A method and device for testing magnetic field based on NSiV bicolor center

Abstract

The application provides a kind of MNF magnetic field test method and device based on NSiV double color heart, it includes optical fiber laser (1), magnetic field testing device (2), photoelectric conversion module (3), ADC module (4), microprocessor (5), computer (6).The application adopts the principle of evanescent field enhancement Mach-Zehnder, through diamond NSiV double color heart nanometer material coating MNF for sensing, the light source output by optical fiber laser excites diamond NSiV double color heart nanometer material to make it produce fluorescence, and interference occurs with the light beam in sensing unit.When the magnetic field changes, the spectrometer will detect different interference spectrum, define new average sensitivity as the judgment standard of sensor performance, so as to realize real-time monitoring of magnetic field.The application takes magnetic field detection as the target, effectively solves the problems of traditional magnetic field sensor, such as magnetic hysteresis, flammable, large volume, not easy to operate, etc., and realizes real-time measurement of magnetic field.

Description

Technical Field

[0001] This invention patent relates to a method and device for testing the magnetic field of MNF based on NSiV dual color centers, belonging to the field of fiber optic sensing technology. Background Technology

[0002] Magnetic fields are among the most common physical quantities, with increasingly widespread applications in biology, medicine, education, and the military. Their application in the military is particularly urgent, as warfare in the information age is inseparable from magnetic fields, and electromagnetic control has become a crucial factor in victory. Currently, magnetic field sensors are widely used in the military field for magnetic mine sweeping, underwater magnetic detection, and ship magnetic navigation. Underwater magnetic detection can compensate for errors caused by underwater noise in traditional sonar detection.

[0003] Traditional magnetic field detection methods primarily rely on electrical signal detection. However, the devices carrying these signals are often made of metal, which inherently alters the magnetic field and introduces significant errors. Furthermore, some large magnetic field environments contain oil, particularly current transformers. Detection based on electrical signals poses risks of flammability and explosion in such environments. Additionally, demagnetization and hysteresis can significantly contribute to measurement errors.

[0004] Compared to traditional electronic sensors, fiber optic sensors offer advantages such as high signal-to-noise ratio, remote monitoring capability, immunity to electromagnetic interference, high sensitivity, and greater flexibility. Currently, many fiber optic sensors have been developed for detecting temperature, stress, and magnetic fields. However, many fiber optic sensors for magnetic field detection utilize magnetostriction and magnetohydrodynamics as sensing materials, which have limited detection capabilities for weak magnetic fields. Diamond NSiV dichromatic centers, using this sensing material, can detect weak magnetic fields, and the presence of an evanescent field can effectively improve detection sensitivity.Bian Ce et al. (Bian Ce. Research on Sensing Characteristics and Fiber Integration Technology of Nanodiamond Nitrogen-Vacancy Color Centers [D]. Northwest University, 2021. DOI:10.27405 / d.cnki.gxbdu.2021.002188.) studied the sensing characteristics and fiber integration technology of nanodiamond nitrogen-vacancy color centers. However, their research used spatial light modulation, which is easily affected by environmental interference in practical applications. Our proposed method, on the other hand, integrates optical coupling into optical fibers for transmission, improving the application value of fiber optic sensors. This method uses diamond two-color centers to improve sensing characteristics; Zhang Junying et al. (Zhang Junying. Research on Novel Fiber Optic Magnetic Field Sensing Technology [D]. Northwest University, 2019. DOI:10.27405 / d.cnki.gxbdu.2019.000277.) proposed a novel fiber optic magnetic field sensing technology, but this technology uses a magnetofluid-filled Mach-Zehnder structure, which is caused by an evanescent field causing optical path difference, while this technology is caused by fluorescence excitation to generate optical path difference, and the two are fundamentally different; Hatano Y et al. (Hatano Y, Shin J, Nishitani D, et al. Simultaneous thermometry and magnetometry using afiber-coupled quantum diamond sensor[J]. Applied Physics Letters, 2021, 118(3): 034001.) proposed a technique for simultaneous temperature and magnetic force measurement using a fiber-coupled quantum diamond sensor. This method connects diamond in a block form to the surface of an optical fiber. In this type of method, the optical fiber only plays the role of transmitting light and is not a sensing method. It is mainly achieved through microwave frequency modulation. This method adopts a fully optical method and belongs to fiber optic sensing. Zhang J et al. (Zhang J, Wang C, Chen Y, et al. Fiber structures and material science in optical fiber magnetic field sensors[J]. Frontiers of Optoelectronics, 2022, 15(1): 34.) summarized the structure and magnetic sensing materials of fiber optic magnetic field sensors. However, these methods all belong to sensing by changing the optical path difference caused by the evanescent field, while this method generates the optical path difference by fluorescence excitation. Therefore, there is an essential difference between them. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes an MNF magnetic field testing method and apparatus based on NSiV dual-color centers, which solves the current problems of magnetic field detection being easily affected by the environment and the difficulty in detecting weak magnetic fields, and enables the detection of some relatively weak magnetic fields.

