Magnetic imaging device and imaging method based on diamond NV color center and Kerr effect

Abstract

A magnetic imaging device and imaging method based on diamond NV color center and Kerr effect, a spin-manipulated light source module provides a beam of incident laser light, which passes through a dichroic mirror system and is focused by a microscope objective lens and then irradiated onto the NV color center of a diamond probe, and the fluorescence generated by the NV color center returns to the dichroic mirror system through the microscope objective lens and enters the fluorescence detection module; a polarized light generating module generates polarized light, which passes through the dichroic mirror system through transmission and / or reflection, enters the microscope objective lens, and then irradiates onto a sample placed on a displacement stage, and after being reflected by the sample, part of the polarized light enters the microscope objective lens again, and then passes through the dichroic mirror system and enters the polarized light detection and imaging module. The present invention realizes high-resolution, global, and wide-field imaging of samples through compatibility design.

Description

Technical field:

[0001] The present invention belongs to the technical field of magnetic materials and magnetic field measurement, and specifically relates to a magnetic imaging device and method based on diamond NV color centers and magneto-optical Kerr effect (also referred to as Kerr effect in this application). It can be used to perform high spatial resolution and global magnetic imaging of materials, and has important application value in the fields of physics, materials, electronics and industrial detection. Background technology:

[0002] The measurement of 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 using nitrogen-vacancy color centers (hereinafter referred to as NV color centers) in diamond has emerged. The principle is to use a diamond with an NV color center as the front end of the probe and place it near the sample to be measured. Under the action of the sample leakage magnetic field, the spin state of the NV color center is affected by the magnetic field and the Zeeman energy level splits. By manipulating the spin with microwaves and exciting the transition with lasers, the tiny magnetic field signal can be detected by observing and analyzing the fluorescence data radiated by the NV color center. By moving the sample with a high-precision translation stage, the surface leakage magnetic field at different positions of the sample can be detected, thereby realizing the scanning imaging of the magnetization state of the sample. Thanks to the small size and high precision of the NV color center, this method can achieve magnetic imaging with nanometer-level spatial resolution. However, this method cannot achieve global synchronous imaging, and it takes a long time to image a target of a large area by scanning, so the detection size is also small. Magneto-optical Kerr imaging is a technique that uses the magneto-optical Kerr effect to image samples. It can image the entire sample and has a large imaging range, ranging from hundreds of microns to several millimeters. However, due to optical diffraction and other reasons, the resolution of magneto-optical Kerr microscope imaging is difficult to be better than 200nm. Magneto-optical Kerr imaging is different from imaging based on NV color centers in principle, and its optical system and operation method are also different. Therefore, traditional equipment and imaging methods cannot achieve compatibility between the two imaging technologies.

[0003] In the existing technical solutions, although the magnetic field measurement technology based on NV color centers has the characteristics of high spatial resolution and can theoretically reach the level of several nanometers, it is basically based on single-point scanning to realize the imaging of the magnetization state of magnetic samples. Not only can it not achieve synchronous global imaging, but it also takes a long time to scan a large area of ​​the sample surface; while magneto-optical Kerr imaging can achieve global time-synchronous imaging, and the imaging field of view is wider, which can reach hundreds of microns to several millimeters. However, the imaging resolution is limited by optical diffraction and is generally not better than 200nm.

[0004] Since the optical path of the imaging system based on diamond NV color centers is a confocal optical path, which is different from the configuration, principle and operation method of the magneto-optical Kerr microscopy imaging system, it is impossible to implement the two imaging technologies on the same optical path in the traditional way. Summary of the invention:

[0005] In order to solve the above technical problems existing in the prior art, the present invention proposes a magnetic imaging device and imaging method based on diamond NV color center and Kerr effect. Through compatibility design, the above two magnetic measurement methods can be implemented in the same device, thereby achieving high-resolution, global and large-field imaging of the sample. The so-called high resolution means that the spatial imaging resolution is higher than the ordinary optical microscopy resolution limit, that is, the resolution is better than 200nm.

[0006] In order to achieve the above-mentioned invention objectives, this application specifically adopts the following technical solutions.

[0007] A magnetic imaging device based on diamond NV color center and Kerr effect, the device comprises a spin manipulation light source module 1, a polarized light generation module 2, a fluorescence detection module 3, a polarized light detection and imaging module 4, a microscope objective 5, a diamond probe with NV color center 9, an NV color center probe arm 10, a microwave emission device 12, and a translation stage 13; the characteristics are:

[0008] The spin manipulation light source module 1 is used to provide a beam of incident laser light, which passes through a dichroic mirror system, so that the laser light is transmitted and / or reflected by the dichroic mirror, and after being focused by a microscope objective lens 5, is irradiated onto the NV color center of a diamond probe 9, and the diamond probe 9 is clamped by an NV color center probe arm 10;

[0009] The microwave transmitting device 12 is arranged near the NV center of the diamond probe 9 and is used to transmit an electromagnetic pulse sequence to control the spin state of the NV center;

[0010] The fluorescence generated by the NV color center of the diamond probe 9 returns to the dichroic mirror system through the microscope objective 5, is transmitted and / or reflected by the dichroic mirror system, and enters the fluorescence detection module 3;

[0011] The polarized light generating module 2 is used to generate light with linear polarization properties, i.e., polarized light. The polarized light is transmitted and / or reflected by the dichroic mirror system, enters the microscope objective 5, and then irradiates the sample 11 placed on the translation stage 13. After the polarized light is reflected by the sample, part of it enters the microscope objective 5 again, and then enters the polarized light detection and imaging module 4 after being transmitted and / or reflected by the dichroic mirror system.

