Frequency generating device and method for generating a frequency

Abstract

The present invention discloses a frequency generating device, comprising: an atomic gas cell containing alkali metal atom vapor and inert gas atom vapor; a magnetic coil disposed around the atomic gas cell and configured to provide a magnetic field with a preset magnetic induction intensity for the atomic gas cell; a pumping unit configured to emit a first laser to the atomic gas cell; a detection unit configured to emit a second laser to the atomic gas cell; a signal receiving unit configured to receive the second laser transmitted through the atomic gas cell and convert the optical signal into an electrical signal; a self-excited oscillation unit respectively coupled to the signal receiving unit and the magnetic coil and configured to apply an excitation magnetic field to the atomic gas cell through the magnetic coil according to the electrical signal; after self-excited oscillation is formed in the inert gas atoms, output a preset frequency according to the electrical signal. The frequency generating device has extremely high precision, and by adjusting the preset magnetic induction intensity, a frequency signal meeting the requirements can be output.

Description

Technical Field

[0001] The present invention relates to the field of quantum precision measurement technology, and in particular, to a frequency generating device and a method for generating a frequency. Background Art

[0002] The nuclear magnetic resonance gyroscope was proposed by General Electric Company of the United States in 1953. Subsequently, companies such as General Precision, Singer, and Litton have also successively carried out research on nuclear magnetic resonance gyroscopes.

[0003] The basic principle of the nuclear magnetic resonance gyroscope is to use a beam of circularly polarized pump light to polarize electrons. The electrons transfer angular momentum to atomic nuclei through spin-exchange collisions to achieve nuclear spin polarization. When there is an external magnetic field, the atomic nuclei will perform Larmor precession around the external magnetic field. If there is rotation around the axis of the external magnetic field, the Larmor precession frequency will change at this time. The rotation information can be obtained by detecting the Larmor precession frequency at this time.

[0004] The nuclear magnetic resonance gyroscope has the advantages of high precision, simple structure, and easy miniaturization, and is expected to become a navigation-level gyroscope device for large-scale applications in the future. At present, the research on nuclear magnetic resonance gyroscopes mainly focuses on two aspects. On the one hand, factors and solutions for improving its sensitivity and precision are sought from the principle. On the other hand, through experiments, factors such as force, light, electricity, magnetism, and heat during the device construction process are considered, and various parameters in the device are optimized. Finally, on the basis of reducing the volume, the sensitivity and zero-bias uncertainty of the device are further improved and optimized.

[0005] In the prior art, there is a technical solution for constructing a frequency generator based on an atomic clock, while there is still a technical gap in constructing a frequency generator using the nuclear magnetic resonance principle. Summary of the Invention

[0006] In view of at least one defect of the prior art, the present invention provides a frequency generating device, including:

[0007] An atomic gas cell containing alkali metal atom vapor and inert gas atom vapor;

[0008] A magnetic coil disposed around the atomic gas cell and configured to provide a magnetic field with a preset magnetic induction intensity for the atomic gas cell, so that the alkali metal atoms and inert gas atoms perform Larmor precession around the direction of the preset magnetic induction intensity;

[0009] A pump unit configured to emit a first laser to the atomic gas cell to polarize the alkali metal atoms, and the polarized alkali metal atoms make the inert gas atoms spin-polarized through spin-exchange collisions;

[0010] A detection unit configured to emit a second laser into the atomic gas cell, wherein the deflection of the polarization plane of the second laser varies according to the change in the magnetic field within the atomic gas cell;

[0011] A signal receiving unit configured to receive the second laser transmitted through the atomic gas cell and convert the optical signal into an electrical signal;

[0012] A self-excited oscillation unit coupled to the signal receiving unit and the magnetic coil respectively, configured to apply an excitation magnetic field to the atomic gas cell through the magnetic coil according to the electrical signal, and after self-excited oscillation is formed in the inert gas atoms, the self-excited oscillation unit outputs a preset frequency according to the electrical signal.

[0013] According to one aspect of the present invention, in the frequency generating device:

[0014] The preset frequency output by the self-excited oscillation unit is determined by the preset magnetic induction intensity.

[0015] According to one aspect of the present invention, in the frequency generating device:

[0016] The pumping unit emits the first laser along the direction of the preset magnetic induction intensity, and the frequency of the first laser is the frequency at which the alkali metal atoms transition from the ground state to the first excited state;

[0017] The detection unit emits the second laser along a direction perpendicular to the preset magnetic induction intensity, and the frequency of the second laser is detuned from the frequency at which the alkali metal atoms transition from the ground state to the second excited state by a preset frequency;

[0018] The signal receiving unit further includes:

[0019] A half-wave plate configured to adjust the polarization direction of the second laser transmitted through the atomic gas cell;

[0020] A polarization beam splitter prism disposed downstream of the optical path of the half-wave plate and configured to split the second laser into two optical signals with perpendicular polarization directions;

[0021] A first photodetector disposed downstream of the optical path of the polarization beam splitter prism and configured to convert one of the two optical signals with perpendicular polarization directions into an electrical signal;

[0022] A second photodetector disposed downstream of the optical path of the polarization beam splitter prism and configured to convert the other of the two optical signals with perpendicular polarization directions into an electrical signal;

[0023] A balanced detector, coupled to the first photodetector and the second photodetector, is configured to perform differential processing on the electrical signals output by the first photodetector and the second photodetector, and output the polarization information of the polarization plane of the second laser.

