Self-excited Mx rubidium atom magnetometer device and working method

Abstract

The invention provides a self-excitation type Mx rubidium atom magnetometer device and a working method, the self-excitation type Mx rubidium atom magnetometer device comprises an atom magnetometer probe and an atom magnetometer driving circuit, and the atom magnetometer probe is connected with the atom magnetometer driving circuit; the atom magnetometer probe comprises a VCSEL laser tube, an electro-optical modulator, a 1 / 4 slide, a rubidium atom gas chamber and a photosensitive tube. The atom magnetometer driving circuit comprises a lock-in amplifier, a phase shifter, an EOM driver and a laser tube driver. According to the invention, the atom magnetometer driving circuit synchronously modulates the polarization state and the light intensity of the pumping laser in the rubidium atom magnetometer to form an auto-excitation feedback loop, so that the problem that the radio frequency magnetic field feedback auto-excitation working mode adopted by the traditional Mx magnetometer is not suitable for the rubidium atom magnetometer is solved; and an instable feedback loop is formed.

Description

Self-excited Mx rubidium atomic magnetometer device and its working method Technical Field

[0001] This invention relates to a magnetometer, specifically to a self-excited Mx rubidium atomic magnetometer device and its operating method. Background Technology

[0002] Atomic magnetometers measure weak magnetic fields by utilizing the interaction of light with atoms, offering the advantage of high sensitivity. They are based on the Zeeman effect of alkali metal atoms, where the ground-state energy levels of an atom undergo Zeeman splitting in an external magnetic field. Measuring the magnitude of the external magnetic field can be transformed into measuring the transition frequencies of adjacent Zeeman energy levels within the atom.

[0003] Atomic magnetometers can be classified into two types based on their method of detecting magnetic resonance signals: Mz-type magnetometers and Mx-type magnetometers. Mz-type magnetometers detect signals proportional to the longitudinal component of the magnetic moment. This detection method offers high accuracy, but requires electronic circuitry to scan and track the frequency points of the magnetic resonance signal, resulting in a relatively slow measurement speed and a tendency to lose lock-on when the external magnetic field changes rapidly. Mx-type magnetometers, on the other hand, shift the optically detected signal by 90 degrees and feed it back to coils around the atomic gas cell, forming a self-excited oscillation circuit. This continuously outputs a Larmor frequency signal proportional to the external magnetic field without the need for scanning. Mx-type magnetometers can continuously measure external magnetic fields, offering a fast response and wide dynamic range, representing a significant advantage over the Mz tracking mode.

[0004] Cesium atomic magnetometers in alkali metal atomic magnetometers all adopt the Mx self-excitation mode. However, due to the small atomic mass and large gyromagnetic ratio of rubidium atoms, a strong external magnetic field is required to achieve optical magnetic resonance. The radio frequency magnetic field feedback self-excitation mode used in the traditional Mx magnetometer scheme is not suitable for rubidium atomic magnetometers. Therefore, current rubidium atomic magnetometers all adopt the Mz tracking mode.

[0005] Existing technologies, such as patent CN107015172A which discloses a rubidium atomic magnetometer and a magnetic field measurement method, still require frequency tracking and locking, and thus still belong to the Mz atomic magnetometer category; patent CN112485732B which discloses a magnetometer calibration method and device based on rubidium atomic magnetic resonance spectrum, mainly calibrates the measurement accuracy and deviation of the magnetometer under weak magnetic field conditions, but fails to solve the problem that the radio frequency magnetic field feedback self-excited working mode used by the traditional Mx magnetometer is not suitable for rubidium atomic magnetometers. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a self-excited Mx rubidium atomic magnetometer device and its operating method.

[0007] A self-excited Mx rubidium atomic magnetometer device according to the present invention includes: an atomic magnetometer probe and an atomic magnetometer driving circuit, wherein the atomic magnetometer probe is connected to the atomic magnetometer driving circuit; the atomic magnetometer probe includes: a VCSEL laser tube (vertical cavity surface-emitting laser), an electro-optic modulator, a quarter-wave plate (when light is incident from the normal direction through the waveplate, the phase difference between the ordinary ray [o-ray] and the extraordinary ray [e-ray] is equal to π / 2 or an odd multiple thereof, such a wafer is called a quarter-wave plate or 1 / 4-wave plate), a rubidium atomic gas cell, and a phototube; the VCSEL laser tube produces The generated laser beam passes through an electro-optic modulator, a quarter-glass slide, a rubidium atom gas cell, and finally reaches a phototube. The atomic magnetometer driving circuit includes a lock-in amplifier (an amplifier that performs phase-sensitive detection on alternating signals), a phase shifter (a device that can adjust the phase of a wave), an EOM (electro-optic modulator) driver, and a laser tube driver. The phototube is connected to the lock-in amplifier, the lock-in amplifier is connected to the phase shifter, the phase shifter is connected to the EOM driver and the laser tube driver, the EOM driver is connected to the electro-optic modulator, and the laser tube driver is connected to a VCSEL laser tube.

