Nondestructive testing device based on NV color center

Abstract

The invention relates to the technical field of quantum nondestructive sensing, and the scheme is as follows: a nondestructive testing device based on an NV color center comprises a sensor, a magnetizer, a laser module, a microwave module and a data processing module, based on the differential noise reduction principle of exciting light and photoluminescence, structural processing is performed around a small section of optical fiber connected with the diamond NV color center, and the NV color center is obtained. Through the structural design of the truncated optical fiber, part of excitation light is obtained and converted by a photodiode in a short distance in the form of spatial light, meanwhile, efficient obtaining of differential excitation light is achieved through the design of a miniaturized and spatial light type light collecting structural part, and meanwhile development and application of an integrated and miniaturized sensor are promoted.

Description

Technical Field

[0001] The present invention relates to the field of quantum nondestructive sensing technology, and in particular to a nondestructive testing device based on NV color centers. Background Art

[0002] Magnetic flux leakage detection has always been an important research direction in the field of nondestructive testing. Magnetic flux leakage detection equipment using traditional magnetic sensors has been relatively complete, and its functions have their own advantages and disadvantages. This application is based on the research of quantum precision measurement, a new detection technology, and plans to make new breakthroughs in the field of magnetic flux leakage nondestructive testing based on quantum sensing. In recent years, the research and development of solid-state spin color center systems in the field of quantum precision has been rapid. Among them, diamond NV color centers (nitrogen-vacancy centers) can produce photoluminescence under the irradiation of lasers of specific wavelengths (such as 532nm lasers). The fluorescence intensity is related to the external physical environment (such as magnetic fields, temperature, etc.), and diamond NV color centers have extremely high stability and practicality. Therefore, in related fields, quantum sensing research is often carried out around diamond NV color centers.

[0003] The power of the excitation light to the diamond NV color center is often unstable, which will cause unnecessary fluctuations in the fluorescence intensity generated by the solid spin color center, bring noise to the detection, and affect the accuracy and stability of the detection results. The present invention is designed based on this problem and proposes a corresponding solution. Summary of the invention

[0004] The present invention proposes a nondestructive testing device based on NV color centers to solve the problems existing in the prior art.

[0005] To achieve the above object, the present invention provides the following technical solution: a nondestructive testing device based on NV color center, comprising:

[0006] A sensor, comprising a diamond NV color center, a truncated optical fiber, a microwave radiation structure, a first filter, a second filter, a first photodiode and a second photodiode, wherein the truncated optical fiber comprises a first end, a second end and a truncated region, the diamond NV color center is arranged on a side close to the first end, and excitation light is loaded from the second end and stimulates the diamond NV color center to generate photoluminescence after transmission; the first photodiode is configured to sense the excitation light overflowing from the truncated region and generate a first electrical signal, the first filter is arranged on the collection side of the first photodiode, and is used to filter out the excitation light; the second photodiode is configured to sense the photoluminescence and generate a second electrical signal, the second filter is arranged on the collection side of the second photodiode, and is used to filter out the photoluminescence; the microwave radiation structure is configured to radiate a microwave field to the diamond NV color center;

[0007] A magnetizer, used to magnetize the object to be detected and form a detection area for the sensor to perform sensing detection;

[0008] A laser module, used for emitting excitation light of a set wavelength toward the second end;

[0009] A microwave module, used for transmitting a microwave signal of a set frequency to the microwave radiation structure;

[0010] The data processing module is used to perform differential processing according to the first electrical signal and the second electrical signal.

[0011] In a further solution, the data processing module includes a differential unit, and the differential unit performs differential processing on the first electrical signal and the second electrical signal.

[0012] In a further embodiment, the sensor further comprises two TIR lenses, wherein one TIR lens is located between the first photodiode and the cut-off region, for collecting the excitation light overflowing from the cut-off region and transmitting it to the first photodiode, and the other TIR lens is located between the second photodiode and the diamond NV color center, for collecting the photofluorescence generated by the diamond NV color center and transmitting it to the second photodiode.

[0013] In a further solution, a fiber channel for the truncated optical fiber to pass through is provided on the light collection side of the TIR lens.

[0014] In a further solution, the sensor further includes an aperture, and the aperture is arranged on the collection side of the first photodiode.

