A differential integrated diamond quantum magnetic sensor and a preparation method thereof

Abstract

The application discloses a differential integrated diamond quantum magnetic sensor and a preparation method and a magnetic field detection method thereof. The sensor comprises a pump light source, a multi-layer stacked diamond NV color center chip and a weak magnetic tube shell packaging module. The multi-layer stacked chip is composed of a first photodiode, a first optical filter, a silicon-based gasket, a diamond with NV color centers, a second optical filter and a second photodiode, and a microwave antenna is arranged on the two optical filters. The silicon-based gasket is provided with an open cavity for accommodating the diamond, an inclined side wall and a laser incidence channel. The pump light is incident from the side of the diamond and is reflected multiple times inside the diamond to improve the NV color center excitation efficiency. Two photodiodes respectively receive reference light signals and fluorescence signals, and the magnetic field measurement results are obtained through transimpedance amplification, dynamic trimming and differential demodulation. The application can suppress common-mode noise, reduce material magnetic interference by combining a weak magnetic packaging, improve magnetic field detection sensitivity, and support the realization of device miniaturization, low noise and batch manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of quantum sensing and precision magnetic field measurement technology, and relates to a differential integrated diamond quantum magnetic sensor, its preparation method and differential magnetic field detection method. Background Technology

[0002] High-sensitivity magnetic field measurement is a key supporting technology in fields such as geophysics, biomedicine, and space science. Although quantum effect-based magnetic field measurement schemes, such as superconducting quantum interference devices (SQUIDs) and atomic magnetometers, have achieved ultra-high sensitivity on the order of femtotes (fT), they are generally limited by harsh operating conditions such as low temperature, heating, or magnetic shielding, making them difficult to apply in complex environments.

[0003] Diamond NV center solid-state quantum sensors offer a new path to overcome the aforementioned bottlenecks due to their unique advantages, including room temperature operation, wide dynamic range, high spatial resolution, and biocompatibility. Currently, most mainstream diamond magnetic sensors employ confocal or wide-field microscopic optical paths, relying on discrete optical components, high-precision displacement stages, and bulky laser sources. This results in complex and bulky overall structures, limiting their application to controlled laboratory environments and hindering their development in outdoor detection, pipeline inspection, and wearable devices.

[0004] Although subsequent solutions using fiber-coupled diamond probes have emerged, reducing the size of the probe section, this solution still requires an external desktop laser for optical pumping and readout. In essence, it has not escaped the dependence on large optical systems, and its portability and system integration are still limited, failing to meet the requirements for low-power, miniaturized in-situ magnetic field measurement.

[0005] In addition, existing diamond quantum magnetic sensors face the following problems in practical applications: (1) Insufficient compatibility design between microwave radiating antennas and optical detection structures makes efficient integration difficult; (2) Common-mode noise, such as intensity noise of laser light sources, directly affects magnetic measurement sensitivity, and there is a lack of effective noise suppression methods; (3) Magnetic interference problems of packaging materials limit the actual application accuracy of the sensor. Therefore, it is necessary to develop an on-chip quantum magnetic sensor that highly integrates pump light sources, diamond NV color center chips, filters, microwave antennas, and photodetectors. This sensor can achieve system miniaturization while solving technical problems such as compatibility between microwave and optical chips, common-mode noise suppression, and packaging interference, thus meeting the requirements for in-situ magnetic field measurement that balances high sensitivity, miniaturization, low interference, and low cost.

[0006] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a differential integrated diamond quantum magnetic sensor and its preparation method and differential magnetic field detection method, to solve the problems of large size, low integration and insufficient common-mode noise suppression capability of existing diamond quantum magnetic sensors, and to achieve miniaturized and highly sensitive magnetic field measurement.

[0008] To achieve the above and other related objectives, this invention provides a differential integrated diamond quantum magnetic sensor, its fabrication method, and a differential magnetic field detection method.

