A fiber-based NV color center array sensor

Abstract

The application relates to the technical field of magnetic field detection, and specifically discloses an NV color center array sensor based on an optical fiber, which comprises a multi-channel optical fiber probe group, a microwave radiation unit, an optical path and signal acquisition unit and a data processing unit; the multi-channel optical fiber probe group comprises at least two sensing optical fibers, all the sensing optical fibers are connected to the same diamond block, or each sensing optical fiber is separately connected to a diamond particle, and the diamond block and the diamond particle both comprise NV color centers; the microwave radiation unit is arranged close to the NV color centers of the sensing optical fibers and is used for providing a microwave field; the optical path signal acquisition unit is used for emitting laser and conducting the laser to the NV color centers of the multi-channel optical fiber probe group and receiving the fluorescence generated by the NV color centers; and the data processing unit calculates the fluorescence returned by the NV color centers in each channel to obtain a detection result of a workpiece to be detected. The application can realize multi-channel efficient detection of the workpiece to be detected and can keep the system compact and portable.

Description

Technical Field

[0001] This invention relates to the field of magnetic field detection technology, and more specifically to an NV color center array sensor based on optical fiber. Background Technology

[0002] Currently, the mainstream magnetic field detection technology based on diamond NV centers (nitrogen-vacancy centers) adopts a single-channel sensing architecture and a wide-field microscopic imaging scheme. However, these two schemes have the following objective drawbacks:

[0003] 1) Single-channel solutions have limited channels and low scanning efficiency. Existing single-channel NV color center magnetometer probes have a limited number of channels, requiring single-point or single-line step-by-step scanning for large-area inspection of workpieces. This method is extremely time-consuming and has very low scanning efficiency, making it difficult to meet the actual needs of industrial sites for rapid inspection and large-area screening.

[0004] 2) Wide-field microscopy imaging schemes are overly complex in structure and bulky in size. While wide-field microscope-based NV color center measurement systems, adopted to address efficiency issues, can achieve area array imaging, they heavily rely on complex optical systems (such as high-precision microscope objectives and large-area uniform beam-expanding illumination paths) and large supporting control equipment. This results in an overly complex overall system structure, large size, and high cost. Such equipment lacks portability and is fundamentally unsuitable for in-service testing in confined spaces and complex working conditions.

[0005] Therefore, existing NV color core detection technology is caught in a dilemma of "low efficiency of single-channel equipment" and "large size and complex structure of wide-field equipment", and cannot balance detection efficiency with the portability and flexibility of the equipment. How to provide a hardware architecture that can achieve high-efficiency multi-channel sensing while maintaining a compact and portable system is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of the above problems, the present invention proposes an NV color center array sensor based on optical fiber to overcome or at least partially solve the above problems.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an NV color center array sensor based on optical fiber, comprising: a multi-channel optical fiber probe group, a microwave radiation unit, an optical path and signal acquisition unit, and a data processing unit; The multi-channel fiber optic probe group includes at least two sensing fibers, all of which are connected to the same diamond block, or each sensing fiber is individually connected to a diamond particle. Both the diamond block and the diamond particle contain NV color centers. The microwave radiation unit is positioned close to the NV color center of the sensing fiber to provide a microwave field. The optical path signal acquisition unit is used to emit laser light and transmit it to the NV color center of the multi-channel fiber optic probe group, and to receive the fluorescence generated by the NV color center; The multi-channel fiber optic probe group contacts the surface of the workpiece to be tested, and the data processing unit calculates the fluorescence returned by the NV color center in each channel to obtain the detection result of the workpiece to be tested.

[0008] Furthermore, the microwave radiation unit includes a microwave antenna, a microwave signal source, and an amplifier; The microwave antenna is wound around the outer periphery of the sensing optical fiber and positioned close to the NV color center; The microwave signal source generates a microwave signal to drive the NV color center, which is then amplified by the amplifier and transmitted to the microwave antenna via an SMA radio frequency cable.

[0009] Furthermore, the optical path signal acquisition unit includes a laser, an optical fiber beam splitter, and multiple independent sub-optical paths; each independent sub-optical path includes an independent optical fiber circulator, a filter, and a photodetector. The laser emitted by the laser is split into multiple laser beams by the fiber optic beam splitter, and each laser beam is transmitted to each channel of the multi-channel fiber optic probe group through the corresponding independent sub-optical path. In each of the independent sub-optical paths, the laser is transmitted through the fiber optic circulator to the NV color center of the corresponding channel; the fluorescence generated by the NV color center enters the corresponding photodetector after passing through the fiber optic circulator and the filter.

