An integrated quantum diamond magnetometer

Abstract

The application discloses integrated quantum diamond magnetometer, belongs to quantum magnetic sensing technical field, including by laser, optical fiber beam splitter, optical fiber probe, diamond particle, filter system, optical detector, microwave source, isolator, microwave antenna, phase-locked control system and scanning module composition;Adopt high numerical aperture optical fiber and diamond color center optical coupling, improve the transmission efficiency of excitation light and fluorescence;The microwave structure is integrated in the optical fiber probe, realizes the all-fiber integration of the light and microwave system integration;The optical fiber probe is filled with high transmission solidified material between the diamond, avoids the color center damage;The scanning module composed of the non-magnetic object table and the displacement table can realize the relative displacement of the probe and the sample, complete the three-dimensional scanning imaging of the strong gradient magnetic field. The integrated quantum diamond magnetometer provided by the application solves the problems of low integration degree of traditional equipment, light path drift and inability to realize gradient field scanning, and is convenient for equipment landing and popularization.

Description

Technical Field

[0001] This invention relates to the field of quantum magnetic sensing technology, and in particular to an integrated quantum diamond magnetometer. Background Technology

[0002] Magnetic field detection schemes based on diamond color centers have seen significant development in the field of quantum measurement in recent years due to their small sensing unit size, high detection accuracy, and stable physicochemical properties. They represent one of the most promising research directions for miniaturized, high-precision magnetic field sensing. However, existing diamond color center-based magnetic field detection systems all employ spatial optical detection technology, resulting in large device footprints and high stability requirements. Submicron-level optical path drift can lead to the loss of fluorescence signals from individual color centers or the masking of effective magnetic detection signals from ensemble color centers. Fiber optic transmission, compared to spatial optical transmission, offers higher stability and is easier to integrate, making it a promising candidate for the development of diamond color center magnetic field sensors.

[0003] There are currently two main methods for combining diamond NV centers with optical fibers: (1) mixing diamond particles containing NV centers into fused optical fibers, but the melting point of silica optical fibers is about 1750℃, and NV centers are easily destroyed at this temperature; (2) directly adhering diamond blocks to the end face of optical fibers, but the numerical aperture of ordinary optical fibers is limited, the efficiency of light excitation and fluorescence collection is not high, and the color centers in the block ensemble are discretely distributed, with a spatial resolution of more than 100 micrometers, and the magnetic signal is easily submerged in strong gradient field measurements.

[0004] Existing patent literature also has the aforementioned limitations. Chinese patent CN117890837A, "A Fiber Optic Quantum Magnetic Field Sensor and Its Fabrication Method," discloses a fiber optic quantum magnetic field sensor that integrates microwave transmission and optical path by placing a conductive antenna within the fiber cladding. However, this scheme embeds the microwave antenna inside the cladding, posing a risk of electro-optic crosstalk, and the fabrication process is complex. Chinese patent CN119199663A, "A System for Measuring Planar Vector Magnetic Fields," discloses a system for measuring planar vector magnetic fields. It achieves high isolation of the two-axis magnetic components by optimizing the orientation of the diamond NV color center crystal axis. However, this system uses a combination of spatial optical path and fiber coupling, resulting in limited integration.

[0005] In addition, existing fiber optic diamond magnetometers often only achieve fiber optic integration at the fiber head, with microwave control and optical systems separated, resulting in insufficient system integration and making it difficult to meet the needs of high-resolution magnetic field scanning applications. Summary of the Invention

[0006] The purpose of this invention is to provide an integrated quantum diamond magnetometer that solves the problems of low integration, low optical signal coupling efficiency, and difficulty in achieving spatial scanning imaging of strong gradient magnetic fields in existing diamond color center magnetic field detection devices.

