A dual-resonance coherent population trapping magnetometer and its implementation method

Abstract

This invention proposes a dual-resonance coherent population trapping magnetometer and its implementation method, which can effectively suppress optical noise of lasers, improve sensitivity, and increase the lower limit of the measurement range. It includes: 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, and a λ / 2 waveplate. 87 The system includes an Rb atom gas cell, a second PBS, a first photodiode, a second photodiode, a differential amplifier, and a dual-channel lock-in amplifier. The first VCSEL laser, the second VCSEL laser, the first collimating lens, the second collimating lens, the first PBS, and the λ / 2 waveplate are located at... 87 On the left side of the Rb atomic gas cell, the first VCSEL laser and the first collimating lens are located to the left of the first PBS, and the second VCSEL laser and the second collimating lens are located below the first PBS. The laser output from the second VCSEL laser is reflected by the first PBS and propagates towards the right atomic gas cell.

Description

Technical Field

[0001] This invention belongs to the field of atomic magnetometer technology, specifically relating to a dual-resonance coherent population trapping magnetometer and its implementation method. Background Technology

[0002] Coherent population-trapped magnetometers (CPT magnetometers) are characterized by high detection sensitivity and have important applications in military and civilian fields such as magnetic target detection, space physics, and geological exploration. A CPT magnetometer is an instrument that uses a laser as a light source to detect the Zeeman effect of atoms in a magnetic field through the interaction between the laser and atoms, thereby achieving the measurement of external magnetic fields. CPT magnetometers are characterized by no dead zone, low power consumption, small size, high sensitivity, and are entirely optical and radiation-free.

[0003] Under an external magnetic field, atoms undergo the Zeeman effect, causing hyperfine levels to degenerate and split. The splitting distance between these levels varies with the external magnetic field. 87 Taking the 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: Where in the formula To reduce Planck's constant, ω 0,0 Let m1 and m2 be the transition angular frequencies between two energy levels where the ground-state magnetic quantum number is zero, and m1 and m2 represent the magnetic quantum numbers of the ground-state energy levels, respectively. The transition angular frequency between ground state energy levels is represented by γ, where γ is the gyromagnetic ratio and B is the external magnetic field strength. Under a weak magnetic field, 87 After the Rb ground state energy level splits, the multiple CPT spectral lines formed will also shift linearly with the magnetic field. Therefore, the magnitude of the magnetic field strength can be deduced by measuring the microwave frequency difference at the peak of the corresponding CPT spectral line.

[0004] Existing CPT magnetometers generally employ circularly polarized dual-color lasers interacting with atoms, resulting in relatively poor CPT signal quality and affecting the magnetometer's sensitivity. The main reasons affecting the CPT signal quality obtained by existing methods include: only two sidebands of the multicolor light obtained using modulated VCSEL lasers carry the CPT signal, while other sideband components contribute only noise, making the background light signal amplitude much larger than the CPT signal amplitude; the VCSEL output light has a wide linewidth, approximately 50MHz, resulting in strong FM-AM noise in the CPT signal; and the VCSEL laser's own optical power fluctuates, introducing laser power noise (AM noise).

[0005] In addition, existing CPT magnetometers use a single-beam laser to interact with atoms, and the obtained CPT signal is as follows: Figure 2 As shown in the figure below, this scheme has two problems, 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, when a single circularly polarized laser scans microwaves, it can only scan in a single direction, either increasing or decreasing the microwave direction, thus only obtaining one magnetically sensitive CPT resonance peak, either the leftmost or rightmost CPT resonance peak, and cannot simultaneously obtain information from two magnetically sensitive CPT resonance peaks. Summary of the Invention

[0006] This invention proposes a dual-resonance coherent population trapping magnetometer and its implementation method, which can effectively suppress the optical noise of lasers, improve sensitivity, and increase the lower limit of the measurement range.

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

[0008] A dual-resonance coherent population trapping magnetometer includes: 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, and a λ / 2 waveplate 12. 87 The system includes an Rb atom gas chamber 13, a second PBS 14, a first photodiode 15, a second photodiode 16, a differential amplifier 17, and a dual-channel lock-in amplifier 18; among which...