[0009] This invention provides a differential integrated diamond quantum magnetic sensor, the sensor comprising: a multilayer stacked diamond NV color center chip and a weak magnetic tube shell packaging module;

[0010] The pump source is located on the side of the diamond with the NV color center. The pump source includes a laser diode and a laser diode heat sink. The laser diode is located to the upper left of the laser diode heat sink.

[0011] The multilayer diamond NV center chip consists of, from top to bottom, a first photodiode, a first filter, a silicon-based pad, a diamond with NV centers, a second filter, and a second photodiode; both the first and second filters have microwave antennas on their surfaces; the silicon-based pad has an opening in the middle for placing the diamond with NV centers, and has sloping sidewalls on three sides and a transverse channel on one side;

[0012] The weak magnetic packaging module includes a PCB, a housing pin, an RF non-magnetic housing, and metal leads. The PCB is connected to the inside and bottom of the RF non-magnetic housing. The PCB inside the RF non-magnetic housing is located below the multilayer diamond NV color center chip and is connected to the housing pin via the metal leads. The two layers of microwave antennas on the housing pin are electrically interconnected with the housing pin via the metal leads. The PCB at the bottom of the RF non-magnetic housing is connected to the housing pins on both sides of the RF non-magnetic housing. The electrodes on the heat sink surfaces of the first photodiode and the laser diode are electrically interconnected with the housing pin via the metal leads.

[0013] Preferably, the excitation wavelength of the laser diode is 450nm~570nm.

[0014] Preferably, the first filter is a short-pass filter with a transmission band of 490nm~600nm and a cutoff band of 600nm~800nm; the second filter is a long-pass filter with a transmission band of 625nm~780nm and a cutoff band of 400nm~620nm; the transmittance of the cutoff band of both filters is 1 / 10. 4 ~1 / 10 6 .

[0015] Preferably, the thin film material of the first filter and the second filter is a high / low refractive index composite thin film formed by the overlapping deposition of tantalum pentoxide and silicon dioxide, with a thickness of 1μm~25μm.

[0016] Preferably, the diamond of the NV color center is a chamfered diamond, and the angle between the incident laser and the sidewall satisfies the total internal reflection condition, so that the laser is reflected multiple times within the diamond to the NV color center.

[0017] Preferably, the lateral area of ​​the silicon-based pad is 0.25 mm². 2 ~100mm 2 The thickness is 200μm~800μm; the inclined sidewall surface of the silicon-based pad is plated with a gold or silver metal film with a thickness of 30nm~1000nm.

[0018] Preferably, both microwave antennas are fabricated on one side of the diamond near the NV color center, and aligned so that the diamond is in a spatially uniform microwave region. The material of the microwave antenna is a gold or silver metal film with a thickness of 30nm~1000nm.

[0019] Preferably, the surface of the radio frequency non-magnetic tube shell in the weak magnetic tube shell packaging module is plated with a gold or nickel metal film with a thickness of 1μm~10μm; the tube shell pin material is 4J80 weak magnetic material with a frequency range of DC-4GHz; the tube shell cover plate and the tube shell base are hermetically sealed by parallel seam welding, and the overall tube shell residual magnetism is 20nT~1000nT.

[0020] Preferably, the electrodes of the second photodiode are located on the back side of the photosensitive surface, and the electrodes are electrically connected to the upper surface layer through the PCB with solder joints and metal leads.

[0021] This invention also provides a method for fabricating a differential integrated diamond quantum magnetic sensor, the method comprising:

[0022] Tantalum pentoxide / silicon dioxide is deposited on both sides of a glass wafer substrate to form a high / low refractive index composite film, and a metal layer is formed on its surface to obtain upper and lower filters with a microwave antenna structure.

[0023] A silicon dioxide hard mask is formed on the surface of a silicon wafer. A silicon-based pad with inclined sidewalls is obtained by photolithography, dry etching and wet anisotropic etching, and a metal thin film is deposited on its surface.

