Double-resonance coherent population trapping magnetometer and implementation method

Abstract

The invention provides a double-resonance coherent population trapping magnetometer and an implementation method thereof, which can effectively suppress optical noise of laser, improve sensitivity and increase a lower limit range of a measurement range. Comprising a first microwave source, a second microwave source, a first current source, a second current source, a first Bias-T, a second Bias-T, a first VCSEL laser, a second VCSEL laser, a first collimating lens, a second collimating lens, a first PBS, a lambda / 2 wave plate, an 87Rb atomic gas chamber, a second PBS, a first photodiode, a second photodiode, a differential amplifier and a two-way lock-in amplifier. The first VCSEL laser, the second VCSEL laser, the first collimating lens, the second collimating lens, the first PBS and the lambda / 2 wave plate are located on the left side of the 87Rb atomic gas chamber, the first VCSEL laser and the first collimating lens are located on the left side of the first PBS, the second VCSEL laser and the second collimating lens are located below the first PBS, and the lambda / 2 wave plate is located on the right side of the 87Rb atomic gas chamber. And the laser output by the second VCSEL laser is reflected by the first PBS and then propagates towards the right side atomic gas chamber.

Description

Technical Field

[0001] The invention belongs to the technical field of atomic magnetometers, and in particular relates to a double-resonance coherent population trapping magnetometer and an implementation method thereof. Background Art

[0002] The coherent population trapped magnetometer (CPT magnetometer) has the characteristics of high detection sensitivity and has important applications in military and civilian fields such as magnetic target detection, space physics, and geological exploration. The CPT magnetometer is an instrument that uses laser as a light source and detects the Zeeman effect of atoms in a magnetic field through the interaction between laser and atoms, thereby realizing external magnetic field measurement. The CPT magnetometer has the characteristics of no dead zone, low power consumption, small size, high sensitivity, and all-optical radiation-free.

[0003] Under an external magnetic field, the atoms undergo the Zeeman effect, causing the hyperfine energy levels to degenerate and split, and the distance between the energy levels changes with the external magnetic field. 87 Taking Rb atom as an example, the 52S1 / 2 ground state undergoes Zeeman splitting under an external magnetic field. According to the Breit-Rabi formula, the energy difference between the Fg=1 and Fg=2 ground state energy levels is In the formula is the reduced Planck constant, ω 0,0 is the transition angular frequency between two energy levels with zero ground state magnetic quantum number, m1 and m2 represent the magnetic quantum numbers of the ground state energy levels, represents the transition angular frequency between ground state energy levels, γ is the gyromagnetic ratio, and B is the external magnetic field strength. In a weak magnetic field, 87 The multiple CPT spectral lines formed after the splitting of the Rb ground state energy level will also move linearly with the magnetic field. Therefore, as long as the microwave frequency difference at the peak of the corresponding CPT spectral line is measured, the magnitude of the magnetic field strength can be inferred.

[0004] Existing CPT magnetometers generally use circularly polarized two-color lasers to interact with atoms, and the quality of CPT signals is relatively poor, which affects the sensitivity of the magnetometer. The main reasons affecting the quality of CPT signals obtained by existing solutions include: only two sideband laser components in the polychromatic light obtained by modulating VCSEL lasers carry CPT signals, and other sideband laser components only contribute noise, making the background light signal amplitude much larger than the CPT signal amplitude; the line width of VCSEL output light is relatively wide, about 50MHz, which makes the CPT signal accompanied by strong FM-AM noise; the optical power of the VCSEL laser itself will also fluctuate, which brings laser optical power noise AM noise.

[0005] In addition, the existing CPT magnetometer uses a single laser beam to interact with atoms, and the CPT signal obtained is as follows: Figure 2 As shown in the figure below, there are two problems with this solution. One is ω 0,0The corresponding middle CPT spectral line cannot be eliminated, and this resonance peak limits its detection lower limit under a weak magnetic field; secondly, a single circularly polarized laser can only scan in a single direction of increasing or decreasing the microwave when scanning the microwave, so that only one magnetically sensitive CPT resonance peak can be obtained, the leftmost CPT resonance peak or the rightmost CPT resonance peak, and the information of two magnetically sensitive CPT resonance peaks cannot be obtained at the same time. Summary of the invention

[0006] The present invention provides a double-resonance coherent population trapped magnetometer and an implementation method thereof, which can effectively suppress the optical noise of the laser, improve the sensitivity, and increase the lower limit of the range.