[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 waveplate 12 are located at... 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 to the left of the first PBS 11, and the second VCSEL laser 8 and the second collimating lens 10 are located below the first PBS 11. The laser output by the second VCSEL laser 8 is reflected by the first PBS 11 and propagates towards the right atomic gas chamber.

[0010] The second PBS14, the first photodiode 15, and the second photodiode 16 are placed 87On the right side of the Rb atom gas chamber 13, the first photodiode 15 is located to the right of the second PBS 14, and the second photodiode 16 is located below the second PBS 14. The reflected laser light from the second PBS 14 is input to the first photodiode 15. The signals from 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-channel lock-in amplifier 18. The weak signal is subtracted and amplified before being input to the dual-channel lock-in amplifier 18. The dual-channel lock-in amplifier 18 is also connected to the first microwave source 1 and the second microwave source 2. The dual-channel lock-in amplifier 18 obtains a microwave control signal through demodulation, which is used to control the output microwave frequency of the first microwave source 1 and the second microwave source 2, thereby completing the locking of the magnetometer and the measurement of the magnetic field.

[0011] A method for implementing a dual-resonance coherent population trapping magnetometer includes the following steps:

[0012] Step 1: Use a constant temperature control module to... 87 The Rb atom gas chamber 13, the first VCSEL laser 7, and the second VCSEL laser 8 are subjected to constant temperature control, so that... 87 The Rb atom 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 a 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 injected into the first VCSEL laser 7. The output power of the first microwave source 1 is adjusted so that the ±1st order sideband energy of the multicolor 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 injected into the second VCSEL laser 8. The output power of the second microwave source 2 is adjusted so that the ±1st order sideband energy of the multicolor 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 [frequency value]. 87 The Rb atom D1 line multicolor absorption spectrum was scanned; the output current of the second current source 4 was scanned to lock the frequency of the second VCSEL laser 8 to [value missing]. 87 On the polychromatic absorption spectrum of the D1 line of Rb atoms; such as Figure 3 As shown.

[0015] Step 4: Scan the center microwave frequency f output by the first microwave source 1.hfs1 And modulate the reference signal Asin(2πf) mod The input signal is fed into the reference channel of channel 1 (CH1) of the dual-channel lock-in amplifier 18. After the output signal of the second PBS14 is amplified by the differential amplifier circuit 17, it is input into the signal channel of channel 1 (CH1) of the dual-channel lock-in amplifier 18. The lock-in amplifier obtains the corresponding CPT resonance signal. After obtaining the CPT resonance signal, the center microwave frequency f output by the first microwave source 1 is controlled by PID control. hfs1 The system completes the locking and tracking of the CPT resonance point; simultaneously, it scans the center microwave frequency f output by the second microwave source 2. hfs2 And modulate the reference signal Acos(2πf) mod The input signal is fed into the reference channel of channel 2 (CH2) of the dual-channel lock-in amplifier 18. After the output signal of the second PBS14 is amplified by the differential amplifier circuit 17, it is input into the signal channel of channel 2 (CH2) of the dual-channel lock-in amplifier 18. The lock-in amplifier obtains the corresponding CPT resonance signal. After obtaining the CPT resonance signal, the center microwave frequency f output by the second microwave source 2 is controlled by PID control. hfs2 Complete the locking and tracking of the CPT resonance point;

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

[0017] The beneficial effects of this invention are:

[0018] 1. This invention uses the interaction between linearly polarized laser and atoms to obtain the optical rotation signal when linearly polarized light undergoes CPT resonance through differential detection. This can effectively suppress 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 this invention through the magneto-optical rotation effect of linearly polarized laser, such as... Figure 2 As shown in the figure above, due to ω 0,0 Multiple CPT resonance interferences obtained from time-polarized lasers destructively lead to ω under a weak magnetic field. 0,0 The CPT resonance peak at that time was basically eliminated, thereby raising the detection limit of the CPT magnetometer;

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

[0021] 4. This invention uses two laser beams with opposite microwave frequency scanning directions, allowing for simultaneous acquisition of... Figure 2 The external magnetic field value can be calculated by subtracting the resonant frequencies of the two CPT signals from each other, which can double the sensitivity.

[0022] 5. This invention uses two linearly polarized lasers to interact with atoms, and uses differential detection to obtain the optical rotation signal when the two linearly polarized lasers resonate at CPT. At the same time, the resonance frequencies of the two resonance peaks are measured to calculate the magnitude of the external magnetic field.