[0024] Diamond with NV color centers, lower filter, silicon-based pad and upper filter are bonded sequentially to form a wafer-level bonded sample, and then the sample is processed into a chip to obtain a bonded chip;

[0025] The bonding chip and photodiode are packaged in a housing, and electrical connection is achieved by wire bonding. The housing is then sealed by parallel seam welding.

[0026] Preferably, one side of the central opening area of ​​the silicon-based pad is fully opened for side laser incidence, while the other three sides form an inclined sidewall structure.

[0027] Preferably, during the bonding process, the microwave antennas of the two filters are aligned with high precision to ensure spatial matching; the antenna of the upper filter is led out through the metal lead on the surface of the silicon-based pad, and the lower filter is slightly larger than the silicon-based pad to expose the electrical connection area for wire bonding.

[0028] The present invention also provides a differential magnetic field detection method based on the aforementioned differential integrated diamond quantum magnetic sensor, the method comprising the following steps:

[0029] The pump source laser pumps the NV color center in diamond to induce spin polarization; at the same time, a bias magnetic field is applied to induce Zeeman splitting in the ms=±1 energy level.

[0030] A microwave source generates a modulated microwave signal, which is coupled to the diamond surface through a microwave antenna to drive the NV color center with microwaves.

[0031] The fluorescence signal generated by the NV color center and the separated reference light signal are filtered and then received by the second photodiode and the first photodiode, and converted into corresponding current signals.

[0032] The two current signals are converted into voltage signals by a dual-channel transimpedance amplifier circuit, and then differential processing and demodulation are performed to extract the detection signals related to the magnetic field change, and finally obtain the magnetic field measurement results.

[0033] Preferably, in the differential processing, when there is a difference in the intensity of the two photocurrent signals, signal balancing is performed at the analog end by dynamically adjusting the gain of the transimpedance amplifier circuit, so that the two signals are suppressed under the same intensity level; or a digital closed-loop mode is selected, and noise suppression is achieved by real-time dynamic adjustment of the two signals by the host computer.

[0034] Preferably, in the differential processing, signal balancing is performed at the analog end by dynamically adjusting the gain of the transimpedance amplifier circuit, or real-time dynamic differential processing is performed at the digital end by the host computer.

[0035] As described above, the differential integrated diamond quantum magnetic sensor and its fabrication method of the present invention have the following beneficial effects: By employing a side-excitation sandwich stacked structure, the pump light source, diamond NV color center chip, filter, microwave antenna, and photodetector are integrated into a single module, significantly reducing the system size. Multiple total internal reflections within the chamfered diamond extend the optical path, improving the fluorescence excitation efficiency of the NV color center. The balanced differential detection structure constructed using upper and lower filters and dual photodiodes effectively suppresses common-mode noise, increasing the magnetic field sensitivity by approximately 7.9 times. Simultaneously, the microwave antenna is directly fabricated on the filter surface, and near-magnetic-free shell packaging and wafer-level MEMS mass production processes are used to achieve a balance between high sensitivity, miniaturization, low interference, and low cost, demonstrating promising prospects for large-scale application. Attached Figure Description

[0036] Figure 1 The diagram shows the internal structure of the lateral excitation integrated quantum magnetic sensor of the present invention.

[0037] Figure 2 The diagram shown is a schematic of the wire bonding of the lateral excitation integrated quantum magnetic sensor of the present invention.

[0038] Figure 3 The diagram shown is a schematic of the wire bonding of the lateral excitation integrated quantum magnetic sensor of the present invention.

[0039] Figure 4 The diagram shown is a schematic of the diamond total internal reflection excitation of the present invention, wherein (a) is a total internal reflection simulation diagram and (b) is a total internal reflection physical diagram.

[0040] Figures 5a-5d The diagram shown is a flow chart of the filter process for the integrated quantum sensor of this invention.

[0041] Figures 6a-6d The diagram shown is a process flow chart of the silicon pad for the integrated quantum sensor of the present invention.

[0042] Figures 7a-7d The diagram shown is a wafer bonding flowchart of the integrated quantum sensor of the present invention.