[0007] To achieve the above objectives, the present invention provides an integrated quantum diamond magnetometer, including a magnetic field measurement module and a scanning module; The magnetic field measurement module consists of a laser, an optical fiber beam splitter, an optical fiber probe, diamond particles, a filtering system, a photodetector, a microwave source, an isolator, a microwave antenna, and a phase-locked loop control system. The fiber optic probe is a high numerical aperture fiber, and the diamond particles are located on the end face of the fiber optic probe, at the very front of the entire device. The microwave antenna is wound or plated onto the outer wall of the fiber optic probe; The laser emits an optical signal for exciting the spin defects in diamond. The optical signal passes through the transmission optical fiber, then through the optical fiber beam splitter and the optical fiber probe, and excites the color centers in the diamond particle to produce fluorescence. After the fluorescence is collected by the fiber optic probe, it returns along the same path and is separated from the incident light path by the fiber optic beam splitter. After entering the filtering system to filter out the light source and ambient interference light, it is collected by the photodetector. The microwave signal generated by the microwave source is transmitted to the microwave antenna through the isolator and then radiated to the diamond particle through the microwave antenna. By using microwave scanning resonance, the intensity change of diamond fluorescence is detected, the energy level change of the spin ground state is obtained, and then the magnetic field strength at the location of the diamond color center can be obtained. The phase-locked loop control system is connected to the photodetector and the microwave source respectively. On the one hand, it receives the feedback electrical signal from the photodetector, and on the other hand, it outputs a modulation control signal to the microwave source to modulate the output signal of the microwave antenna. The phase-locked loop control system is also used to output magnetic field-related electrical signals for magnetic field signal analysis. The scanning module is located directly below the fiber optic probe and the diamond particles, and consists of a non-magnetically isolated stage, a displacement stage, and the sample to be tested. The non-magnetic isolation stage is located at the bottom of the scanning module; the displacement stage is fixedly installed on the upper surface of the non-magnetic isolation stage, and the sample to be tested is placed in the center of the upper surface of the displacement stage, directly below the diamond particles.

[0008] The displacement stage enables the fiber optic probe and diamond particles to move in three dimensions relative to the sample under test. At each step position, the magnetic field at the fixed position is measured using microwave scanning resonance, ultimately achieving multi-dimensional scanning imaging of the strong gradient magnetic field in the sample under test.

[0009] Preferably, the color center in the diamond particle is a single color center.

[0010] Preferably, the diamond particles are micro-nano sized particles.

[0011] Preferably, the wavelength of the light emitted by the laser is related to the type of color center defect.

[0012] Preferably, a curing material with high transmittance to excitation light and fluorescence from the color center is filled between the fiber optic probe and the diamond particles to ensure alignment between the color center and the focal point of the focusing fiber, thereby satisfying the scanning and detection function of a strong gradient field. The high transmittance curing material can be highly transparent silicone, silica, or UV adhesive.

[0013] Preferably, the diamond color center is an NV color center, a Si-V color center, or a solid spin color center in silicon carbide that has magnetic field sensitive properties.

[0014] Preferably, the fiber optic probe is any one of high numerical aperture photonic crystal fiber, superlens fiber, or microlens fiber.

[0015] Therefore, the present invention employs the above-mentioned integrated quantum diamond magnetometer, which has the following beneficial effects: (1) The present invention uses high numerical aperture optical fiber to optically couple with diamond color center, which effectively improves the excitation efficiency of excitation light and the collection efficiency of fluorescence signal, and gives full play to the high sensitivity magnetic field detection advantage of diamond color center. (2) The entire optical path is designed with full fiber optics, and the microwave antenna is integrated into the fiber optic probe to realize the integrated arrangement of the optical system and the microwave control system. The overall equipment is miniaturized and more portable. (3) The microwave radiation system in this invention is directly wound or plated on the fiber optic probe, which reduces the instability caused by the separate application of the optical manipulation system and the radio frequency operating system. At the same time, the single-end sensor facilitates scanning applications. (4) Achieve strong gradient magnetic field scanning imaging: The addition of a gradient scanning module composed of a non-magnetic isolation stage and a three-dimensional displacement stage enables high-precision relative movement between the probe and the sample to be tested, and completes strong gradient magnetic field three-dimensional scanning imaging of objects such as quadrupole magnetic traps and geomagnetic samples, thus expanding the application range of the device. (5) This invention can achieve low-cost, high-sensitivity, and integrated magnetic field measurement, which is conducive to the application of diamond magnetometer.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the diamond NV color center structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the energy levels of the ground-state electron spin in an embodiment of the present invention; Figure 3 This is a schematic diagram of the magnetic field measurement module structure according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the superlens fiber optic structure according to an embodiment of the present invention; Figure 5This is a schematic diagram of the photonic crystal fiber structure according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the scanning module structure according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure and magnetic field strength of a quadrupole magnetic trap according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the magnetic field gradient distribution at the center of the quadrupole magnetic trap according to an embodiment of the present invention.

[0018] Figure label: 1. Laser; 2. Fiber beam splitter; 3. Fiber optic probe; 4. Diamond particles; 5. Filtering system; 6. Photodetector; 7. Microwave source; 8. Isolator; 9. Microwave antenna; 10. Phase-locked control system; 11. Non-magnetic isolation stage; 12. Displacement stage; 13. Sample to be tested. Detailed Implementation

[0019] The following detailed description of embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0020] This invention uses diamond NV color centers as the detection core, combined with a magnetic field measurement module and a scanning module, to complete single-point detection of magnetic fields and three-dimensional scanning imaging of strong gradient magnetic fields.