[0023] 6. This invention can effectively suppress the optical noise of lasers, improve sensitivity, and increase the lower limit of the measurement range. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a dual-resonance coherent population trapping magnetometer according to the present invention;

[0025] Figure 2 This is a schematic diagram of a CPT signal using a single circularly polarized light.

[0026] Figure 3 This is a specific embodiment of the present invention. 87 Rb atom D1 line polychromatic light absorption spectrum;

[0027] Figure 4 In specific embodiments of the present invention, linearly polarized laser at different microwave frequencies and 87 CPT resonance level of Rb atom interaction. Detailed Implementation

[0028] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the drawings are merely exemplary and are intended to illustrate the principles and spirit of the present invention, and are not intended to limit the scope of the present invention.

[0029] like Figure 1 As shown, a dual-resonance coherent population trapping magnetometer of the present invention includes: 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, and a λ / 2 waveplate 12. 87 The system includes an Rb atom gas chamber 13, a second PBS 14, a first photodiode 15, a second photodiode 16, a differential amplifier 17, and a dual-channel lock-in amplifier 18; among which...

[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 waveplate 12 are located at... 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 to the left of the first PBS 11, and the second VCSEL laser 8 and the second collimating lens 10 are located below the first PBS 11. The laser output by the second VCSEL laser 8 is reflected by the first PBS 11 and propagates towards the right atomic gas chamber.

[0031] The second PBS14, the first photodiode 15, and the second photodiode 16 are placed 87 On the right side of the Rb atom gas chamber 13, the first photodiode 15 is located to the right of the second PBS 14, and the second photodiode 16 is located below the second PBS 14. The reflected laser light from the second PBS 14 is input to the first photodiode 15. The signals from 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-channel lock-in amplifier 18. The weak signal is subtracted and amplified before being input to the dual-channel lock-in amplifier 18. The dual-channel lock-in amplifier 18 is also connected to the first microwave source 1 and the second microwave source 2. The dual-channel lock-in amplifier 18 obtains a microwave control signal through demodulation, which is used to control the output microwave frequency of the first microwave source 1 and the second microwave source 2, thereby completing the locking of the magnetometer and the measurement of the magnetic field.

[0032] The first Bias-T 5 couples the microwave output from the first microwave source 1 with the current from the first current source 3, driving the first VCSEL laser 7 to output multicolor laser. The second Bias-T 6 couples the microwave output from the second microwave source 2 with the current from the second current source 4, driving the second VCSEL laser 8 to output multicolor laser. The output power of the first microwave source 1 and the second microwave source 2 is adjusted to maximize the ±1st order sideband energy of the multicolor laser output by the first VCSEL laser 7 and the second VCSEL laser 8.

[0033] The lasers output by the first VCSEL laser 7 and the second VCSEL laser 8 are linearly polarized lasers. The polarization direction of the linearly polarized laser output by the first VCSEL laser 7 is adjusted so that it directly transmits through the first PBS 11. The polarization direction of the linearly polarized laser output by the second VCSEL laser 8 is adjusted so that it is reflected through the first PBS 11, ensuring that both laser beams pass through... 87 The Rb atom gas cells 13 do not overlap.

[0034] like Figure 3 As shown, in this embodiment, the 87Using Rb atoms as the working atoms, the laser frequencies output by the first VCSEL laser 7 and the second VCSEL laser 8 are locked at a frequency that is scanned by the currents of the first current source 3 and the second current source 4. 87 On the energy level of the Rb atom in the D1 line excited state Fe=1; such as Figure 3 On the absorption spectrum outlined by the dashed line; two laser beams pass through 87 After the Rb atom gas chamber 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 detect the light intensity signals in the two polarization directions respectively.

[0035] In this embodiment, the λ / 2 waveplate 12 is used to adjust the polarization direction of the two linearly polarized laser beams. By rotating the λ / 2 waveplate 12, the output laser light intensity of the two polarization directions of the second PBS 14 is equal, that is, the differential voltage obtained after the light 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 ground state at mF=0, and scan in two opposite directions, linearly increasing and linearly decreasing, respectively. hfs1 and f hfs2 , used to obtain their respective CPT resonance signals.