[0043] Figures 8a-8c The diagram shown is an electrical packaging flowchart of the integrated quantum sensor of the present invention.

[0044] Figure 9 The diagram shown is a block diagram of the integrated quantum sensor differential testing system of the present invention.

[0045] Figure 10 The graph shown is a magnetic measurement sensitivity curve of the integrated quantum sensor of the present invention.

[0046] Explanation of reference numerals in the attached figures

[0047] 2 First filter 3 Silicon-based pads 4 diamond 5 Second filter 6 Second photodiode 7 PCB 8 laser diode 9 Laser diode heat sink 10 Case pins 11 PCB 12 RF non-magnetic housing 13 microwave antenna 14 Metal leads 101 Glass 102 Tantalum pentoxide 103 silicon dioxide 104 Metal 105 silicon 106 BCB 107 Photodetector 108 Tube shell 109 PCB Detailed Implementation

[0048] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0049] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components.

[0050] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0051] In the detailed description of embodiments of the present invention, for ease of explanation, the schematic diagrams illustrating the device structure may be partially enlarged without adhering to the general scale, and the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. Furthermore, in actual manufacturing, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0052] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for devices in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or there may be one or more layers in between.

[0053] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0054] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0055] Example 1

[0056] like Figures 1-3 As shown, this embodiment provides a differential integrated diamond quantum magnetic sensor, which includes: a pump light source, a multilayer stacked diamond NV color center chip, and a weak magnetic tube shell packaging module.

[0057] The pump source is a miniaturized green light source with an excitation wavelength range of 450nm to 570nm. The light emission principle is a laser diode (LD) or a light-emitting diode (LED). The laser diode 8 is mounted on the upper left of the laser diode heat sink 9 and is located on the side of the diamond 4, providing laser pumping from the side.

[0058] The multilayer diamond NV color center chip consists of, from top to bottom, a first photodiode 1, a first filter 2, a silicon-based pad 3, a diamond 4 with NV color centers, a second filter 5, and a second photodiode 6. The first photodiode 1 and the second photodiode 6 convert the received optical signals into electrical signals, respectively.

[0059] The first filter 2 is a short-pass filter with a transmission band of 490nm~600nm, a cutoff band of 600nm~800nm, and a transmittance of 1 / 106 at 610nm, which can achieve the filtering of NV colors in the NV color center. - Effective filtration of fluorescence, through NV 0 The background fluorescence and green excitation light are then differentially divided with the fluorescence receiver to suppress common-mode noise in the laser. The second filter 5 is a long-pass filter with a transmission band of 625nm~780nm and a cutoff band of 400nm~620nm, and a transmittance of 1 / 10 at 620nm. 6 Highly efficient filtering of background light, through NV - Fluorescence.

[0060] Both the first filter 2 and the second filter 5 are equipped with microwave antennas 13. The microwave antennas 13 are fabricated using a metal layer, with the material being a single or multiple layer of gold or silver metal film, and a thickness between 30 nm and 1000 nm. The microwave antennas 13 are both fabricated on the side closest to the diamond 4, used to radiate microwave signals to the diamond. The microwave antennas on the surface of the first filter 2 are led out through metal leads 14 on the surface of the silicon-based pad. The second filter 5 is slightly larger than the silicon-based pad 3, exposing the electrical leads on its surface. The two layers of microwave antennas 13 are aligned with high precision to ensure spatial matching, placing the diamond 4 within a uniform microwave region.

[0061] The silicon-based pad 3 is fabricated by depositing silicon dioxide as an insulating layer and a hard mask protective layer on the silicon crystal surface, followed by photolithography to prepare an opening pattern, reactive ion etching (RIE) to pattern the silicon dioxide layer, and wet anisotropic etching to fabricate the through-hole on the silicon substrate. The silicon-based pad 3 has a central cavity with a lateral area between 0.25 mm² and 100 mm² for placing the diamond 4. The silicon-based pad 3 has a thickness between 200 μm and 800 μm, with beveled sidewalls on three sides, and is coated with a single or multiple layer of gold or silver metal film 104 with a thickness between 30 nm and 1000 nm. One side of the central opening area is completely open for subsequent side incidence of laser light; the beveled sidewalls on the other three sides improve the collection efficiency of light signals hitting the sidewalls through reflection, while also providing mechanical protection for the diamond 4.