[0007] The present invention is achieved through the following technical solutions.

[0008] A double-resonance coherent population trapped magnetometer, comprising: a first microwave source 1, a second microwave source 2, a first current source 3, a second current source 4, a first Bias-T 5, a second Bias-T 6, a first VCSEL laser 7, a second VCSEL laser 8, a first collimating lens 9, a second collimating lens 10, a first PBS 11, a λ / 2 wave plate 12, 87 Rb atomic gas chamber 13, second PBS 14, first photodiode 15, second photodiode 16, differential amplifier 17, dual-path phase-locked amplifier 18; wherein,

[0009] The first VCSEL laser 7, the second VCSEL laser 8, the first collimating lens 9, the second collimating lens 10, the first PBS 11, and the λ / 2 wave plate 12 are located 87 On the left side of the Rb atomic gas chamber 13, the first VCSEL laser 7 and the first collimating lens 9 are located on the left side of the first PBS 11, the second VCSEL laser 8 and the second collimating lens 10 are located below the first PBS 11, and the laser output by the second VCSEL laser 8 is reflected by the first PBS 11 and propagates toward the right atomic gas chamber.

[0010] The second PBS 14, the first photodiode 15 and the second photodiode 16 are placed 87On the right side of the Rb atomic gas chamber 13, the first photodiode 15 is located on the right side of the second PBS 14, the second photodiode 16 is located below the second PBS 14, and the reflected laser of the second PBS 14 is input to the first photodiode 15; the signals of the first photodiode 15 and the second photodiode 16 are transmitted to the differential amplifier circuit 17, the differential amplifier circuit 17 is connected to the dual-path phase-locked amplifier 18, the weak signals are subtracted and amplified, and then input to the dual-path phase-locked amplifier 18, the dual-path phase-locked amplifier 18 is connected to the first microwave source 1 and the second microwave source 2 at the same time, the dual-path phase-locked amplifier 18 obtains the microwave control signal by demodulation, which is used to control the microwave frequency output by the first microwave source 1 and the second microwave source 2, so as to complete the locking and magnetic field measurement of the magnetometer.

[0011] A method for realizing a double-resonance coherent population trapping magnetometer comprises the following steps:

[0012] Step 1: Use constant temperature control module to 87 The Rb atomic gas chamber 13, the first VCSEL laser 7 and the second VCSEL laser 8 are temperature-controlled. 87 The Rb atomic gas chamber 13, the first VCSEL laser 7 and the second VCSEL laser 8 operate at their respective operating temperatures;

[0013] Step 2: The first microwave source 1 outputs microwave frequency f hfs1 +f dev sin(2πf mod ), the second microwave source 2 outputs microwave frequency f hfs2 +f dev cos(2πf mod ), the first current source 3 and the first microwave source 1 are coupled through the first Bias-T 5, and the first microwave source 1 is injected into the first VCSEL laser 7, and the output power of the first microwave source 1 is adjusted so that the ±1st level sideband energy of the multi-color laser output by the first VCSEL laser 1 is the strongest; the first current source 4 and the second microwave source 2 are coupled through the second Bias-T 6, and the second microwave source 2 is injected into the second VCSEL laser 8, and the output power of the second microwave source 2 is adjusted so that the ±1st level sideband energy of the multi-color laser output by the second VCSEL laser 8 is the strongest;

[0014] Step 3: Scan the output current of the first current source 3 to lock the frequency of the first VCSEL laser 7 at 87 The output current of the second current source 4 is scanned to lock the frequency of the second VCSEL laser 8 at 87 Rb atom D1 line polychromatic light absorption spectrum; Figure 3 shown.