[0024] According to one aspect of the present invention, wherein the self-excited oscillation unit further includes:

[0025] A lock-in amplifier, coupled to the balanced detector, is configured to perform phase demodulation on the deflection information of the polarization plane of the second laser, and output two mutually orthogonal magnetic field information on a plane perpendicular to the preset magnetic induction intensity;

[0026] A PID control module, coupled to the lock-in amplifier, is configured to apply an excitation magnetic field to the atomic gas cell through the magnetic coil according to two mutually orthogonal magnetic field information on a plane perpendicular to the preset magnetic induction intensity, and the direction of the excitation magnetic field includes one of the directions of two mutually orthogonal magnetic fields on a plane perpendicular to the preset magnetic induction intensity.

[0027] According to one aspect of the present invention, wherein the lock-in amplifier is further configured to:

[0028] Perform demodulation according to the Larmor precession frequency of the alkali metal atoms.

[0029] According to one aspect of the present invention, in the frequency generating device: the PID control module is further configured to:

[0030] When the difference between the frequency of the excitation magnetic field and the Larmor precession frequency of the inert gas atoms is less than a preset value, output the magnetic field frequency in another direction perpendicular to the direction of the excitation magnetic field.

[0031] According to one aspect of the present invention, wherein the PID control module is further configured to:

[0032] When the difference between the frequency of the excitation magnetic field and the Larmor precession frequency of the inert gas atoms is less than a preset value, stop applying the excitation magnetic field to the atomic gas cell through the magnetic coil.

[0033] According to one aspect of the present invention, wherein the self-excited oscillation unit further includes:

[0034] An AC power supply, coupled between the PID control module and the magnetic coil, the PID control module outputs an excitation magnetic field signal to the AC power supply, and the AC power supply is configured to:

[0035] Convert the excitation magnetic field signal into a current signal and apply it to the magnetic coil.

[0036] According to one aspect of the present invention, the pumping unit further comprises:

[0037] A first laser for emitting the first laser;

[0038] A first noise attenuator coupled to the first laser and configured to stabilize the output optical power of the first laser;

[0039] A first wavelength locker including a half-wave plate and a polarization beam splitter prism, located downstream of the optical path of the first noise attenuator, and configured to output a partial splitting signal for locking the wavelength of the first laser;

[0040] A first beam expander located downstream of the optical path of the first optical intensity regulator and configured to expand the spot diameter of the first laser;

[0041] A linear polarizer located downstream of the optical path of the first beam expander and configured to adjust the first laser into linearly polarized light;

[0042] A quarter-wave plate located downstream of the optical path of the linear polarizer and configured to adjust the first laser into circularly polarized light.

[0043] According to one aspect of the present invention, the detection unit further comprises:

[0044] A second laser for emitting the second laser;

[0045] A second noise attenuator coupled to the second laser and configured to stabilize the output optical power of the second laser;

[0046] A second wavelength locker including a half-wave plate and a polarization beam splitter prism, located downstream of the optical path of the second noise attenuator, and configured to output a partial splitting signal for locking the wavelength of the second laser;

[0047] A second beam expander located downstream of the optical path of the second optical intensity regulator and configured to expand the spot diameter of the second laser;

[0048] A Glan-Taylor prism located downstream of the optical path of the second beam expander and configured to adjust the second laser into linearly polarized light.

[0049] According to one aspect of the present invention, the magnetic coil includes a three-dimensional Helmholtz coil, and the frequency generating device further comprises:

[0050] A DC power supply coupled to the magnetic coil and configured to convert the static magnetic field signal of the preset magnetic induction intensity into a current signal and apply it to the magnetic coil;

[0051] An AC power supply, coupled to the magnetic coil, configured to convert an alternating magnetic field signal into a current signal and apply it to the magnetic coil. The frequency of the alternating magnetic field is equal to the Larmor precession frequency of the alkali metal atoms, and the direction of the alternating magnetic field is the direction of the preset magnetic induction intensity.

[0052] A magnetic shielding cylinder, arranged around the magnetic coil, configured to cancel the external residual magnetic field.

[0053] The present invention also provides a method for generating a frequency using the frequency generating device as described above, including:

[0054] Providing a magnetic field with a preset magnetic induction intensity for the atomic gas chamber through the magnetic coil;

[0055] Emitting the first laser to the atomic gas chamber through the pumping unit;

[0056] Emitting the second laser to the atomic gas chamber through the detection unit;

[0057] Receiving the second laser transmitted through the atomic gas chamber by the signal receiving unit and converting the optical signal into an electrical signal;

[0058] Applying an excitation magnetic field to the atomic gas chamber by the self-excitation oscillation unit according to the electrical signal, and after self-excitation oscillation is formed in the inert gas atoms, outputting a preset frequency by the self-excitation oscillation unit according to the electrical signal.

[0059] According to one aspect of the present invention, the method further includes:

[0060] Changing the preset frequency output by the self-excitation oscillation unit by changing the preset magnetic induction intensity.

[0061] In the frequency generating device and the method for generating a frequency provided by the present invention, the nuclear spin precession frequency is output in a self-excitation oscillation manner, and the output frequency can be changed by adjusting the magnetic induction intensity of the static magnetic field, which is faster and more effective compared to the method of detecting the frequency through the FID signal (free induction decay signal). Moreover, the frequency output by the frequency generating device and the method for generating a frequency provided by the present invention is stable. Compared with other types of frequency output devices, the structure of the frequency generating device provided by the present invention is simple and easier to implement. Compared with the existing technical solutions of nuclear magnetic resonance gyroscopes, there is no need to apply an oscillating magnetic field in a direction perpendicular to the pumping light and scan, which simplifies the steps of detecting nuclear magnetic resonance signals. In addition, the nuclear magnetic resonance signals are detected by a frequency detection method, which overcomes the problem of inaccuracy in the peak detection process, has high detection accuracy and fast response speed, and can quickly extract the nuclear precession frequency. Description of the Drawings

[0062] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other accompanying drawings can be obtained based on these drawings without exceeding the scope of protection required by the present application.