[0062] The thickness of diamond-4 with NV color centers ranges from 1 μm to 700 μm. The refractive index of diamond-4 is approximately 2.42, corresponding to a total internal reflection angle of 24.4°. The diamond-4 samples are cut and polished to form a chamfered structure, ensuring that the angle between the incident laser and the sidewall of diamond-4 satisfies the total internal reflection condition.

[0063] The magnetic weakening housing package module includes a housing base and a housing cover. The housing surface is plated with a metal layer, which is a single or multi-layer metal film of gold or nickel, with a thickness of 1μm to 10μm. The housing has housing leads 10, which can operate in a frequency range from DC to 4GHz. The lead material is 4J80 magnetic weakening alloy. It is hermetically sealed by soldering or parallel sealing, and the overall remanence of the housing is in the range of 20nT to 1000nT. The housing base is soldered to PCB 11 for encapsulation.

[0064] The internal electrical connections of the housing are achieved through wire bonding, including: the connection between the laser diode 8 and the housing pin 10; the connection between the electrodes of the first photodiode 1 and the second photodiode 6 and the housing pin 10; the parallel connection of the microwave antennas on the surfaces of the first filter 2 and the second filter 5; and the electrical interconnection between the microwave antenna 13 and the housing pin 10. Since the electrode of the second photodiode 6 is located on the back of the photosensitive surface, it is electrically connected to the upper surface of the PCB7 via the metal electrodes, which is equipped with solder joints and metal leads 14 on the surface.

[0065] like Figure 4 As shown, this invention provides a method for total internal reflection excitation of diamond. When the incident laser satisfies the total internal reflection condition, the laser is confined inside the diamond to achieve multiple reflections, forming a simulated... Figure 4 The long-path total internal reflection excitation shown in (a) is as shown in the actual sample. Figure 4 As shown in (b), approximately 20 times the NV color center excitation efficiency can be achieved compared to the vertical excitation architecture.

[0066] Example 2

[0067] like Figures 5a-8c As shown, this embodiment provides a method for fabricating a differential integrated diamond quantum magnetic sensor, the method comprising the following steps:

[0068] S1. Preparation of the filter ( Figures 5a-5d The process involves depositing tantalum pentoxide (102) and silicon dioxide (103) materials on a glass 101 wafer substrate using an overlapping, multi-layer deposition method to construct a high / low refractive index composite thin film. After single-sided film deposition, the same film system is deposited on the back side, effectively reducing warping caused by stress introduced to the wafer substrate by single-sided deposition. Finally, metallization is performed on the surface to fabricate a microwave radiating antenna. This step involves fabricating two types of filters: a short-pass filter (transmittance band 490nm~600nm, cutoff band 600nm~800nm, transmittance at 610nm 1 / 10). 6 ) and long-pass filters (transmitting wavelength 625nm~780nm, cutoff wavelength 400nm~620nm, transmittance 1 / 10 at 620nm) 6 ).

[0069] S2, Preparation of silicon-based pads ( Figures 6a-6dSilicon dioxide 103 is deposited on the surface of a silicon wafer 105 as an insulating layer and a hard mask protective layer. An opening pattern for a silicon-based protective trench is fabricated on the surface of the silicon dioxide layer using photolithography. Subsequently, dry etching is used to pattern the silicon dioxide layer 103, and wet anisotropic etching is used to etch the vias in the silicon substrate, fabricating a silicon-based pad 3 with a slanted sidewall structure. One side of the central opening area is completely open for subsequent side incidence of laser light; the other three sides have slanted sidewalls, which improve the collection efficiency by reflecting the light signal hitting the sidewalls. Simultaneously, a diamond 4 is placed within the silicon interconnect to provide mechanical protection for the diamond 4. Finally, a metal thin film is deposited to reflect visible light.

