequency calibration of the saturated absorption spectrum of the D2 line of cesium atoms.

[0016] Figure 9 The result diagram provided by this invention is the frequency calibration result of the saturated absorption spectrum of the D2 line of cesium atoms.

[0017] Figure 10 This is a schematic diagram of a general-purpose device for atomic and molecular spectral frequency calibration provided by the present invention.

[0018] Figure 11 This is a schematic diagram of the thermal shielding structure design for an ultra-stable optical reference cavity.

[0019] Figure 12 A schematic diagram of the vacuum device structure design for an ultra-stable optical reference cavity.

[0020] Figure 13 For cesium atoms nD J Schematic diagram of a fine structure measurement device. Detailed Implementation

[0021] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0022] like Figures 1 to 13 As shown, Figure 1 The cavity structure for an ultra-stable optical reference cavity. Figure 11 The thermal shielding structure design for the ultra-stable optical reference cavity Figure 12Design of a vacuum device structure for an ultra-stable optical reference cavity. For example... Figure 1 As shown, the ultra-stable optical reference cavity structure mainly consists of two parts: a material with an ultra-low coefficient of thermal expansion and a high-reflectivity cavity mirror (reflectivity > 99.999%). The cavity typically uses ULE glass as the material with an ultra-low coefficient of thermal expansion, which can effectively suppress the influence of temperature on the cavity length of the ultra-stable optical reference cavity. Figure 1 As shown, the ultra-stable optical reference cavity adopts a three-layer thermal shielding structure design, effectively isolating the external temperature from the ultra-stable optical reference cavity and maintaining good temperature stability inside the cavity. Figure 12 As shown, the ultrastable optical reference cavity employs an ion pump to maintain a long-term vacuum state within the cavity. Through these measures, the ultrastable optical reference cavity can provide a highly stable frequency reference for spectral calibration. A specific embodiment for cesium atom saturated absorption spectroscopy laser frequency calibration is described below, such as... Figure 8 As shown, the oscilloscope 107 simultaneously acquires the saturated absorption spectrum signal of cesium atoms and the transmission signal of the laser output from the single-frequency laser 35 entering the ultra-stable optical reference cavity 105. Combined with... Figure 5 It can be seen that transition peak ① corresponds to the cesium atom 6S 1 / 2 F=4→6P 3 / 2 The energy level transition peak at F'=5, transition peak ② corresponds to the 6S atom of cesium. 1 / 2 F=4→6P 3 / 2 The energy level crossover peaks are F'=4 and F'=5. After the single-frequency laser 33 performs a mode-hopping-free scan, the oscilloscope 107 can acquire the transmission signal received by the photodetector 106, such as... Figure 9 The embedding diagram is shown below. F' can be adopted as follows: Figure 3 The apparatus shown performs precise measurements. Using a known frequency F', the frequency spacing between transition peak ① and transition peak ② can be measured. This embodiment discloses a method for calibrating atomic and molecular spectral frequencies, specifically including obtaining the free spectral path of an ultrastable optical reference cavity, and measuring the nD of cesium atoms. J The document consists of four parts: fine structure measurement of atomic Rydberg states (electromagnetically induced transparent spectral signals), frequency calibration of saturated absorption spectra of D2 lines of cesium atoms, and extension of frequency calibration for general atomic and molecular spectra. Each component corresponds to the serial number in the accompanying drawings of the technical disclosure document, and each step and component's function is described in detail and completely.

[0023] An ultrastable optical reference cavity is essentially a high-precision Fabry-Perot resonant cavity (FP cavity), composed of two parallel, highly reflective mirrors (typically >99.999%), creating a standing wave field within the cavity. For a non-confocal cavity, its resonant frequency and free spectral path are as follows: ; ; Where, the laser frequency n is the resonant frequency of the resonant cavity, q is the longitudinal mode number, c is the speed of light in vacuum, n is the refractive index of the cavity medium, L is the geometric distance between the two cavity mirrors, and Δn FSR The free spectral range (FSR) of an ultrastable optical cavity is physically defined as the frequency interval between two adjacent maximum transmission peaks of the transmitted laser. It can be seen that Δn FSR The value of Δn depends on the geometric distance L between the two cavity mirrors. Therefore, based on the actual spectral measurement requirements, different L values ​​of ultrastable optical reference cavities are selected to achieve the desired measurement accuracy. For example, when the frequency spacing of atomic or molecular spectral transition peaks is on the order of hundreds of MHz, then the Δn of the ultrastable optical reference cavity... FSR The size also needs to be on the order of hundreds of MHz. Theoretically, the Δn of an ultrastable optical reference cavity... FSR The smaller the value, the higher the measurement accuracy of the spectrum; however, the geometric distance L between the two mirrors of the ultrastable optical cavity also increases, leading to higher manufacturing costs. Furthermore, when measuring the spacing between atomic and molecular spectral transition peaks, it is necessary to simultaneously measure the free spectral path Δn of the ultrastable optical cavity. FSR This is because the short-term linear frequency drift rate of an ultra-stable optical reference cavity is typically around 50 mHz / s.