[0012] The present invention further includes the following preferred technical solutions:

[0013] The dichroic mirror system comprises a first dichroic mirror 6, a second dichroic mirror 7, and a third dichroic mirror 8;

[0014] The first dichroic mirror 6, the second dichroic mirror 7, and the third dichroic mirror 8 are configured as follows:

[0015] The second dichroic mirror 7 is tiltedly arranged at the intersection of the incident laser light emitted by the spin-manipulated light source module 1 and the polarized light emitted by the polarized light generating module 2, and can transmit or reflect the incident laser light, reflect or transmit the polarized light, and make the incident laser light and the polarized light have the same optical path after being transmitted or reflected by the second dichroic mirror 7;

[0016] The first dichroic mirror 6 is disposed above the microscope objective 5 and is capable of receiving the laser light or polarized light after being transmitted or reflected by the second dichroic mirror 7 and reflecting the laser light or polarized light into the microscope objective 5;

[0017] The third dichroic mirror 8 is arranged between the first dichroic mirror 6 and the fluorescence detection module 3, and can make the polarized light reflected by the sample pass through the microscope objective 5 and the first dichroic mirror 6 in sequence, and then reflect it into the polarized light detection and imaging module 4. At the same time, it can make the fluorescence emitted by the NV color center pass through the objective lens 5, the first dichroic mirror 6 and the third dichroic mirror 8 and enter the fluorescence detection module 3.

[0018] The spin manipulation light source module 1 is composed of a laser source 1a, a first optical fiber 1b, a second optical fiber 1d, an optical modulator 1c, an optical fiber coupler 1e and a first convex lens 1f;

[0019] The optical modulator 1c is used to control the on-off of the light in the spin-controlled light source module 1.

[0020] When the optical modulator 1c is a fiber-coupled modulator, the laser source 1a, the optical modulator 1c, and the fiber coupler 1e are connected in sequence through optical fibers in a front-to-back order, and the first convex lens 1f is placed at the rear end of the fiber coupler 1e to focus the incident laser onto the dichroic mirror system;

[0021] When the optical modulator 1c is a free space light modulator, the laser source 1a and the fiber coupler 1e are connected by optical fiber, the optical modulator 1c and the first convex lens 1f are placed at the rear end of the fiber coupler 1e, and the order of the optical modulator 1c and the first convex lens 1f can be swapped; the modulated laser is incident into the dichroic mirror system.

[0022] All or part of the components of the spin-manipulated light source module 1 are placed on an adjustment frame to adjust the direction of the incident light so that the laser emitted by the spin-manipulated light source module 1 is focused on the NV color center of the diamond probe 9 after passing through the microscope objective 5 .

[0023] The incident laser provided by the spin-manipulation light source module 1 is a monochromatic light source with a wavelength ranging from 500nm to 600nm, and the light source can be pulse modulated.

[0024] The polarized light generating module 2 is composed of a light source 2a, a second convex lens 2b and a polarizer 2c;

[0025] The light source 2a may be selected from, but not limited to, LED lamps, mercury lamps, xenon lamps, and light output through optical fiber coupling; the polarizer 2c refers to a device that can convert non-polarized light into linearly polarized light after passing through this element;

[0026] The light source 2a is placed at the front side, and the positions of the second convex lens 2b and the polarizer 2c at the rear side can be swapped; the second convex lens 2b and the polarizer 2c can also be directly integrated with the light source 2a to become a linearly polarized light source.

[0027] The polarized light generating module 2 generates linearly polarized light with a wavelength between 300 nm and 530 nm.

[0028] The fluorescence detection module 3 is composed of a first filter 3a, a fiber coupler 3b, an optical fiber 3c, and a first photodetector 3d;

[0029] The fluorescence generated by the NV color center of the diamond probe 9 enters the first filter 3a, is collected into the optical fiber 3c through the optical fiber coupler 3b, and then enters the first photodetector 3d, where the optical signal is converted into an electrical signal.

[0030] The fluorescence detection module 3 is composed of a second filter 3f, an aperture 3g and a second photodetector 3h;

[0031] Among them, the second filter 3f and the aperture 3g can be swapped; after the fluorescence generated by the NV color center of the diamond probe 9 enters the fluorescence detection module 3, it is focused on the light hole of the aperture 3g and passes through, and is received by the second photodetector 3h, and other interference light is shielded by the aperture 3g.

[0032] Among them, the first filter 3a and the second filter 3f refer to filtering devices with a passband between 540nm-1000nm, which are used to filter out the light emitted by the spin manipulation light source module 1 and reflected through the optical path into the fluorescence detection module 3, and only allow the fluorescence emitted by the NV color center due to the change in spin state to pass through the filter.

[0033] All or some of the components of the fluorescence detection module 3 are placed on an adjustment frame to adjust the position of the fiber coupler 3b or the aperture 3g. The fluorescence emitted by the NV color center passes through the objective lens 5 and is focused at the entrance of the fiber coupler 3b or at the small hole of the aperture 3g to be detected by the first photodetector 3d or the second photodetector 3h.

[0034] The polarized light detection and imaging module 4 includes a polarizer 4a and a camera 4d. The polarization state of the light beam is detected by the polarizer 4a and the camera 4d is used to perform imaging.

