A magnetic detection device based on diamond NV color centers and Kerr effect

Abstract

This invention provides a magnetic detection device based on diamond NV centers and the Kerr effect. It achieves the sharing of light sources and optical paths between magnetic detection technologies based on the magneto-optical Kerr effect and those based on NV centers, combining the two technologies and greatly simplifying the device structure. This increases the intensity of the optical signal received by the detection module, reduces noise interference in the signal, and thus improves the accuracy of magnetic detection. It can simultaneously meet the requirements of rapid and high-resolution detection, and improve the overall detection speed while ensuring detection accuracy.

Description

Technical Field

[0001] This invention belongs to the field of magnetic material measurement technology, and relates to the magnetic detection of objects, specifically to a magnetic detection device based on diamond NV color centers and Kerr effect. Background Technology

[0002] Measuring the magnetization state of magnetic materials is of great significance in physics, materials science, electronics, and industrial production. In recent years, a magnetic measurement method utilizing nitrogen-vacancy centers (NV centers) in diamond has emerged. The principle involves using a diamond probe tip containing NV centers, placed near the sample. Under the influence of the sample's leakage magnetic field, the spin state of the NV centers undergoes Zeeman level splitting. By manipulating the spin with microwaves and exciting the transition with lasers, the minute magnetic field signal can be detected by observing and analyzing the fluorescence data emitted by the NV centers. Furthermore, by combining this with a high-precision displacement stage to move the sample, the surface leakage magnetic field at different locations on the sample can be detected, thus achieving magnetic scanning or imaging of the sample. Thanks to the small size and high precision of the NV centers, this method can achieve magnetic detection with nanometer-level spatial resolution, but it also results in excessively long scanning times.

[0003] Magneto-optical Kerr effect-based magnetic detection technology detects the magnetism of an object by emitting a beam of polarized light towards it and detecting the polarization state of the reflected light. When the polarized light converges at a point on the object, the magnetism at that point can be measured. Furthermore, by combining this with a high-precision displacement stage to move the sample, magnetic measurements at different locations on the sample can be achieved, thus enabling scanning or imaging of the sample's magnetism. While the magneto-optical Kerr effect occurs almost in real-time, its detection speed is fast, but due to the optical diffraction limit, the resolution of magneto-optical Kerr effect-based magnetic detection is difficult to exceed 200 nm.

[0004] To leverage the advantages of magnetic detection technologies based on the magneto-optical Kerr effect and those based on NV color centers, it is often desirable to combine the two. However, due to the differences in their optical systems and operating methods, it is difficult to achieve a combination of the two imaging technologies.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] To address the technical problem of combining existing magnetic detection technologies based on the magneto-optical Kerr effect with those based on NV centers, this invention provides a magnetic detection device based on diamond NV centers and the Kerr effect. The device comprises a light source module, a fluorescence detection module, a Kerr effect detection module, a diamond NV center probe module, and a displacement stage. The displacement stage supports and moves the object under test. The diamond NV center probe module includes a microwave emitting device for manipulating the spin of the NV center and a probe with the NV center positioned close to the test location on the object. The light source... The light emitted by the module includes at least polarized light and light that causes the NV color center to fluoresce. The light emitted by the light source module illuminates the NV color center and the measured position of the object under test. The magnetic detection device also includes a dichroic mirror, which is configured to deflect green light and red light to different directions. The light emitted by the light source module is generally green. The light reflected by the object under test and the fluorescence emitted by the NV color center are decomposed into red light and green light by the dichroic mirror. The red light decomposed by the dichroic mirror enters the fluorescence detection module, and the green light decomposed by the dichroic mirror enters the Kerr effect detection module.

[0007] Optionally, the light source module includes a light source and a polarizer. The light emitted by the light source is a generally green monochromatic laser. After passing through the polarizer, the monochromatic laser emitted by the light source is polarized and emitted from the light source module.

[0008] More preferably, a lens is provided in the optical path between the light source and the polarizer.

[0009] More preferably, the light source module further includes an optical fiber, through which the light emitted by the light source propagates.