[0015] In a further embodiment, the microwave radiation structure is a microstrip antenna.

[0016] In a further solution, the cut-off area includes two left and right optical fiber sections, and the core areas of the two optical fiber sections are completely aligned or partially overlapped.

[0017] In a further embodiment, a reflective film is provided in the cladding region on the cross section of the optical fiber.

[0018] In a further solution, an anti-reflection film is provided in the core region of the optical fiber section.

[0019] In a further solution, the cut-off area further includes a fixing member, and the fixing member is used to fix the relative positions of the two optical fiber sections.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention is based on the differential noise reduction principle of excitation light and photofluorescence, and performs structural processing around a small section of optical fiber connected to the diamond NV color center. Through the truncated optical fiber structure design, part of the excitation light is acquired and converted by the photodiode in the form of spatial light within a short distance. At the same time, through the miniaturized, spatial light-type light collection structural component design, efficient acquisition of differential excitation light is achieved, and the development and application of integrated and miniaturized sensors are promoted. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0022] Figure 1 It is a system diagram of the nondestructive testing device in the embodiment;

[0023] Figure 2 A schematic diagram of a sensor in an embodiment;

[0024] Figure 3 A schematic diagram of a completely truncated optical fiber in an embodiment;

[0025] Figure 4 A schematic diagram of partially overlapping truncated optical fibers in an embodiment;

[0026] Figure 5 Schematic diagram of the design of the tapered optical fiber section in the embodiment;

[0027] Figure 6 Schematic diagram of the installation of the diaphragm in the embodiment. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example

[0030] See attached Figure 1 This embodiment provides a nondestructive testing device based on NV color centers, including a sensor 1, a magnetizer 2, a laser module 3, a microwave module 4 and a data processing module 5.

[0031] In this example, if the attached Figure 2As shown, it includes a diamond NV color center 101, a truncated optical fiber 102, a microwave radiation structure 103, a first filter 104, a second filter 105, a first photodiode 106 and a second photodiode 107. The truncated optical fiber 102 includes a first end 1021, a second end 1022 and a truncation region 1023. The diamond NV color center 101 is arranged on a side close to the first end 1021 and away from the truncation region 1023 (the truncation region 1023 is a portion forming a gap between the first end 1021 and the second end 1022). The excitation light is loaded from the second end 1022 and stimulates the diamond NV color center 101 to produce photoluminescence after transmission.

[0032] The first photodiode 106 (with Figure 2 The first filter 104 is arranged between the collection side of the first photodiode 106 and the cut-off area 1023 to filter out the excitation light; the second photodiode 107 (with Figure 2 From the perspective of the embodiment, the second photodiode 107 is arranged above the diamond NV color center 101 and is configured to sense photofluorescence and generate a second electrical signal. The second filter 105 is arranged between the collection side of the second photodiode 107 and the diamond NV color center 101 to filter out the photofluorescence.

[0033] The microwave radiation structure 103 is configured to radiate a microwave field to the diamond NV color center 101 (the specific location of which is not limited, for example, Figure 2 As shown, it is located on the left side of the diamond NV color center 101), wherein, as a preference, the two photodiodes may be avalanche diodes, the truncated optical fiber 102 may be a single-mode optical fiber, and the diamond NV color center 101 contains an ensemble NV color center.

[0034] The sensor 1 in this example can be regarded as an independent remote probe. In the actual design, it should also include some shell structures so that the above components can be installed in the shell to form a whole with it.

[0035] In addition, the cut-off area 1023 should include two left and right fiber sections, and the core areas of the two fiber sections are completely aligned (see the attached Figure 3 ) or partially overlap (see Appendix Figure 4 ), the design of the diamond NV color center 101 in the truncated area is intended to allow a portion of the excitation light to leak from the truncated area and be collected by the first photodiode 106 and converted into a first electrical signal, while a portion of the excitation light continues to be transmitted along the truncated optical fiber 102 to achieve the excitation of the diamond NV color center 101.