[0035] The analyzer 4a refers to a linear polarizer, and the analyzer 4a is but not limited to any of the following:

[0036] Thin-film polarizer or Glan-Taylor prism or Glan-Thompson prism;

[0037] The optional range of the camera 4d includes but is not limited to a CCD camera or a CMOS camera.

[0038] The polarized light detection and imaging module 4 also includes one or more filters arranged at any position before the camera 4d, and the bandpass range of the filters is adapted to the light source emitted by the polarized light generating module 2, and is between 300nm-530nm.

[0039] The polarized light detection and imaging module 4 further includes a compensator arranged in front of the analyzer 4 a , and the compensator refers to a λ / 4 compensation glass sheet adapted to the polarized light generating module 2 .

[0040] The polarized light detection and imaging module 4 also includes a third convex lens, which can be inserted between any optical elements in front of the camera in the polarized light detection and imaging module to adjust the position of the image formed after the sample passes through the microscope objective 5.

[0041] Based on the aforementioned magnetic imaging device based on diamond NV color center and Kerr effect, the present application also discloses a global magnetic imaging method, characterized in that the global magnetic imaging method includes the following contents:

[0042] Turn on the light source of the polarized light generating module 2. After being focused and polarized by the convex lens, the light source becomes polarized light. After being reflected or transmitted by the dichroic mirror system, the polarized light enters the microscope objective 5 and then irradiates the sample 11 placed on the translation stage 13.

[0043] By adjusting the movement of the translation stage 13, the sample is placed in the focal area of ​​the objective lens;

[0044] After the polarized light is reflected by the sample 11, part of it enters the microscope objective 5 again, and then enters the polarized light detection and imaging module 4 after being transmitted or reflected by the dichroic mirror system;

[0045] Rotate the polarizer 4a in the polarized light detection and imaging module so that the angle between its polarization direction and the polarization direction of the polarizer 2c in the polarized light generation module 2 is between 80° and 100°;

[0046] The analyzer 4a in the polarized light detection and imaging module detects the polarization state of the light beam and uses the camera 4d to perform imaging. The photo obtained by the camera can obtain the magnetization state information of the sample surface, that is, realize magneto-optical Kerr imaging.

[0047] Based on the aforementioned magnetic imaging device based on diamond NV color center and Kerr effect, the present application also discloses a high-resolution magnetic imaging method. In the present application, the so-called high resolution means that the spatial imaging resolution is higher than the ordinary optical microscopic resolution limit, that is, the resolution is better than 200nm; the method comprises the following steps:

[0048] Adjust the direction of the laser emitted by the spin control light source module 1 so that the laser is reflected or transmitted through the dichroic mirror system into the microscope objective lens 5, and then irradiated onto the NV color center after being focused by the microscope objective lens 5. Initialize the spin of the NV color center electrons by irradiating the laser emitted by the spin control light source module 1;

[0049] The laser is stopped, and a sequence of electromagnetic pulses is emitted through the microwave emission device 12 to manipulate the spin state of the NV color center;

[0050] The electromagnetic pulse sequence is selected so that the electromagnetic pulse frequency is coherent with the energy difference between spins S=0 and S=1, or the energy difference between spins S=0 and S=-1, and the pulse duration is half the Rabi oscillation period of the electron spin, that is, a π / 2 pulse;

[0051] After the electromagnetic pulse emission is completed, the NV color center electrons are allowed to evolve freely for a set time τ;

[0052] Then input an electromagnetic pulse with a duration of π / 2;

[0053] After the electromagnetic pulse is emitted again, an incident laser is input again through the spin control light source module 1 to focus on the NV color center, and the NV color center will generate fluorescence;

[0054] Part of the fluorescence returns to the dichroic mirror system through the microscope objective 5, and then enters the fluorescence detection module 3 through transmission or reflection of the dichroic mirror system; the magnitude of the magnetic field at the diamond NV color center is calculated by analyzing the fluorescence signal received by the photodetector;

[0055] Then, the sample is stepped by controlling the horizontal movement of the translation stage. By repeating the above measurement steps, the magnitude of the stray magnetic field at a certain height above different areas of the sample is measured to obtain the magnetic distribution imaging of the sample.

[0056] More preferably,

[0057] The selected electromagnetic pulse sequence is the Ramsey sequence;

[0058] The time τ is set to be less than the transverse relaxation time of the electron spin of the NV color center.

[0059] Based on the solution disclosed in the present application, the same instrument can simultaneously perform high-resolution imaging based on NV color centers and magneto-optical imaging based on the magneto-optical Kerr effect, meeting the requirements of high spatial resolution and large-field global imaging. At the same time, the sample can be globally characterized by Kerr imaging first, and then a local specific area can be finely characterized with high resolution by NV color center magnetic measurement. Description of the drawings:

[0060] Figure 1 It is a schematic diagram of the overall structure of the magnetic imaging device based on magneto-optical Kerr imaging and diamond nitrogen vacancy color center and a structural diagram of each module included in the present invention;

[0061] Figure 2 A flowchart of the method for simultaneously realizing high-resolution imaging and magneto-optical Kerr imaging based on NV color centers;

[0062] Figure 3 This is a configuration diagram of another implementation scheme of the fluorescence detection module.