[0037] like Figure 1 As shown, in this embodiment, the microwave frequency output by the first microwave source 1 is f. hfs1 The output microwave frequency is modulated using frequency modulation, with a modulation depth of 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 The output microwave frequency is modulated using frequency modulation, with a modulation depth of 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 modulation reference signals to the dual-channel lock-in amplifier 18 for demodulation of the two CPT resonant signals. The modulation reference signal of the first microwave source 1 is in phase with the modulation signal of the first microwave source 1, expressed as Asin(2πf mod The servo signal obtained after passing through the lock-in amplifier is fed back to the first microwave source 1 to control and lock the output frequency of the first microwave source 1; the modulation reference signal of the second microwave source 2 is kept in phase with the modulation signal of the second microwave source 2, expressed as Acos(2πf mod The servo signal obtained after passing through the lock-in amplifier is fed back to the second microwave source 2 to control and lock the output frequency of the second microwave source 2.

[0039] In this embodiment, f is completed. hfs1 and f hfs2 After scanning, the dual-resonance CPT resonance signal is obtained through the dual-channel lock-in amplifier 18. Then, the servo output of the dual-channel lock-in amplifier 18 is controlled by PID to set f hfs1 and f hfs2 Lock onto the corresponding CPT resonance points, and then calculate the magnetic field value using the following formula: B = (f hfs1 -f hfs2 ) / Γ, where the influence of higher-order nonlinear terms in the crowding effect is neglected under weak magnetic field, and Γ is the ratio between frequency and magnetic field, which is approximately 28Hz / nT.

[0040] In this embodiment, a constant temperature control module is used for temperature control. The constant temperature control module includes a temperature sensor, a PID control unit, and a heating element. The temperature sensor controls the temperature... 87 The temperatures of the Rb atom 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 a PID control unit to achieve the following: 87 Temperature control of Rb atom gas chamber 13, first VCSEL laser 7 and second VCSEL laser 8.

[0041] This invention also proposes a method for implementing a dual-resonance coherent population trapping magnetometer, which specifically includes the following steps:

[0042] Step 1: Use a constant temperature control module to... 87 The Rb atom gas chamber 13, the first VCSEL laser 7, and the second VCSEL laser 8 are subjected to constant temperature control, so that... 87 The Rb atom 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 f.hfs1 +f dev sin(2πf mod The second microwave source 2 outputs a 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 injected into the first VCSEL laser 7. The output power of the first microwave source 1 is adjusted so that the ±1st order sideband energy of the multicolor 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 injected into the second VCSEL laser 8. The output power of the second microwave source 2 is adjusted so that the ±1st order sideband energy of the multicolor 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 [frequency value]. 87 The Rb atom D1 line multicolor absorption spectrum was scanned; the output current of the second current source 4 was scanned to lock the frequency of the second VCSEL laser 8 to [value missing]. 87 On the polychromatic absorption spectrum of the D1 line of Rb atoms; such as Figure 3 As shown.

[0045] Step 4: Scan the center microwave frequency f output by the first microwave source 1. hfs1 And modulate the reference signal Asin(2πf) mod The input signal is fed into the reference channel of channel 1 (CH1) of the dual-channel lock-in amplifier 18. After the output signal of the second PBS14 is amplified by the differential amplifier circuit 17, it is input into the signal channel of channel 1 (CH1) of the dual-channel lock-in amplifier 18. The lock-in amplifier obtains the corresponding CPT resonance signal. After obtaining the CPT resonance signal, the center microwave frequency f output by the first microwave source 1 is controlled by PID control. hfs1 The system completes the locking and tracking of the CPT resonance point; simultaneously, it scans the center microwave frequency f output by the second microwave source 2. hfs2 And modulate the reference signal Acos(2πf) mod The input signal is fed into the reference channel of channel 2 (CH2) of the dual-channel lock-in amplifier 18. After the output signal of the second PBS14 is amplified by the differential amplifier circuit 17, it is input into the signal channel of channel 2 (CH2) of the dual-channel lock-in amplifier 18. The lock-in amplifier obtains the corresponding CPT resonance signal. After obtaining the CPT resonance signal, the center microwave frequency f output by the second microwave source 2 is controlled by PID control. hfs2 Complete the locking and tracking of the CPT resonance point;

