An omnidirectional chip atomic magnetometer based on topological surface-emitting lasers

Abstract

The present invention discloses an omnidirectional chip atomic magnetometer based on a topological surface emitting laser, which is characterized by comprising a topological PCSEL, a focusing lens, a beam shaping unit, a combined quarter wave plate, an atomic gas chamber, a photodetector, a filter module, a laser frequency stabilization unit, a laser modulation unit, a direct current and a precession alternating current coupler. The present invention adopts a topological PCSEL to replace a traditional light source, and simultaneously utilizes a combined quarter wave plate to form a light beam into spatially independent circularly polarized light and linearly polarized light, and utilizes the characteristic that the quantum axes of the circularly polarized light and the linearly polarized light transmitted in the same direction are perpendicular to each other, and realizes a magnetic resonance omnidirectional optical pump atomic magnetometer by modulating the optical field parameters instead of the traditional alternating magnetic field, which has great practical significance for realizing high-sensitivity measurement of magnetic fields on an external field motion platform. The present invention can realize omnidirectional high-sensitivity measurement of magnetic fields by realizing the optical and magnetic double resonance effect.

Description

Technical Field

[0001] The invention belongs to the field of quantum magnetic detection, and in particular relates to an omnidirectional optically pumped atomic magnetometer based on a topological surface emitting laser. Background Art

[0002] The laser-pumped atomic magnetometer is based on the typical atomic Zeeman effect and combines optical and magnetic double resonance technology to achieve precise measurement of magnetic fields. Today, it has become an important tool for studying and utilizing physical processes related to magnetic fields. However, the current international magnetic sensors with excellent performance are generally complex systems, expensive, and have poor portability. These shortcomings limit their application in field environments. In order to overcome this limitation, people have successfully developed a small-sized, low-power chip-type atomic magnetometer, which is now widely used in hidden magnetic target detection, earthquake prediction, resource exploration, geological surveys, biomedicine and other fields.

[0003] The present invention adopts a photonic crystal surface emitting laser (PCSEL), which can keep the lasing mode unchanged under the continuous change of structure and material parameters by regulating topological evolution to construct a topological protection mechanism, thereby greatly improving the mode selectivity and stability of PCSEL, and realizing robust single-mode lasing under process errors and environmental disturbances. The topological body PCSEL with a size of only a few microns has good vertical emission directivity, narrow line width, and single-mode lasing characteristics, and has the characteristics of high power, surface emission and stable single-mode operation. It can realize full spectrum, large area, extremely low divergence angle, and high-power laser output. It is a new type of laser with great potential, which can be used to overcome the shortcomings of traditional semiconductor lasers such as large divergence angle, poor monochromaticity, and low brightness. It has important application prospects in the fields of atomic clocks, atomic magnetic sensors, quantum precision measurement, laser radar, space communications, sensing and laser processing.

[0004] The magnetic resonance effect of the magnetic moment vector and tensor model has a problem of magnetic measurement blind area. Studies have shown that the optical magnetic resonance amplitude is related to the angle between the polarization direction of the light field and the direction of the external magnetic field. When the photon axis and the external magnetic field form a specific angle, the amplitude of the magnetic resonance signal will be very small, and the magnetometer system will completely lose its magnetic measurement capability, commonly known as the dead zone. The polarization plane rotation magnetic sensor based on the magnetic moment tensor resonance model increases the complexity of the system and reduces the magnetic measurement bandwidth. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide an omnidirectional chip atomic magnetometer based on topological surface emitting lasers. The present invention solves the inherent shortcomings of vertical cavity surface emitting lasers (VCSEL) and distributed feedback lasers (DFB) commonly used in traditional chip-type optically pumped atomic magnetometers, and the problem of dead zones in magnetic measurement by conventional atomic magnetometers.