[0063] Among them, spin manipulation light source module 1, polarized light generation module 2, fluorescence detection module 3, polarized light detection and imaging module 4, microscope objective 5, first dichroic mirror 6, second dichroic mirror 7, third dichroic mirror 8, diamond probe 9, NV probe arm 10, sample 11, microwave transmitting device 12, high-precision translation stage 13, laser source 1a, first optical fiber 1b, light modulator 1c, second optical fiber 1d, optical fiber coupler 1e, first convex lens 1f, light source 2a, second convex lens 2b, polarizer 2c, first filter 3a, optical fiber coupler 3b, optical fiber 3c, first photodetector 3d, analyzer 4a, third convex lens 4b, third filter 4c, camera 4d, second filter 3f, aperture 3g, second photodetector 3h. Specific implementation method:

[0064] Below, the technical solutions recorded in the claims and the invention content are further explained and illustrated in detail in conjunction with the drawings of the specification.

[0065] See attached Figure 1 The present application discloses a magnetic imaging device based on magneto-optical Kerr imaging and diamond nitrogen vacancy color center, which includes a spin-manipulated light source module 1, a polarized light generating module 2, a fluorescence detection module 3, a polarized light detection and imaging module 4, a microscope objective 5, a diamond probe with an NV color center 9, an NV color center probe arm 10, a microwave transmitting device 12, and a translation stage 13.

[0066] The spin manipulation light source module 1 is used to provide a beam of incident laser light, which passes through a dichroic mirror system, so that the laser light is transmitted and / or reflected by the dichroic mirror, and after being focused by a microscope objective lens 5, it is irradiated onto the NV color center of a diamond probe 9, and the diamond probe 9 is clamped by an NV color center probe arm 10; a microwave transmitting device 12 is arranged close to one side of the NV color center of the diamond probe 9, and is used to emit an electromagnetic pulse sequence to manipulate the spin state of the NV color center; the fluorescence generated by the NV color center of the diamond probe 9 returns to the dichroic mirror system through the microscope objective lens 5, is transmitted and / or reflected by the dichroic mirror system, and enters the fluorescence detection module 3; the polarized light generating module 2 is used to generate light with linear polarization properties, that is, polarized light, which is transmitted and / or reflected by the dichroic mirror system, enters the microscope objective lens 5, and then irradiates onto a sample 11 placed on a displacement stage 13, and after being reflected by the sample, part of the polarized light enters the microscope objective lens 5 again, and then enters the polarized light detection and imaging module 4 after being transmitted and / or reflected by the dichroic mirror system.

[0067] In the present application, the dichroic mirror system is preferably configured in the following manner, but a person skilled in the art should clearly understand that the dichroic mirror system used in the present application is only a preferred embodiment and is not a limitation on the configuration method of the dichroic mirror system.

[0068] In a preferred embodiment of the present application, the dichroic mirror system comprises a first dichroic mirror 6, a second dichroic mirror 7, and a third dichroic mirror 8;

[0069] The second dichroic mirror 7 is tiltedly arranged at the intersection of the incident laser light emitted by the spin-manipulated light source module 1 and the polarized light emitted by the polarized light generating module 2, and can transmit or reflect the incident laser light, reflect or transmit the polarized light, and make the incident laser light and the polarized light have the same optical path after being transmitted or reflected by the second dichroic mirror 7;

[0070] The first dichroic mirror 6 is disposed above the microscope objective 5 and is capable of receiving the laser light or polarized light after being transmitted or reflected by the second dichroic mirror 7 and reflecting the laser light or polarized light into the microscope objective 5;

[0071] The third dichroic mirror 8 is arranged between the first dichroic mirror 6 and the fluorescence detection module 3, and can make the polarized light reflected by the sample pass through the microscope objective 5 and the first dichroic mirror 6 in sequence, and then reflect it into the polarized light detection and imaging module 4. At the same time, it can make the fluorescence emitted by the NV color center pass through the objective lens 5, the first dichroic mirror 6 and the third dichroic mirror 8 and enter the fluorescence detection module 3.

[0072] It is clear to those skilled in the art that any combination of dichroic mirror systems that can realize the above-mentioned optical path of the incident laser of the spin-manipulated light source module 1 by projection or reflection, the fluorescence generated by the NV color center entering the fluorescence detection module 3, and the polarized light generated by the polarized light generating module 2 entering the microscope objective 5, irradiating the sample 11, and entering the polarized light detection and imaging module 4 after emission, can achieve the purpose of the present invention and obtain the same technical effect. For example, those skilled in the art can also easily think of replacing the second dichroic mirror 7 and the third dichroic mirror 8 in the above-mentioned embodiment with a total reflection lens. When the positions of the second dichroic mirror 7 and the third dichroic mirror 8 are both total reflection mirrors, there should be a mechanical device to control the insertion and removal of the two total reflection lenses. When inserted, a certain function can be realized, and then taken out, the optical path is switched to realize another function.

[0073] Therefore, based on the spirit of the present invention, a person of ordinary skill in the art can easily obtain various combinations of color mirrors or lenses to realize two different light paths, and the color mirror or lens combinations of these dichroic mirror systems should be covered within the scope of protection of this application. The spin-manipulated light source module 1 provides an incident light, which is a monochromatic light source with a wavelength range between 500nm-600nm, and the light source can be pulse modulated. Module 1 can be composed of a laser source 1a, a first optical fiber 1b and a second optical fiber 1d, an optical modulator 1c, an optical fiber coupler 1e and a first convex lens 1f. The optical modulator is used to control the on and off of the light in module 1. If the optical modulator is a fiber-coupled modulator, it is placed between the first optical fiber 1b and the second optical fiber 1d. If it is a free-space light modulator, it is placed at the rear end of the optical fiber coupler 1e.