[0036] Regarding the design of the cut-off area 1023, considering that a large part of the excitation light leaked from the fiber section is still emitted along the axial direction of the fiber, this part of the excitation light can neither excite the diamond NV color center 101 nor be easily collected and transmitted toward the first photodiode 106 (in this example, a TIR lens is used to collect the excitation light, and a large part of the excitation light reflected along the axial direction of the fiber is difficult to be collected by the TIR lens). In order to optimize this problem and improve the collection efficiency of the excitation light leaked from the cut-off area 1023, in some preferred designs, a reflective film is also provided in the cladding area on the fiber section, and the excitation light leaked along the axial direction is reflected by the reflective film to diverge to the surroundings, thereby improving the collection efficiency. Of course, there may be other designs, such as setting the cladding at the two fiber sections to a cone shape, as shown in the attached Figure 5 As shown, by changing the incident angle between the excitation light and the cladding, the probability of the excitation light diverging in all directions is increased. Of course, this design can also be combined with the design of the aforementioned reflective film.

[0037] Regarding the design of the cut-off region 1023, in order to ensure sufficient excitation light to excite the diamond NV color center 101, in some preferred designs, an anti-reflection film is set in the core area on the optical fiber section, so that the excitation light irradiating the core area can reduce reflection and is easier to enter the core for transmission.

[0038] In this example, the magnetizer 2 is used to magnetize the object to be tested and form a detection area for the sensor 1 to perform sensing detection. Specifically, the magnetizer 2 includes a straight iron core and two permanent magnets. The two permanent magnets are arranged in parallel on the same side of the straight iron core, and the magnetic poles of the two are arranged in opposite directions. The sensor 1 is located between the two permanent magnets. For this example, the combined structure of the magnetizer 2 and the sensor 1 is used as a probe structure of the quantum detector. It is relatively independent of other components and can be used as a remote device when used.

[0039] In this example, the laser module 3 is used to emit excitation light of a set wavelength to the second end 1022. Generally, the excitation light emitted by the laser module 3 is a green laser with a wavelength of 532nm. Of course, the laser module 3 also includes functions such as controllable light intensity.

[0040] In this example, the microwave module 4 is used to transmit a microwave signal of a set frequency to the microwave radiation structure 103. Generally, the microwave signal is around 2.87 GHz, and it is connected to the remote microwave radiation structure through a radio frequency transmission line. Regarding the microwave radiation structure 103, it can be a coil wound with copper wire or a microstrip antenna. The structures are different, and the description here is not a limitation to it.

[0041] In this example, the data processing module 5 is used for data analysis and processing. By comparing and processing the two electrical signals, the detection accuracy can be effectively improved and the laser noise interference can be reduced. In the exemplary scheme, the data processing module 5 includes a differential unit, which performs differential processing on the first electrical signal and the second electrical signal, realizes noise reduction through differentiation, and eliminates the error influence caused by laser power fluctuation.

[0042] Considering that a large part of the excitation light overflowing from the cutoff region 1023 and the photoluminescence at the first end 1021 will not be received by the photodiode, the lower light collection efficiency will affect the measurement accuracy. Based on this, in some preferred designs, such as the attached Figure 2 As shown, the sensor 1 also includes two TIR (Total Internal Reflection) lenses 108, one of which is located between the first photodiode 106 and the cut-off area 1023, and is used to collect the excitation light overflowing from the cut-off area 1023 and transmit it to the first photodiode 106, and the other TIR lens 108 is located between the second photodiode 107 and the diamond NV color center 101, and is used to collect the photofluorescence generated by the diamond NV color center 101 and transmit it to the second photodiode 107.

[0043] The current TIR lens is mainly used for converging small-sized light sources, so its structural design is not conducive to the efficient collection of light signals leaked from the optical fiber. Therefore, in a further solution, the light collection side of the TIR lens 108 is provided with an optical fiber channel for the truncated optical fiber 102 to pass through. Exemplarily, the optical fiber channel includes two optical fiber grooves facing each other front and back. The truncated optical fiber 102 passes through the light collection side of the TIR lens 108 through the optical fiber groove. The truncation area 1023 is located inside the light collection side at this time, thereby increasing the total amount of photofluorescence entering the light collection side and improving the collection efficiency. Of course, there are other solutions for the formation of the optical fiber channel, such as making a front-to-back through-hole on the light collection side.

[0044] Considering that even if an optical fiber channel is set on the light collection side of the TIR lens 108, a large part of the excitation light overflowing from the cut-off area 1023 will still not be received by the photodiode, in order to further optimize this problem, in some other schemes, a light reflection structure, such as a reflective lens, can be set on the side of the cut-off area 1023 away from the first photodiode 104, which is no longer shown in the drawings here.