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

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

[0048] It will be apparent to those skilled in the art that the embodiments of the present invention are not limited to the details of the exemplary embodiments described above, and that the embodiments of the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the embodiments of the present invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the embodiments of the present invention is defined by the appended claims rather than the foregoing description. Therefore, all variations falling within the meaning and scope of equivalents of the claims are intended to be encompassed within the embodiments of the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims. Furthermore, it is clear that the word "comprising" does not exclude other units or steps, and the singular does not exclude the plural. Multiple units, modules, or devices recited in the system, apparatus, or terminal claims may also be implemented by the same unit, module, or device through software or hardware. The terms "first," "second," etc., are used to indicate names and do not indicate any particular order.

[0049] Finally, it should be noted that the above embodiments 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 embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the embodiments of the present invention should not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dual-resonance coherent population trapping magnetometer, characterized in that, include: First microwave source (1), second microwave source (2), first current source (3), second current source (4), first Bias-T (5), second Bias-T (6), first VCSEL laser (7), second VCSEL laser (8), first collimating lens (9), second collimating lens (10), first PBS (11), λ / 2 waveplate (12). 87 The structure includes an Rb atom gas chamber (13), a second PBS (14), a first photodiode (15), a second photodiode (16), a differential amplifier (17), and a dual-channel lock-in 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 waveplate (12) are located at... 87 On the left side of the Rb atomic gas cell (13), the first VCSEL laser (7) and the first collimating lens (9) are located to the left of the first PBS (11), and the second VCSEL laser (8) and the second collimating lens (10) are located below the first PBS (11). The laser output by the second VCSEL laser (8) is reflected by the first PBS (11) and propagates towards the right atomic gas cell. The lasers output by the first VCSEL laser (7) and the second VCSEL laser (8) are linearly polarized lasers. The polarization direction of the linearly polarized laser output by the first VCSEL laser (7) is adjusted so that it directly transmits through the first PBS (11). The polarization direction of the linearly polarized laser output by the second VCSEL laser (8) is adjusted so that it is reflected through the first PBS (11), and it is ensured that both laser beams pass through the first PBS (11). 87 The Rb atom gas cells (13) do not overlap; 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 ground state at mF=0, and scan in two opposite directions, linearly increasing and linearly decreasing, respectively. and , used to obtain their respective CPT resonance signals.

2. The dual-resonance coherent population trapping magnetometer as described 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 atom gas chamber (13), the first photodiode (15) is located below the second PBS (14), and the second photodiode (16) is located to the right of the second PBS (14). The reflected laser from the second PBS (14) is input to the first photodiode (15). The signals from 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-channel lock-in amplifier (18). The weak signal is subtracted and amplified before being input to the dual-channel lock-in amplifier (18). The dual-channel lock-in amplifier (18) is simultaneously connected to the first microwave source (1) and the second microwave source (2). The dual-channel lock-in amplifier (18) obtains the microwave control signal through demodulation, which is used to control the output microwave frequency of the first microwave source (1) and the second microwave source (2), thereby completing the locking of the magnetometer and the measurement of the magnetic field.

3. A dual-resonance coherent population trapping magnetometer as described in claim 1 or 2, characterized in that, The first Bias-T (5) couples the microwave output from the first microwave source (1) with the current of the first current source (3) to drive the first VCSEL laser (7) to output multicolor laser. The second Bias-T (6) couples the microwave output from the second microwave source (2) with the current of the second current source (4) to drive the second VCSEL laser (8) to output multicolor laser. The output power of the first microwave source (1) and the second microwave source (2) is adjusted so that the ±1st order sideband energy of the multicolor laser output by the first VCSEL laser (7) and the second VCSEL laser (8) is maximized.

4. A dual-resonance coherent population trapping magnetometer as described in claim 1 or 2, characterized in that, The 87 Rb atoms are the working atoms. By scanning the currents 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 a frequency of 1. 87 On the energy level of the Rb atom D(1) line excited state Fe=1; two laser beams pass through 87 After the Rb atom gas cell (13), the second PBS (14) separates the components of the two linearly polarized lasers in their two polarization detection directions, and the first photodiode (15) and the second photodiode (16) detect the light intensity signals in the two polarization directions respectively.