[0074] In addition, the spin-manipulated light source module 1 may also be composed of the following structures: a collimated laser light source and a free-space spatial light modulator. All or some of the components of the spin-manipulated light source module 1 may be placed on an adjustment frame to adjust the direction of the incident light so that the spin-manipulated light is focused on the NV color center after passing through the objective lens 5.

[0075] The polarized light generating module 2 is composed of a light source 2a, a second convex lens 2b and a polarizer 2c. The light source 2a may be selected from, but not limited to, an LED lamp, a mercury lamp, a xenon lamp, light output through optical fiber coupling, etc. The polarizer 2c is a device that can convert non-polarized light into linear polarized light after passing through the element. The positions of the convex lens 2b and the polarizer 2c can be swapped. The polarized light generated by the polarized light generating module 2 has a wavelength between 300nm and 530nm.

[0076] The fluorescence detection module 3 is composed of a first filter 3a, a fiber coupler 3b, an optical fiber 3c, and a first photodetector 3d.

[0077] The fluorescence generated by the NV color center of the diamond probe 9 enters the first filter 3a, is collected into the optical fiber 3c through the optical fiber coupler 3b, and then enters the first photodetector 3d, where the optical signal is converted into an electrical signal.

[0078] Among them, the first filter 3a refers to a filter device with a passband between 540nm-1000nm, and its function is to filter out the light emitted by the spin-manipulated light source module 1 and the module and reflected through the optical path into the fluorescence detection module 3, and only allow the fluorescence emitted by the NV color center due to the change in spin state to pass through the filter. After the fluorescence is collected into the optical fiber 3c by the optical fiber coupler 3b, it enters the first photodetector 3d. Among them, the first photodetector 3d refers to a device that can convert optical signals into electrical signals, such as a photodiode, a camera, etc. All or some of the components of the fluorescence detection module 3 can be placed on an adjustment frame to adjust the position of the optical difficult point coupler. After the fluorescence emitted by the NV color center passes through the objective lens 5, it is just focused on the light coupler, enters the optical fiber 3c, and is detected by the first photodetector 3d.

[0079] As attached Figure 3 As shown, in another preferred embodiment of the present application, the fluorescence detection module 3 may also be composed of a second filter 3f, an aperture 3g and a second photodetector 3h;

[0080] Among them, the second filter 3f and the aperture 3g can be swapped; after the fluorescence generated by the NV color center of the diamond probe 9 enters the fluorescence detection module 3, it is focused on the light hole of the aperture 3g and passes through, and is received by the second photodetector 3h, and other interference light is shielded by the aperture 3g.

[0081] Similarly, the second filter 3f is a filter device with a passband between 540nm-1000nm, which is used to filter out the light emitted by the spin-manipulated light source module 1 and reflected through the optical path into the fluorescence detection module 3, and only allows the fluorescence emitted by the NV color center due to the change in the spin state to pass through the filter. All or part of the components of the fluorescence detection module 3 are placed on an adjustment frame to adjust the position of the aperture 3g. After the fluorescence emitted by the NV color center passes through the objective lens 5, it is focused on the small hole of the aperture 3g and detected by the second photodetector 3h.

[0082] The polarized light detection and imaging device 4 is composed of an analyzer 4a, a third convex lens 4b (optional), a third filter 4c (optional), and a camera 4d. The analyzer 4a refers to a linear polarizer, which can be a thin film polarizer or a Glan Taylor prism, or a Glan Thompson prism; the optional range of the camera 4d includes but is not limited to a CCD camera or a CMOS camera. The bandpass range of the third filter 4c is adapted to the light source emitted by the polarized light generating module, which is between 300nm-530nm. The third convex lens 4b can adjust the position of the image formed after the sample passes through the objective lens, so that the imaging focus of the sample falls exactly on the camera photosensitive chip, thereby obtaining a clear Kerr picture. In addition, a compensator can be added in front of the analyzer 4a, and the compensator refers to a λ / 4 compensation glass plate whose wavelength λ is adapted to the module 2.

[0083] As attached Figure 2 As shown, based on the aforementioned magnetic imaging device based on diamond NV color center and Kerr effect, the present application also discloses a global magnetic imaging method, characterized in that the global magnetic imaging method includes the following contents:

[0084] Turn on the light source of the polarized light generating module 2. After being focused and polarized by the convex lens, the light source becomes polarized light. After being reflected or transmitted by the dichroic mirror system, the polarized light enters the microscope objective 5 and then irradiates the sample 11 placed on the translation stage 13.

[0085] By adjusting the movement of the translation stage 13, the sample 11 is placed in the focal area of ​​the objective lens;

[0086] After the polarized light is reflected by the sample 11, part of it enters the microscope objective 5 again, and then enters the polarized light detection and imaging module 4 after being transmitted or reflected by the dichroic mirror system;

[0087] Rotate the polarizer 4a in the polarized light detection and imaging module so that the angle between its polarization direction and the polarization direction of the polarizer 2c in the polarized light generation module 2 is between 80° and 100°;

[0088] The analyzer 4a in the polarized light detection and imaging module detects the polarization state of the light beam and uses the camera 4d to perform imaging. The photo obtained by the camera can obtain the magnetization state information of the sample surface, that is, realize magneto-optical Kerr imaging.