[0024] Precise measurement of Δn of the ultra-stable optical reference cavity FSR This is a key step in the invention. The measurement method of the invention utilizes laser frequency stabilization technology, locking two single-frequency lasers with the same center wavelength onto two adjacent longitudinal modes of an ultra-stable optical reference cavity, and then beating the two frequency-stabilized laser beams to achieve the free spectral path Δn of the ultra-stable optical cavity. FSR Precise measurement.

[0025] Obtaining the free spectral path of an ultrastable optical reference cavity: The ultra-stable optical reference cavity 14 is a high-precision Fabry-Perot resonant cavity with a mirror reflectivity greater than 99.999%. The cavity body uses ULE glass as an ultra-low thermal expansion coefficient material and is equipped with a three-layer thermal shielding structure and a vacuum maintenance device, which can effectively suppress the influence of temperature and external environment on the cavity length. The short-term linear frequency drift rate is controlled within 50 mHz / s. The specific steps are as follows: Both single-frequency fiber laser 1 and single-frequency fiber laser 21 are started, and the Pound-Drever-Hall frequency stabilization technology is used to lock single-frequency fiber laser 1 to the first longitudinal mode of the ultra-stable optical reference cavity 14, and single-frequency fiber laser 21 to the second longitudinal mode of the ultra-stable optical reference cavity 14 adjacent to the first longitudinal mode.

[0026] The laser output from the single-frequency fiber laser 1 is frequency modulated by the fiber acousto-optic modulator 2 and then enters the fiber beam splitter 3 with a splitting ratio of 50:50, which splits it into a laser beam a and a laser beam b. The laser beam a is used for laser frequency stabilization, and the laser beam b is used for subsequent beat frequency.

[0027] The signal generator 29 outputs a phase modulation signal to drive the fiber electro-optic modulator 4 to perform phase modulation on the a-beam laser, so that the a-beam laser generates ±1-order sidebands; after the a-beam laser is phase-modulated by the fiber electro-optic modulator 4, it enters the fiber combiner 5 with a splitting ratio of 50:50, and then is output to free space through the fiber collimator 6.

[0028] The laser beam in free space passes sequentially through a λ / 2 waveplate 7, a polarizing beam splitter 8, a λ / 4 waveplate 9, a plano-convex lens 10, a reflector 11, a reflector 12, and a reflector 13 before entering the ultra-stable optical reference cavity 14. The plano-convex lens 10 is used to achieve mode matching between the laser and the ultra-stable optical reference cavity 14.

[0029] A portion of the laser beam resonates with the ultra-stable optical reference cavity 14 and is transmitted to a beam splitter prism 15 with a splitting ratio of 50:50. After splitting, the beam enters the photodetector 16 and the charge-coupled device camera 17 respectively to monitor the resonance signal and the beam pattern. The other portion of the laser beam does not resonate with the ultra-stable optical reference cavity 14 and is reflected back to the polarization beam splitter 8. Because the laser beam passes through the λ / 4 waveplate 9 twice, its polarization state changes. The reflected laser beam is transmitted through the polarization beam splitter prism 8, and after passing through the reflector 25 and the plano-convex lens 26, it is received by the photodetector 27.

[0030] The reflected signal received by the photodetector 27 and the phase modulation signal output by the signal generator 29 are simultaneously fed into the mixer 30 for mixing and demodulation to obtain the Pound-Drever-Hall error signal. This error signal is then input to the proportional-integral-differential circuit 31 for processing.

[0031] The feedback signal output from the proportional-integral-differential circuit 31 is divided into two parts: ① and ②. Part ① is input to the fiber optic acousto-optic modulator 2 for fast frequency feedback, and part ② is input to the piezoelectric ceramic modulation end of the single-frequency fiber laser 1 for slow frequency feedback, ultimately achieving frequency locking of the single-frequency fiber laser 1. The frequency stabilization process of the single-frequency fiber laser 21 is the same as that of the single-frequency fiber laser 1, and the corresponding components are the fiber optic acousto-optic modulator 22, the fiber beam splitter 23, the fiber electro-optic modulator 24, the signal generator 32, the mixer 33, and the proportional-integral-differential circuit 34.