[0015] Step 4: Scan the central microwave frequency f output by the first microwave source 1hfs1 , and modulate the reference signal Asin(2πf mod ) is input to the reference channel of channel 1 (CH1) of the dual-channel phase-locked amplifier 18, the output signal of the second PBS 14 is amplified by the differential amplifier circuit 17 and then input to the signal channel of channel 1 (CH1) of the dual-channel phase-locked amplifier 18, and the corresponding CPT resonance signal is obtained by the phase-locked amplifier. After the CPT resonance signal is obtained, the central microwave frequency f output by the first microwave source 1 is controlled by PID. hfs1 , complete the locking and tracking of the CPT resonance point; at the same time, scan the central microwave frequency f output by the second microwave source 2 hfs2 , and modulate the reference signal Acos(2πf mod ) is input to the reference channel of channel 2 (CH2) of the dual-channel phase-locked amplifier 18, the output signal of the second PBS 14 is amplified by the differential amplifier circuit 17 and then input to the signal channel of channel 2 (CH2) of the dual-channel phase-locked amplifier 18, and the corresponding CPT resonance signal is obtained by the phase-locked amplifier. After the CPT resonance signal is obtained, the central microwave frequency f output by the second microwave source 2 is controlled by PID. hfs2 , complete the locking and tracking of the CPT resonance point;

[0016] Step 5: Calculate the magnetic field value according to the following formula: B = (f hfs1 -f hfs2 ) / Γ, where Γ is the ratio between frequency and magnetic field, which is approximately 28Hz / nT.

[0017] Beneficial effects of the present invention:

[0018] 1. The present invention uses linearly polarized laser to interact with atoms, and obtains the optical rotation signal when the linearly polarized light undergoes CPT resonance through differential detection, which can effectively suppress the laser intensity AM noise and laser frequency FM-AM noise, improve the signal-to-noise ratio, and enhance the sensitivity of the magnetometer;

[0019] 2. The CPT signal obtained by the magneto-optical rotation effect of linearly polarized laser is as follows: Figure 2 As shown in the figure above, due to the 0,0 Multiple CPT resonances obtained by linear polarization lasers interfere destructively, resulting in a weak magnetic field, ω 0,0 The CPT resonance peak is basically eliminated, thus improving the detection limit of the CPT magnetometer;

[0020] 3. The present invention uses two linearly polarized laser beams to interact with atoms, wherein the microwave frequency in one laser beam is ω 0,0 Start scanning in the direction of increase, the microwave frequency in the other laser beam changes from ω 0,0 Start scanning in a decreasing direction;

[0021] 4. The present invention uses two laser beams with microwave frequencies scanning in opposite directions, which can simultaneously obtain Figure 2 The two CPT resonance signals on the left and right sides are directly subtracted from each other to calculate the external magnetic field value, which can double the sensitivity.

[0022] 5. The present invention uses two linearly polarized laser beams to interact with atoms, and uses differential detection to obtain the optical rotation signals when the two linearly polarized laser beams undergo CPT resonance, and simultaneously measures the resonance frequencies of the two resonance peaks to calculate the magnitude of the external magnetic field;

[0023] 6. The present invention can effectively suppress the optical noise of the laser, improve the sensitivity, and increase the lower limit of the range. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of a double-resonance coherent population trapping magnetometer of the present invention;

[0025] Figure 2 Schematic diagram of CPT signal using single circularly polarized light;

[0026] Figure 3 In the specific implementation mode of the present invention 87 Rb atomic D1 line polychromatic light absorption spectrum;

[0027] Figure 4 In the specific embodiment of the present invention, the linearly polarized laser is subjected to different microwave frequencies. 87 CPT resonance energy levels of the interaction of Rb atoms. DETAILED DESCRIPTION

[0028] The exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the accompanying drawings are only exemplary and are intended to illustrate the principles and spirit of the present invention, rather than to limit the scope of the present invention.