[0010] Furthermore, the light source module also includes an optical fiber coupler, which is disposed at the light-emitting end of the optical fiber. The light emitted by the light source passes through the optical fiber and exits from the optical fiber coupler.

[0011] More preferably, the light source module further includes an optical modulator disposed on the optical fiber.

[0012] Optionally, the light source module includes a monochromatic light source and a polarized light source. The monochromatic light source emits a generally green monochromatic laser, and the polarized light source includes a laser source and a polarizer. The light emitted by the laser source is polarized after passing through the polarizer, and the monochromatic laser and the polarized light are combined and emitted from the light source module.

[0013] Optionally, the light source module further includes a beam combiner, wherein one of the light emitted by the monochromatic light source and the light emitted by the polarized light source is transmitted through the beam combiner, and the other is reflected by the beam combiner, and the light emitted by the monochromatic light source and the light emitted by the polarized light source after passing through the beam combiner propagate along the same optical axis.

[0014] Optionally, the Kerr effect detection module includes a Wollaston prism and a balance detector. The light reflected by the object under test is split into two beams by the Wollaston prism and enters the balance detector respectively. The balance detector outputs a corresponding signal according to the polarization state of the two received beams of light.

[0015] Optionally, the magnetic detection device further includes a beam splitter, through which the light emitted by the light source module illuminates the NV color center and the test object; the fluorescence emitted by the NV color center enters the fluorescence detection module through the beam splitter; and the light reflected by the test object enters the Kerr effect detection module through the beam splitter.

[0016] Preferably, the fluorescence detection module includes a filter and a photodetector, wherein the filter is configured to allow the fluorescence emitted by the NV color center to pass through while blocking other light except for the fluorescence.

[0017] Furthermore, the passband of the filter is 600nm-700nm.

[0018] Preferably, the wavelength of the light emitted by the light source module is 450nm-600nm.

[0019] Optionally, the magnetic detection device further includes a microscope objective lens. Light irradiated onto the object under test is focused by the microscope objective lens onto the measured position and the NV color center. The light reflected by the object under test and the fluorescence emitted by the NV color center are deflected by the microscope objective lens and then enter the Kerr effect detection module and the fluorescence detection module, respectively.

[0020] The present invention has at least the following beneficial effects: it realizes the sharing of light source and optical path between magnetic detection technology based on magneto-optical Kerr effect and magnetic detection technology based on NV color center, combining the two magnetic detection technologies and greatly simplifying the equipment structure; it increases the intensity of the light signal received by the detection module, reduces noise interference in the signal, and thus improves the accuracy of magnetic detection; it can simultaneously meet the needs of rapid detection and high-resolution detection, and improve the overall detection speed while ensuring detection accuracy. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of one embodiment of the present invention.

[0022] Figure 2This is a schematic diagram of the overall structure of another embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram of the overall structure of another embodiment of the present invention. Implementation

[0024] To make the objectives and features of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that the drawings are all in a very simplified form and use non-precise ratios, and are only used to conveniently and clearly assist in illustrating the objectives of the embodiments of the present invention.

[0025] Please see Figures 1 to 3 This invention provides a magnetic detection device based on diamond NV centers and the Kerr effect, including a light source module 100, a fluorescence detection module 200, a Kerr effect detection module 300, a diamond NV center probe module 600, and a displacement stage 400. The displacement stage 400 is used to support and move the object under test 500. The diamond NV center probe module 600 includes a microwave emitting device 620 for manipulating the spin of the NV center 610 and a probe 630 with the NV center 610. The NV center 610 of the probe 630 is close to the test position of the object under test 500. The light emitted by the light source module 100 includes at least polarized light. The NV color center 610 emits fluorescent light, and the light emitted by the light source module 100 illuminates the NV color center 610 and the measured position of the object 500. The magnetic detection device also includes a dichroic mirror 700, which is configured to deflect green and red light to different directions. The light emitted by the light source module 100 is generally green. The light reflected by the object 500 and the fluorescence emitted by the NV color center 610 are decomposed into red and green light by the dichroic mirror 700. The red light decomposed by the dichroic mirror 700 enters the fluorescence detection module 200, and the green light decomposed by the dichroic mirror 700 enters the Kerr effect detection module 300.