[0089] Likewise, see Appendix Figure 2 Based on the aforementioned magnetic imaging device based on diamond NV color center and Kerr effect, the present application also discloses a high-resolution magnetic imaging method, the method comprising the following steps:

[0090] Adjust the direction of the laser emitted by the spin control light source module 1 so that the laser is reflected or transmitted through the dichroic mirror system into the microscope objective lens 5, and then irradiated onto the NV color center after being focused by the microscope objective lens 5. Initialize the spin of the NV color center electrons by irradiating the laser emitted by the spin control light source module 1;

[0091] The laser is stopped, and a sequence of electromagnetic pulses is emitted through the microwave emission device 12 to manipulate the spin state of the NV color center;

[0092] An electromagnetic pulse sequence is selected so that the electromagnetic pulse frequency is coherent with the energy difference between spins S=0 and S=1, or the energy difference between spins S=0 and S=-1, and the pulse duration is half the Rabi oscillation period of the electron spin, that is, a π / 2 pulse; the selected electromagnetic pulse sequence is a Ramsey sequence;

[0093] After the electromagnetic pulse emission is completed, the NV color center electrons are allowed to evolve freely for a set time τ; in the present application, the set time τ is less than the transverse relaxation time of the NV color center electron spin.

[0094] Then input an electromagnetic pulse with a duration of π / 2;

[0095] After the electromagnetic pulse is emitted again, an incident laser is input again through the spin control light source module 1 to focus on the NV color center, and the NV color center will generate fluorescence;

[0096] Part of the fluorescence returns to the dichroic mirror system through the microscope objective 5, and then enters the fluorescence detection module 3 through transmission or reflection of the dichroic mirror system; the magnitude of the magnetic field at the diamond NV color center is calculated by analyzing the fluorescence signal received by the photodetector;

[0097] Then, by controlling the horizontal movement of the stage, the sample is stepped, and by repeating the above measurement steps, the magnitude of the stray magnetic field at a certain height above different regions of the sample is measured to obtain the magnetic distribution imaging of the sample. This application uses the color properties of nitrogen vacancies in diamond for magnetic imaging, and the spatial resolution can reach the sub-nanometer level.

[0098] When the magneto-optical Kerr imaging and diamond nitrogen vacancy color center magnetic imaging device disclosed in the present application are used for testing, if the magneto-optical Kerr imaging and diamond nitrogen vacancy color center magnetic imaging device includes a spin-controlled light source module 1, a polarized light generation module 2, a fluorescence detection module 3, a polarized light detection and imaging module 4, a microscope objective 5, a dichroic mirror 6, a dichroic mirror 7, a dichroic mirror 8, etc., after the spin-controlled light source module 1, the polarized light generation module 2, the fluorescence detection module 3, and the polarized light detection and imaging module 4 are all turned on, high-resolution imaging based on diamond NV color center and magneto-optical Kerr imaging can be performed simultaneously. At this time, it is necessary to configure a filter with a passband of 540nm-1000nm in the fluorescence detection module 3 to filter out other interference light; configure a filter with a passband wavelength less than 530nm in the polarized light detection and imaging module 4 to filter out interference light sources and allow the polarized light reflected by the sample 11 to enter the camera for imaging.

[0099] If the configuration of the device based on magneto-optical Kerr imaging and diamond nitrogen vacancy color center magnetic imaging includes a spin-controlled light source module 1, a polarized light generating module 2, a fluorescence detection module 3, a polarized light detection and imaging module 4, a microscope objective 5, a dichroic mirror 6, a total reflection mirror 7, a total reflection mirror 8, etc., after the spin-controlled light source module 1, the polarized light generating module 2, the fluorescence detection module 3, the polarized light detection and imaging module 4 are all turned on, high-resolution imaging and magneto-optical Kerr imaging based on diamond NV color center need to be carried out in batches one after another. That is, when performing high-resolution imaging based on the diamond NV color center, it is necessary to switch the optical path by inserting the total emission mirror 7 and the total reflection mirror 8 into the optical path or removing them from the optical path, so that the light from the spin-controlled light source module 1 is incident on the objective lens, and the fluorescence emitted by the NV color center is received by the fluorescence detection module 3; when performing magneto-optical Kerr imaging, it is necessary to switch the optical path by inserting the total emission mirror 7 and the total reflection mirror 8 into the optical path or removing them from the optical path, so that the polarized light generating module 2 and the polarized light detection and imaging module 4 are connected to the optical path, and magneto-optical Kerr imaging is performed.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A magnetic imaging device based on diamond NV color center and Kerr effect, the magnetic imaging device comprising a spin manipulation light source module (1), a polarized light generation module (2), a fluorescence detection module (3), a polarized light detection and imaging module (4), a microscope objective (5), a diamond probe with NV color center (9), an NV color center probe arm (10), a microwave emission device (12), and a translation stage (13); characterized in that: The spin control light source module (1) is used to provide a beam of incident laser light, which passes through a dichroic mirror system, so that the laser light is transmitted and / or reflected by the dichroic mirror, and after being focused by a microscope objective lens (5), is irradiated onto the NV color center of a diamond probe (9), and the diamond probe (9) is clamped by an NV color center probe arm (10); the spin control light source module (1) is composed of a laser source (1a), a first optical fiber (1b), a second optical fiber (1d), an optical modulator (1c), a second optical fiber coupler (1e) and a first convex lens (1f); the optical modulator (1c) is used to control the on and off of light in the spin control light source module (1); A microwave transmitting device (12) is arranged close to one side of the NV color center of the diamond probe (9) and is used to transmit an electromagnetic pulse sequence to control the spin state of the NV color center; The fluorescence generated by the NV color center of the diamond probe (9) returns to the dichroic mirror system through the microscope objective lens (5), is transmitted and / or reflected by the dichroic mirror system, and enters the fluorescence detection module (3); The polarized light generating module (2) is composed of a light source (2a), a second convex lens (2b) and a polarizer (2c), and is used to generate light with linear polarization properties, namely polarized light. The polarized light is transmitted and / or reflected by a dichroic mirror system, enters a microscope objective (5), and then irradiates a sample (11) placed on a displacement stage (13). After being reflected by the sample, part of the polarized light enters the microscope objective (5) again, and then is transmitted and / or reflected by the dichroic mirror system before entering a polarized light detection and imaging module (4). The polarized light detection and imaging module (4) includes an analyzer (4a) and a camera (4d). The polarization state of the light beam is detected by the analyzer (4a) and an image is formed by the camera (4d). The dichroic mirror system comprises a first dichroic mirror (6), a second dichroic mirror (7), and a third dichroic mirror (8) configured in the following manner; The second dichroic mirror (7) is tiltedly arranged at the intersection of the light paths of the incident laser light emitted by the spin-manipulated light source module (1) and the polarized light emitted by the polarized light generating module (2), and can transmit or reflect the incident laser light, and reflect or transmit the polarized light, and make the light paths of the incident laser light and the polarized light consistent after being transmitted or reflected by the second dichroic mirror (7); The first dichroic mirror (6) is arranged above the microscope objective lens (5), and is capable of receiving the laser light or polarized light transmitted or reflected by the second dichroic mirror (7), and reflecting the laser light or polarized light into the microscope objective lens (5); The third dichroic mirror (8) is arranged between the first dichroic mirror (6) and the fluorescence detection module (3), and can make the polarized light reflected by the sample pass through the microscope objective lens (5) and the first dichroic mirror (6) in sequence, and then reflect it into the polarized light detection and imaging module (4), and at the same time make the fluorescence emitted by the NV color center pass through the microscope objective lens (5), the first dichroic mirror (6) and the third dichroic mirror (8) to enter the fluorescence detection module (3); the fluorescence detection module (3) is composed of a first filter (3a), a first optical fiber coupler (3b), an optical fiber (3c), and a first photodetector (3d).