[0045] Since the intensity of the photofluorescence and the leaked excitation light is different, in the system based on differential and phase-locked, the starting height of the electrical signals formed by the two lights on the measurement spectrum is different, which is not conducive to the program design and processing of the differential process. Figure 6As shown, the sensor further includes an aperture 100. Since the intensity of photofluorescence is generally weaker than the intensity of the excitation light, in order to meet the detection needs, the aperture 100 can be set on the collection side of the first photodiode 106 (exemplarily, it can be located between one of the TIR lenses 108 and the first filter 104). The intensity of the excitation light is adjusted by the aperture 100. During adjustment, the adjustment degree of the aperture 100 is judged by observing the voltage starting height of the measurement spectrum line.

[0046] In order to maintain the relative stability of the two optical fiber end sections in the cut-off region 1023, Figure 4 As shown, the cut-off area also includes a fixing member 109, and the fixing member 109 is used to fix the relative positions of the two optical fiber sections. In an exemplary solution, the fixing member 109 can be a transparent tube body (with optical fiber sections plugged into both ends) or a component such as a V-shaped positioning frame.

[0047] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0048] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A nondestructive testing device based on NV color center, characterized in that: Include: A sensor, comprising a diamond NV color center, a truncated optical fiber, a microwave radiation structure, a first filter, a second filter, a first photodiode and a second photodiode, wherein the truncated optical fiber comprises a first end, a second end and a truncated region, the diamond NV color center is arranged on a side close to the first end, and excitation light is loaded from the second end and stimulates the diamond NV color center to generate photoluminescence after transmission; the first photodiode is configured to sense the excitation light overflowing from the truncated region and generate a first electrical signal, the first filter is arranged on the collection side of the first photodiode, and is used to filter out the excitation light; the second photodiode is configured to sense the photoluminescence and generate a second electrical signal, the second filter is arranged on the collection side of the second photodiode, and is used to filter out the photoluminescence; the microwave radiation structure is configured to radiate a microwave field to the diamond NV color center; A magnetizer, used to magnetize the object to be detected and form a detection area for the sensor to perform sensing detection; A laser module, used for emitting excitation light of a set wavelength to the second end; A microwave module, used for transmitting a microwave signal of a set frequency to the microwave radiation structure; The data processing module is used to perform differential processing according to the first electrical signal and the second electrical signal.

2. The nondestructive testing device based on NV color center according to claim 1 is characterized in that: The data processing module includes a differential unit, and the differential unit performs differential processing on the first electrical signal and the second electrical signal.

3. The nondestructive testing device based on NV color center according to claim 1 is characterized in that: The sensor also includes two TIR lenses, one of which is located between the first photodiode and the cut-off region, and is used to collect the excitation light overflowing from the cut-off region and transmit it to the first photodiode, and the other TIR lens is located between the second photodiode and the diamond NV color center, and is used to collect the photofluorescence generated by the diamond NV color center and transmit it to the second photodiode.

4. The nondestructive testing device based on NV color center according to claim 3 is characterized in that: The light collection side of the TIR lens is provided with an optical fiber channel for the truncated optical fiber to pass through.

5. The nondestructive testing device based on NV color center according to claim 1 is characterized in that: The sensor further comprises an aperture, which is arranged on the collection side of the first photodiode.

6. The nondestructive testing device based on NV color center according to claim 1 is characterized in that: The microwave radiation structure is a microstrip antenna.

7. The nondestructive testing device based on NV color center according to claim 1 is characterized in that: The cut-off area includes two left and right optical fiber sections, and the core areas of the two optical fiber sections are completely aligned or partially overlapped.

8. The nondestructive testing device based on NV color centers according to claim 7, characterized in that: A reflective film is provided in the cladding region on the cross section of the optical fiber.

9. The nondestructive testing device based on NV color center according to claim 7, characterized in that: An anti-reflection film is provided in the core region of the optical fiber section.

10. The nondestructive testing device based on NV color centers according to claim 7, characterized in that: The cutting area also includes a fixing member, which is used to fix the relative positions of the two optical fiber sections.

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