[0008] Preferably, the atomic magnetometer probe is further provided with a VCSEL laser tube temperature control device, and the atomic magnetometer driving circuit is further provided with a laser tube temperature control driver. The laser tube temperature control driver is connected to the VCSEL laser tube temperature control device, and the VCSEL laser tube temperature control device is connected to the VCSEL laser tube.

[0009] Preferably, the atomic magnetometer probe is further provided with a rubidium atomic gas temperature control device, and the atomic magnetometer driving circuit is further provided with an atomic gas temperature control drive, the atomic gas temperature control drive is connected to the rubidium atomic gas temperature control device, and the rubidium atomic gas temperature control device is connected to the rubidium atomic gas chamber.

[0010] Preferably, the VCSEL laser tube generates a pump laser with a center wavelength of 795 nm (a process that uses light to raise electrons from a lower energy level in an atom or molecule to a higher energy level).

[0011] Preferably, when the modulated signal modulated by the electro-optic modulator reaches the peak, the polarization direction of the laser is parallel to the fast axis of the quarter-glass slide; when the modulated signal modulated by the electro-optic modulator reaches the trough, the polarization direction of the laser forms a 45-degree angle with the fast axis of the quarter-glass slide.

[0012] Preferably, the electrical signal detected by the phototube is amplified by a lock-in amplifier and then phase-shifted by a phase shifter by 90 degrees.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The present application constructs a self-excited feedback loop by synchronously modulating the polarization state and light intensity of the pump laser in the rubidium atomic magnetometer through the atomic magnetometer driving circuit. This solves the problem that the radio frequency magnetic field feedback self-excited working mode used in the traditional Mx magnetometer is not suitable for the rubidium atomic magnetometer and forms an unstable feedback loop. The present invention provides a stable implementation scheme for the self-excited rubidium atomic magnetometer. Attached Figure Description

[0014] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 is a schematic diagram of a self-excited Mx rubidium atomic magnetometer device; as shown in the figure: Detailed Implementation

[0015] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0016] Example 1 This example proposes a scheme for implementing a self-excited Mx rubidium atomic magnetometer using optical modulation, solving the problem that existing radio frequency coil feedback methods are not suitable for Mx rubidium atomic magnetometers. Among various operating modes of magnetometers, the Mx self-excited mode has a fast response speed, wide dynamic range, and is less prone to loss of lock-up when the ambient magnetic field changes rapidly, showing significant advantages over the Mz tracking mode. In alkali metal magnetometers, commercially available cesium atomic magnetometers all use the Mx self-excited mode. However, due to the small atomic mass and large gyromagnetic ratio of rubidium atoms, the traditional radio frequency magnetic field feedback self-excited mode used in the Mx mode forms an unstable feedback loop. Therefore, current rubidium-medium atomic magnetometers all use the Mz tracking mode. This example uses synchronous modulation of the pump laser polarization state and intensity to form a self-excited feedback loop in the rubidium atomic magnetometer, providing a stable implementation scheme for a self-excited rubidium atomic magnetometer.

[0017] Specifically, as shown in Figure 1, this embodiment includes: an atomic magnetometer probe and an atomic magnetometer driving circuit. The atomic magnetometer probe is connected to the atomic magnetometer driving circuit. The atomic magnetometer probe includes: a VCSEL laser tube 1, a rubidium atomic gas temperature control device 2, an electro-optic modulator 3, a 1 / 4 glass slide 4, a rubidium atomic gas chamber 5, a phototube 6, and a VCSEL laser tube temperature control device 7. The atomic magnetometer driving circuit includes: a lock-in amplifier 8, a phase shifter 9, an EOM driver 10, a laser tube driver 11, an atomic gas temperature control driver 12, and a laser tube temperature control driver 13.

[0018] The laser beam generated by VCSEL laser tube 1 passes through electro-optic modulator 3, quarter-glass slide 4, rubidium atomic gas cell 5, and then reaches phototube 6. Phototube 6 is connected to lock-in amplifier 8, which is connected to phase shifter 9. Phase shifter 9 is connected to EOM driver 10 and laser tube driver 11. EOM driver 10 is connected to electro-optic modulator 3, and laser tube driver 11 is connected to VCSEL laser tube 1. Laser tube temperature control driver 13 is connected to VCSEL laser tube temperature control device 7, which is connected to VCSEL laser tube 1. Atomic gas temperature control driver 12 is connected to rubidium atomic gas temperature control device 2, which is connected to rubidium atomic gas cell 5.