2. The magnetic imaging device based on diamond NV color center and Kerr effect according to claim 1, characterized in that: When the optical modulator (1c) is a fiber-coupled modulator, the laser source (1a), the optical modulator (1c), and the second optical fiber coupler (1e) are connected in sequence through optical fibers in a front-to-back order, and the first convex lens (1f) is placed at the rear end of the second optical fiber coupler (1e) to focus the incident laser onto the dichroic mirror system; When the optical modulator (1c) is a free space optical modulator, the laser source (1a) and the second optical fiber coupler (1e) are connected via an optical fiber, the optical modulator (1c) and the first convex lens (1f) are placed at the rear end of the second optical fiber coupler (1e), and the order of the optical modulator (1c) and the first convex lens (1f) can be swapped; the modulated laser is incident on the dichroic mirror system.

3. The magnetic imaging device based on diamond NV color center and Kerr effect according to claim 2, characterized in that: All or part of the components of the spin-manipulated light source module (1) are placed on an adjustment frame to adjust the direction of incident light so that the laser light emitted by the spin-manipulated light source module (1) is focused on the NV color center of the diamond probe (9) after passing through the microscope objective lens (5).

4. The magnetic imaging device based on diamond NV color center and Kerr effect according to claim 1, characterized in that: The incident laser provided by the spin-manipulation light source module (1) is a monochromatic light source with a wavelength ranging from 500nm to 600nm, and the light source can be pulse modulated.

5. The magnetic imaging device based on diamond NV color center and Kerr effect according to any one of claims 1 to 3, characterized in that: The light source (2a) of the polarized light generating module (2) is selected from LED lamps, mercury lamps, xenon lamps, and light output through optical fiber coupling; the polarizer (2c) refers to a device that can convert non-polarized light into linearly polarized light after passing through this element; The light source (2a) is placed on the front side, and the positions of the second convex lens (2b) and the polarizer (2c) on the rear side can be swapped; or the second convex lens (2b) and the polarizer (2c) can be directly integrated with the light source (2a) to form a linearly polarized light source.

6. The magnetic imaging device based on diamond NV color center and Kerr effect according to claim 5, characterized in that: The light with linear polarization properties generated by the polarized light generating module (2) has a wavelength between 300nm and 530nm.

7. The magnetic imaging device based on diamond NV color center and Kerr effect according to any one of claims 1 to 3, characterized in that: The fluorescence generated by the NV color center of the diamond probe (9) enters the first filter (3a), is collected into the optical fiber (3c) through the first optical fiber coupler (3b), and then enters the first photodetector (3d), where the optical signal is converted into an electrical signal.

8. The magnetic imaging device based on diamond NV color center and Kerr effect according to any one of claims 1 to 3, characterized in that: The fluorescence detection module (3) is composed of a second filter, an aperture (3g) and a second photodetector (3h); The second filter (3f) and the aperture (3g) can be swapped; after the fluorescence generated by the NV color center of the diamond probe (9) enters the fluorescence detection module (3), it is focused on the light hole of the aperture (3g) and passes through, and is received by the second photodetector (3h), and other interference light is shielded by the aperture (3g).

