A magnetic field sensor with fiber-optic integrated diamond NV color centers

Abstract

This invention belongs to the field of fiber optic sensor technology and discloses a fiber-optic integrated diamond NV color center magnetic field sensor, comprising a laser light source, a magnetic field fiber optic sensing mechanism, a bias permanent magnet, a microwave waveguide mechanism, a first data processing mechanism, and a second data processing mechanism. The laser light source is connected to one side of the magnetic field fiber optic sensing mechanism through a first pigtail and a circulator, exciting the magnetic field fiber optic sensing mechanism to emit fluorescence. The circulator is connected to the first data processing mechanism, and the other side of the magnetic field fiber optic sensing mechanism is connected to the second data processing mechanism. The fluorescence enters the first data processing mechanism and the second data processing mechanism in a coupled manner.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensor technology, and in particular to a magnetic field sensor with an integrated diamond NV color center in an optical fiber. Background Technology

[0002] Magnetism is one of the earliest physical phenomena recognized by humankind. Thousands of years ago, the ancient Chinese used natural lodestone to create the compass, realizing the basic application of magnetic fields and thus promoting the development of geography and maritime trade. Historically, the exploration of magnetic field applications has greatly promoted the progress of human civilization. Today, applications related to magnetic fields make significant contributions to ensuring the normal functioning of our production and lives, with important applications in fields such as biomedicine, geographic surveying, and driving navigation. Therefore, magnetic field measurement has broad application prospects, and magnetic field measurement technology continues to develop with the advancement of science and technology. Optically detected magnetic resonance (ODMR) technology is a new method for measuring magnetic fields. Its principle involves simultaneously using laser pumping and microwave frequency sweeping to spin-modulate the NV color center, while measuring the ODMR spectrum of the fluorescence intensity emitted by the NV color center as the microwave frequency changes. A dip in fluorescence intensity will appear on the spectrum because the microwave frequency satisfies the energy level difference between different spin states of the NV color center. In the absence of an external magnetic field, there is only one depression. However, in the presence of an external magnetic field, the degenerate energy levels will split due to the Zeeman effect, causing the number of depressions to increase from one to two. The magnitude of the magnetic field can be obtained by solving the Hamiltonian equation based on the difference in microwave frequencies between the two depressions. Compared with traditional magnetic field measurement methods, this method can improve the sensitivity of measuring the magnitude of the magnetic field by two orders of magnitude.

[0003] Existing magnetic field sensors have low sensitivity and cannot meet the needs of related technical detection. Summary of the Invention

[0004] The purpose of this invention is to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides a magnetic field sensor with an integrated diamond NV color center in an optical fiber, comprising a laser light source, a magnetic field optical fiber sensing mechanism, a bias permanent magnet, a microwave waveguide mechanism, a first data processing mechanism, and a second data processing mechanism.

[0006] The laser source is connected to one side of the magnetic field fiber optic sensing mechanism via a first pigtail and a circulator, exciting the magnetic field fiber optic sensing mechanism to emit fluorescence. The circulator is connected to the first data processing mechanism, and the other side of the magnetic field fiber optic sensing mechanism is connected to the second data processing mechanism. The fluorescence enters the first data processing mechanism and the second data processing mechanism in a coupled manner.

[0007] Preferably, the magnetic field fiber optic sensing mechanism includes a diamond sheet and single-mode optical fibers disposed on both sides of the diamond sheet, wherein one of the single-mode optical fibers is connected to a circulator.

[0008] Preferably, the first data processing mechanism includes a third pigtail, a first fiber optic filter, a second pigtail, and a first data processing module connected in sequence, with the third pigtail connected to a circulator.

[0009] Preferably, the second data processing mechanism includes a second fiber optic filter, a fourth pigtail, and a second data processing module connected in sequence, with the second fiber optic filter connected to another single-mode fiber.

[0010] Preferably, there are two bias permanent magnets, which are respectively disposed on the upper and lower sides of the diamond sheet.

[0011] Preferably, the microwave waveguide mechanism includes a microwave waveguide and a microwave source, the microwave source is connected to the microwave waveguide, and the microwave waveguide is made of copper wire wound on a diamond sheet.