[0019] This embodiment also provides a working scheme, including the following steps: Step S1, the VCSEL laser tube 1 generates a pump laser with a center wavelength of 795nm; Step S2, after the pump laser's polarization direction is modulated by the electro-optic modulator 3, it becomes circularly polarized light after passing through a 1 / 4 glass plate 4; Step S3, the pump laser pumps rubidium atoms in the rubidium atom gas chamber 5, completing the polarization process of the rubidium atoms. At this time, the phototube 6 detects the minimum value of the rubidium atom brightness signal in the rubidium atom gas chamber 5; Step S4, the electrical signal detected by the phototube 6 is amplified by the lock-in amplifier 8 and then phase-shifted by the phase shifter 9 by 90 degrees; Step S5, the phase shifter 9 outputs a signal to the EOM driver 10, and the EOM driver 10 drives the electro-optic modulator 3 to complete the pump laser polarization process. Modulation of the pump laser polarization direction: When the modulation signal reaches the peak, the pump laser polarization direction is parallel to the fast axis of the quarter glass plate 4, and is linearly polarized, losing the polarizing effect of atoms; when the modulation signal reaches the trough, the pump laser polarization direction forms a 45-degree angle with the fast axis of the quarter glass plate 4, and becomes circularly polarized after passing through the quarter glass plate 4, possessing the maximum polarization effect; in step S6, the phase shifter 9 outputs a signal to the laser tube driver 11, and the laser tube driver 11 drives the VCSEL laser tube 1, changing the optical power of the VCSEL laser tube 1; in step S7, when the polarization state and optical power of the pump laser are simultaneously modulated, and the modulation phase is 90 degrees out of phase with the signal of the phototube 6, the lock-in amplifier 8 outputs a Larmor frequency signal.

[0020] Example 2 is a preferred example of Example 1.

[0021] As shown in Figure 1, this embodiment consists of two main components: an atomic magnetometer probe and an atomic magnetometer driving circuit. The atomic magnetometer probe primarily includes optical components such as a VCSEL laser tube 1, a VCSEL laser tube temperature control device 7, an electro-optic modulator 3, a quarter-glass slide 4, a rubidium atomic gas chamber 5, a rubidium atomic gas temperature control device 2, and a phototube 6. The atomic magnetometer driving circuit primarily includes electronic components such as a lock-in amplifier 8, a phase shifter 9, an EOM driver 10, a laser tube driver 11, a laser tube temperature control driver 13, and an atomic gas temperature control driver 12.

[0022] The working process of the self-excited rubidium atomic magnetometer using optical modulation is as follows: VCSEL laser tube 1 generates a pump laser with a center wavelength of 795nm. The wavelength of VCSEL laser tube 1 is temperature-dependent, requiring the cooperation of VCSEL laser tube temperature control device 7 and laser tube temperature control drive 13 to maintain a constant temperature. The rubidium atomic gas chamber 5 also needs to maintain an operating temperature of approximately 90 degrees Celsius to maintain sufficient rubidium atom density. The temperature control of the rubidium atomic gas chamber 5 is achieved by rubidium atomic gas temperature control device 2 and atomic gas temperature control drive 12.

[0023] The pump laser passes through electro-optic modulator 3, which modulates its polarization direction. After passing through quarter-glass slide 4, it becomes circularly polarized light, pumping rubidium atoms in rubidium atom gas cell 5, completing the polarization process of the rubidium atoms. At this time, phototube 6 detects the minimum value of the brightness signal. The electrical signal detected by phototube 6 is amplified by lock-in amplifier 8, and then phase-shifted by phase shifter 9 by 90 degrees. It is then input to EOM driver 10 to drive electro-optic modulator 3, completing the modulation of the polarization direction of the pump laser: when the modulation signal peaks, the polarization direction is parallel to the fast axis of quarter-glass slide 4, resulting in linearly polarized light, which loses its polarizing effect; when the modulation signal troughs, the polarization direction forms a 45-degree angle with the fast axis of quarter-glass slide 4, resulting in circularly polarized light after passing through quarter-glass slide 4, possessing the maximum polarization effect. At the same time, the output signal of phase shifter 9 also drives VCSEL laser tube 1 through laser tube driver 11, changing its optical power. When the polarization state and optical power of the pump laser are simultaneously modulated, and the modulation phase differs from the phase of the signal of phototube 6 by 90 degrees, the above device can output a stable Larmor frequency signal, realizing the self-excited working state of Mx.