[0070] S3, wafer-level bonding ( Figures 7a-7d The diamond sample 4, with BCB106 or deposited metal on its surface, is thermo-bonded to the second filter 5 at the wafer level. The diamond 4 is located within the uniform region of the microwave radiating antenna on the filter surface. After four-layer bonding, a wafer-level bonded sample with a stepped structure is formed. The microwave antennas 13 on the filter surface are all fabricated on the side close to the diamond 4. Therefore, the microwave antennas on the surface of the first filter 2 are led out through the metal leads 14 on the surface of the silicon interconnect layer. The second filter 5 is slightly larger than the silicon interconnect layer, exposing the electrical leads on the surface layer.

[0071] S4, Electrical Packaging ( Figures 8a-8c The bonded chip is bonded or glued to the upper and lower photodetectors 107 (i.e., the first photodiode 1 and the second photodiode 6) and then placed inside the housing 108. The housing 108 includes a laser diode 8 soldered to the side and a PCB 109 soldered to the bottom. The laser diode 8 is pumped by laser light incident from the side of the silicon interconnect layer. Since the lower second photodiode 6 is located on the back of the photosensitive surface, the metal electrode is electrically connected to the upper surface of the PCB 7 using the PCB 109 with solder joints and metal leads 14 on its surface. Then, wire bonding is used to achieve the internal electrical connections, including the connection between the laser diode 8 and the housing pins 10, the electrical connection between the upper and lower photodiode electrodes and the housing pins 10, the parallel connection of the microwave antennas 13 on the surfaces of the two filters, and the electrical interconnection between the microwave antennas 13 and the housing pins 10. After the electrical connections are completed, parallel seam welding is used to encapsulate the housing cover plate and the housing 108. Parallel seam welding effectively improves the overall hermeticity of the package.

[0072] Example 3

[0073] like Figure 9 As shown, this embodiment provides a differential magnetic field detection method using a differential integrated diamond quantum magnetic sensor.

[0074] The integrated quantum magnetic sensor testing system consists of two parts: a front-end sensor and a back-end electronics system. An external power supply powers the front-end sensor, providing a constant current to drive the laser diode, generating a green laser to laser-pump the diamond 4NV color center. Particles in the ground state are pumped to an excited state and then return to the ground state via radiative transitions, simultaneously producing fluorescence. Applying a bias magnetic field causes the previously degenerate ms=±1 energy level to undergo Zeeman splitting, generating a 2γB resonant frequency with the ms=0 energy level. NV The displacement, where γ is the gyromagnetic ratio, B NV This represents the projected component of the magnetic field along the NV color center axis. The magnitude of the external magnetic field can be obtained by detecting changes in the operating frequency.

[0075] The modulated radio frequency signal generated by the microwave source is transmitted sequentially to the diamond surface through the tube lead 10, metal lead 14, microwave transmission line, and microwave antenna 13, simultaneously driving the excited NV color centers with spatial microwaves. The fluorescence signal emitted by the diamond 4 and the green light signal from the laser are optically filtered by the upper and lower filters and then reach the first photodiode 1 and the second photodiode 6, respectively, and are converted into two current signals.

[0076] Two current signals are transmitted through electrical connections within the tube housing to the transimpedance amplifier circuit in the back-end electronics, where they are converted into voltage signals and differentially divided. The dual-channel transimpedance amplifier circuit has adjustable gain; when there is a difference in the intensity of the two photoelectric signals, the gain can be adjusted at the analog end for balancing. During differential detection, common-mode noise is minimized at the same intensity level, resulting in a better signal-to-noise ratio detection signal during magnetic field detection. Furthermore, this invention is not limited to analog end balancing; it can be paired with a digital closed-loop testing system. Data processing is performed on the digital end via a host computer, and a microwave frequency sweep of 2.4GHz-3.2GHz is applied to the NV color center to obtain demodulated signals along the four axes of the diamond NV color center. One frequency is selected as the resonant frequency for magnetic measurement. The amplitude spectral density of the test system is obtained by performing a Fourier transform on the demodulated voltage signal within 1 second using the lock-in amplifier. Then, the slope and gyromagnetic ratio of the demodulated signal are converted into the magnetic noise spectral density of the system, which serves as a characterization of the sensitivity of the diamond quantum magnetometer.