[0029] like Figure 1 As shown, a double-resonance coherent population trapping magnetometer of the present invention comprises: a first microwave source 1, a second microwave source 2, a first current source 3, a second current source 4, a first Bias-T 5, a second Bias-T 6, a first VCSEL laser 7, a second VCSEL laser 8, a first collimating lens 9, a second collimating lens 10, a first PBS 11, a λ / 2 wave plate 12, 87 Rb atomic gas chamber 13, second PBS 14, first photodiode 15, second photodiode 16, differential amplifier 17, dual-path phase-locked amplifier 18; wherein,

[0030] The first VCSEL laser 7, the second VCSEL laser 8, the first collimating lens 9, the second collimating lens 10, the first PBS 11, and the λ / 2 wave plate 12 are located 87 On the left side of the Rb atomic gas chamber 13, the first VCSEL laser 7 and the first collimating lens 9 are located on the left side of the first PBS 11, the second VCSEL laser 8 and the second collimating lens 10 are located below the first PBS 11, and the laser output by the second VCSEL laser 8 is reflected by the first PBS 11 and propagates toward the right atomic gas chamber;

[0031] The second PBS 14, the first photodiode 15 and the second photodiode 16 are placed 87 On the right side of the Rb atomic gas chamber 13, the first photodiode 15 is located on the right side of the second PBS 14, the second photodiode 16 is located below the second PBS 14, and the reflected laser of the second PBS 14 is input to the first photodiode 15; the signals of the first photodiode 15 and the second photodiode 16 are transmitted to the differential amplifier circuit 17, the differential amplifier circuit 17 is connected to the dual-path phase-locked amplifier 18, the weak signals are subtracted and amplified, and then input to the dual-path phase-locked amplifier 18, the dual-path phase-locked amplifier 18 is connected to the first microwave source 1 and the second microwave source 2 at the same time, the dual-path phase-locked amplifier 18 obtains the microwave control signal by demodulation, which is used to control the microwave frequency output by the first microwave source 1 and the second microwave source 2, so as to complete the locking and magnetic field measurement of the magnetometer.

[0032] The first Bias-T 5 couples the microwave output by the first microwave source 1 with the first current source 3, drives the first VCSEL laser 7 to output multi-color laser, couples the microwave output by the second microwave source 2 with the second current source 4 through the second Bias-T 6, drives the second VCSEL laser 8 to output multi-color laser, and adjusts the output power of the first microwave source 1 and the second microwave source 2 to maximize the ±1st level sideband energy of the multi-color laser output by the first VCSEL laser 7 and the second VCSEL laser 8.

[0033] The laser beams output by the first VCSEL laser 7 and the second VCSEL laser 8 are linearly polarized laser beams. The polarization direction of the linearly polarized laser beam output by the first VCSEL laser 7 is adjusted so that it is directly transmitted through the first PBS 11. The polarization direction of the linearly polarized laser beam output by the second VCSEL laser 8 is adjusted so that it is reflected through the first PBS 11. The two laser beams are ensured to pass through 87 The Rb atomic gas chamber 13 does not overlap.

[0034] like Figure 3 As shown, in this embodiment, the 87Rb atoms are used as working atoms. By scanning the current of the first current source 3 and the second current source 4, the laser frequencies output by the first VCSEL laser 7 and the second VCSEL laser 8 are locked at 87 The Rb atom D1 line excited state Fe = 1 energy level; Figure 3 On the dotted line in the absorption spectrum; two laser beams pass through 87 After the Rb atomic gas cell 13, the second PBS 14 separates the components of the two linearly polarized laser beams in their two polarization detection directions, and the first photodiode 15 and the second photodiode 16 respectively detect the light intensity signals in the two polarization directions.

[0035] In this embodiment, the λ / 2 wave plate 12 is used to adjust the polarization directions of the two linearly polarized laser beams. The λ / 2 wave plate 12 is rotated so that the output laser light intensities in the two polarization directions of the second PBS 14 are equal, that is, the differential voltage obtained after the optical signals detected by the first photodiode 15 and the second photodiode 16 pass through the differential amplifier circuit 17 is 0.