[0021] Example 1 like Figure 1 As shown, a diamond NV color center is formed by the pairing of an N substitution atom and a C vacancy to form an NV defect center.

[0022] like Figure 2 As shown, the three energy levels of the ground state spin of the diamond NV color center. In The fluorescence intensity of the NV color center in the excited state is higher than that in the state. The NV center is a state of flux, therefore its spin state can be detected by fluorescence intensity. The spin state of the NV center is initialized to a state of flux under the influence of excitation light. state, in The NV color centers of the state can be modulated to low fluorescence intensity by resonant microwaves. state.

[0023] like Figure 3As shown, the magnetic field measurement module of the integrated quantum diamond magnetometer of the present invention consists of a laser 1, an optical fiber beam splitter 2, an optical fiber probe 3, a diamond particle 4, a filtering system 5, a photodetector 6, a microwave source 7, an isolator 8, a microwave antenna 9, and a phase-locked control system 10. The fiber optic probe 3 can be made of high numerical aperture photonic crystal fiber, superlens fiber, or microlens fiber. For example... Figure 4 As shown, superlens fibers generally consist of ordinary optical fibers, extended optical fibers, and superlenses; photonic crystal fibers are another method for increasing numerical aperture, and their structure is as follows. Figure 5 As shown, microlens optical fibers are generally composed of ordinary optical fibers, extended optical fibers, and microlenses. Microlenses are generally fabricated on the end face of the optical fiber using micro-nano fabrication processes.

[0024] A laser 1 adapted to the NV color center is selected, with the output wavelength controlled between 480 and 550 nm. The excitation light emitted from the laser 1 is guided through the transmission fiber to the fiber optic beam splitter 2, and then transmitted by the fiber optic beam splitter 2 to the front-end fiber optic probe 3. The excitation light passes through the highly transparent solidified material on the probe end face and irradiates the micro-nano-sized diamond particles 4, completing the spin state initialization of the NV color center.

[0025] Diamond particle 4 generates fluorescence upon stimulation. Based on the reversibility of the optical path, the fluorescence is efficiently collected by the high numerical aperture fiber optic probe 3 and returned to the fiber optic beam splitter 2 along the original optical path. The fiber optic beam splitter 2 separates the fluorescence from the incident excitation light. The fluorescence signal is sent to the filtering system 5 to filter out stray light and light source interference, and then collected by the photodetector 6. Microwave source 7 generates microwave signals, which are then transmitted to microwave antenna 9, which is wound / plated on the outer wall of fiber optic probe 3, after passing through isolator 8. Microwave antenna 9 applies resonant microwaves to the NV color center inside diamond particle 4.

[0026] The phase-locked control system 10 receives the electrical signal output from the photodetector 6 on one hand, and outputs a modulation signal to the microwave source 7 on the other hand, forming a closed-loop control. By combining microwave scanning resonance with phase-locked amplification technology, the fluorescence intensity change is monitored, the spin ground state energy level shift of the NV color center is analyzed, and finally the magnetic field strength at the location of the diamond particle 4 is obtained.

[0027] Furthermore, lock-in amplification technology is used to monitor changes in the magnetic field, avoiding the time loss caused by the generally used large-range scanning resonant microwave signal, and leveraging the system's sensing sensitivity advantage for rapid analytical measurement of the magnetic field.

[0028] However, it should be noted that for a specific phase-locked control source, the sensitivity range of the diamond magnetometer is limited to the magnetic resonance bandwidth. In order to make full use of the advantages of the diamond quantum sensor in magnetic field measurement range, it is necessary to perform a wide-range magnetic field measurement calibration on the diamond magnetometer. Then, during the measurement process, the magnetic field tracking measurement can be achieved by adjusting the phase-locked center frequency in time, so as to take advantage of the wide-range magnetic field measurement while maintaining high sensitivity.

[0029] Example 2 Based on Specific Embodiment 1, taking a quadrupole magnetic trap as an example, the cross-sectional magnetic field structure of a typical quadrupole magnetic trap is as follows: Figure 7 As shown, the magnetic field strength at the tip of the magnetic pole reaches 3.6. The gradient at the center of the magnetic trap is approximately The distance between magnetic poles is on the order of millimeters, much smaller than the size of a typical magnetic detector, making it difficult for conventional magnetic field detectors to be compatible. Figure 8 The diagram shows the correspondence between the magnetic field at the center of the quadrupole magnetic trap (shown by the dashed line) and its position. Here, we use a fiber optic diamond scanning device designed for strong gradient magnetic fields, based on an integrated quantum diamond magnetometer proposed in this invention, to scan and detect high gradient magnetic fields in the magnetic trap.