[0006] A method and apparatus for testing the magnetic field of MNF based on NSiV two-color centers, wherein the specific implementation process of the method and apparatus is as follows:

[0007] It includes a laser (1), a magnetic field testing device (2), a photoelectric conversion module (3), an ADC module (4), a microprocessor (5), and a computer (6); the specific implementation process of the method is as follows:

[0008] The fiber laser (1) has a center wavelength of 532nm and an intensity of 20mw to generate optical signals;

[0009] The magnetic field testing device (2) includes a rotating magnetic base (2-1), an N-pole magnet (2-2), an S-pole magnet (2-3), a magnetic base power supply device (2-4), and a sensing unit (2-5), wherein:

[0010] N-level magnets (2-2) and S-level magnets (2-3) are placed at both ends of the rotating magnetic base (2-1). The magnetic force of the N-level magnets (2-2) and S-level magnets (2-3) can be adjusted through the magnetic base power supply device (2-4). In addition, the sensing unit (2-5) is placed on the rotating magnetic base (2-1).

[0011] The sensing unit (2-5) is a Mach-Zehnder structure formed by fusing large-core multimode fiber (2-5-1) with MNF (2-5-2) and large-core multimode fiber (2-5-4). In addition, diamond NSiV two-color center nanomaterial (2-5-3) is coated on the waist cone center of MNF (2-5-2).

[0012] The specific fabrication process of the sensing unit (2-5) includes the fabrication and sizing of the Mach-Zehnder structure, and the fabrication and coating of the diamond NSiV dual-color center nanomaterial (2-5-3), wherein:

[0013] The large-core multimode fiber (2-5-1) is 10cm long and has a core diameter of 30μm. The MNF (2-5-2) is a tapered single-mode fiber with a length of 3cm. The transition region (2-5-2-1) is 1.1cm long, and the waist cone (2-5-2-2) is 0.9m long and has a waist cone diameter of 20μm. First, the center part of the single-mode fiber is tapered using an oxyhydrogen flame taper until the length is 9mm. Second, one end of the MNF (2-5-2) is fused to the large-core multimode fiber (2-5-1) using a fusion splicer until the loss is 0. Finally, the other end of the MNF (2-5-2) is fused to the large-core multimode fiber (2-5-4) using a fusion splicer until the loss is 0.

[0014] The fabrication of the diamond NSiV dual-color core nanomaterial (2-5-3) involved first selecting a quartz glass slide as a substrate and depositing 3 nm of diamond using MPCVD under N2 conditions. The parameters were set as follows: methane flux 2.5 sccm, H2 flux 232.4 sccm, N2 flux 1 sccm, temperature 900℃, power 1200 W, pressure 4030 Pa, and deposition time 50 min. Next, Si was deposited with the following parameters: power 50 W, pressure 1 Pa, and vacuum degree 9E. -4, deposition time was 70s, finally, annealing was performed to generate double vacancies, methane and nitrogen were turned off, parameters were set as follows: H2 flux increased to 155sccm, temperature set to 700℃, after standing for 1.5 hours and cooling to room temperature, diamond NSiV two-color core nanomaterial (2-5-3) was taken out, a quantitative amount of diamond NSiV two-color core nanomaterial (2-5-3) powder was dissolved in 30ml of anhydrous ethanol, and ultrasonic treatment was performed for 2 hours to make it uniformly dispersed into diamond NSiV two-color core nanomaterial (2-5-3) suspension;