[0036] In this embodiment, the output microwave frequencies of the first microwave source 1 and the first microwave source 2 start from the transition frequency of the two energy levels of the mF=0 ground state, and scan f in two opposite directions of linear increase and linear decrease, respectively. hfs1 and f hfs2 , used to obtain the respective CPT resonance signals respectively.

[0037] like Figure 1 As shown, in this embodiment, the microwave frequency output by the first microwave source 1 is f hfs1 , frequency modulation is used to modulate the microwave frequency output, and the modulation depth is f dev , the modulation frequency is f mod , then the output microwave signal is f hfs1 +f dev sin(2πf mod ); The microwave frequency output by the second microwave source 1 is f hfs2 , frequency modulation is used to modulate the microwave frequency output, and the modulation depth is f dev , the modulation frequency is f mod When the modulation phase of the second microwave source 2 differs from that of the first microwave source 1 by π / 2, the output microwave signal is f hfs2 +f dev cos(2πf mod ).

[0038] In this embodiment, the first microwave source 1 and the second microwave source 2 respectively input the modulation reference signal into the dual-path phase-locked amplifier 18 for demodulation of two CPT resonance signals. The modulation reference signal of the first microwave source 1 is consistent with the modulation signal of the first microwave source 1 in phase, which is expressed as Asin(2πf mod ), the servo signal obtained after the phase-locked amplifier is fed back to the first microwave source 1, which is used to control and lock the output frequency of the first microwave source 1; the modulation reference signal of the second microwave source 2 is consistent with the modulation signal of the second microwave source 2 in phase, which is expressed as Acos(2πf mod ), the servo signal obtained after passing through the phase-locked amplifier is fed back to the second microwave source 2, and is used to control and lock the output frequency of the second microwave source 2.

[0039] In this embodiment, complete f hfs1 and f hfs2 After scanning, the dual-resonance CPT resonance signal is obtained through the dual-channel phase-locked amplifier 18, and the servo output of the dual-channel phase-locked amplifier 18 is controlled by PID to hfs1 and f hfs2 Lock them at the corresponding CPT resonance points respectively, and then calculate the magnetic field value according to the following formula: B = (f hfs1 -f hfs2 ) / Γ, where the influence of higher-order nonlinear terms in the packing effect is ignored under weak magnetic fields, where Γ is the ratio between frequency and magnetic field, which is approximately 28 Hz / nT.

[0040] In this embodiment, a constant temperature control module is used to perform constant temperature control. The constant temperature control module includes a temperature sensor, a PID control unit and a heating device. 87 The temperatures of the Rb atomic gas chamber 13, the first VCSEL laser 7 and the second VCSEL laser 8 are collected, and then the amplitude of the AC heating signal is controlled by the PID control unit to respectively achieve 87 Constant temperature control of the Rb atomic gas cell 13 , the first VCSEL laser 7 , and the second VCSEL laser 8 .

[0041] The present invention also proposes a method for realizing a double-resonance coherent population trapping magnetometer, which specifically comprises the following steps:

[0042] Step 1: Use constant temperature control module to 87 The Rb atomic gas chamber 13, the first VCSEL laser 7 and the second VCSEL laser 8 are temperature-controlled. 87 The Rb atomic gas chamber 13, the first VCSEL laser 7 and the second VCSEL laser 8 operate at their respective operating temperatures;

[0043] Step 2: The first microwave source 1 outputs microwave frequency fhfs1 +f dev sin(2πf mod ), the second microwave source 2 outputs microwave frequency f hfs2 +f dev cos(2πf mod ), the first current source 3 and the first microwave source 1 are coupled through the first Bias-T 5, and the first microwave source 1 is injected into the first VCSEL laser 7, and the output power of the first microwave source 1 is adjusted so that the ±1st level sideband energy of the multi-color laser output by the first VCSEL laser 1 is the strongest; the first current source 4 and the second microwave source 2 are coupled through the second Bias-T 6, and the second microwave source 2 is injected into the second VCSEL laser 8, and the output power of the second microwave source 2 is adjusted so that the ±1st level sideband energy of the multi-color laser output by the second VCSEL laser 8 is the strongest;

[0044] Step 3: Scan the output current of the first current source 3 to lock the frequency of the first VCSEL laser 7 at 87 The output current of the second current source 4 is scanned to lock the frequency of the second VCSEL laser 8 at 87 Rb atom D1 line polychromatic light absorption spectrum; Figure 3 shown.