[0010] Furthermore, the fiber optic circulator includes an excitation light injection port, a bidirectional multiplexing port, and a fluorescence output port; wherein, the excitation light injection port is connected to the fiber optic beam splitter, the bidirectional multiplexing port is connected to the corresponding sensing fiber, and the fluorescence output port is connected to the filter; the excitation light injection port and the fiber optic beam splitter, as well as the bidirectional multiplexing port and the sensing fiber, are connected by fiber optic flanges or by fiber optic fusion splicing.

[0011] Furthermore, the data processing unit is connected to the host computer via a communication module, and is used to provide raw measurement data or gradient data of the temperature or magnetic field of the workpiece under test according to the instructions of the host computer.

[0012] Furthermore, when the data processing unit provides gradient data of the workpiece to be tested, the temperature or magnetic field of the workpiece to be tested is collected through the multi-channel fiber optic probe group, and the temperature difference or magnetic field difference between any two adjacent channels is calculated to obtain the temperature gradient or magnetic field gradient at different positions of the workpiece to be tested.

[0013] Furthermore, the multi-channel fiber optic probe group moves along the surface of the workpiece under the drive of the scanning platform. The data processing unit records the temperature gradient or magnetic field gradient at each position of the workpiece and transmits it to the host computer. The host computer generates a temperature gradient image or magnetic field gradient image of the workpiece based on the temperature gradient or magnetic field gradient at each position of the workpiece.

[0014] Furthermore, each sensing fiber in the multi-channel fiber optic probe group forms a 1 M one-dimensional array or N An M-dimensional array, where N and M are both positive integers greater than 2.

[0015] Furthermore, the spacing between any two adjacent sensing fibers is 50μm-3000μm, and the concentration of the NV color center is at the ppm level.

[0016] Furthermore, it also includes a bias magnet, which is positioned close to the multi-channel fiber optic probe group to provide a reference magnetic field with a known direction and magnitude for the NV color center.

[0017] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: This invention combines multiple channels of NV color centers into an array sensor within a single device, enabling the NV color center sensor to achieve better performance during measurement. Specifically, this is reflected in: 1. An array composed of multiple NV color centers can achieve N times more data volume compared to a single probe, thus achieving more efficient detection. 2. An array consisting of multiple NV color centers reads data at the same time, which can effectively avoid common-mode noise interference. When using a single NV color center for reading, the noise received at different sampling times may be different, resulting in poor data consistency. However, the NV color center array collects data at the same time, avoiding this situation and improving data quality.

[0018] 3. Data from NV color center array sensors can be processed differentially to calculate gradients and tensors, yielding multiple sets of effective information. High-sensitivity gradient and tensor information is essential for fields such as high-sensitivity nondestructive testing.

[0019] 4. Compared to using multiple NV color center probes directly, the channel integration of the present invention significantly reduces the volume and fixes the relative positions between NV color center probes. Compared to using a wide-field NV microscope, the present invention is much smaller and more convenient. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a multi-channel fiber optic probe group in an embodiment of the present invention, in which all sensing fibers share the same diamond block. Figure 2 This is a schematic diagram of a multi-channel fiber optic probe group in an embodiment of the present invention, where each sensing fiber is individually connected to a diamond particle. Figure 3 This is a schematic diagram of the structure of an NV color center array sensor based on optical fiber provided in an embodiment of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention discloses an NV color center array sensor based on optical fiber, comprising: a multi-channel optical fiber probe group, a microwave radiation unit, an optical path and signal acquisition unit, and a data processing unit; The multi-channel fiber optic probe group contains at least two sensing fibers, all of which are connected to the same diamond block, or each sensing fiber is connected to a diamond particle individually. Both the diamond block and the diamond particle contain NV color centers. The microwave radiation unit is positioned close to the NV color center of the sensing fiber to provide a microwave field; The optical signal acquisition unit is used to emit laser light and transmit it to the NV color center of the multi-channel fiber optic probe group, and to receive the fluorescence generated by the NV color center; The multi-channel fiber optic probe array contacts the surface of the workpiece under test. The data processing unit calculates the fluorescence returned by the NV color centers in each channel to obtain the detection result of the workpiece. The core of this invention lies in the integration of multiple fiber optic NV color center sensor channels, specifically employing two feasible approaches. The first approach is as follows: Figure 1As shown, multiple sensing fibers share a single diamond. This scheme uses a bulk diamond, and by fixing a one-dimensional or two-dimensional fiber array to the same diamond with UV adhesive, multi-channel fiber sensing can be achieved using a single diamond. Since all channels are fixed to the same diamond, the NV color centers are aligned, and the required radio frequency can be provided by a single radio frequency coil.