[0015] The diamond NSiV two-color center nanomaterial (2-5-3) was coated onto the waist cone center of MNF (2-5-2) using a drop-coating method. First, the diamond was pipetted onto the surface.

[0016] A suspension of diamond NSiV two-color core nanomaterial (2-5-3) was drop-coated onto the center of the waist cone of MNF (2-5-2) and dried in an oven at 80°C for 2 hours. After the oven cooled to room temperature, the diamond NSiV two-color core nanomaterial (2-5-3) was uniformly coated onto the center of the waist cone of MNF (2-5-2).

[0017] The method and apparatus for testing MNF magnetic fields based on NSiV two-color centers are further characterized in that: the implementation process is as follows:

[0018] Step 1: Perform localization and fitting processing on the sensing peak within the 600-700nm range:

[0019] The optical fiber spectrum is approximated using a Gaussian function, which is a well-known formula. However, the location of the troughs can be determined through fitting and localization.

[0020]

[0021] Take the logarithm of both sides:

[0022]

[0023] Let lnI(λ) = y, Substituting a, b, and c into formula (2) yields...

[0024] y = aλ 2 +bλ+c (3)

[0025]

[0026] In the formula, I(λ) represents the light intensity corresponding to different wavelengths, and λ peak Δλ represents the wavelength value corresponding to the wave peak, Δλ represents the wavelength change, and A represents a constant. Substituting the collected wavelength data into formulas (3) and (4) yields the center wavelength value corresponding to the wave peak. Formula (3) is a quadratic polynomial fitting form, so the least squares method is used to fit the data.

[0027] Step 2: Change the magnetic field strength and scan the wavelengths corresponding to different magnetic field strengths. When the magnetic field strength increases, the sensing peak shifts upward, and the microprocessor collects the changing wavelengths.

[0028] Step 3: Take points from the collected drift wavelength group, using I... peak Five intersection points are marked perpendicularly with ±0.17n (n=0, 1, 2) as the center, resulting in five groups, denoted as L1, L2, L3, L4, and L5. Each group corresponds to a sensitivity. Since there are errors in wavelength fitting at each point, and the spectrum will be deformed at various points, the average sensitivity is used to define the sensor's response to changes in the magnetic field.

[0029] Step 4: Define the average sensitivity formula as follows:

[0030] The formula for the average sensitivity is:

[0031]

[0032]

[0033]

[0034] In formula (5), s1 represents the sensitivity of group L1. The sensitivity formulas for groups L1, L2, L3, L4, and L5 are the same as those for group L1. In formula (6), d1, d2, d3, d4, and d5 represent the intensity values ​​at the five groups L1, L2, L3, L4, and L5, respectively. In formula (7), s1, s2, s3, s4, and s5 represent the intensity sensitivities of the five groups L1, L2, L3, L4, and L5, respectively. I1, I2, I3, I4, and I5 represent different magnetic field intensities, and b1, b2, b3, b4, and b5 represent the values ​​when the magnetic field intensity is 0. The average sensitivity of this sensor is obtained by processing the collected data through a microprocessor. The final average sensitivity is displayed by computer.

[0035] The beneficial effects of this invention are as follows:

[0036] 1. Compared with the invention patent "A Method and Apparatus for Testing the Magnetic Field of MNF Based on MoSFe Coating" filed by the inventor on the same day, although both methods are applicable to the detection of magnetic fields, the latter focuses on the detection of weaker magnetic fields, which are on the order of mT, and uses the evanescent field principle to cause optical path difference. This method focuses on the detection of weak magnetic fields, which are on the order of nT, and uses fluorescence excitation to cause optical path difference.