[0026] The light emitted by the light source module 100 illuminates the NV color center 610, causing it to fluoresce. Based on the mechanism of the NV color center, this fluorescence is predominantly red. Therefore, the majority of the red light after decomposition by the dichroic mirror 700 is the fluorescence of the NV color center 610. In other words, the majority of the light entering the fluorescence detection module 200 is the fluorescence of the NV color center 610. The light emitted by the light source module 100 illuminates the test object 500 and is reflected by it. Since the light emitted by the light source module 100 is predominantly green, and the magneto-optical Kerr effect does not affect the wavelength of the light, the light reflected by the test object 500, carrying the magnetic information of the test object 500, is still predominantly green. Therefore, the majority of the green light after decomposition by the dichroic mirror 700 is the light reflected by the test object 500. In other words, the majority of the light entering the Kerr effect detection module 300 is the light reflected by the test object 500.

[0027] As described above, the light source module 100 enables the sharing of light source and optical path between the magnetic detection technology based on the magneto-optical Kerr effect and the magnetic detection technology based on the NV color center, combining the two magnetic detection technologies and greatly simplifying the equipment structure. Through the dichroic mirror, the light reflected by the test object 500 and the fluorescence of the NV color center 610 are separated. Since the dichroic mirror 700 can make one of the red and green light almost completely transparent and the other almost completely reflected when decomposing the red and green light, the light energy loss is small, which increases the intensity of the light signal received by the fluorescence detection module 200 and the Kerr effect detection module 300, reduces noise interference in the signal, and thus improves the accuracy of magnetic detection.

[0028] In use, light emitted by the light source module 100, including at least polarized light, is projected onto the object under test 500. The polarization state of the light reflected by the object under test 500 changes due to the measured position of the object under test 500. The light reflected by the object under test 500 enters the Kerr effect detection module 300 at least through a dichroic mirror. The Kerr effect detection module 300 outputs a corresponding signal based on the polarization state of the received light. An external device further analyzes this signal to determine the magnetism at the corresponding position of the object under test 500. The object under test 500 is moved by the displacement stage 400, causing the light emitted by the light source module 100 to scan along a preset trajectory on the surface of the object under test 500. Combined with the signal output by the Kerr effect detection module 300 at the corresponding time, the magnetism at each position in the corresponding trajectory is obtained, thereby realizing the scanning detection of the magnetism of the object under test 500. Alternatively, based on the scanning detection results, the magnetism of the detected area of ​​the object under test 500 can be further imaged. Since the magnetic detection technology based on the magneto-optical Kerr effect has a fast detection speed, the detection of the test object 500 using the signal output by the Kerr effect detection module 300 is also fast. This allows for rapid preliminary detection of the test object 500 and facilitates the selection of areas that need further detection at a higher resolution.

[0029] After selecting the area for further detection, an electromagnetic pulse sequence is emitted by a microwave transmitter 620 to manipulate the spin state of the NV color center 610. After the spin state of the NV color center 610 is adjusted, light emitted by the light source module 100, including light capable of causing the NV color center 610 to fluoresce, is projected onto the NV color center 610. The NV color center 610 fluoresces under the action of the light emitted by the light source module 100. The NV color center 610 is close to the test position of the test object 500, so the fluorescence of the NV color center 610 is affected by the magnetism of the test position of the test object 500. The fluorescence enters the fluorescence detection module 200 at least through a dichroic mirror. The fluorescence detection module 200 outputs a corresponding signal based on the received fluorescence. External equipment further analyzes the signal to determine the magnetism of the corresponding position of the test object 500. The test object 500 is moved by the displacement stage 400, causing a relative positional change between the NV color center 610 and the test object 500, and scanning along a preset trajectory. Combined with the signal output by the fluorescence detection module 200 at the corresponding time, the magnetism at each position in the corresponding trajectory is obtained, thereby realizing the scanning detection of the magnetism of the test object 500. Alternatively, based on the scanning detection results, the magnetism of the detected area of ​​the test object 500 can be further imaged. Since the magnetic detection technology based on NV color centers has a high detection resolution, it can perform higher resolution detection or imaging of the magnetism of the detected area, thus meeting the requirements of higher resolution detection.