[0032] The b-beam laser output from the frequency-stabilized single-frequency fiber laser 1 and the d-beam laser output from the single-frequency fiber laser 21 are combined using a fiber combiner 20 with a splitting ratio of 50:50. The combined beam is then input to a high-speed photodetector 19 for beat frequency measurement to obtain the beat frequency signal. This beat frequency signal is then input to a spectrum analyzer 18 to measure its frequency, thus obtaining the free spectral path Δn of the ultra-stable optical reference cavity 14. FSR =1.998503 (±3×10) -6 The signal has a beat frequency linewidth of 96.7 ± 0.3 Hz and a measurement accuracy on the order of 0.1 kHz. The free spectral range is on the order of gigahertz.

[0033] Cesium atom nD J Fine structure measurement of cesium-10 ... J The fine-structure splitting of Rydberg states involves the following steps: The Pound-Drever-Hall frequency stabilization technique based on electronic sidebands is used to lock the probe light to the D2 line (first transition line, center wavelength 852nm) of cesium atoms.

[0034] The single-frequency laser 35 is activated, and its output laser light is split into an e-beam and an f-beam after passing through a λ / 2 waveplate 36 and a polarizing beam splitter 37. The e-beam is used for laser frequency stabilization, and the f-beam is a cesium atom nD beam. J The probe light of the fine structure measurement device. The e-beam laser passes sequentially through mirror 38, mirror 39, and fiber coupler 40 before being coupled to fiber electro-optic modulator 41. Signal generator 55 drives fiber electro-optic modulator 41 to perform phase modulation on the e-beam laser, generating ±1st order sidebands. Signal generator 56 performs external phase modulation on signal generator 55, generating electronic sidebands. After being output to free space by fiber collimator 42, the e-beam laser passes sequentially through λ / 2 waveplate 43 and polarization beam splitter 44 for reflection, and then through λ / 4 waveplate 45 and plano-convex lens 46, where plano-convex lens 46 is used to achieve mode matching between the laser and the ultra-stable optical reference cavity 14. After passing through mirrors 47 and 48, the e-beam enters the ultra-stable optical reference cavity 14. A portion of the laser resonates with the ultra-stable optical reference cavity 14 and is transmitted to a beam splitter prism 49 with a splitting ratio of 50:50. After being split, the beam enters the photodetector 50 and the charge-coupled device camera 51, respectively, to monitor the resonance signal and the beam pattern. The other portion of the laser does not resonate with the ultra-stable optical reference cavity 14 and is reflected back to the polarization beam splitter prism 44.

[0035] Because the laser beam passes through the λ / 4 waveplate 45 twice, its polarization state changes. The reflected laser beam is transmitted through the polarizing beam splitter prism 44, and after passing through the reflector 52 and the plano-convex lens 53, it is received by the photodetector 54. The reflected signal received by the photodetector 54 and the external phase modulation signal output by the signal generator 56 simultaneously enter the mixer 57 for mixing and demodulation to obtain the Pound-Drever-Hall error signal. This error signal is then input to the proportional-integral-differential circuit 58 for processing.

[0036] The feedback signal output by the proportional-integral-differential circuit 58 is divided into two parts, ⑤ and ⑥: part ⑤ provides fast feedback to the single-frequency laser 35 to modulate the current of the driving diode, and part ⑥ provides slow feedback to the single-frequency laser 35 to adjust the driving voltage of the piezoelectric ceramic, ultimately locking the frequency of the probe light to the cesium atom D2 line. The cavity mirror coating center wavelengths of the ultra-stable optical reference cavity 14 are 852nm and 1018nm, corresponding to the probe light wavelength and the subsequent 509nm coupling seed light wavelength, respectively, which meets the requirements of claim 6. The single-frequency fiber laser 60 is started, which has two fiber output ports, g and h, where the g output port is the frequency-doubled 509nm laser, used as the cesium atom nD line. J The coupling light for fine structure measurement; the h output port is a 1018nm seed light, used to acquire the transmission signal of the ultrastable optical reference cavity 14.