[0037] 2. Compared with the invention patent "A Method and Apparatus for Testing Magnetic Field and Temperature Dual Parameters of NSiV Two-Color Centers" filed on the same day by the inventor, although both methods can detect weak magnetic fields, the latter focuses on the detection of weak magnetic fields under temperature influence. This method focuses on the detection of weak magnetic fields under external environmental magnetic field conditions.

[0038] 3. Compared with the invention patent "A Method and Apparatus for Dual-Parameter Testing of Magnetic Field and Stress on MoSFe Coating" filed on the same day by the inventor, although both methods can detect magnetic fields, the method mentioned in "A Method and Apparatus for Dual-Parameter Testing of Magnetic Field and Stress on MoSFe Coating" focuses on the detection of weak magnetic fields under stress and uses the evanescent field principle to cause optical path difference. This method focuses on the detection of weak magnetic fields in environments where the external environment has little influence and uses fluorescence excitation to cause optical path difference.

[0039] 4. Compared with the invention patent "SPR-based D-type photonic crystal fiber magnetic field sensitive sensing device and method" filed by the inventor on November 19, 2020, although both methods can detect magnetic fields, the method mentioned in "SPR-based D-type photonic crystal fiber magnetic field sensitive sensing device and method" focuses on the SPR principle of photonic crystal fibers. This method focuses on the principle of NSiV dual-color core magnetic sensing material coated with Mach-Zehnder, and achieves weak magnetic field detection, which can reach the nT level. Attached Figure Description

[0040] For ease of explanation, the present invention will be described in detail below with reference to the accompanying drawings.

[0041] Figure 1 This is a flowchart of a method and apparatus for testing the magnetic field of MNF based on NSiV two-color centers;

[0042] Figure 2 A diagram of a test apparatus for a method and device for testing MNF magnetic fields based on NSiV two-color centers;

[0043] Figure 3This is a structural diagram of the sensing unit of a method and device for testing MNF magnetic fields based on NSiV two-color centers;

[0044] Figure 4 This is a test spectrum of an MNF magnetic field testing method and device based on NSiV two-color centers; Detailed Implementation

[0045] To make the purpose, technical solution and advantages of this invention patent clearer, the invention patent is described below with reference to specific implementation examples shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of this invention patent. Furthermore, in the following description, descriptions of some well-known structures and technologies are omitted to avoid unnecessary confusion regarding the concept of this invention patent.

[0046] Implementation examples are as follows Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, this specific embodiment adopts the following technical solution: a method and apparatus for testing MNF magnetic fields based on NSiV two-color centers, the specific implementation process of the method is as follows:

[0047] like Figure 1 As shown, the present invention adopts a straight-through optical path diagram, which connects the laser (1), magnetic field testing device (2), photoelectric conversion module (3), ADC module (4), microprocessor (5), and computer (6) in sequence;

[0048] like Figure 2 As shown, the 532nm light emitted by the fiber laser (1) is transmitted to the sensing unit (2-5), where Mach-Zehnder interference occurs. By adjusting the size of the magnetic base power supply device (2-4), the magnitude of the magnetic field generated by the N-pole magnet (2-2) and the S-pole magnet (2-3) is changed. The change in the magnetic field causes a change in the intensity of the interference spectrum transmitted from the sensing unit (2-5).

[0049] like Figure 3As shown, the Mach-Zehnder effect of the sensing unit (2-5) is enhanced by utilizing the evanescent field, thereby improving the sensitivity of the magnetic field test. Specifically, when the beam emitted by the fiber laser (1) is transmitted from the large-core multimode fiber (2-5-1) to the MNF (2-5-2), part of the light is transmitted in the cladding, and the other part is transmitted directly in the core. When the light transmitted in the cladding is transmitted to the waist cone (2-5-2-2), it excites 600-800nm ​​light in the diamond NSiV two-color center nanomaterial (2-5-3). The evanescent field will cause a larger optical path difference between the light in the cladding and the light in the core. When the light transmitted in the cladding and the light transmitted in the core are transmitted to the large-core multimode fiber (2-5-4), they will be recoupled to the core, at which point the Mach-Zehnder interference phenomenon occurs. When the magnetic field changes, the intensity of the interference spectrum in the spectrometer (3) changes.