[0063] Figure 1 shows a frequency generation device provided by an embodiment of the present invention;

[0064] Figure 2 shows a frequency generation device provided by an embodiment of the present invention;

[0065] Figure 3 shows the output frequency signal of a frequency generation device provided by an embodiment of the present invention;

[0066] Figure 4 shows the output frequency signal of a frequency generation device provided by an embodiment of the present invention;

[0067] Figure 5 shows a method for generating a frequency provided by an embodiment of the present invention. Detailed implementation manners

[0068] The following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of them. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present application.

[0069] The above has introduced the embodiments of the present application in detail. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application. At the same time, changes or deformations made by those skilled in the art based on the idea of the present application, within the specific implementation manner and application scope of the present application, all fall within the scope of protection of the present application. In summary, the content of this specification should not be construed as a limitation to the present application.

[0070] The present invention provides a frequency generation device constructed using the principle of nuclear magnetic resonance. By causing the self-excited oscillation of inert gas atoms, an oscillation signal with the same frequency as the Larmor precession frequency of the inert gas atoms is generated, and the output of this oscillation signal can be used as a high-precision standard frequency signal.

[0071] According to an embodiment of the present invention, as Figure 1As shown, the present invention provides a frequency generating device 100, comprising an atomic gas chamber 110, a magnetic coil 120, a pump unit 130, a detection unit 140, a signal receiving unit 150 and a self-excited oscillation unit 160. Among them:

[0072] The atomic gas chamber 110 contains alkali metal atomic vapor and inert gas atomic vapor. Optionally, the alkali metal atoms include 87 Rb, the noble gas atoms include 131 Xe, 129 The alkali metal atoms and the inert gas atoms have spins, and in a static magnetic field with uniform magnetic induction intensity, the magnetic core is subjected to a moment perpendicular to the plane formed by its spin magnetic moment and the magnetic induction intensity, so that the magnetic core undergoes Larmor precession around the magnetic induction intensity direction of the static magnetic field.

[0073] The magnetic coil 120 is disposed around the atomic gas chamber 110 and is configured to provide a magnetic field of a preset magnetic induction intensity B0 for the atomic gas chamber 110, so that the alkali metal atoms and the inert gas atoms undergo Larmor precession around the direction of the magnetic induction intensity B0. Optionally, the preset magnetic induction intensity B0 is sent to a DC power supply through an external signal generator, and then the preset magnetic induction intensity B0 is converted into a current signal through the DC power supply and applied to the magnetic coil 120.

[0074] The pump unit 130 is configured to emit a first laser to the atomic gas chamber 110 to polarize the alkali metal atoms, and the polarized alkali metal atoms cause the spin polarization of the inert gas atoms through spin exchange collision. Optionally, the frequency of the first laser emitted by the pump unit 130 is equal to the frequency of the alkali metal atoms transitioning from the ground state to the first excited state, for example: the wavelength of the first laser is 87 The D1 line of Rb atom (795nm). The wavelength is 87 The laser of Rb atom D1 line is emitted into the atomic gas chamber 110. 87 The outermost electrons of the Rb atom are spin polarized, and the polarized electrons transfer angular momentum to 131 The nucleus of Xe, 131 The spin polarization of the Xe nucleus, and thus the polarization of the inert gas atoms by the alkali metal atoms with high polarizability, completes the process of mixed polarization. The spin magnetic moment of the polarized inert gas atoms is arranged along the direction of the preset magnetic induction intensity B0, which is manifested as a macroscopic magnetic moment M along the direction of the preset magnetic induction intensity B0.

[0075] The detection unit 140 is configured to emit a second laser into the atomic gas cell 110, and the deflection of the polarization plane of the second laser changes according to the change of the magnetic field in the atomic gas cell 110. Optionally, the frequency of the second laser emitted by the detection unit 140 is equal to the frequency of the transition of the alkali metal atom from the ground state to the second excited state ( 87 the frequency of the D2 line of the Rb atom) detuned by a preset frequency. For example: 87 the D2 line (780 nm) of the Rb atom is detuned by a preset wavelength. Taking 87 a linearly polarized light with the D2 line of the Rb atom detuned by a preset wavelength is emitted into the atomic gas cell 110. Due to the Faraday rotation effect, the polarization plane of the linearly polarized light will be affected by the magnetic field in the atomic gas cell 110. The deflection direction of the polarization plane is related to the magnetic field direction, and the deflection angle of the polarization plane is related to the magnetic induction intensity. Therefore, when there is a changing magnetic field in the atomic gas cell 110, the direction and angle of the deflection of the polarization plane of the second laser change with the direction and magnetic induction intensity of the magnetic field. Therefore, by measuring the direction and angle of the deflection of the polarization plane of the second laser, the change information of the direction and magnetic induction intensity of the magnetic field in the atomic gas cell 110 can be calculated.

[0076] The signal receiving unit 150 is configured to receive the second laser transmitted through the atomic gas cell 110 and convert the optical signal into an electrical signal. Optionally, the signal receiving unit 150 includes a polarization beam splitter prism and a balanced detector. The second laser transmitted through the atomic gas cell 110 is divided into two beams of light with perpendicular polarization directions by the polarization beam splitter prism, and then the deflection information of the polarization plane of the second laser is obtained by the balanced detector.