[0030] Through the aforementioned step-by-step detection, firstly, magnetic detection based on the Kerr effect is performed to conduct preliminary imaging and determine the area to be further detected. Then, magnetic detection based on the NV color center is used to further detect this area. Only the area requiring high-resolution detection is subjected to magnetic detection based on the NV color center. This can simultaneously meet the requirements of rapid detection and high-resolution detection, and improve the overall detection speed while ensuring detection accuracy.

[0031] It should be noted that the NV color center 610 is largely transparent. Even if the NV color center 610 is placed in the optical path above the object under test 500, both the light illuminating the object under test 500 and the light reflected from the object under test 500 can pass through the NV color center 610. Furthermore, the NV color center 610 has minimal influence on the polarization state of the light passing through it, to the point that this influence can be ignored in magnetic detection based on the magneto-optical Kerr effect. Therefore, when using the same light source module 100, there is no need to consider the obstruction problem of the NV color center 610 in the optical path, which greatly simplifies the optical path structure.

[0032] For one embodiment of the light source module 100, please refer to Figure 1The light source module 100 includes a light source 110 and a polarizer 120. The light emitted by the light source 110 is a generally green monochromatic laser. After passing through the polarizer 120, the monochromatic laser emitted by the light source 110 is polarized and exits the light source module 100. The exit light from the light source module 100 obtained in this way is both polarized light that can be used for magnetic detection based on the Kerr effect and green light that can excite fluorescence of NV color centers. Without replacing the light source module 100 or any of its components, it can be used simultaneously for magnetic detection based on the magneto-optical Kerr effect and NV color centers. This greatly simplifies the optical path and the corresponding equipment structure. Furthermore, there is no need to switch the optical path in different detection modes, making the optical path and light easy to maintain stability, reducing debugging time, and improving efficiency.

[0033] Figure 1 The diagram illustrates a more varied implementation of the light source module 100, in which a lens 130 can be positioned between the light source 110 and the polarizer 120 to adjust the light emitted by the light source 110 to meet corresponding detection requirements. The lens 130 can also be configured with appropriate lens groups to achieve similar functions. Furthermore, an optical fiber 140 can be provided to allow light emitted from the light source 110 to propagate through it, making the positioning of the light source 110 more flexible. Further, when using the optical fiber 140 for light propagation, an optical fiber coupler 160 can be provided. For example, an optical fiber coupler 160 can be positioned at the light-emitting end of the optical fiber 140, allowing light emitted from the light source 110 to pass through the optical fiber 140 and exit from the optical fiber coupler 160, facilitating installation and adjustment in appropriate equipment. An optical modulator 150 can also be provided as needed to modulate or control the on / off state of the light emitted from the light source module 100, for example, in… Figure 1 In the embodiment of the light source module 100 shown, the light modulator 150 is disposed on the optical fiber 140.

[0034] Figure 2 Another implementation of the light source module 100 is shown, wherein the light source module 100 includes a monochromatic light source 112 and a polarized light source. The monochromatic light source 112 emits a generally green monochromatic laser, and the polarized light source includes a laser source 111 and a polarizer 120. The light emitted from the laser source 111 is polarized by the polarizer 120. The monochromatic laser emitted from the monochromatic light source 112 and the polarized light emitted from the polarized light source are combined and then exit the light source module 100. Furthermore, the aforementioned monochromatic laser and polarized light can be combined using a beam combiner 130. For details, please refer to [link to relevant documentation]. Figure 2 The light source module 100 also includes a beam combiner 130. One of the light emitted by the monochromatic light source 112 and the light emitted by the polarized light source is transmitted through the beam combiner 130, and the other is reflected by the beam combiner 130. The light emitted by the monochromatic light source 112 and the light emitted by the polarized light source propagate along the same optical axis after passing through the beam combiner. Figure 2In the process, the light emitted by the monochromatic light element 112 is reflected by the beam combiner 130, and the light emitted by the polarized light source is projected onto the beam combiner 130. The light emitted from the beam combiner 130 propagates along the same optical axis, thereby making the light emitted from the light source module 100 appear as a beam of light.