[0045] Step 4: Scan the central microwave frequency f output by the first microwave source 1 hfs1 , and modulate the reference signal Asin(2πf mod ) is input to the reference channel of channel 1 (CH1) of the dual-channel phase-locked amplifier 18, the output signal of the second PBS 14 is amplified by the differential amplifier circuit 17 and then input to the signal channel of channel 1 (CH1) of the dual-channel phase-locked amplifier 18, and the corresponding CPT resonance signal is obtained by the phase-locked amplifier. After the CPT resonance signal is obtained, the central microwave frequency f output by the first microwave source 1 is controlled by PID. hfs1 , complete the locking and tracking of the CPT resonance point; at the same time, scan the central microwave frequency f output by the second microwave source 2 hfs2 , and modulate the reference signal Acos(2πf mod ) is input to the reference channel of channel 2 (CH2) of the dual-channel phase-locked amplifier 18, the output signal of the second PBS 14 is amplified by the differential amplifier circuit 17 and then input to the signal channel of channel 2 (CH2) of the dual-channel phase-locked amplifier 18, and the corresponding CPT resonance signal is obtained by the phase-locked amplifier. After the CPT resonance signal is obtained, the central microwave frequency f output by the second microwave source 2 is controlled by PID. hfs2 , complete the locking and tracking of the CPT resonance point;

[0046] Step 5: Calculate the magnetic field value according to the following formula: B = (f hfs1-f hfs2 ) / Γ, where Γ is the ratio between frequency and magnetic field, which is approximately 28Hz / nT.

[0047] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0048] It is obvious to those skilled in the art that the embodiments of the present invention are not limited to the details of the above exemplary embodiments, and that the embodiments of the present invention can be implemented in other specific forms without departing from the spirit or basic features of the embodiments of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the embodiments of the present invention is limited by the attached claims rather than the above description, so it is intended to include all changes that fall within the meaning and scope of the equivalent elements of the claims in the embodiments of the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved. In addition, it is obvious that the word "comprising" does not exclude other units or steps, and the singular does not exclude the plural. Multiple units, modules or devices stated in the system, device or terminal claims can also be implemented by the same unit, module or device through software or hardware. The words first, second, etc. are used to indicate names, and do not indicate any particular order.

[0049] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solutions of the embodiments of the present invention and are not intended to limit them. Although the embodiments of the present invention have been described in detail with reference to the above preferred implementation modes, those skilled in the art should understand that the technical solutions of the embodiments of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A double-resonance coherent population trapping magnetometer, characterized in that: include: The first microwave source 1, the second microwave source 2, the first current source 3, the second current source 4, the first Bias-T 5, the second Bias-T 6, the first VCSEL laser 7, the second VCSEL laser 8, the first collimating lens 9, the second collimating lens 10, the first PBS 11, the λ / 2 wave plate 12, 87 Rb atomic gas chamber 13, second PBS 14, first photodiode 15, second photodiode 16, differential amplifier 17, dual-path phase-locked amplifier 18; wherein, The first VCSEL laser 7, the second VCSEL laser 8, the first collimating lens 9, the second collimating lens 10, the first PBS 11, and the λ / 2 wave plate 12 are located 87 On the left side of the Rb atomic gas chamber 13, the first VCSEL laser 7 and the first collimating lens 9 are located on the left side of the first PBS 11, the second VCSEL laser 8 and the second collimating lens 10 are located below the first PBS 11, and the laser output by the second VCSEL laser 8 is reflected by the first PBS 11 and propagates toward the right atomic gas chamber.