[0077] The self-excitation oscillation unit 160 is respectively coupled to the signal receiving unit 150 and the magnetic coil 120, and is configured to apply an excitation magnetic field to the atomic gas cell 110 through the magnetic coil 120 according to the electrical signal. Moreover, after self-excitation oscillation is formed in the inert gas atoms, the self-excitation oscillation unit 160 outputs a preset frequency according to the electrical signal. Optionally, the self-excitation oscillation unit 160 includes a lock-in amplifier and a PID control module. The lock-in amplifier is coupled to the balanced detector and is configured to demodulate the change information of the magnetic field through phase demodulation according to the deflection information of the polarization plane of the second laser. The PID control module is coupled to the lock-in amplifier, uses the change information of the magnetic field as the input signal of the PID control module, and the PID control module generates an alternating magnetic field signal (excitation magnetic field signal) according to the input signal and outputs it to the magnetic coil 120, and applies an excitation magnetic field to the atomic gas cell 110 through the magnetic coil 120. When no alternating magnetic field is applied, the macroscopic magnetic moment M of the polarized inert gas atoms is along the direction of the preset magnetic induction intensity B0. When an alternating magnetic field perpendicular to the direction of the preset magnetic induction intensity B0 is applied, it is equivalent to applying two annular static magnetic fields with opposite directions on the plane perpendicular to the direction of the preset magnetic induction intensity B0. The macroscopic magnetic moment M of the inert gas atoms generates a projection on the plane perpendicular to the direction of the preset magnetic induction intensity B0, and the generated magnetic field can be decomposed into two mutually orthogonal alternating magnetic fields on the plane perpendicular to the direction of the preset magnetic induction intensity B0. The frequencies of these two mutually orthogonal alternating magnetic fields are equal to the Larmor precession frequency of the inert gas atoms.

[0078] The self-excitation oscillation unit 160 and the atomic gas cell 110 form a closed loop. By setting the P parameter, I parameter, and D parameter of the PID control module, self-excitation oscillation can be gradually formed in the atomic gas cell 110. Optionally, the initial values of the PID control module are set such that the P parameter is a preset value, the I parameter is 0, and the D parameter is 0. The P parameter, I parameter, and D parameter are gradually modulated according to the feedback magnetic field change information. When the frequency of the output excitation magnetic field is near the Larmor precession frequency of the inert gas atoms, self-excitation oscillation is formed in the atomic gas cell 110, and the magnetic field change is obvious. The self-excitation oscillation frequency of the system, that is, the Larmor precession frequency of the inert gas atoms, can be read out according to the feedback magnetic field change information.

[0079] According to an embodiment of the present invention, in the frequency generating device 100: the preset frequency output by the self-excitation oscillation unit 160 is determined by the preset magnetic induction intensity.

[0080] The frequency generation device 100 provided by the above embodiments of the present invention outputs magnetic field information including the Larmor precession frequency of inert gas atoms in the atomic gas chamber 110 by causing self-excited oscillation of the system in the atomic gas chamber 110, and then outputs the Larmor precession frequency of the inert gas atoms by processing the magnetic field information. The frequency generation device 100 has extremely high precision, and moreover, the Larmor precession frequency of the inert gas atoms is related to the static magnetic field applied to the atomic gas chamber 100. By adjusting the preset magnetic induction intensity B0 of the static magnetic field, a high-precision frequency signal that meets the requirements can be output.

[0081] According to an embodiment of the present invention, as Figure 2 shown, in the frequency generation device 100 provided by the present invention:

[0082] The magnetic induction intensity pumping unit 130 emits the first laser along the direction of the preset magnetic induction intensity B0, and the frequency of the first laser is the frequency of the transition of the alkali metal atoms from the ground state to the first excited state. As Figure 2 shown, the preset magnetic induction intensity B0 is along the Z-axis direction, and the pumping unit 130 emits the first laser along the Z-axis direction.

[0083] The detection unit 140 emits the second laser along a direction perpendicular to the direction of the preset magnetic induction intensity B0, and the frequency of the second laser is detuned by a preset frequency from the frequency of the transition of the alkali metal atoms from the ground state to the second excited state. As Figure 2 shown, the detection unit 140 emits the second laser along the Y-axis direction, and the Y-axis is perpendicular to the Z-axis.

[0084] The signal receiving unit 150 further includes: a half-wave plate 151, a polarization beam splitter prism 152, a first photodetector 153, a second photodetector 154, and a balanced detector 155. Among them:

[0085] The half-wave plate 151 is configured to adjust the polarization direction of the second laser transmitted through the atomic gas chamber 150.

[0086] The polarization beam splitter prism 152 is disposed downstream of the optical path of the half-wave plate 151 and is configured to divide the second laser into two optical signals with perpendicular polarization directions.

[0087] The first photodetector 153 is disposed downstream of the optical path of the polarization beam splitter prism 152 and is configured to convert one of the two optical signals with perpendicular polarization directions into an electrical signal.

[0088] The second photodetector 154 is disposed downstream of the optical path of the polarization beam splitter prism 152 and is configured to convert the other of the two optical signals with perpendicular polarization directions into an electrical signal.

[0089] The balanced detector 155 is coupled to the first photodetector 153 and the second photodetector 154, and is configured to perform differential processing on the electrical signals output by the first photodetector 153 and the second photodetector 155, and output the deflection information of the polarization plane of the second laser.

[0090] According to an embodiment of the present invention, as Figure 2 shown, the self-oscillation unit 160 further includes: a lock-in amplifier 161 and a PID control module 162. Wherein:

[0091] The lock-in amplifier 161 is coupled to the balanced detector 155, and is configured to perform phase demodulation on the deflection information of the polarization plane of the second laser to obtain the change information of the magnetic field. The change information of the magnetic field includes two mutually orthogonal alternating magnetic fields on a plane perpendicular to the preset magnetic induction intensity B0. As Figure 2 shown, the lock-in amplifier 161 obtains the magnetic field information in the X-axis direction and the magnetic field information in the Y-axis direction through phase demodulation.