[0035] Please see Figure 1 , Figure 2 The Kerr effect detection module 300 includes a Wollaston prism 310 and balance detectors 321 and 322. Light reflected from the object under test 500 is split into two beams by the Wollaston prism 310 and enters the balance detectors 321 and 322 respectively. The balance detectors 321 and 322 output corresponding signals based on the polarization states of the two received beams. The Wollaston prism 310 can decompose light into two beams with mutually perpendicular polarization states. Therefore, by receiving the two decomposed beams through the balance detectors 321 and 322 and comparing and analyzing the received beams, the Kerr angle of the light reflected from the object under test 500 can be measured, thereby enabling the detection of the magnetism and strength of the object under test 500.

[0036] Please see Figure 1 , Figure 2 To further enhance the magnetic detection device, a beam splitter 800 is also included. Light emitted from the light source module 100 is directed through the beam splitter 800 to the NV color center 610 and the object under test 500. Fluorescence emitted from the NV color center 610 is directed through the beam splitter 800 into the fluorescence detection module 200. Light reflected from the object under test is directed through the beam splitter 800 into the Kerr effect detection module 300. By setting the beam splitter 800, light emitted from the light source module 100 can be incident on the object under test 500 in a direction perpendicular to the object under test, and light reflected from the object under test 500 propagates in a direction perpendicular to the object under test, ensuring that the incident and reflected light from the object under test propagate along the same path, further reducing the space occupied by the optical path.

[0037] To further improve the detection accuracy of the fluorescence detection module 200, the fluorescence detection module 200 includes a filter 220 and a photodetector 210. The filter 220 is configured to allow fluorescence emitted by the NV color center 610 to pass through while blocking other light outside the fluorescence. For example, the passband of the filter 220 is 600nm-700nm. The photodetector 210 calculates the magnetism of the test object 500 at the corresponding position based on the received fluorescence, including at least the intensity information.

[0038] Preferably, in order for the light emitted by the light source module 100 to cause the NV color center 610 to fluoresce, the wavelength of the light emitted by the light source module 100 is 450nm-600nm.

[0039] Please see Figure 1 , Figure 2In order to further converge the light propagating toward the test object 500 or the NV color center 610, the magnetic detection device provided by the present invention may further include a microscope objective lens 900. The light irradiated onto the test object 500 is converged by the microscope objective lens 900 to the test position or the NV color center 610. The light reflected by the test object 500 and the fluorescence emitted by the NV color center 610 are deflected by the microscope objective lens 900 and enter the Kerr effect detection module 300 and the fluorescence detection module 200 respectively.

[0040] Figure 1 , Figure 2 The diagram illustrates the form in which light emitted from the light source module 100 is incident on the test object 500 in a vertical direction. It can be understood that the light emitted from the light source module 100 can also be incident on the test object 500 at a certain angle. Please refer to [link / reference]. Figure 3 This diagram illustrates an embodiment in which light emitted from a light source module 100 is incident on a test object 500 at a certain angle. Figure 1 , Figure 2 The main difference lies in the fact that the light emitted by the light source module 100 is incident obliquely onto the object under test 500 and reflected along the corresponding reflected light path. The fluorescence emitted by the NV color center 610 has no clear directionality. Therefore, the positions of the dichroic mirror 700, the fluorescence detection module 200, and the Kerr effect detection module 300 can be set according to the light path reflected by the object under test 500. For the specific detection method and detection principle, please refer to the foregoing content, which will not be repeated here.