[0024] The second type is as follows Figure 2 As shown, each channel uses an independent diamond. This scheme uses granular diamond, with one diamond particle fixed on each sensing fiber. Since the orientation of the NV color centers is different, multiple radio frequency frequencies need to be applied in a radio frequency coil to drive the NV color centers. This can be achieved through a digital frequency synthesizer (DDS).

[0025] Specifically, the overall principle of this invention is as follows: Figure 3 As shown, it mainly includes the following: A multi-channel fiber optic probe array consists of at least two sensing fibers forming a fiber array. The end faces of the fiber array are fixed to the same diamond block using optical adhesive, or each sensing fiber is fixed to a diamond particle using optical adhesive, forming a diamond NV center sensing unit. Both the diamond block and the diamond particles contain high-concentration NV centers at the ppm level for sensing external magnetic fields. The sensing array can be 1... M one-dimensional array or N The M-channel multidimensional array, where N and M are both positive integers greater than 2, allows for the simultaneous acquisition of more gradient directions, such as XY gradients and gradient tensors, and also enables faster scanning speeds. The sensing fibers between adjacent channels are spaced 50μm-3000μm apart. These fibers are used to transmit excitation light (532nm green light) and collect red fluorescence generated by the NV color centers.

[0026] The microwave radiation unit specifically includes a microwave antenna, a microwave signal source, and an amplifier. The microwave signal source can be a data acquisition board connected to a host computer. Under the control of the host computer, it generates microwave signals to drive the NV color centers, which are then amplified and transmitted to the microwave antenna via an SMA RF cable. The microwave antenna is wound around the outer periphery of a fiber optic array composed of sensing fibers or fixed near the end face of the fiber optic array with UV adhesive. The microwave antenna is used to radiate a microwave field to manipulate the electron spin state of the NV color centers.

[0027] The optical signal acquisition unit includes a laser, an optical fiber beam splitter, and multiple independent sub-optical paths; each independent sub-optical path contains an independent optical fiber circulator, a filter, and a photodetector. The laser emitted by the laser is split into multiple laser beams by an optical fiber beam splitter. Each laser beam is transmitted to the respective channels of the multi-channel optical fiber probe group through a corresponding independent sub-optical path. In each independent sub-optical path, the laser is transmitted through an optical fiber circulator to the NV color center of the corresponding channel; the fluorescence generated by the NV color center enters the corresponding photodetector after passing through the optical fiber circulator and filter.

[0028] The fiber optic circulator includes an excitation light injection port, a bidirectional multiplexing port, and a fluorescence output port. The excitation light injection port is connected to the fiber optic beam splitter, and the bidirectional multiplexing port is connected to the corresponding sensing fiber. The fluorescence output port is connected to the filter. The excitation light injection port and the fiber optic beam splitter, as well as the bidirectional multiplexing port and the sensing fiber, are connected by fiber optic flanges or by fiber optic fusion splicing.

[0029] The data processing unit includes an analog-to-digital converter (ADC), an FPGA, and a communication module. The ADC performs analog-to-digital conversion on the fluorescence signal acquired by the photodetector. The FPGA is used for demodulation and data processing of multi-channel data, and the communication module is used for communication with the host computer. The FPGA provides the raw temperature or magnetic field measurement data, gradient data, or tensor data of the workpiece under test according to the instructions from the host computer.

[0030] When the host computer requires gradient data, the FPGA controls a multi-channel fiber optic probe group to collect the temperature or magnetic field of the workpiece under test, or simultaneously collect the temperature and magnetic field. The magnetic field can be a scalar or a vector. Then, the temperature difference ΔT=T1-T2 and / or the magnetic field difference ΔB=B1-B2 between any two adjacent channels are calculated to obtain the temperature gradient and / or magnetic field gradient at different positions of the workpiece under test.

[0031] The multi-channel fiber optic probe group moves along the surface of the workpiece under test under the drive of the scanning platform. The FPGA records the temperature gradient or magnetic field gradient at each position of the workpiece under test and transmits it to the host computer. The host computer generates a temperature gradient image or magnetic field gradient image of the workpiece under test based on the temperature gradient or magnetic field gradient at each position of the workpiece under test.