9. The magnetic imaging device based on diamond NV color center and Kerr effect according to claim 7, characterized in that: in, The first filter (3a) is a filter device with a passband between 540nm and 1000nm, and is used to filter out the light emitted by the spin-manipulated light source module (1) and reflected through the optical path into the fluorescence detection module (3), and only allows the fluorescence emitted by the NV color center due to the change in the spin state to pass through the filter.

10. The magnetic imaging device based on diamond NV color center and Kerr effect according to claim 8, characterized in that: in, The second filter (3f) is a filter device with a passband between 540nm and 1000nm, and is used to filter out the light emitted by the spin-manipulated light source module (1) and reflected through the optical path into the fluorescence detection module (3), and only allows the fluorescence emitted by the NV color center due to the change in the spin state to pass through the filter.

11. The magnetic imaging device based on diamond NV color center and Kerr effect according to claim 8, characterized in that: All or some of the components of the fluorescence detection module (3) are placed on an adjustment frame for adjusting the position of the first optical fiber coupler (3b) or the aperture (3g). After passing through the microscope objective (5), the fluorescence emitted by the NV color center is focused at the entrance of the first optical fiber coupler (3b) or at the small hole of the aperture (3g) and is detected by the first photodetector (3d) or the second photodetector (3h).

12. The magnetic imaging device based on diamond NV color center and Kerr effect according to any one of claims 1 to 3, characterized in that: The analyzer (4a) is a linear polarizer, and the analyzer (4a) is any one of the following: Thin-film polarizer, Glan-Taylor prism, or Glan-Thompson prism; The camera (4d) comprises: a CCD camera or a CMOS camera.

13. The magnetic imaging device based on diamond NV color center and Kerr effect according to claim 12, characterized in that: The polarized light detection and imaging module (4) further comprises one or more third filters (4c) arranged at any position in front of the camera (4d); the bandpass range of the third filter (4c) is adapted to the light source emitted by the polarized light generating module (2) and is between 300nm and 530nm.

14. The magnetic imaging device based on diamond NV color center and Kerr effect according to claim 13, characterized in that: The polarized light detection and imaging module (4) further comprises a compensator arranged in front of the analyzer (4a), wherein the compensator is a λ / 4 compensation glass sheet adapted to the polarized light generating module (2).

15. The magnetic imaging device based on diamond NV color center and Kerr effect according to claim 13 or 14, characterized in that: The polarized light detection and imaging module (4) further comprises a third convex lens (4b). A third convex lens (4b) is inserted between any optical elements in front of the camera in the polarized light detection and imaging module to adjust the position of the image formed after the sample passes through the microscope objective lens (5).

16. A global magnetic imaging method based on the device according to any one of claims 1 to 15, characterized in that: The global magnetic imaging method comprises the following contents: Turn on the light source of the polarized light generating module. After being focused and polarized by the convex lens, the light source becomes polarized light. After being reflected or transmitted by the dichroic mirror system, the polarized light enters the microscope objective lens and then irradiates the sample placed on the translation stage. By adjusting the movement of the translation stage, the sample is placed in the focal area of ​​the microscope objective lens; After the polarized light is reflected by the sample, part of it enters the microscope objective again, and then enters the polarized light detection and imaging module after being transmitted or reflected by the dichroic mirror system; Rotate the polarizer in the polarized light detection and imaging module so that the angle between its polarization direction and the polarization direction of the polarizer in the polarized light generation module is between 80° and 100°; The analyzer in the polarized light detection and imaging module detects the polarization state of the light beam and uses the camera to perform imaging. The photos obtained by the camera can obtain the magnetization state information of the sample surface, that is, realize magneto-optical Kerr imaging.

17. A high-resolution magnetic imaging method based on the device according to any one of claims 1 to 15, characterized in that: The method includes the following: Adjust the direction of the laser emitted by the spin control light source module so that the laser is reflected or transmitted through the dichroic mirror system into the microscope objective lens, and after being focused by the microscope objective lens, it is irradiated onto the NV color center, and the electron spin of the NV color center is initialized by the laser irradiation emitted by the spin control light source module; Stop the laser and send out a sequence of electromagnetic pulses through a microwave transmitter to manipulate the spin state of the NV color center; The electromagnetic pulse sequence is selected so that the electromagnetic pulse frequency is coherent with the energy difference between spins S=0 and S=1, or the energy difference between spins S=0 and S=-1, and the pulse duration is half the Rabi oscillation period of the electron spin, that is, a π / 2 pulse; After the electromagnetic pulse emission is completed, the NV color center electrons are allowed to evolve freely for a set time τ; Then input an electromagnetic pulse with a duration of π / 2; After the electromagnetic pulse is emitted again, an incident laser is input again through the spin control light source module to focus it on the NV color center, and the NV color center will produce fluorescence; Part of the fluorescence returns to the dichroic mirror system through the microscope objective lens, and then enters the fluorescence detection module through transmission or reflection of the dichroic mirror system; the magnitude of the magnetic field at the diamond NV color center is calculated by analyzing the fluorescence signal received by the photodetector; Then, the sample is stepped by controlling the horizontal movement of the translation stage. By repeating the above measurement steps, the magnitude of the stray magnetic field at a certain height above different areas of the sample is measured to obtain the magnetic distribution imaging of the sample.

18. The high-resolution magnetic imaging method according to claim 17, characterized in that: The selected electromagnetic pulse sequence is the Ramsey sequence; The time τ is set to be less than the transverse relaxation time of the electron spin of the NV color center.

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