[0037] The g-fiber output port of the single-frequency fiber laser 60 is connected to the fiber collimator 61, which outputs the 509nm laser into free space. The laser then passes sequentially through the λ / 2 waveplate 62, the polarizing beam splitter 63, the reflector 64, the reflector 65, the plano-convex lens 66, and the dichroic beam splitter 67 before entering the alkali metal atom gas chamber 68. The plano-convex lens 66 focuses the 509nm laser, and the alkali metal atoms in the alkali metal atom gas chamber 68 are Cs. The dichroic beam splitter 67 transmits the 509nm coupling light and reflects the 852nm probe light.

[0038] The probe light frequency stabilization module 59 outputs a frequency-stabilized 852nm probe light, which passes sequentially through a λ / 2 waveplate 74, a polarizing beam splitter 73, a reflector 72, a reflector 71, a plano-convex lens 70, and a filter 69 before entering the alkali metal atom gas chamber 68. The filter 69 is used to filter out coupling light, preventing it from entering the probe light frequency stabilization module 59. The 509nm coupling light and the 852nm probe light enter the alkali metal atom gas chamber 68 in opposite directions and collinearly. The 852nm probe light propels cesium atoms from the 6S... 1 / 2 State excitation to 6P 3 / 2 In this state, 509nm coupled light pulls cesium atoms from 6P... 3 / 2 State excitation up to 53D J Ridburg state.

[0039] A single-frequency fiber laser 60 is controlled to perform frequency scanning, and the mode-free range of the 1018nm seed light is set to be greater than 2GHz to ensure that the oscilloscope 79 can simultaneously acquire the electromagnetically induced transparency spectral signal and the transmission signal of the ultra-stable optical reference cavity 14. The intensity signal of the probe light after passing through the alkali metal atom gas cell 68 is simultaneously acquired. This signal passes sequentially through a dichroic beam splitter 67, a filter 75, a plano-convex lens 76, and a reflector 77 before being received by a photodetector 78. The filter 75 is used to filter out coupling light, preventing it from entering the photodetector 78. This signal serves as the atomic and molecular spectral signal (i.e., the electromagnetically induced transparency spectral signal). The transmission signal of the 1018nm seed light is simultaneously acquired. The seed light passes sequentially through a fiber collimator 80, a λ / 2 waveplate 81, a polarizing beam splitter prism 82, a plano-convex lens 83, a reflector 84, and a reflector 85 before entering the ultra-stable optical reference cavity 14. The transmission signal after passing through the ultra-stable optical reference cavity 14 is received by a photodetector 86. Based on the obtained free spectral path Δn of the ultrastable optical reference cavity 14 FSR Based on the characteristic that the coupled light wavelength is 509 nm, the frequency spacing F between the two transmitted signals was determined to be twice the FSR measurement value, i.e., F = 3.997006 GHz. Using this known frequency F, the acquired electromagnetically induced transparency spectral signal was frequency-calibrated to obtain the cesium atom 53D. 3 / 2 and 53D 5 / 2 Frequency spacing of states.

[0040] Cesium atom saturated absorption spectrum frequency calibration: This section uses the cesium atom as the target atom and performs frequency calibration on its saturated absorption spectrum. The center wavelength of the single-frequency laser 35 is 852 nm, and the wavelength tuning range covers the cesium atom 6S... 1 / 2 F = 4 → 6P 3 / 2 The transitions at F=3, 4, and 5 are defined by the following steps: The single-frequency laser 35 is activated, and its output laser light is split into beam i and beam j after passing through a λ / 2 waveplate 87 and a polarizing beam splitter 88. Beam i is used to generate the saturated absorption spectrum of cesium atoms, and beam j is used to generate the transmission signal of the ultra-stable optical reference cavity 105. Beam i is then split into beam k and beam l after passing through a λ / 2 waveplate 89 and a polarizing beam splitter 90. Beam k serves as a weaker probe light with an intensity of approximately 80 μW, while beam l serves as a stronger pump light with an intensity of approximately 800 μW. Beam l passes sequentially through mirrors 92 and 93, a λ / 2 waveplate 94, and a polarizing beam splitter 95, and then passes collinearly with beam k through the alkali metal atom gas chamber 108. The alkali metal atoms in the alkali metal atom gas chamber 108 are Cs. The single-frequency laser 35 is controlled to perform frequency scanning, and the mode-free range of the single-frequency laser 35 is set to be greater than 500MHz, so that the oscilloscope 107 can simultaneously acquire the saturated absorption spectrum signal and the transmission signal of the ultra-stable optical reference cavity 105. The free spectral path of the ultra-stable optical reference cavity 105 is about 500MHz, which is on the order of hundreds of megahertz, and meets the requirements of claim 7.