[0092] The PID control module 162 is coupled to the lock-in amplifier 161, and is configured to apply an excitation magnetic field to the atomic gas cell 110 through the magnetic coil 120 according to the change information of the magnetic field. The direction of the excitation magnetic field is one of the directions of the two mutually orthogonal alternating magnetic fields on the plane perpendicular to the preset magnetic induction intensity B0. As Figure 2 shown, the direction in which the PID control module 162 applies the excitation magnetic field to the atomic gas cell 110 through the magnetic coil 120 is the Y-axis direction.

[0093] According to an embodiment of the present invention, the lock-in amplifier 161 is further configured to:

[0094] Demodulate according to the Larmor precession frequency of the alkali metal atoms. Optionally, the alkali metal atoms are 87 Rb atoms, 87 The Larmor precession frequency of Rb atoms is about 70 kHz, which is much higher than the Larmor precession frequency of inert gas atoms. 87 The magnetic field generated by the oscillation of Rb atoms is superimposed on the magnetic field generated by the oscillation of inert gas atoms, 87 The magnetic field frequency generated by the oscillation of Rb atoms is about 70 kHz, which is equivalent to the carrier frequency. Through 87 the Larmor precession frequency of Rb atoms for the first demodulation, the magnetic field frequency signal generated by the oscillation of inert gas atoms can be obtained.

[0095] Optionally, the filtering bandwidth of the lock-in amplifier 161 covers the Larmor precession frequency of inert gas atoms. For example: 131The Larmor precession frequency of Xe is about 35 Hz, and the filtering bandwidth of the lock-in amplifier 161 is set at 50 Hz.

[0096] According to an embodiment of the present invention, in the frequency generating device 100, the PID control module 162 is further configured to:

[0097] When the difference between the frequency of the excitation magnetic field and the Larmor precession frequency of the inert gas atoms is less than a preset value, output the magnetic field frequency in another direction perpendicular to the direction of the excitation magnetic field.

[0098] The balance detector 155 obtains the deflection information of the polarization plane of the second laser, and the lock-in amplifier 161 demodulates the phase of the deflection information of the polarization plane of the second laser to obtain the magnetic field change information. The magnetic field change information includes two mutually orthogonal alternating magnetic fields on a plane perpendicular to the preset magnetic induction intensity B0, that is, the alternating magnetic field information of the X-axis and the alternating magnetic field information of the Y-axis.

[0099] The PID control module 162 applies an excitation magnetic field to the atomic gas cell 110 through the magnetic coil 120, and the direction of the excitation magnetic field is one of the directions of the two mutually orthogonal alternating magnetic fields on the plane perpendicular to the preset magnetic induction intensity B0. That is, the PID control module 162 applies an excitation magnetic field along the Y-axis direction to the atomic gas cell 110 through the magnetic coil 120.

[0100] Therefore, in the demodulation signal of the lock-in amplifier 161, the alternating magnetic field information of the Y-axis includes the magnetic field formed by the superposition of the inert gas atomic nucleus spin precession magnetic field and the excitation magnetic field, while the alternating magnetic field information of the X-axis only includes the inert gas atomic nucleus spin precession magnetic field.

[0101] Due to the magnetic field separation, after the system forms self-excited oscillation, the lock-in amplifier 161 outputs the magnetic field frequency in another direction perpendicular to the direction of the excitation magnetic field, that is, outputs the frequency of the alternating magnetic field of the X-axis, and the frequency of the alternating magnetic field of the X-axis is the Larmor precession frequency of the inert gas atoms.

[0102] According to an embodiment of the present invention, the PID control module 162 is further configured to:

[0103] After the inert gas atoms form self-excited oscillation, stop applying the excitation magnetic field to the atomic gas cell 100 through the magnetic coil 120.

[0104] When the frequency of the excitation magnetic field applied by the PID control module 162 to the atomic gas chamber 110 through the magnetic coil 120 is near the Larmor precession frequency of the inert gas atoms, the inert gas atoms generate self-excited oscillations, and the amplitude of the output magnetic field signal gradually increases. After a period of time, the self-excited oscillations gradually stabilize. At this time, if the PID control module 162 is turned off, the free induction decay signal (FID) of the inert gas atoms can be observed, and the frequency of this free induction decay signal is the Larmor precession frequency of the inert gas atoms.

[0105] According to an embodiment of the present invention, the self-excited oscillation unit 160 further includes: an AC power supply 163, which is coupled between the PID control module 162 and the magnetic coil 120. The PID control module 162 outputs an excitation magnetic field signal to the AC power supply 163, and the AC power supply 163 is configured to:

[0106] Convert the excitation magnetic field signal into a current signal and apply it to the magnetic coil 120.

[0107] According to an embodiment of the present invention, as Figure 2 shown, the pumping unit 130 further includes: a first laser 131, a first noise attenuator 132, a first wavelength locker 133, a first beam expander 134, a linear polarizer 135, and a quarter-wave plate 136. Among them:

[0108] The first laser 131 is used to emit the first laser.

[0109] The first noise attenuator 132 is coupled to the first laser 131 and is configured to stabilize the output optical power of the first laser.

[0110] The first wavelength locker 133 includes a half-wave plate 1331 and a polarization beam splitter prism 1332, which is located downstream of the optical path of the first noise attenuator 132 and is configured to output a partial splitting signal to lock the wavelength of the first laser.

[0111] The first beam expander 134 is located downstream of the optical path of the first optical intensity regulator 133 and is configured to expand the spot diameter of the first laser.

[0112] The linear polarizer 135 is located downstream of the optical path of the first beam expander 134 and is configured to adjust the first laser into linearly polarized light.

[0113] The quarter-wave plate 136 is located downstream of the optical path of the linear polarizer 135 and is configured to adjust the first laser into circularly polarized light and incident it on the atomic gas chamber 110 to polarize the alkali metal atoms and the inert gas atoms.