[0024] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0025] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A self-excited Mx rubidium atomic magnetometer device, characterized in that, include: An atomic magnetometer probe and an atomic magnetometer driving circuit, wherein the atomic magnetometer probe is connected to the atomic magnetometer driving circuit; The atomic magnetometer probe includes: a VCSEL laser tube (1), an electro-optic modulator (3), a quarter glass slide (4), a rubidium atomic gas cell (5), and a phototube (6); the laser beam generated by the VCSEL laser tube (1) passes through the electro-optic modulator (3), the quarter glass slide (4), the rubidium atomic gas cell (5), and reaches the phototube (6); the atomic magnetometer driving circuit includes: a lock-in amplifier (8), a phase shifter (9), an EOM driver (10), and a laser tube driver (11); the phototube (6) is connected to the lock-in amplifier (8), the lock-in amplifier (8) is connected to the phase shifter (9), the phase shifter (9) is connected to the EOM driver (10) and the laser tube driver (11), the EOM driver (10) is connected to the electro-optic modulator (3), and the laser tube driver (11) is connected to the VCSEL laser tube (1).

2. The self-excited Mx rubidium atomic magnetometer device according to claim 1, characterized in that: The atomic magnetometer probe is also equipped with a VCSEL laser tube temperature control device (7), and the atomic magnetometer driving circuit is also equipped with a laser tube temperature control driver (13). The laser tube temperature control driver (13) is connected to the VCSEL laser tube temperature control device (7), and the VCSEL laser tube temperature control device (7) is connected to the VCSEL laser tube (1).

3. The self-excited Mx rubidium atomic magnetometer device according to claim 1, characterized in that: The atomic magnetometer probe is also equipped with a rubidium atomic gas temperature control device (2), and the atomic magnetometer drive circuit is also equipped with an atomic gas temperature control drive (12). The atomic gas temperature control drive (12) is connected to the rubidium atomic gas temperature control device (2), and the rubidium atomic gas temperature control device (2) is connected to the rubidium atomic gas chamber (5).

4. The self-excited Mx rubidium atomic magnetometer device according to claim 1, characterized in that: The VCSEL laser tube (1) generates a pump laser with a center wavelength of 795 nm.

5. The self-excited Mx rubidium atomic magnetometer device according to claim 1, characterized in that: When the modulated signal modulated by the electro-optic modulator (3) reaches the peak, the polarization direction of the laser is parallel to the fast axis of the quarter glass plate (4). When the modulated signal modulated by the electro-optic modulator (3) reaches the trough, the polarization direction of the laser is at a 45-degree angle to the fast axis of the quarter glass plate (4).

6. The self-excited Mx rubidium atomic magnetometer device according to claim 1, characterized in that: The electrical signal detected by the phototube (6) is amplified by the lock-in amplifier (8) and then phase-shifted by 90 degrees by the phase shifter (9).

7. A method of operating the self-excited Mx rubidium atomic magnetometer device according to any one of claims 1-6, characterized in that, Includes the following steps: Step S1: The VCSEL laser tube (1) generates a pump laser with a center wavelength of 795 nm. Step S2: After the pump laser is modulated in polarization direction by the electro-optic modulator (3), it becomes circularly polarized light after passing through a 1 / 4 glass plate (4). Step S3: The rubidium atoms in the rubidium atom gas chamber (5) of the pump laser complete the polarization process of the rubidium atoms. At this time, the phototube (6) detects the minimum value of the rubidium atom brightness signal in the rubidium atom gas chamber (5). Step S4: The electrical signal detected by the phototube (6) is amplified by the lock-in amplifier (8) and then phase-shifted by the phase shifter (9) by 90 degrees. Step S5: The phase shifter (9) outputs a signal to the EOM driver (10), and the EOM driver (10) drives the electro-optic modulator (3) to complete the polarization of the pump laser. Modulation of direction: When the modulation signal reaches the peak, the polarization direction of the pump laser is parallel to the fast axis of the 1 / 4 glass plate (4), and is linearly polarized, losing the polarization effect of the atoms; when the modulation signal reaches the trough, the polarization direction of the pump laser is at a 45-degree angle to the fast axis of the 1 / 4 glass plate (4), and becomes circularly polarized after passing through the 1 / 4 glass plate (4), possessing the maximum polarization effect; in step S6, the phase shifter (9) outputs a signal to the laser tube driver (11), and the laser tube driver (11) drives the VCSEL laser tube (1) to change the optical power of the VCSEL laser tube (1); in step S7, when the polarization state and optical power of the pump laser are simultaneously modulated, and the phase difference between the modulation phase and the signal of the photosensitive tube (6) is 90 degrees, the lock-in amplifier (8) outputs a Larmor frequency signal.

Images