[0050] like Figure 4 As shown, the interference spectrum exhibits intensity drift when the magnetic field changes. Since the troughs of all interference spectra converge at a single point, the degree of drift varies across these troughs. Furthermore, errors exist in the fitting process; therefore, I is used as the reference value. peak Five intersection points are marked perpendicularly with ±0.17n (n=0, 1, 2) as the center, for a total of five groups. The average sensitivity is used to define the sensor's response to changes in the magnetic field. Therefore, this invention proposes a novel sensitivity determination method, namely, the average sensitivity. The average sensitivity of the magnetic field sensor can be calculated according to formulas (5) and (6).

Claims

1. A method and apparatus for testing the magnetic field of MNF based on NSiV two-color centers, characterized in that: It includes a fiber laser (1), a magnetic field testing device (2), a photoelectric conversion module (3), an ADC module (4), a microprocessor (5), and a computer (6); the specific implementation process of the method is as follows: The fiber laser (1) has a center wavelength of 532nm and an intensity of 20mw to generate optical signals; The magnetic field testing device (2) includes a rotating magnetic base (2-1), an N-pole magnet (2-2), an S-pole magnet (2-3), a magnetic base power supply device (2-4), and a sensing unit (2-5), wherein: N-level magnets (2-2) and S-level magnets (2-3) are placed at both ends of the rotating magnetic base (2-1). The magnetic force of the N-level magnets (2-2) and S-level magnets (2-3) can be adjusted through the magnetic base power supply device (2-4). In addition, the sensing unit (2-5) is placed on the rotating magnetic base (2-1). The sensing unit (2-5) is a Mach-Zehnder structure formed by fusing large-core multimode fiber (2-5-1) with MNF (2-5-2) and large-core multimode fiber (2-5-4). In addition, diamond NSiV two-color center nanomaterial (2-5-3) is coated on the waist cone center of MNF (2-5-2). The specific fabrication process of the sensing unit (2-5) includes the fabrication and sizing of the Mach-Zehnder structure, and the fabrication and coating of the diamond NSiV dual-color center nanomaterial (2-5-3), wherein: The large-core multimode fiber (2-5-1) is 10cm long and has a core diameter of 105μm. The MNF (2-5-2) is a tapered multimode fiber with a core diameter of 35μm and a length of 3cm. The transition region (2-5-2-1) is 1.1cm long, and the waist cone (2-5-2-2) is 0.9cm long and has a waist cone diameter of 20μm. First, the center part of the single-mode fiber is tapered using an oxyhydrogen flame tapering machine until the length is 9mm. Second, one end of the MNF (2-5-2) is fused to the large-core multimode fiber (2-5-1) using a fusion splicer until the loss is 0. Finally, the other end of the MNF (2-5-2) is fused to the large-core multimode fiber (2-5-4) using a fusion splicer until the loss is 0. The fabrication of the diamond NSiV dual-color core nanomaterial (2-5-3) involved first selecting a quartz glass slide as a substrate and depositing 3 nm of diamond using MPCVD under N2 conditions. The parameters were set as follows: methane flux 2.5 sccm, H2 flux 232.4 sccm, N2 flux 1 sccm, temperature 900℃, power 1200 W, pressure 4030 Pa, and deposition time 50 min. Next, Si was deposited with the following parameters: power 50 W, pressure 1 Pa, and vacuum degree 9E. -4, deposition time was 70s, finally, annealing was performed to generate double vacancies, methane and nitrogen were turned off, parameters were set as follows: H2 flux increased to 155sccm, temperature set to 700℃, after standing for 1.5 hours and cooling to room temperature, diamond NSiV two-color core nanomaterial (2-5-3) was taken out, a quantitative amount of diamond NSiV two-color core nanomaterial (2-5-3) powder was dissolved in 30ml of anhydrous ethanol, and ultrasonic treatment was performed for 2 hours to make it uniformly dispersed into diamond NSiV two-color core nanomaterial (2-5-3) suspension; The diamond NSiV two-color core nanomaterial (2-5-3) was coated onto the waist cone center of MNF (2-5-2) using