[0012] Preferably, both the first data processing module and the second data processing module include a bias control circuit, an avalanche photodiode, an amplifier circuit, a filter circuit, and a conversion circuit. The bias control circuit is connected to the avalanche photodiode, which is used to receive fluorescence signals. The avalanche photodiode, the amplifier circuit, the filter circuit, and the conversion circuit are connected in sequence.

[0013] Therefore, the present invention has the following beneficial effects:

[0014] (1) The laser is transmitted to the diamond sheet by optical fiber and the fluorescence emitted by the NV color center in the diamond sheet is received by optical fiber. The laser can enter the diamond sheet in a coupled manner, and the fluorescence can also enter the optical fiber in a coupled manner, which improves the transmission efficiency of the laser and the reception efficiency of the fluorescence, thereby improving the sensitivity of the sensor to measure the magnetic field.

[0015] (2) The diamond sheet is fixed by attaching a single-mode optical fiber to each side of the diamond sheet. The function of transmitting microwaves emitted by the microwave source to the vicinity of the diamond sheet is realized by using copper wire as a microwave waveguide and winding it around the diamond sheet. The extensive use of optical fiber and copper wire in the sensor greatly reduces the size of the sensor.

[0016] (3) A scheme in which a pair of bias permanent magnets are placed symmetrically on the upper and lower sides of the diamond sheet to apply a bias magnetic field to the NV color center in the diamond sheet to eliminate the influence of the internal stress of the diamond crystal on the NV color center, thereby further improving the magnetic field detection sensitivity.

[0017] (4) A first data processing module and a second data processing module are used to receive the fluorescence emitted by the NV color center. The bias voltage of the avalanche photodiode in the first and second data processing modules is controlled by a bias control circuit. The influence of ambient temperature changes on the gain can be eliminated by changing the bias voltage of the avalanche photodiode. The amplifier circuit amplifies the weak photocurrent output by the avalanche photodiode, which is difficult to detect, into a strong photocurrent that is easy to detect. The filter circuit filters out various experimental noises in the strong photocurrent output by the amplifier circuit to improve the signal-to-noise ratio of the photocurrent. The current-to-voltage circuit converts the difficult-to-detect current signal into a voltage signal that is easy to detect. Finally, the weak fluorescence emitted by the NV color center, which is difficult to detect, can be converted into a strong photovoltage with a high signal-to-noise ratio that is easy to detect, further improving the magnetic field detection sensitivity.

[0018] 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

[0019] Figure 1 This is a structural diagram of a fiber-optic integrated diamond NV color center magnetic field sensor.

[0020] Figure 2 This is a schematic diagram of a diamond sheet with NV color centers of the present invention being excited by a laser and emitting fluorescence;

[0021] Figure 3 This is a structural diagram of the magnetic field fiber optic sensing mechanism of the present invention;

[0022] Figure 4 This is a structural diagram of the first data processing module of the present invention.

[0023] Figure Labels

[0024] 1. Laser source; 2. First pigtail; 3. Circulator; 4. Magnetic field fiber optic sensing mechanism; 41. Diamond sheet; 42. Single-mode fiber; 5. Bias permanent magnet; 6. Second fiber optic filter; 7. Fourth pigtail; 8. Second data processing module; 9. Microwave waveguide; 10. Microwave source; 11. First data processing module; 12. Second pigtail; 13. First fiber optic filter; 14. Third pigtail; 15. Laser; 16. Fluorescence; 17. Microwave. Detailed Implementation

[0025] Example

[0026] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use. They are only for the convenience of describing this invention 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 limiting this invention.

[0027] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0029] refer to Figure 1 A magnetic field sensor with fiber-optic integrated diamond NV color centers includes a laser light source 1, a magnetic field fiber sensing mechanism 4, a bias permanent magnet 5, a microwave waveguide mechanism, a first data processing mechanism, and a second data processing mechanism.