[0077] like Figure 10 As shown, in terms of sensitivity performance at the resonant frequency, the sensitivity without differential detection is 3.697 nT·Hz. -1 / 2 Differential suppression was implemented to suppress common-mode noise from sources such as lasers, resulting in a 7.9-fold improvement in sensitivity performance, optimized to 0.466 nT·Hz. -1 / 2 .

[0078] In summary, this invention integrates a light source, a diamond NV color center chip, a filter, a microwave antenna, and a photodetector into an on-chip quantum magnetic sensing module. It improves fluorescence efficiency and magnetic field sensitivity through total internal reflection excitation and balanced differential detection. Furthermore, by combining weak magnetic packaging and wafer-level MEMS technology, it achieves device miniaturization, low noise, and mass production. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial applicability.

[0079] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A differential integrated diamond quantum magnetic sensor, characterized in that, The sensor includes: a pump light source, a multi-layer stacked diamond NV color center chip, and a weak magnetic tube shell package module; The pump source is located on the side of the diamond with NV color center, and the pump source includes a laser diode and a laser diode heat sink, with the laser diode located above the laser diode heat sink; The multilayer diamond NV center chip is composed of a first photodiode, a first filter, a silicon-based pad, a diamond with NV centers, a second filter, and a second photodiode stacked from top to bottom; both the first filter and the second filter have microwave antennas on their surfaces; the silicon-based pad has an opening in the middle for placing the diamond with NV centers, and the opening has a transverse channel; The weak magnetic tube shell packaging module includes a PCB, shell pins, an RF non-magnetic tube shell, and metal leads. The PCB is connected to the inside and bottom of the RF non-magnetic tube shell. The PCB inside the RF non-magnetic tube shell is located below the multilayer diamond NV color center chip and is connected to the shell pins via the metal leads. The two layers of microwave antennas are electrically interconnected with the shell pins via the metal leads. The PCB at the bottom of the RF non-magnetic tube shell is connected to the shell pins on both sides of the RF non-magnetic tube shell. The electrodes on the heat sink surfaces of the first photodiode and the laser diode are electrically interconnected with the shell pins via the metal leads.

2. The differential integrated diamond quantum magnetic sensor according to claim 1, characterized in that, The excitation wavelength of the laser diode is 450nm~570nm.

3. The differential integrated diamond quantum magnetic sensor according to claim 1, characterized in that, The first filter is a short-pass filter with a transmission band of 490nm~600nm and a cutoff band of 600nm~800nm; the second filter is a long-pass filter with a transmission band of 625nm~780nm and a cutoff band of 400nm~620nm; the transmittance of the cutoff band of both filters is 1 / 10. 4 ~1 / 10 6 .

4. A differential integrated diamond quantum magnetic sensor according to claim 1, characterized in that, The first and second filters are made of a high / low refractive index composite film formed by the overlapping deposition of tantalum pentoxide and silicon dioxide, with a thickness of 1 μm to 25 μm.

5. A differential integrated diamond quantum magnetic sensor according to claim 1, characterized in that, The diamond of the NV color center is a chamfered diamond, and the angle between the incident laser and the sidewall satisfies the condition of total internal reflection, so that the laser is reflected multiple times inside the diamond to the NV color center.

6. A differential integrated diamond quantum magnetic sensor according to claim 1, characterized in that, The lateral area of ​​the silicon-based pad is 0.25 mm². 2 ~100mm 2 The thickness is 200μm~800μm; the inclined sidewall surface of the silicon-based pad is plated with a gold or silver metal film with a thickness of 30nm~1000nm.