[0041] The intensity signal of the k-beam probe light after passing through the alkali metal atom gas cell 108 is simultaneously acquired. This signal passes sequentially through a polarizing beam splitter 95, a plano-convex lens 96, and a reflector 97 before being received by a photodetector 98 as the atomic and molecular spectral signal (i.e., the cesium atom saturated absorption spectral signal). The transmission signal of the j-beam laser is simultaneously acquired. The j-beam laser passes sequentially through a λ / 2 waveplate 99, a polarizing beam splitter 100, a reflector 101, a plano-convex lens 102, a reflector 103, and a reflector 104 before entering the ultra-stable optical reference cavity 105. The transmission signal after passing through the ultra-stable optical reference cavity 105 is received by a photodetector 106. Based on the free spectral path (approximately 500 MHz) of the ultra-stable optical reference cavity 105, the acquired saturated absorption spectral signal is frequency-calibrated to obtain the cesium atom 6S. 1 / 2 F=4→6P 3 / 2 The frequency spacing between the transition peaks of F=3, 4, and 5.

[0042] General Atomic and Molecular Spectral Frequency Calibration Extension: The method in this embodiment is not limited to cesium atom spectral frequency calibration, but can also be applied to the spectral frequency calibration of other atoms and molecules, such as molecules that can be C2H2, CO2, or O2, and atoms that can be K, Rb, etc. The specific steps are as follows: Depending on the type of target atom or molecule, a suitable atomic and molecular spectroscopy device 112 is selected to replace the alkali metal atom gas chamber 68 or alkali metal atom gas chamber 108 in the above embodiments. Based on the frequency spacing of the spectral transition peaks of the target atom or molecule, an ultra-stable optical reference cavity 121 with a matching cavity length is selected to adapt its free spectral path to the measurement requirements. The single-frequency laser 109 is activated, and its output laser light is split into m-beams and n-beams after passing through a λ / 2 waveplate 110 and a polarizing beam splitter prism 111. The m-beams are used to generate atomic and molecular spectra, and the n-beams are used to generate the transmission signal of the ultra-stable optical reference cavity 121. A single-frequency laser 109 is controlled to perform frequency scanning, and the intensity signals of m laser beams after passing through the atomic and molecular spectroscopy device 112 are simultaneously acquired. These signals are received by the photodetector 113 as atomic and molecular spectral signals. Simultaneously, the transmission signals of n laser beams are acquired. These n laser beams sequentially pass through a λ / 2 waveplate 115, a polarizing beam splitter 116, a reflector 117, a plano-convex lens 118, a reflector 119, and a reflector 120 before entering an ultra-stable optical reference cavity 121. The transmission signals after passing through the ultra-stable optical reference cavity 121 are received by the photodetector 122. The atomic and molecular spectral signals and the transmission signals are simultaneously input to an oscilloscope 114. Based on the free spectral path of the ultra-stable optical reference cavity 121, the frequency of the atomic and molecular spectral signals is calibrated, completing the spectral frequency calibration of the target atom or molecule.

[0043] like Figure 2 As shown, embodiments of the present invention also provide an apparatus for calibrating atomic and molecular spectral frequencies, used to implement the method for calibrating atomic and molecular spectral frequencies, the apparatus comprising: A free spectral path measurement system for measuring the free spectral path of an ultrastable optical reference cavity; A single-frequency laser source, used to generate tunable single-frequency laser light; A beam splitter, connected to a single-frequency laser source, is used to split the single-frequency laser beam into a spectrum generation beam and a reference beam. The spectrum generation module is located in the optical path of the spectrum generation beam and is used to enable the spectrum generation beam to interact with atoms or molecules to generate atomic and molecular spectral signals. The first detection device is used to receive and convert atomic and molecular spectral signals into a first electrical signal; The second detection device is used to receive the transmission signal of the reference beam after passing through the ultra-stable optical reference cavity and convert it into a second electrical signal. A synchronous acquisition device, electrically connected to the first detection device and the second detection device, is used to synchronously acquire the first electrical signal and the second electrical signal; and The calibration processing unit, connected to the synchronous acquisition device and the free path measurement system, is used to perform frequency calibration on the atomic and molecular spectral signals acquired by the synchronous acquisition device based on the free path measured by the free path measurement system.

[0044] It should be noted that this device is a device corresponding to the above method. All implementation methods in the above method embodiments are applicable to this embodiment and can achieve the same technical effect.