a drop-coating method. First, a suspension of the prepared diamond NSiV two-color core nanomaterial (2-5-3) was drawn up with a syringe and dropped onto the waist cone center of MNF (2-5-2). The suspension was dried in an oven at 80°C for 2 hours. After the oven cooled to room temperature, the diamond NSiV two-color core nanomaterial (2-5-3) was uniformly coated onto the waist cone center of MNF (2-5-2). The method and apparatus for testing MNF magnetic fields based on NSiV two-color centers are further characterized in that: The beam emitted by the fiber laser (1) is transmitted to the sensing unit (2-5) in the magnetic field testing device (2). The diamond NSiV two-color center nanomaterial (2-5-3) on the waist cone of the MNF (2-5-2) will emit fluorescence of 600-800nm. The excitation light and the original beam are coupled at the large core multimode fiber (2-5-4) to produce Mach-Zehnder interference. When the magnetic field changes, the intensity of the excitation light will decrease as the magnetic field increases. The interference light at the large core multimode fiber (2-5-4) changes. As the magnetic field changes, the spectral intensity in the sensing unit (2-1) drifts. The optical signal is converted into an electrical signal by the photoelectric conversion module (3) and transmitted to the ADC module (4) to convert the continuous analog signal into a discrete digital signal and perform data acquisition. The acquired data is processed by the microprocessor (5). The method and apparatus for testing MNF magnetic fields based on NSiV two-color centers are further characterized in that: the implementation process is as follows: Step 1: Perform localization and fitting processing on the sensing peak within the 600-700nm range: The optical fiber spectrum is approximated using a Gaussian function, which is a well-known formula. However, the location of the troughs can be determined through fitting and localization. Take the logarithm of both sides: make Substituting a, b, and c into formula (2) yields... y=aλ 2 +bλ+c (3) In the formula, I(λ) represents the light intensity corresponding to different wavelengths, and λ peak Δλ represents the wavelength value corresponding to the wave peak, Δλ represents the wavelength change, and A represents a constant. Substituting the collected wavelength data into formulas (3) and (4) yields the center wavelength value corresponding to the wave peak. Formula (3) is a quadratic polynomial fitting form, so the least squares method is used to fit the data. Step 2: Change the magnetic field strength and scan the wavelengths corresponding to different magnetic field strengths. When the magnetic field strength increases, the sensing peak shifts upward, and the microprocessor collects the changing wavelengths. Step 3: Take points from the collected drift wavelength group, using I... peak Five intersection points are marked perpendicularly with ±0.17n (n=0, 1, 2) as the center, resulting in five groups, denoted as L1, L2, L3, L4, and L5. Each group corresponds to a sensitivity. Since there are errors in wavelength fitting at each point, and the spectrum will be deformed at various points, the average sensitivity is used to define the sensor's response to changes in the magnetic field. Step 4: Define the average sensitivity formula as follows: The formula for the average sensitivity is: In formula (5), s1 represents the sensitivity of group L1. The sensitivity formulas for groups L1, L2, L3, L4, and L5 are the same as those for group L1. In formula (6), d1, d2, d3, d4, and d5 represent the intensity values ​​at the five groups L1, L2, L3, L4, and L5, respectively. In formula (7), s1, s2, s3, s4, and s5 represent the intensity sensitivities of the five groups L1, L2, L3, L4, and L5, respectively. I1, I2, I3, I4, and I5 represent different magnetic field intensities, and b1, b2, b3, b4, and b5 represent the values ​​when the magnetic field intensity is 0. The average sensitivity of this sensor is obtained by processing the collected data through a microprocessor. The final average sensitivity is displayed by computer.

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