[0032] In another embodiment, a bias magnet is also included, positioned close to the multi-channel fiber optic probe array, to provide a reference magnetic field of known direction and magnitude for the NV color center. The bias magnet can be a permanent magnet or an electromagnet; in situations where a magnetic field exists in the measurement environment, a separate bias magnet may not be necessary.

[0033] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0034] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An NV color center array sensor based on optical fiber, characterized in that, include: Multi-channel fiber optic probe assembly, microwave radiation unit, optical path and signal acquisition unit, and data processing unit; The multi-channel fiber optic probe group includes at least two sensing fibers, all of which are connected to the same diamond block, or each sensing fiber is individually connected to a diamond particle. Both the diamond block and the diamond particle contain NV color centers. The microwave radiation unit is positioned close to the NV color center of the sensing fiber to provide a microwave field. The optical path signal acquisition unit is used to emit laser light and transmit it to the NV color center of the multi-channel fiber optic probe group, and to receive the fluorescence generated by the NV color center; The multi-channel fiber optic probe group contacts the surface of the workpiece to be tested, and the data processing unit calculates the fluorescence returned by the NV color center in each channel to obtain the detection result of the workpiece to be tested.

2. The fiber-optic-based NV color center array sensor as described in claim 1, characterized in that, The microwave radiation unit includes a microwave antenna, a microwave signal source, and an amplifier; The microwave antenna is wound around the outer periphery of the sensing optical fiber and positioned close to the NV color center; The microwave signal source generates a microwave signal to drive the NV color center, which is then amplified by the amplifier and transmitted to the microwave antenna via the SMA radio frequency cable.

3. The fiber-optic-based NV color center array sensor as described in claim 1, characterized in that, The optical path signal acquisition unit includes a laser, an optical fiber beam splitter, and multiple independent sub-optical paths; each independent sub-optical path includes an independent optical fiber circulator, a filter, and a photodetector. The laser emitted by the laser is split into multiple laser beams by the fiber optic beam splitter, and each laser beam is transmitted one-to-one to the respective channels of the multi-channel fiber optic probe group through the corresponding independent sub-optical path. In each of the independent sub-optical paths, the laser is transmitted through the fiber optic circulator to the NV color center of the corresponding channel; the fluorescence generated by the NV color center enters the corresponding photodetector after passing through the fiber optic circulator and the filter.

4. The fiber-optic-based NV color center array sensor as described in claim 3, characterized in that, The fiber optic circulator includes an excitation light injection port, a bidirectional multiplexing port, and a fluorescence output port; wherein, the excitation light injection port is connected to the fiber optic beam splitter, the bidirectional multiplexing port is connected to the corresponding sensing fiber, and the fluorescence output port is connected to the filter; the excitation light injection port and the fiber optic beam splitter, as well as the bidirectional multiplexing port and the sensing fiber, are connected by fiber optic flanges or by fiber optic fusion splicing.

5. The fiber-optic-based NV color center array sensor as described in claim 1, characterized in that, The data processing unit is connected to the host computer via a communication module and is used to provide raw measurement data or gradient data of the temperature or magnetic field of the workpiece to be measured according to the instructions of the host computer.

6. The fiber-optic-based NV color center array sensor as described in claim 5, characterized in that, When the data processing unit provides gradient data of the workpiece to be tested, the temperature or magnetic field of the workpiece to be tested is collected through the multi-channel fiber optic probe group, and the temperature difference or magnetic field difference between any two adjacent channels is calculated to obtain the temperature gradient or magnetic field gradient at different positions of the workpiece to be tested.

7. The fiber-optic-based NV color center array sensor as described in claim 6, characterized in that, The multi-channel fiber optic probe group moves along the surface of the workpiece under the drive of the scanning platform. The data processing unit records the temperature gradient or magnetic field gradient at each position of the workpiece and transmits it to the host computer. The host computer generates a temperature gradient image or magnetic field gradient image of the workpiece based on the temperature gradient or magnetic field gradient at each position of the workpiece.

8. The fiber-optic-based NV color center array sensor as described in claim 1, characterized in that, The sensing fibers in the multi-channel fiber optic probe group constitute 1 M one-dimensional array or N An M-dimensional array, where N and M are both positive integers greater than 2.

9. The fiber-optic-based NV color center array sensor as described in claim 1, characterized in that, The spacing between any two adjacent sensing fibers is 50μm-3000μm, and the concentration of the NV color center is at the ppm level.

10. The fiber-optic-based NV color center array sensor as described in claim 1, characterized in that, It also includes a bias magnet, which is positioned close to the multi-channel fiber optic probe group to provide a reference magnetic field with a known direction and magnitude for the NV color center.

Images