[0006] The present invention adopts a topological surface emitting laser (i.e., a topological PCSEL, refer to the patent document of publication number CN113805462A) to replace the traditional light source, which has a diameter of only a few microns, has good vertical emission directivity, narrow line width, high power, surface emission, and single-mode lasing characteristics, and can achieve full spectrum, large area, extremely low divergence angle, and high-power laser output. At the same time, the present invention proposes to use a combined quarter-wave plate to make the light beam form spatially independent circularly polarized light and linearly polarized light, and use the characteristics that the quantum axes of the circularly polarized light and the linearly polarized light transmitted in the same direction are perpendicular to each other, and realize the magnetic resonance omnidirectional optical pump atomic magnetometer by modulating the optical field parameters instead of the traditional alternating magnetic field, which has great practical significance for realizing high-sensitivity measurement of magnetic fields on an external field motion platform. The present invention generates a spatially independent circularly polarized light and linearly polarized light synthetic light beam by combining a quarter-wave plate, and the synthetic light beam passes through the atomic magnetic sensing gas chamber, and at least ensures that the angle between the intrinsic quantum axis direction of a part of the light and the direction of the external magnetic field meets the measurement magnetic field requirement. When the laser parameter modulation frequency is equal to the Larmor frequency, the optical and magnetic double resonance effect can be achieved, thereby completing the omnidirectional and high-sensitivity measurement of the magnetic field.

[0007] The technical solution of this program is as follows:

[0008] The invention discloses an omnidirectional chip atomic magnetometer based on a topological surface emitting laser, characterized in that it comprises: a topological PCSEL 1, a beam shaping unit (including a focusing lens 2 and a collimating lens 3), a polarizer 4, a combined quarter wave plate 5 (synthesized by two quarter wave plates with an optical axis angle of 45°), an atomic gas chamber 6, a photodetector 7, a photocurrent amplifier 8, a topological PCSEL heat preservation and temperature control device 9, an atomic gas chamber heat preservation and temperature control device 10, a filter module 11, a laser frequency stabilization unit (including a DC signal modulation and demodulation module 12, a DC signal servo feedback module 13, and a voltage-controlled voltage source 14), a laser modulation unit (including a precession signal demodulation module 15, a precession servo feedback module 16, a direct digital frequency synthesis module 17, and a high-stability crystal oscillator 18), and a DC current and precession AC current coupler 19.

[0009] The topological body PCSEL1 acts as a light source, and under the drive of the DC current and the precession AC current coupler 19, emits laser light that can be used to excite atomic transitions in the atomic gas chamber 6;

[0010] The focusing lens 2 and the collimating lens 3 are used to collimate and shape the light emitted by the topological body PCSEL1 into parallel light and incident on the polarizer 4;

[0011] The polarizer 4 is used to change the polarization state of the incident laser into linear polarized light incident on the combined quarter wave plate 5;

[0012] The combined quarter wave plate 5 is used to generate a spatially separated circular polarized light and linear polarized light composite light beam for the incident linear polarized light, which is incident on the atomic gas chamber 6;

[0013] The atomic gas chamber 6 is filled with high-purity sensing atoms (such as cesium, rubidium, potassium, sodium, helium, etc.), which are used to generate magnetic resonance after being excited by the incident light beam, sense the magnetic field to be measured, and output a light signal containing the sensed magnetic field to be measured; at the same time, the gas chamber needs to be treated with anti-relaxation (such as filling with appropriate buffer gas, or coating the inner surface of the gas chamber with high molecular materials such as paraffin wax);

[0014] The photoelectric detector 7 converts the optical signal output by the atomic gas chamber 6 and the sensed magnetic field to be measured into an electrical signal;

[0015] The photocurrent amplifier 8 appropriately amplifies the photocurrent output by the photodetector 7;

[0016] The topological PCSEL heat preservation and temperature control device 9 and the atomic gas chamber heat preservation and temperature control device 10 are used to insulate and control the working environment of the topological PCSEL and the atomic gas chamber, making their operation more stable and reducing the influence of external temperature fluctuations on the chip magnetometer;

[0017] The filter module 11 separates the DC signal and the high-frequency signal detected by the photodetector 7;

[0018] The DC signal modulation and demodulation module 12 modulates and demodulates the DC signal output from the filter module 11;

[0019] The DC signal servo feedback module 13 appropriately amplifies and filters the signal demodulated and output by the DC signal modulation and demodulation module 12 and then feeds it back to the voltage-controlled voltage source 14;

[0020] The precession signal demodulation module 15 demodulates the high frequency signal output from the filter module 11;

[0021] The precession servo feedback module 16 appropriately amplifies and filters the precession demodulated signal to control the direct digital frequency synthesis module 17;

[0022] The direct digital frequency synthesis module 17 outputs an AC signal, and the laser is modulated through a DC current and a precession AC current coupler 19. The frequency of the AC signal corresponds to the Larmor precession frequency of the atom in the magnetic field to be measured, and the magnetic field size of the magnetic field to be measured is measured through the Larmor precession frequency.