[0030] The specific component structure is as follows:

[0031] The magnetic field fiber optic sensing mechanism 4 includes a diamond sheet 41 and single-mode optical fibers 42 disposed on both sides of the diamond sheet 41. A single-mode optical fiber with a thickness of approximately 500 μm and an area of ​​approximately 1 mm² is selected. 2 For the diamond sheet 41, two single-mode optical fibers 42, each approximately 40cm long, are selected. The coating layer on both ends of these two single-mode optical fibers 42 is removed by 3cm. A portion of each end of the two single-mode optical fibers 42 is then cut off using a fiber optic cleaver to make the fiber end faces flat. High-refractive-index adhesive is evenly applied to both sides of the diamond sheet 41, and the two single-mode optical fibers 42 are symmetrically attached to both sides of the diamond sheet 41. After the adhesive solidifies, the fabrication of the magnetic field fiber optic sensing mechanism 4 is complete. Fiber optic connectors are attached to the other two ends of the two single-mode optical fibers 42.

[0032] The microwave waveguide mechanism includes a microwave waveguide 9 and a microwave source 10. The microwave source 10 is connected to the microwave waveguide 9. The microwave waveguide 9 is made of copper wire, which is wound around a diamond sheet 41. A section of copper wire about 10 cm long and 0.5 mm thick is selected as the microwave waveguide 9, and the microwave waveguide 9 is wound evenly around the diamond sheet 41 10 times.

[0033] A laser source 1 is connected to one of the single-mode fibers 42 of the magnetic field fiber optic sensing mechanism 4 via a first pigtail 2 and a circulator 3 to excite fluorescence emitted by the diamond sheet 41. The fluorescence is coupled into a first data processing mechanism, which includes a third pigtail 14, a first fiber filter 13, a second pigtail 12, and a first data processing module 11 connected in sequence. The third pigtail 14 is connected to the circulator 3. The other side of the magnetic field fiber optic sensing mechanism 4 is connected to a second data processing mechanism, which includes a second fiber filter 6, a fourth pigtail 7, and a second data processing module 8 connected in sequence. The second fiber filter 6 is connected to another single-mode fiber 42. The fluorescence is coupled into both the first and second data processing mechanisms. Both the first and second data processing modules 11 and 8 include a bias control circuit, an avalanche photodiode, an amplifier circuit, a filter circuit, and a conversion circuit. The bias control circuit is connected to the avalanche photodiode, which receives the fluorescence signal. The avalanche photodiode, amplifier circuit, filter circuit, and conversion circuit are connected in sequence. An avalanche photodiode (APD) is a PN junction-type photodetector diode that utilizes the avalanche multiplication effect generated by the PN junction under a large reverse bias to amplify the photoelectric signal and achieve high photodetection sensitivity. A typical avalanche photodiode generally has a four-layer structure: P+, I, P, and N+. The P+ and N+ layers are heavily doped regions connected to electrodes, the I layer is the drift region, and the P layer is the multiplication region. In an avalanche photodiode, photons are injected from the P+ layer and then absorbed in the I layer, generating electron-hole pairs. These electron-hole pairs are accelerated towards the P layer by a reverse bias voltage. Upon reaching the P layer, they possess high kinetic energy and collide with lattice atoms, ionizing them and generating new electron-hole pairs. These newly generated electron-hole pairs, again accelerated by the reverse bias voltage, gain high kinetic energy and collide with lattice atoms, causing further ionization and generating new electron-hole pairs. This process is a continuous, avalanche-like chain reaction. During operation, the number of charge carriers generated by ionization far exceeds the number generated by photon absorption, resulting in a hundreds-fold avalanche-like increase in the number of photogenerated charge carriers. Applying avalanche photodiodes to photodetector magnetic resonance technology can convert the difficult-to-detect fluorescence emitted by the NV color center into an easily detectable amplified photocurrent. Further amplification of the current by an amplification circuit and filtering of experimental noise by a filtering circuit can further improve the sensitivity of the sensor.