[0114] According to an embodiment of the present invention, as Figure 2As shown, the pumping unit 130 further includes: a third photodetector 137, a saturable absorption device (not shown in the figure). Among them:

[0115] The third photodetector 137 is coupled to the polarization beam splitter prism 1332, obtains a partially polarized light signal output by the polarization beam splitter prism 1332, and converts the polarized light signal into an electrical signal.

[0116] The saturable absorption device is coupled to the third photodetector 137 and the first laser 131, and is configured to adjust the wavelength of the first laser emitted by the first laser 131 according to the electrical signal output by the third photodetector 137, so as to lock the wavelength of the first laser at the transition frequency of the alkali metal atom from the ground state to the first excited state (for example: 87 The D1 line frequency of Rb atoms).

[0117] According to an embodiment of the present invention, as Figure 2 shown, the detection unit 140 further includes: a second laser 141, a second noise attenuator 142, a second wavelength locker 143, a second beam expander 144, and a Glan-Taylor prism 145. Among them:

[0118] The second laser 141 is used to emit the second laser.

[0119] The second noise attenuator 142 is coupled to the second laser 141 and is configured to stabilize the output optical power of the second laser.

[0120] The second wavelength locker 143 includes a half-wave plate 1431 and a polarization beam splitter prism 1432, is located downstream of the optical path of the second noise attenuator 142, and is configured to output a partially split optical signal to lock the wavelength of the second laser.

[0121] The second beam expander 144 is located downstream of the optical path of the second optical intensity regulator 143 and is configured to expand the spot diameter of the second laser.

[0122] The Glan-Taylor prism 145 is located downstream of the optical path of the second beam expander 144 and is configured to adjust the second laser into linearly polarized light.

[0123] According to an embodiment of the present invention, as Figure 2 shown, the detection unit 140 further includes: a fourth photodetector 146, a wavelength meter (not shown in the figure). Among them:

[0124] The fourth photodetector 146 is coupled to the polarization beam splitter prism 1432, obtains a partially polarized light signal output by the polarization beam splitter prism 1432, and converts the polarized light signal into an electrical signal.

[0125] The wavemeter is coupled to the fourth photodetector 146 and the second laser 141, and is configured to adjust the wavelength of the second laser emitted by the second laser 141 according to the electrical signal output by the fourth photodetector 146, so as to lock the wavelength of the second laser at the frequency of the transition frequency of the alkali metal atom from the ground state to the second excited state detuned by a preset wavelength (for example: to 87 lock at a far detuned frequency of the D2 line frequency of the Rb atom).

[0126] According to an embodiment of the present invention, as Figure 2 shown, wherein the magnetic coil 120 includes a three-dimensional Helmholtz coil, and the frequency generating device 100 further includes: a DC power supply 170, an AC power supply 180, and a magnetic shielding cylinder 190. Among them:

[0127] The DC power supply 170 is coupled to the magnetic coil 120 and is configured to convert a static magnetic field signal of a preset magnetic induction intensity B0 into a current signal and apply it to the magnetic coil 120.

[0128] Optionally, the DC power supply 170 applies static magnetic fields B x0 、B y0 、B z0 to the magnetic coil 120 in the X-axis, Y-axis, and Z-axis directions as shown respectively.

[0129] The AC power supply 180 is coupled to the magnetic coil 120 and is configured to convert an alternating magnetic field signal into a current signal and apply it to the magnetic coil 120. The frequency of the alternating magnetic field is equal to the Larmor precession frequency of the alkali metal atom, and the direction of the alternating magnetic field is the same as the direction of the preset magnetic induction intensity B0, that is, the same as the emission direction of the first laser. For example: the magnetic induction intensity of the alternating magnetic field is B c cos(ω c t), where ω c is 87 the Larmor precession frequency of the Rb atom, and the direction of the alternating magnetic field is the Z-axis direction shown in the figure.

[0130] The magnetic shielding cylinder 190 is arranged around the magnetic coil 120 and is configured to cancel the external residual magnetic field.

[0131] The following verifies the technical effects of the frequency generating device 100 provided by the above embodiments of the present invention through experiments. Construct a frequency generating device 100 as Figure 2 shown, wherein the alkali metal atom is 87 Rb, and the inert gas atom is 131Xe. The direction in which the pumping unit 130 emits the first laser is the Z-axis direction shown in the figure, which is also the direction of the preset magnetic induction intensity B0. The direction in which the detection unit 140 emits the second laser is the Y-axis direction shown in the figure. The PID control module 162 applies an alternating magnetic field to the atomic gas chamber 110 through the magnetic coil 120, and the direction of this alternating magnetic field is Figure 2 the Y-axis direction shown in the figure.

[0132] Reference signals with the same frequency but different phases are used to demodulate the signals detected by the balanced detector 155, and the filter bandwidth is set at 50 Hz, while 131 the Larmor precession frequency of Xe is approximately around 35 Hz, which is within the filter bandwidth range. By demodulating with different phases, the magnetic fields in the Y-axis and X-axis directions are separated, corresponding to the outputs of channel 1 and channel 2 of the lock-in amplifier 161 respectively. The two outputs are respectively connected to the PID control module 162.

[0133] As Figure 3 shown, first, turn on output channel 1 of the lock-in amplifier 161. The amplitude of the magnetic field signal output by channel 1 gradually increases with time, indicating that the system gradually starts self-excited oscillation. After a period of time, the self-excited oscillation gradually stabilizes. The amplitude of this magnetic field signal contains the excitation magnetic field of the self-excited oscillation and also contains 131 the magnetic field generated by the precession of Xe nuclei. Then turn off the PID control module 162, and it can be observed that 131 the free induction decay signal (FID) of Xe.