[0023] The highly stable crystal oscillator 18 provides a standard frequency reference for the direct digital frequency synthesis module 17;

[0024] The DC current and precession AC current coupler 19 couples the laser frequency stabilization control signal generated by the voltage-controlled voltage source 14 and the AC signal generated by the direct digital frequency synthesis module 17, and feeds back to the topological PCSEL for laser frequency stabilization and fast modulation.

[0025] The specific adjustment method of the omnidirectional chip atomic magnetometer based on the topological surface emitting laser of the present invention is:

[0026] The topological state PCSEL1 generates a frequency-stabilized laser and modulates laser parameters (such as amplitude and frequency) through the drive of a DC current and a precession AC current coupler 19, and emits a light beam for exciting atomic transitions in the gas chamber 6. The light emitted by the topological state PCSEL1 is collimated and shaped into parallel light by a focusing lens 2 and a collimating lens 3, and the polarization state of the laser is changed into linearly polarized light by a polarizer 4; then, a spatially separated circular and linearly polarized light composite beam is generated by combining a quarter-wave plate 5, and is incident on the atomic gas chamber 6. The circularly polarized component and the linearly polarized component in the composite beam have mutually perpendicular intrinsic quantum axes, so no matter how the direction of the external magnetic field to be measured changes, at least one beam of light has an angle between the polarization direction and the external magnetic field direction that meets the magnetic measurement requirements, there is no detection blind spot, and omnidirectional measurement is achieved. The transmitted output light beam of the atomic gas chamber 6 is incident on the photodetector 7 for photoelectric conversion, and the output photocurrent is appropriately amplified by the photocurrent amplifier 8; the DC signal and high-frequency signal in the photocurrent are separated by the filter module 11, wherein the DC component is used to control the laser frequency, and the high-frequency component is used to measure the magnetic field size.

[0027] The DC signal modulation and demodulation module 12 modulates and demodulates the DC signal, and controls the DC signal servo feedback module 13, which is finally fed back to the voltage-controlled voltage source 14, and the laser frequency of the PCSEL is stabilized through the DC current and the precession AC current coupler 19.

[0028] The precession signal demodulation module 15 demodulates the AC signal and controls the precession servo feedback module 16, which is fed back to the direct digital frequency synthesis module 17, and the laser is modulated through the DC current and the precession AC current coupler 19. The AC signal frequency corresponds to the Larmor precession frequency of the atom in the magnetic field to be measured, and the magnitude of the magnetic field is measured through the Larmor precession frequency.

[0029] The high stability crystal oscillator 18 provides a frequency reference for the direct digital frequency synthesis module 17. The temperature insulation and control device 9 and the atomic gas chamber temperature insulation and control device 10 insulate and control the working environment of the PCSEL and the atomic gas chamber 6 to make their operation more stable and reduce the influence of external temperature fluctuations on the chip magnetometer.

[0030] The present invention has the following beneficial effects:

[0031] The present invention provides an omnidirectional chip atomic magnetometer based on a topological surface emitting laser, which uses a topological surface emitting laser to replace a traditional light source, and has excellent characteristics such as small size, vertical emission, narrow line width, high power, surface emission, and single-mode lasing. It can achieve full spectrum, large area, extremely low divergence angle, and high-power laser output, and has important application prospects in the field of chip atomic magnetometers. At the same time, the invented atomic magnetometer does not have the detection blind spot of a traditional optical pump magnetometer. In a moving platform, no matter how the direction of the magnetic sensor changes relative to the direction of the external magnetic field, it can measure the magnetic field. The system only uses a combined quarter-wave plate to achieve omnidirectional magnetic field measurement, which reduces the complexity of the system and is suitable for scenarios where the direction of the magnetic field to be measured is constantly changing. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a system schematic diagram of the omnidirectional chip atomic magnetometer based on topological surface emitting laser of the present invention.

[0033] Figure 2 The schematic diagram of the synthetic wave plate of the present invention is formed by combining two quarter wave plates with an optical axis angle of 45°.