[0030] Based on the magnetic field measurement module of the quantum diamond magnetometer, add scan-related functions. For example... Figure 6 As shown, this is a schematic diagram of the gradient scanning module of a quantum diamond magnetometer. Figure 3 Based on the integrated quantum diamond magnetometer magnetic field measurement module, a non-magnetic isolation stage 11, a displacement stage 12, and a sample 13 to be tested are added. The displacement stage 12 is used for the three-dimensional movement of the sample 13 to perform magnetic field scanning imaging. Here, the displacement stage 12 can also be directly connected to the fiber optic probe 3, and three-dimensional scanning can be achieved by moving the fiber optic probe.

[0031] The displacement stage 12 is used to realize the three-dimensional movement of the fiber optic probe 3 and diamond particles 4 relative to the quadrupole magnetic trap of the test sample 13. At each step position, the magnetic field at the fixed position is measured by microwave scanning resonance, and finally the multi-dimensional scanning imaging of the strong gradient magnetic field in the quadrupole magnetic trap is realized.

[0032] The scanning method used here is the same phase-locked tracking measurement method as in Example 1.

[0033] Therefore, the present invention adopts the above-mentioned integrated quantum diamond magnetometer, which effectively improves optical coupling efficiency and system integration, and can realize high-precision detection and three-dimensional scanning imaging of strong gradient magnetic fields. The equipment has low cost, high stability, and is easy to implement in engineering and promote application.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An integrated quantum diamond magnetometer, characterized in that, Includes a magnetic field measurement module and a scanning module; The magnetic field measurement module consists of a laser, an optical fiber beam splitter, an optical fiber probe, diamond particles, a filtering system, a photodetector, a microwave source, an isolator, a microwave antenna, and a phase-locked loop control system. The fiber optic probe is a high numerical aperture fiber, and the diamond particles are located on the end face of the fiber optic probe, at the very front of the entire device. The microwave antenna is wound or plated onto the outer wall of the fiber optic probe; The laser emits an optical signal for exciting the spin defects in diamond. The optical signal passes through the transmission optical fiber, then through the optical fiber beam splitter and the optical fiber probe, and excites the color centers in the diamond particle to produce fluorescence. After the fluorescence is collected by the fiber optic probe, it returns along the same path and is separated from the incident light path by the fiber optic beam splitter. After entering the filtering system to filter out the light source and ambient interference light, it is collected by the photodetector. The microwave signal generated by the microwave source is transmitted to the microwave antenna through the isolator and then radiated to the diamond particles through the microwave antenna. The phase-locked control system is connected to the photodetector and the microwave source respectively. On the one hand, it receives the feedback electrical signal from the photodetector, and on the other hand, it outputs a modulation control signal to the microwave source to modulate the output signal of the microwave antenna. The scanning module is located directly below the fiber optic probe and the diamond particles, and consists of a non-magnetically isolated stage, a displacement stage, and the sample to be tested. The non-magnetic isolation stage is located at the bottom of the scanning module; the displacement stage is fixedly installed on the upper surface of the non-magnetic isolation stage, and the sample to be tested is placed in the center of the upper surface of the displacement stage, directly below the diamond particles.

2. The integrated quantum diamond magnetometer according to claim 1, characterized in that, The color centers in a diamond particle are monochromatic.

3. The integrated quantum diamond magnetometer according to claim 1, characterized in that, Diamond particles are micro-nano sized particles.

4. The integrated quantum diamond magnetometer according to claim 1, characterized in that, The wavelength of the light emitted by the laser is related to the type of color center defect.

5. An integrated quantum diamond magnetometer according to claim 1, characterized in that, The space between the fiber optic probe and the diamond particles is filled with a curing material that has high transmittance for excitation light and fluorescence from color centers.

6. The integrated quantum diamond magnetometer according to claim 1, characterized in that, Diamond color centers are NV color centers, Si-V color centers, or solid-state spin color centers in silicon carbide that possess magnetic field-sensitive properties.

7. An integrated quantum diamond magnetometer according to claim 1, characterized in that, The fiber optic probe can be any one of high numerical aperture photonic crystal fiber, superlens fiber, or microlens fiber.

8. An integrated quantum diamond magnetometer according to claim 1, characterized in that, During the measurement process, the phase-locked control system adjusts the center frequency of the phase-locked system to achieve magnetic field tracking measurement, while maintaining high sensitivity and leveraging the advantages of a wide magnetic field range.

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