[0134] As Figure 4 shown, turn on output channel 2 of the lock-in amplifier 161. Since 131 Xe generates self-excited oscillation, the magnetic field generated by the nuclear precession can also be detected in the other direction (X-axis direction). The magnetic field generated by its nuclear precession can be detected through output channel 2. Since phase separation is performed between channel 1 and channel 2, the excitation magnetic field generated by the self-excited oscillation will not crosstalk to channel 2. Therefore, channel 2 only contains the magnetic field generated by the nuclear precession. Outputting this signal can obtain a frequency generation device with a frequency of 131 the nuclear precession frequency of Xe. The output of this frequency generation device is stable and can be used as a frequency standard.

[0135] According to an embodiment of the present invention, the atomic gas chamber 110 includes two inert gas atoms, and the Larmor precession frequencies of the two inert gas atoms are different. The lock-in amplifier 161 includes four output channels. After phase demodulation, the magnetic field change information generated by the Larmor precession of the two inert gas atoms is output respectively (corresponding to the magnetic field change information of the X-axis and the Y-axis generated by the self-excited oscillation of the two inert gas atoms respectively). By setting an appropriate filtering bandwidth, two different oscillation frequencies can be obtained, and the frequency generating device 100 is used as a dual-frequency generator.

[0136] According to an embodiment of the present invention, as Figure 5 shown, the present invention also provides a method 10 for generating a frequency using the frequency generating device 100 as described above, including: step S101 to step S105. Wherein:

[0137] In step S101, a magnetic field with a preset magnetic induction intensity is provided for the atomic gas chamber through the magnetic coil.

[0138] In step S102, the first laser is emitted to the atomic gas chamber through the pumping unit.

[0139] In step S103, the second laser is emitted to the atomic gas chamber through the detection unit.

[0140] In step S104, the second laser transmitted through the atomic gas chamber is received by the signal receiving unit, and the optical signal is converted into an electrical signal.

[0141] In step S105, an excitation magnetic field is applied to the atomic gas chamber by the self-excited oscillation unit according to the electrical signal. After self-excited oscillation is formed in the inert gas atoms, a preset frequency is output by the self-excited oscillation unit according to the electrical signal.

[0142] According to an embodiment of the present invention, the method 10 for generating a frequency further includes:

[0143] By changing the preset magnetic induction intensity, the preset frequency output by the self-excited oscillation unit is changed.

[0144] In the frequency generation device and the method for generating a frequency provided by the present invention, the nuclear spin precession frequency is output by means of self-excited oscillation, and the output frequency can be changed by adjusting the magnetic induction intensity of the static magnetic field, which is faster and more effective than the method of detecting the frequency through the FID signal. Moreover, the frequency output by the frequency generation device and the method for generating a frequency provided by the present invention is stable. Compared with other types of frequency output devices, the structure of the frequency generation device provided by the present invention is simple and easier to implement. Compared with the existing technical solutions of nuclear magnetic resonance gyroscopes, there is no need to apply an oscillating magnetic field in a direction perpendicular to the pump light and scan, which simplifies the steps of detecting nuclear magnetic resonance signals. In addition, by using the method of frequency detection to detect nuclear magnetic resonance signals, the problem of inaccuracy in the peak detection process is overcome, the detection accuracy is high, the response speed is fast, and the nuclear precession frequency can be quickly extracted.

Claims

1. A frequency generating device, characterized in that, Comprising: An atomic gas cell containing alkali metal atom vapor and inert gas atom vapor; A magnetic coil disposed around the atomic gas cell and configured to provide a magnetic field with a preset magnetic induction intensity for the atomic gas cell, so that alkali metal atoms and inert gas atoms perform Larmor precession around the direction of the preset magnetic induction intensity; A pumping unit configured to emit a first laser to the atomic gas cell to polarize the alkali metal atoms, and the polarized alkali metal atoms spin-polarize the inert gas atoms through spin-exchange collisions; A detection unit configured to emit a second laser to the atomic gas cell, and the deflection of the polarization plane of the second laser changes according to the change of the magnetic field in the atomic gas cell; A signal receiving unit configured to receive the second laser transmitted through the atomic gas cell and convert the optical signal into an electrical signal; A self-excited oscillation unit coupled to the signal receiving unit and the magnetic coil respectively, configured to apply an excitation magnetic field to the atomic gas cell through the magnetic coil according to the electrical signal, the atomic gas cell outputs magnetic field change information, and the self-excited oscillation unit adjusts the excitation magnetic field according to the magnetic field change information, so that the inert gas atoms form self-excited oscillation, and outputs the Larmor precession frequency of the inert gas atoms according to the magnetic field change information corresponding to the formation of self-excited oscillation by the inert gas atoms; and, the self-excited oscillation unit can obtain a high-precision Larmor precession frequency signal by adjusting the preset magnetic induction intensity magnetic field of the magnetic field applied to the atomic gas cell.

2. The frequency generating device according to claim 1, wherein The preset frequency output by the self-excited oscillation unit is determined by the preset magnetic induction intensity.