[0034] Figure numerals: 1-topological PCSEL, 2-focusing lens, 3-collimating lens, 4-polarizer, 5-synthetic quarter wave plate, 6-atomic gas chamber, 7-photodetector, 8-photocurrent amplifier, 9-topological PCSEL thermal insulation and temperature control device, 10-atomic gas chamber thermal insulation and temperature control device, 11-filter module, 12-DC signal modulation and demodulation module, 13-DC signal servo feedback module, 14-voltage-controlled voltage source, 15-precession signal demodulation module, 16-precession servo feedback module, 17-direct digital frequency synthesis module, 18-high stability crystal oscillator, 19-DC current and precession AC current coupler. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention but not to limit the scope of the present invention.

[0036] like Figure 1 As shown, the schematic diagram of the omnidirectional chip atomic magnetometer based on the topological surface emitting laser of the present invention includes: a topological PCSEL 1, a focusing lens 2, a collimating lens 3, a polarizer 4, a synthetic quarter-wave plate 5 (synthesized by a quarter-wave plate with an angle of 45° between two optical axes), an atomic gas chamber 6, a photodetector 7, a photocurrent amplifier 8, a topological PCSEL thermal insulation and temperature control device 9, an atomic gas chamber thermal insulation and temperature control device 10, a filter module 11, a DC signal modulation and demodulation module 12, a DC signal servo feedback module 13, a voltage-controlled voltage source 14, a precession signal demodulation module 15, a precession servo feedback module 16, a direct digital frequency synthesis module 17, a high-stability crystal oscillator 18, and a DC current and precession AC current coupler 19.

[0037] The assembly relationship between the various components is as follows: the atomic gas chamber 6 is placed in the magnetic field to be measured, and the topological body PCSEL1 emits a laser that resonates with the atomic transition, which passes through the focusing lens 2, the collimating lens 3, the polarizer 4, the synthetic quarter-wave plate 5, the atomic gas chamber 6, the photodetector 7, and the photocurrent amplifier 8 in sequence, and the DC component and the high-frequency component in the photocurrent are separated through the filter module 11, wherein the DC component passes through the DC signal modulation and demodulation module 12, the DC signal servo feedback module 13, and the voltage-controlled voltage source 14 in sequence, and is input into the DC current and precession AC current coupler 19; wherein the high-frequency component passes through the precession signal demodulation module 15, the precession servo feedback module 16, and the direct digital frequency synthesis module 17 in sequence, and is input into the DC current and precession AC current coupler 19; and finally the topological body PCSEL 1 is controlled.

[0038] The high stability crystal oscillator 18 provides a frequency reference for the direct digital frequency synthesis module 17. The temperature insulation and control device 9 and the atomic gas chamber temperature insulation and control device 10 insulate and control the working environment of the PCSEL and the atomic gas chamber 6 to make their operation more stable and reduce the influence of external temperature fluctuations on the chip magnetometer.

[0039] The working process and principle are as follows:

[0040] The topological PCSEL 1 emits a modulated light beam for exciting atomic transitions in the gas chamber, which is collimated and shaped into parallel light by lens 2 and collimating lens 3, and becomes linearly polarized light by polarizer 4; then a spatially separated circular and linear polarized light composite beam is generated by combining quarter wave plate 5, and incident on atomic gas chamber 6. The circular polarization component and the linear polarization component in the composite beam have mutually perpendicular intrinsic quantum axes, so no matter how the direction of the external magnetic field to be measured changes, at least one beam of light has an angle with the direction of the external magnetic field that meets the magnetic measurement requirements, there is no detection blind spot, and omnidirectional measurement is achieved. The transmitted light beam of the gas chamber is incident on the photodetector 7 for photoelectric conversion, and the output photocurrent is appropriately amplified by the photocurrent amplifier 8; the DC component and the high-frequency component in the photocurrent are separated by the filter module 11. The DC signal modulation and demodulation module 12 modulates and demodulates the DC component, and controls the voltage-controlled voltage source 14 through the DC signal servo feedback module 13, and finally controls the PCSEL frequency through the DC current and the precession AC current coupler 19. The precession signal demodulation module 15 demodulates the high frequency component and controls the direct digital frequency synthesis module 17 through the precession servo feedback module 16, and finally realizes the modulation of the laser through the DC current and the precession AC current coupler 19. At the same time, the direct digital frequency synthesis module 17 converts the result of frequency synthesis into a magnetic field and outputs it externally.

[0041] Although the specific embodiments of the present invention are disclosed for the purpose of illustration, the purpose is to help understand the content of the present invention and implement it accordingly, those skilled in the art will understand that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the best embodiment, and the scope of the present invention is subject to the scope defined in the claims.