[0034] Two bias permanent magnets 5 are provided, one on the upper side and one on the lower side of the diamond sheet 41, respectively. The laser emitted by the laser source 1 is coupled into the NV color centers in the diamond sheet 41 via single-mode fiber 42, exciting the NV color centers and causing them to emit fluorescence. The fluorescence is coupled into the single-mode fibers 42 on both sides of the diamond sheet 41 for transmission, and is finally received by the first data processing module 11 and the second data processing module 8, respectively. In the absence of an external magnetic field, the |m of the NV color centers... s =±1> states are degenerate. The photodetector magnetic resonance spectrum of the fluorescence emitted by the NV color center under continuous laser and microwave spin modulation exhibits a dip. In the presence of an external magnetic field, the |m| of the NV color center... s The ±1 state will split due to the Zeeman effect. The fluorescence emitted by the NV color center under continuous laser and microwave spin modulation will show two symmetrical depressions about the previous depression on the photodetector magnetic resonance spectrum. The magnitude of the magnetic field at the sensor can be obtained by solving the Hamiltonian equation based on the difference in microwave frequency between the two depressions.

[0035] The laser source 1 and microwave source 10 are turned on. While performing a microwave frequency sweep on the magnetic field fiber optic sensing mechanism 4, the fluorescence emitted by the diamond sheet 41 with NV color centers is received through the first data processing module 11 and the second data processing module 8. The structure of the first data processing module 11 is as follows: Figure 4 As shown, the second data processing module 8 has the same structure as the first data processing model. It is implemented by soldering the avalanche photodiode, bias control circuit, amplification circuit, filter circuit, and conversion circuit onto a PCB board and connecting it to a data acquisition card. The conversion circuit is a current-to-voltage circuit. The processed voltage signal is received by the computer through the data acquisition card and converted into a photodetector magnetic resonance spectrum. The magnitude of the magnetic field at the sensor can be obtained by solving the Hamiltonian equation based on the difference in microwave frequencies between the two depressions on the obtained photodetector magnetic resonance spectrum.

[0036] 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. A magnetic field sensor based on fiber integrated diamond NV color centers, characterized by: The application relates to a magnetic field fiber sensing device, which comprises a laser light source, a magnetic field fiber sensing mechanism, bias permanent magnets, a microwave waveguide mechanism, a first data processing mechanism and a second data processing mechanism. The laser light source is connected with one side of the magnetic field fiber sensing mechanism through a first tail fiber and a ring oscillator, the magnetic field fiber sensing mechanism emits fluorescence, the ring oscillator is connected with the first data processing mechanism, the other side of the magnetic field fiber sensing mechanism is connected with the second data processing mechanism, and the fluorescence enters the first data processing mechanism and the second data processing mechanism in a coupling mode. The first data processing module and the second data processing module both comprise a bias control circuit, an avalanche photodiode, an amplification circuit, a filter circuit and a conversion circuit, the bias control circuit is connected with the avalanche photodiode, the avalanche photodiode is used for receiving a fluorescence signal, and the avalanche photodiode, the amplification circuit, the filter circuit and the conversion circuit are sequentially connected. The processed voltage signal is received by a computer through a data acquisition card and is converted and drawn into an optical detection magnetic resonance spectrum, a Hamilton equation is solved according to the difference between the microwave frequencies of two recesses on the obtained optical detection magnetic resonance spectrum, and the magnetic field size at the sensor can be obtained.

2. A high-efficiency optical fiber magnetic field sensor based on diamond NV color centers according to claim 1, characterized in that: The magnetic field fiber sensing mechanism comprises a diamond sheet and single-mode optical fibers arranged on both sides of the diamond sheet, and one single-mode optical fiber is connected with the ring oscillator.

3. A high-efficiency optical fiber magnetic field sensor based on diamond NV color centers according to claim 2, characterized in that: The first data processing mechanism comprises a third tail fiber, a first optical fiber filter, a second tail fiber and a first data processing module which are sequentially connected, and the third tail fiber is connected with the ring oscillator.

4. A high-efficiency optical fiber magnetic field sensor based on diamond NV color centers according to claim 3, characterized in that: The second data processing mechanism comprises a second optical fiber filter, a fourth tail fiber and a second data processing module which are sequentially connected, and the second optical fiber filter is connected with the other single-mode optical fiber.

5. A high-efficiency optical fiber magnetic field sensor based on diamond NV color centers according to claim 4, characterized in that: The microwave waveguide mechanism comprises a microwave waveguide and a microwave source, the microwave source is connected with the microwave waveguide, the microwave waveguide is made of copper wire, and the copper wire is wound on the diamond sheet.

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