2. A double resonance coherent population trapping magnetometer as claimed in claim 1, characterized in that: The second PBS 14, the first photodiode 15 and the second photodiode 16 are placed 87 On the right side of the Rb atomic gas chamber 13, the first photodiode 15 is located on the right side of the second PBS 14, the second photodiode 16 is located below the second PBS 14, and the reflected laser of the second PBS 14 is input to the first photodiode 15; the signals of the first photodiode 15 and the second photodiode 16 are transmitted to the differential amplifier circuit 17, the differential amplifier circuit 17 is connected to the dual-path phase-locked amplifier 18, the weak signals are subtracted and amplified, and then input to the dual-path phase-locked amplifier 18, the dual-path phase-locked amplifier 18 is connected to the first microwave source 1 and the second microwave source 2 at the same time, the dual-path phase-locked amplifier 18 obtains the microwave control signal by demodulation, which is used to control the microwave frequency output by the first microwave source 1 and the second microwave source 2, so as to complete the locking and magnetic field measurement of the magnetometer.

3. A double resonance coherent population trapping magnetometer as claimed in claim 1 or 2, characterized in that: The first Bias-T 5 couples the microwave output by the first microwave source 1 with the first current source 3, drives the first VCSEL laser 7 to output multi-color laser, couples the microwave output by the second microwave source 2 with the second current source 4 through the second Bias-T 6, drives the second VCSEL laser 8 to output multi-color laser, and adjusts the output power of the first microwave source 1 and the second microwave source 2 to maximize the ±1st level sideband energy of the multi-color laser output by the first VCSEL laser 7 and the second VCSEL laser 8.

4. A double resonance coherent population trapping magnetometer as claimed in claim 1 or 2, characterized in that: The laser beams output by the first VCSEL laser 7 and the second VCSEL laser 8 are linearly polarized laser beams. The polarization direction of the linearly polarized laser beam output by the first VCSEL laser 7 is adjusted so that it is directly transmitted through the first PBS 11. The polarization direction of the linearly polarized laser beam output by the second VCSEL laser 8 is adjusted so that it is reflected through the first PBS 11. The two laser beams are ensured to pass through 87 The Rb atomic gas chamber 13 does not overlap.

5. A double resonance coherent population trapping magnetometer as claimed in claim 1 or 2, characterized in that: Said 87 Rb atoms are used as working atoms. By scanning the current of the first current source 3 and the second current source 4, the laser frequencies output by the first VCSEL laser 7 and the second VCSEL laser 8 are locked at 87 The Rb atom D1 line excited state Fe=1 energy level; as shown in the dotted line in the absorption spectrum of Figure 3; Two laser beams pass through 87 After the Rb atomic gas cell 13, the second PBS 14 separates the components of the two linearly polarized laser beams in their two polarization detection directions, and the first photodiode 15 and the second photodiode 16 respectively detect the light intensity signals in the two polarization directions.

6. A double resonance coherent population trapping magnetometer as claimed in claim 1 or 2, characterized in that: The λ / 2 wave plate 12 is used to adjust the polarization directions of the two linearly polarized laser beams. The λ / 2 wave plate 12 is rotated to make the output laser light intensities in the two polarization directions of the second PBS 14 equal, that is, the differential voltage obtained after the optical signals detected by the first photodiode 15 and the second photodiode 16 pass through the differential amplifier circuit 17 is 0.

7. A double resonance coherent population trapping magnetometer as claimed in claim 1 or 2, characterized in that: The output microwave frequencies of the first microwave source 1 and the first microwave source 2 start from the transition frequency of the two energy levels of the mF=0 ground state, and scan f in two opposite directions of linear increase and linear decrease, respectively. hfs1 and f hfs2 , used to obtain the respective CPT resonance signals respectively.