Claims

1. An omnidirectional chip atomic magnetometer based on topological surface emitting laser, characterized in that: It includes a topological PCSEL (1), a beam shaping unit, a polarizer (4), a combined quarter wave plate (5), an atomic gas chamber (6), a photodetector (7), a filter module (11), a laser frequency stabilization unit, a laser modulation unit, a direct current and a precession alternating current coupler (19); The topological PCSEL (1) is used to emit laser light for exciting atomic transition in the atomic gas chamber (6) under the drive of a direct current and a precession alternating current coupler (19); The laser light output by the topological PCSEL (1) is shaped into parallel light by the beam shaping unit and is incident on the polarizer (4); The polarizer (4) is used to change the polarization state of the incident laser light into linear polarized light incident on the combined quarter-wave plate (5); The combined quarter wave plate (5) is used to convert incident linearly polarized light into a composite light beam containing spatially separated circularly polarized light and linearly polarized light, which is incident on the atomic gas chamber (6); wherein the combined quarter wave plate (5) is composed of two quarter wave plates, and the angle between the optical axes of the two quarter wave plates is 45°; The atomic gas chamber (6) is filled with sensing atoms, which are used to generate magnetic resonance after being excited by the incident light beam, and generate a light signal containing the sensed magnetic field to be measured; The photoelectric detector (7) is used to receive the optical signal output by the atomic gas chamber (6) and convert it into an electrical signal; The filter module (11) is used to filter the electrical signal to obtain a direct current signal and a high-frequency signal in the electrical signal; The laser frequency stabilization unit is used to generate a laser frequency stabilization control signal according to the DC signal output by the filter module (11) and send it to the DC current and precession AC current coupler (19); The laser modulation unit is used to generate an AC signal according to the high-frequency signal output by the filter module (11) and send it to the DC current and precession AC current coupler (19); the frequency of the AC signal corresponds to the Larmor precession frequency of the sensing atom in the magnetic field to be measured; and output the AC signal to measure the magnetic field size of the magnetic field to be measured; The DC current and precession AC current coupler (19) is used to couple the laser frequency stabilization control signal and the AC signal and feed them back to the topological PCSEL (1), so as to perform laser frequency stabilization and modulation on the topological PCSEL (1).

2. The omnidirectional chip atomic magnetometer according to claim 1, characterized in that: The beam shaping unit comprises a focusing lens (2) and a collimating lens (3) which are arranged in sequence along the incident direction of the beam.

3. The omnidirectional chip atomic magnetometer according to claim 1 or 2, characterized in that: The electrical signal is amplified by a photocurrent amplifier (8) and then incident on the filter module (11).

4. The omnidirectional chip atomic magnetometer according to claim 1 or 2, characterized in that: The laser frequency stabilization unit comprises a DC signal modulation and demodulation module (12), a DC signal servo feedback module (13), and a voltage-controlled voltage source (14); the DC signal modulation and demodulation module (12) modulates and demodulates the DC signal output by the filter module (11); the DC signal servo feedback module (13) is used to amplify and filter the signal output by the DC signal modulation and demodulation module (12), and then feed it back to the voltage-controlled voltage source (14) to generate the laser frequency stabilization control signal.

5. The omnidirectional chip atomic magnetometer according to claim 1 or 2, characterized in that: The laser modulation unit comprises a precession signal demodulation module (15), a precession servo feedback module (16), a direct digital frequency synthesis module (17), and a high-stability crystal oscillator (18); the precession signal demodulation module (15) is used to demodulate the high-frequency signal output by the filter module (11); the precession servo feedback module (16) is used to amplify and filter the signal output by the precession signal demodulation module (15), and then send it to the direct digital frequency synthesis module (17) to generate the AC signal; and the high-stability crystal oscillator (18) is used to provide a standard frequency reference for the direct digital frequency synthesis module (17).

6. The omnidirectional chip atomic magnetometer according to claim 1, characterized in that: It also comprises a topological PCSEL heat preservation and temperature control device (9) for heat preservation and temperature control of the working environment of the topological PCSEL (1).

7. The omnidirectional chip atomic magnetometer according to claim 1, characterized in that: It also comprises an atomic gas chamber temperature insulation and temperature control device (10) for insulating and controlling the temperature of the working environment of the atomic gas chamber (6).

8. The omnidirectional chip atomic magnetometer according to claim 1, characterized in that: The sensing atom is cesium, rubidium, potassium, sodium or helium.

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