[0045] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for calibrating atomic and molecular spectral frequencies, characterized by, The method comprises: obtaining a free spectral range of the ultra-stable optical reference cavity; synchronously collecting an atomic and molecular spectrum signal and a transmission signal of the ultra-stable optical reference cavity; wherein the atomic and molecular spectrum signal and the transmission signal are respectively generated by splitting laser output by the same single-frequency laser; based on the free spectral range, frequency calibration is performed on the atomic and molecular spectrum signal.

2. The method for calibrating atomic and molecular spectral frequencies according to claim 1, characterized in that, The method comprises: locking a first single-frequency laser at a first longitudinal mode of the ultra-stable optical reference cavity; locking a second single-frequency laser at a second longitudinal mode adjacent to the first longitudinal mode of the ultra-stable optical reference cavity; performing beat frequency on laser output by the first single-frequency laser and the second single-frequency laser to obtain a beat frequency signal; measuring a frequency of the beat frequency signal to obtain the free spectral range of the ultra-stable optical reference cavity.

3. The method for calibrating atomic and molecular spectral frequencies according to claim 2, characterized in that, The atomic and molecular spectrum signal is an electromagnetically induced transparency spectrum signal of an alkali metal atom Rydberg state; synchronously collecting the atomic and molecular spectrum signal and the transmission signal of the ultra-stable optical reference cavity comprises: locking probe light to a D2 transition line of a target alkali metal atom; making the probe light and coupling light collinearly act on the target atom, wherein the coupling light is generated by frequency doubling of seed light output by a single-frequency laser; scanning a frequency of the coupling light, and synchronously collecting a probe light intensity signal after the target atom to obtain the atomic and molecular spectrum signal, and collecting a transmission signal of the seed light after the ultra-stable optical reference cavity.

4. The method for calibrating atomic and molecular spectral frequencies according to claim 3, characterized in that, The atomic and molecular spectrum signal is a saturated absorption spectrum signal of an atom; synchronously collecting the atomic and molecular spectrum signal and the transmission signal of the ultra-stable optical reference cavity comprises: splitting laser output by the single-frequency laser into probe light and pump light; making the probe light and the pump light reversely collinearly act on a target atom chamber; scanning a frequency of the single-frequency laser, and synchronously collecting a probe light intensity signal after the target atom chamber to obtain the atomic and molecular spectrum signal, and collecting a transmission signal of another part of laser output by the single-frequency laser after the ultra-stable optical reference cavity.

5. The method for calibrating atomic and molecular spectral frequencies according to claim 4, characterized in that, locking the probe light to the D2 transition line of the target atom comprises: adopting Pound-Drever-Hall frequency stabilization technology based on an electronic sideband to lock a center frequency of the probe light to the D2 transition line of the target atom.

6. The method for calibrating atomic and molecular spectral frequencies according to claim 5, characterized in that, A center wavelength of a coating film of a cavity mirror of the ultra-stable optical reference cavity comprises a wavelength of the probe light and a wavelength of the seed light.

7. The method for calibrating atomic and molecular spectral frequencies according to claim 6, characterized in that, The free spectral range of the ultra-stable optical reference cavity is in a range of hundreds of megahertz to gigahertz.

8. Apparatus for calibrating atomic and molecular spectral frequencies for carrying out the method for calibrating atomic and molecular spectral frequencies according to any one of claims 1 to 7, characterized in that The device comprises: a free spectral range measurement system for measuring a free spectral range of an ultra-stable optical reference cavity; a single-frequency laser source for generating tunable single-frequency laser; a splitting device connected to the single-frequency laser source, for splitting the single-frequency laser into a spectrum generation beam and a reference beam; a spectrum generation module arranged on an optical path of the spectrum generation beam, for making the spectrum generation beam interact with atoms or molecules to generate an atomic and molecular spectrum signal; a first detection device for receiving and converting the atomic and molecular spectrum signal into a first electric signal; a second detection device for receiving a transmission signal of the reference beam after the ultra-stable optical reference cavity and converting the transmission signal into a second electric signal; a synchronous collection device electrically connected to the first detection device and the second detection device, for synchronously collecting the first electric signal and the second electric signal; and The calibration processing unit is connected with the synchronous acquisition device and the free spectral range measurement system, and is configured to perform frequency calibration on the atomic and molecular spectral signal acquired by the synchronous acquisition device based on the free spectral range measured by the free spectral range measurement system.

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