5. A dual-resonance coherent population trapping magnetometer as described in claim 1 or 2, characterized in that, The λ / 2 waveplate (12) is used to adjust the polarization direction of the two linearly polarized laser beams. Rotating the λ / 2 waveplate (12) makes the output laser light intensity of the two polarization directions of the second PBS (14) equal, that is, the differential voltage obtained after the light signals detected by the first photodiode (15) and the second photodiode (16) pass through the differential amplifier circuit (17) is 0.

6. A dual-resonance coherent population trapping magnetometer as described in claim 1 or 2, characterized in that, The microwave frequency output by the first microwave source (1) is The output microwave frequency is modulated using frequency modulation, with a modulation depth of [value missing]. The modulation frequency is The output microwave signal is then... The microwave frequency output by the second microwave source (1) is... The output microwave frequency is modulated using frequency modulation, with a modulation depth of [value missing]. The modulation frequency is The modulation phase of the second microwave source (2) differs from the modulation phase of the first microwave source (1). In this case, the output microwave signal is .

7. A dual-resonance coherent population trapping magnetometer as described in claim 1 or 2, characterized in that, A constant temperature control module is used for temperature control. This module includes a temperature sensor, a PID control unit, and a heating element. The temperature sensor controls the temperature... 87 The temperatures of the Rb atom 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 achieve the following: 87 Temperature control of the Rb atom gas chamber (13), the first VCSEL laser (7), and the second VCSEL laser (8).

8. A method for implementing a dual-resonance coherent population trapping magnetometer, characterized in that, Based on the dual-resonance coherent population trapping magnetometer as described in any one of claims 1-7, the following steps are included: Step 1: Use a constant temperature control module to... 87 The Rb atom gas chamber (13), the first VCSEL laser (7), and the second VCSEL laser (8) are subjected to constant temperature control, so that... 87 The Rb atom gas chamber (13), the first VCSEL laser (7), and the second VCSEL laser (8) operate at their respective operating temperatures. Step 2: First microwave source (1) outputs microwave frequency The second microwave source (2) outputs microwave frequencies. The first current source (3) and the first microwave source (1) are coupled through the first Bias-T (5) and injected into the first VCSEL laser (7). The output power of the first microwave source (1) is adjusted so that the ±1st order sideband energy of the multicolor laser output by the first VCSEL laser (7) is the strongest. The first current source (4) and the second microwave source (2) are coupled through the second Bias-T (6) and injected into the second VCSEL laser (8). The output power of the second microwave source (2) is adjusted so that the ±1st order sideband energy of the multicolor laser output by the second VCSEL laser (8) is the strongest. Step 3: Scan the output current of the first current source (3) and lock the frequency of the first VCSEL laser (7) at [frequency value]. 87 The Rb atom D1 line multicolor absorption spectrum is scanned; the output current of the second current source (4) is scanned to lock the frequency of the second VCSEL laser (8) at [value missing]. 87 On the polychromatic absorption spectrum of the D1 line of Rb atoms; Step 4: Scan the center microwave frequency output by the first microwave source (1) and modulate the reference signal The reference channel of channel 1 of the dual-channel lock-in amplifier (18) is amplified by the differential amplifier circuit (17) and then input to the signal channel of channel 1 of the dual-channel lock-in amplifier (18). The lock-in amplifier obtains the corresponding CPT resonance signal. After obtaining the CPT resonance signal, the center microwave frequency output by the first microwave source (1) is controlled by PID. The CPT resonance point is locked and tracked; simultaneously, the center microwave frequency output by the second microwave source (2) is scanned. and modulate the reference signal The reference channel of channel 2 of the dual-channel lock-in amplifier (18) is amplified by the differential amplifier circuit (17) and then input to the signal channel of channel 2 of the dual-channel lock-in amplifier (18). The lock-in amplifier obtains the corresponding CPT resonance signal. After obtaining the CPT resonance signal, the center microwave frequency output by the second microwave source (2) is controlled by PID. Complete the locking and tracking of the CPT resonance point; Step 5: Calculate the magnetic field value using the following formula: ,in This is the ratio between frequency and magnetic field, approximately 28 Hz / nT.

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