8. A double resonance coherent population trapping magnetometer as claimed in claim 1 or 2, characterized in that: The microwave frequency output by the first microwave source 1 is f hfs1 , frequency modulation is used to modulate the microwave frequency output, and the modulation depth is f dev , the modulation frequency is f mod , then the output microwave signal is f hfs1 +f dev sin(2πf mod ); The microwave frequency output by the second microwave source 1 is f hfs2 , frequency modulation is used to modulate the microwave frequency output, and the modulation depth is f dev , the modulation frequency is f mod When the modulation phase of the second microwave source 2 differs from that of the first microwave source 1 by π / 2, the output microwave signal is f hfs2 +f dev cos(2πf mod ).

9. A double resonance coherent population trapping magnetometer as claimed in claim 1 or 2, characterized in that: A constant temperature control module is used for constant temperature control, and the constant temperature control module includes a temperature sensor, a PID control unit and a heating device; 87 The temperatures of the Rb atomic gas chamber 13, the first VCSEL laser 7 and the second VCSEL laser 8 are collected, and then the amplitude of the AC heating signal is controlled by the PID control unit to respectively achieve 87 Constant temperature control of the Rb atomic gas cell 13 , the first VCSEL laser 7 , and the second VCSEL laser 8 .

10. A method for realizing a double-resonance coherent population trapping magnetometer, characterized in that: The steps include: Step 1: Use constant temperature control module to 87 The Rb atomic gas chamber 13, the first VCSEL laser 7 and the second VCSEL laser 8 are temperature-controlled. 87 The Rb atomic gas chamber 13, the first VCSEL laser 7 and the second VCSEL laser 8 operate at their respective operating temperatures; Step 2: The first microwave source 1 outputs microwaves at a frequency f hfs1 +f dev sin(2πf mod ), the second microwave source 2 outputs microwave frequency f hfs2 +f dev cos(2πf mod ), the first current source 3 and the first microwave source 1 are coupled through the first Bias-T 5, and the first microwave source 1 is injected into the first VCSEL laser 7, and the output power of the first microwave source 1 is adjusted so that the ±1st level sideband energy of the multi-color laser output by the first VCSEL laser 1 is the strongest; the first current source 4 and the second microwave source 2 are coupled through the second Bias-T 6, and the second microwave source 2 is injected into the second VCSEL laser 8, and the output power of the second microwave source 2 is adjusted so that the ±1st level sideband energy of the multi-color laser output by the second VCSEL laser 8 is the strongest; Step 3: Scan the output current of the first current source 3 to lock the frequency of the first VCSEL laser 7 at 87 The output current of the second current source 4 is scanned to lock the frequency of the second VCSEL laser 8 at 87 The D1 line polychromatic light absorption spectrum of Rb atom; as shown in Figure 3. Step 4: Scan the central microwave frequency f output by the first microwave source 1 hfs1 , and modulate the reference signal Asin(2πf mod ) is input to the reference channel of channel 1 (CH1) of the dual-channel phase-locked amplifier 18, the output signal of the second PBS 14 is amplified by the differential amplifier circuit 17 and then input to the signal channel of channel 1 (CH1) of the dual-channel phase-locked amplifier 18, and the corresponding CPT resonance signal is obtained by the phase-locked amplifier. After the CPT resonance signal is obtained, the central microwave frequency f output by the first microwave source 1 is controlled by PID. hfs1 , complete the locking and tracking of the CPT resonance point; at the same time, scan the central microwave frequency f output by the second microwave source 2 hfs2 , and modulate the reference signal Acos(2πf mod ) is input to the reference channel of channel 2 (CH2) of the dual-channel phase-locked amplifier 18, the output signal of the second PBS 14 is amplified by the differential amplifier circuit 17 and then input to the signal channel of channel 2 (CH2) of the dual-channel phase-locked amplifier 18, and the corresponding CPT resonance signal is obtained by the phase-locked amplifier. After the CPT resonance signal is obtained, the central microwave frequency f output by the second microwave source 2 is controlled by PID. hfs2 , complete the locking and tracking of the CPT resonance point; Step 5: Calculate the magnetic field value according to the following formula: B = (f hfs1 -f hfs2 ) / Γ, where Γ is the ratio between frequency and magnetic field, which is approximately 28Hz / nT.

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