7. A differential integrated diamond quantum magnetic sensor according to claim 1, characterized in that, Both microwave antennas are fabricated on one side of the diamond near the NV color center. The diamond is aligned so that it is in a spatially uniform microwave region. The material of the microwave antenna is a gold or silver metal film with a thickness of 30nm~1000nm.

8. A differential integrated diamond quantum magnetic sensor according to claim 1, characterized in that, The surface of the radio frequency non-magnetic tube shell in the weak magnetic tube shell packaging module is plated with a gold or nickel metal film with a thickness of 1μm~10μm; the tube shell pin material is 4J80 weak magnetic material with a frequency range of DC-4GHz; the tube shell cover plate and the tube shell base are hermetically sealed by parallel seam welding, and the overall tube shell residual magnetism is 20nT~1000nT.

9. A differential integrated diamond quantum magnetic sensor according to claim 1, characterized in that, The electrodes of the second photodiode are located on the back side of the photosensitive surface, and are electrically connected to the upper surface layer via the PCB with solder joints and metal leads.

10. A differential integrated diamond quantum magnetic sensor according to claim 1, characterized in that, The cavity has sloping sidewalls on three sides and a transverse channel on one side.

11. A method for fabricating a differential integrated diamond quantum magnetic sensor as described in any one of claims 1 to 10, characterized in that, The preparation method includes: Tantalum pentoxide / silicon dioxide is deposited on both sides of a glass wafer substrate to form a high / low refractive index composite film, and a metal layer is formed on its surface to obtain upper and lower filters with a microwave antenna structure. A silicon dioxide hard mask is formed on the surface of a silicon wafer. A silicon-based pad with inclined sidewalls is obtained by photolithography, dry etching and wet anisotropic etching, and a metal thin film is deposited on its surface. Diamond with NV color centers, lower filter, silicon-based pad and upper filter are bonded sequentially to form a wafer-level bonded sample, and then the sample is processed into a chip to obtain a bonded chip; The bonding chip and photodiode are packaged in a housing, and electrical connection is achieved by wire bonding. The housing is then sealed by parallel seam welding.

12. The method for fabricating a differential integrated diamond quantum magnetic sensor according to claim 11, characterized in that, The silicon-based pad has a central opening area on one side that is fully open for laser side incidence, while the other three sides form an oblique sidewall structure.

13. The method for fabricating a differential integrated diamond quantum magnetic sensor according to claim 11, characterized in that, During the bonding process, the microwave antennas of the two filters are aligned with high precision to ensure spatial matching; the antenna of the upper filter is led out through the metal lead on the surface of the silicon-based pad, and the lower filter is slightly larger than the silicon-based pad to expose the electrical connection area for wire bonding.

14. A differential magnetic field detection method for a differential integrated diamond quantum magnetic sensor as described in any one of claims 1 to 10, characterized in that, The detection method includes: The pump source laser pumps the NV color center in diamond to induce spin polarization; at the same time, a bias magnetic field is applied to induce Zeeman splitting in the ms=±1 energy level. A microwave source generates a modulated microwave signal, which is coupled to the diamond surface through a microwave antenna to drive the NV color center with microwaves. The fluorescence signal generated by the NV color center and the separated reference light signal are filtered and then received by the second photodiode and the first photodiode, and converted into corresponding current signals. The two current signals are converted into voltage signals by a dual-channel transimpedance amplifier circuit, and then differential processing and demodulation are performed to extract the detection signals related to the magnetic field change, and finally obtain the magnetic field measurement results.

15. The differential magnetic field detection method of a differential integrated diamond quantum magnetic sensor according to claim 14, characterized in that, In the differential processing, signal balancing is performed at the analog end by dynamically adjusting the gain of the transimpedance amplifier circuit, or real-time dynamic differential processing is performed at the digital end by the host computer.

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