[0041] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Therefore, the above descriptions are merely embodiments of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the present invention. Various equivalent changes and modifications are included without departing from the spirit and scope of the present invention, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A magnetic detection device based on diamond NV color centers and the Kerr effect, characterized in that: The device includes a light source module, a fluorescence detection module, a Kerr effect detection module, a diamond NV center probe module, and a displacement stage. The displacement stage is used to support and move the test object. The diamond NV center probe module includes a microwave emitting device for manipulating the spin of the NV center and a probe on which the NV center is located. The NV center of the probe is close to the test position of the test object. The light emitted by the light source module includes at least polarized light and light that causes the NV center to fluoresce. The light emitted by the light source module illuminates the NV center and the test position of the test object. The magnetic detection device further includes a dichroic mirror configured to deflect green and red light in different directions. The light emitted by the light source module is green. The light reflected by the object under test and the fluorescence emitted by the NV color center are decomposed into red and green light by the dichroic mirror. The red light decomposed by the dichroic mirror enters the fluorescence detection module, and the green light decomposed by the dichroic mirror enters the Kerr effect detection module. The dichroic mirror separates the light reflected by the object under test and the fluorescence of the NV color center, thereby increasing the intensity of the corresponding light signals received by the fluorescence detection module and the Kerr effect detection module. The magnetic detection device also includes a beam splitter. The light emitted by the light source module is irradiated by the beam splitter onto the NV color center and the object under test. The fluorescence emitted by the NV color center enters the fluorescence detection module via the beam splitter. The light reflected by the object under test enters the Kerr effect detection module via the beam splitter.

2. The magnetic detection device based on diamond NV color centers and Kerr effect as described in claim 1, characterized in that: The light source module includes a light source and a polarizer. The light emitted by the light source is a green monochromatic laser. After passing through the polarizer, the monochromatic laser emitted by the light source is polarized and emitted from the light source module.

3. The magnetic detection device based on diamond NV color centers and Kerr effect as described in claim 1, characterized in that: The light source module includes a monochromatic light source and a polarized light source. The monochromatic light source emits a green monochromatic laser. The polarized light source includes a laser source and a polarizer. The light emitted by the laser source is polarized after passing through the polarizer. The monochromatic laser and the polarized light are combined and then emitted from the light source module.

4. The magnetic detection device based on diamond NV color centers and Kerr effect as described in claim 3, characterized in that: The light source module also includes a beam combiner. One of the light emitted by the monochromatic light source and the light emitted by the polarized light source is transmitted through the beam combiner, and the other is reflected by the beam combiner. The light emitted by the monochromatic light source and the light emitted by the polarized light source after passing through the beam combiner propagate along the same optical axis.

5. The magnetic detection device based on diamond NV color centers and Kerr effect as described in claim 1, characterized in that: The Kerr effect detection module includes a Wollaston prism and a balance detector. The light reflected by the object being measured is split into two beams by the Wollaston prism and enters the balance detector respectively. The balance detector outputs a corresponding signal according to the polarization state of the two received beams of light.

6. The magnetic detection device based on diamond NV color centers and Kerr effect as described in claim 1, characterized in that: The fluorescence detection module includes a filter and a photodetector. The filter is configured to allow the fluorescence emitted by the NV color center to pass through while blocking other light except for the fluorescence.

7. The magnetic detection device based on diamond NV color centers and Kerr effect as described in claim 6, characterized in that: The passband of the filter is 600nm-700nm.

8. The magnetic detection device based on diamond NV color centers and Kerr effect as described in claim 1, characterized in that: The wavelength of the light emitted by the light source module is 450nm-600nm.

9. The magnetic detection device based on diamond NV color centers and Kerr effect as described in claim 1, characterized in that: The magnetic detection device also includes a microscope objective. Light illuminating the object under test is focused by the microscope objective at the test location and the NV color center. The light reflected by the object under test and the fluorescence emitted by the NV color center are deflected by the microscope objective and enter the Kerr effect detection module and the fluorescence detection module, respectively.

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