3. The frequency generating device according to claim 1 or 2, wherein The pumping unit emits the first laser along the direction of the preset magnetic induction intensity, and the frequency of the first laser is the frequency of the transition of the alkali metal atoms from the ground state to the first excited state; The detection unit emits the second laser along a direction perpendicular to the preset magnetic induction intensity, and the frequency of the second laser is detuned from the preset frequency of the transition of the alkali metal atoms from the ground state to the second excited state; The signal receiving unit further includes: A half-wave plate configured to adjust the polarization direction of the second laser transmitted through the atomic gas cell; A polarization beam splitter prism disposed downstream of the optical path of the half-wave plate and configured to divide the second laser into two optical signals with mutually perpendicular polarization directions; A first photodetector disposed downstream of the optical path of the polarization beam splitter prism and configured to convert one of the two optical signals with mutually perpendicular polarization directions into an electrical signal; A second photodetector disposed downstream of the optical path of the polarization beam splitter prism and configured to convert the other of the two optical signals with mutually perpendicular polarization directions into an electrical signal; A balanced detector coupled to the first photodetector and the second photodetector and configured to perform differential processing on the electrical signals output by the first photodetector and the second photodetector, and output the polarization information of the polarization plane of the second laser.

4. The frequency generating device according to claim 3, wherein the self-excited oscillation unit further comprises: A lock-in amplifier, coupled to the balance detector, configured to perform phase demodulation on the deflection information of the polarization plane of the second laser, and output two mutually orthogonal magnetic field information on a plane perpendicular to the preset magnetic induction intensity; A PID control module, coupled to the lock-in amplifier, configured to apply an excitation magnetic field to the atomic gas cell through the magnetic coil according to two mutually orthogonal magnetic field information on a plane perpendicular to the preset magnetic induction intensity, and the direction of the excitation magnetic field includes one of the directions of two mutually orthogonal magnetic fields on a plane perpendicular to the preset magnetic induction intensity.

5. The frequency generating device according to claim 4, wherein the lock-in amplifier is further configured to: Perform demodulation according to the Larmor precession frequency of the alkali metal atoms.

6. The frequency generating device according to claim 4 or 5, wherein the PID control module is further configured to: When the difference between the frequency of the excitation magnetic field and the Larmor precession frequency of the inert gas atoms is less than a preset value, output a magnetic field frequency in another direction perpendicular to the direction of the excitation magnetic field.

7. The frequency generating device according to claim 4 or 5, wherein the PID control module is further configured to: When the difference between the frequency of the excitation magnetic field and the Larmor precession frequency of the inert gas atoms is less than a preset value, stop applying the excitation magnetic field to the atomic gas cell through the magnetic coil.

8. The frequency generating device according to claim 4 or 5, wherein the self-excited oscillation unit further comprises: An AC power supply, coupled between the PID control module and the magnetic coil, and the PID control module outputs an excitation magnetic field signal to the AC power supply, and the AC power supply is configured to: Convert the excitation magnetic field signal into a current signal and apply it to the magnetic coil.

9. The frequency generating device according to claim 1 or 2, wherein the pumping unit further comprises: A first laser, configured to emit the first laser; A first noise attenuator, coupled to the first laser, configured to stabilize the output optical power of the first laser; A first wavelength locker, including a half-wave plate and a polarization beam splitter prism, located downstream of the optical path of the first noise attenuator, configured to output a partial splitting signal to lock the wavelength of the first laser; A first beam expander, located downstream of the optical path of the first optical intensity regulator, configured to expand the spot diameter of the first laser; A linear polarizer, located downstream of the optical path of the first beam expander, configured to adjust the first laser into linearly polarized light; A quarter-wave plate, located downstream of the optical path of the linear polarizer, configured to adjust the first laser into circularly polarized light.

10. The frequency generating device according to claim 1 or 2, wherein the detection unit further comprises: A second laser, configured to emit the second laser; A second noise attenuator, coupled to the second laser, configured to stabilize the output optical power of the second laser; The second wavelength locker, comprising a half-wave plate and a polarization beam splitter prism, is located downstream of the optical path of the second noise attenuator and is configured to output a partial split optical signal for locking the wavelength of the second laser; The second beam expander, located downstream of the optical path of the second light intensity regulator, is configured to expand the spot diameter of the second laser; The Glan-Taylor prism, located downstream of the optical path of the second beam expander, is configured to adjust the second laser into linearly polarized light.

11. The frequency generating device according to claim 1 or 2, wherein the magnetic coil comprises a three-dimensional Helmholtz coil, and the frequency generating device further comprises: A DC power supply, coupled to the magnetic coil, configured to convert the static magnetic field signal of the preset magnetic induction intensity into an electric current signal and apply it to the magnetic coil; An AC power supply, coupled to the magnetic coil, configured to convert an alternating magnetic field signal into an electric current signal and apply it to the magnetic coil. The frequency of the alternating magnetic field is equal to the Larmor precession frequency of the alkali metal atoms, and the direction of the alternating magnetic field is the direction of the preset magnetic induction intensity; A magnetic shielding cylinder, arranged around the magnetic coil, configured to cancel the external residual magnetic field.

12. A method for generating a frequency using the frequency generating device according to any one of claims 1-11, characterized in that, Comprising: Providing a magnetic field with a preset magnetic induction intensity for the atomic gas cell through the magnetic coil; Emitting the first laser to the atomic gas cell through the pumping unit; Emitting the second laser to the atomic gas cell through the detection unit; Receiving the second laser transmitted through the atomic gas cell through the signal receiving unit and converting the optical signal into an electric signal; Applying an excitation magnetic field to the atomic gas cell by the self-excited oscillation unit according to the electric signal. The atomic gas cell outputs magnetic field change information, and the self-excited oscillation unit adjusts the excitation magnetic field according to the magnetic field change information so that the inert gas atoms form self-excited oscillation; Outputting the Larmor precession frequency of the inert gas atoms according to the magnetic field change information corresponding to the formation of self-excited oscillation by the inert gas atoms; By adjusting the preset magnetic induction intensity magnetic field of the magnetic field applied to the atomic gas cell, a high-precision Larmor precession frequency signal can be obtained.

13. The method according to claim 12, further comprising: Changing the preset frequency output by the self-excited oscillation unit by changing the preset magnetic induction intensity.

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