A microwave-free acceleration sensing device and method based on NV color centers

Abstract

The application discloses a microwave-free acceleration sensing device and method based on NV color centers. The device comprises a capturing module, an excitation module, a sensitive module and a detection module. The capturing module is used for emitting capturing light, generating an optical trap and suspending a diamond. The excitation module is used for emitting excitation light, polarizing the spin state of the NV color center to the 0 state. The sensitive module is used for coupling the spin of the NV color center and plasmons, so as to convert different displacements into different spontaneous emission rates of the NV color center. The detection module is used for detecting the number of effective fluorescent light emitted by the NV color center, and calculating the input force and acceleration to be measured. The application relies on an optical force suspension mechanics quantity measurement system, utilizes the coupling effect of metal plasmons and the spontaneous emission process of the NV color center, detects the number of fluorescent light, obtains the displacement of the mass block under the action of the input force, and then calculates the acceleration. The application does not need an additional microwave field of a traditional NV color center sensing system, and does not need a complex displacement detection light path of a traditional optical force system, and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of inertial measurement, and in particular relates to a microwave-free acceleration sensing device and method based on NV (nitrogen vacancy) color centers. Background Art

[0002] NV color center quantum platforms in diamond are widely used in quantum sensing due to their solid-state properties, easy room-temperature manipulation, and stable fluorescence. However, conventional mechanical measurement systems based on NV color center spin state readout require the application of microwave fields to manipulate the spin state. This introduces noise from the microwave manipulation field, which reduces measurement accuracy, while the required microwave source increases the complexity of the measurement system. Furthermore, the thermal effects introduced by microwave fields can adversely affect biomedical applications such as live cell detection.

[0003] If there is a suitable metal structure near the NV center quantum emitter, the metal will generate plasmons under the action of light, and the spontaneous emission rate of the NV center can be regulated under wavelength resonance conditions. The distance between the metal and the NV center will affect the speed of the NV center's spontaneous emission rate, which is reflected in the number of fluorescence photons emitted by the NV center. The photomechanical suspension system has a high quality factor and high sensitivity due to the fact that its mass block does not need to contact mechanical support. However, the displacement detection scheme it requires usually has difficulty in balancing low optical path complexity and high displacement detection accuracy, and the installation error of the optical components will reduce the sensing performance. Therefore, the quantum photomechanical sensing scheme of NV center fluorescence coupled plasmons provides a new idea for acceleration measurement. Summary of the Invention

[0004] To solve the above problems, the present invention discloses a microwave-free acceleration sensing device and method based on NV color centers. Relying on the photomechanical suspension mechanical quantity measurement system, the coupling effect of the spontaneous radiation process of metal plasmons and NV color centers is utilized. By detecting the number of fluorescence, the displacement of the mass block under the influence of the input force is obtained, and then the acceleration is calculated. The system is simple and practical, with high detection accuracy and sensitivity.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A microwave-free acceleration sensing device based on NV color centers includes a capture module, an excitation module, a sensitive module, and a detection module.

[0007] The capture module is used to generate a light trap and suspend diamond, and includes a capture laser, a first acousto-optic modulator, a beam splitter, and an objective lens.

[0008] Optionally, the trapping laser is used to emit laser trapping light with a wavelength of 1064 nm or 1550 nm;

[0009] The first acousto-optic modulator is used to modulate the intensity of the laser emitted by the capture laser and output it;

[0010] The beam splitter is used to align the two optical channels to the objective lens. In the capture module, it is used to align the capture light output by the first acousto-optic modulator to the objective lens.

[0011] The objective lens is used to focus the two light beams. In the capture module, it is used to focus the capture light to form a stable light trap.

[0012] The excitation module is used to polarize the NV color center spin state, and includes an excitation laser and a second acousto-optic modulator.

[0013] The excitation laser is used to provide laser excitation light with a wavelength of 532 nm or other wavelength that can polarize the NV color center spin;

[0014] The second acousto-optic modulator is used to modulate the intensity of the laser light emitted by the excitation laser and output the modulated laser light, which is reflected by the beam splitter to the objective lens and then focused by the objective lens.

[0015] The sensitive module is used to couple the NV center spin and plasmon to convert the displacement under different input forces into different spontaneous radiation rates of the NV center, including metal structures, diamonds and vacuum chambers.

[0016] The diamond is suspended by the trapped light emitted by the objective lens. The diamond contains NV color centers, which are polarized to spin m by the excitation light focused by the objective lens. s =0 state;

[0017] The metal structure is used to generate plasmons and react to the spontaneous emission process of the NV color center. Its resonance peak is in the NV color center fluorescence band and is used to regulate the spontaneous emission rate of the NV color center. The position of the metal structure remains unchanged.

[0018] The vacuum chamber is used to adjust the pressure at the position of the sensitive module, and the adjustment range is from atmospheric pressure to vacuum environment, so as to achieve stable capture of diamonds and suppress measurement noise.

[0019] The detection module is used to detect the effective fluorescence number emitted by the NV color center and calculate the input force and acceleration, and includes a lens, a filter, a photodetector and a processor.

[0020] The lens is used to collimate the fluorescence emitted by the NV color center and allow it to pass through the filter to reach the photodetector;

[0021] The filter is used to pass fluorescence from 650 nm to 800 nm to distinguish negatively charged NV color centers;

[0022] The photodetector is used to detect the number of photons in real time and send the result to the processor;

[0023] The processor is used to process the number of fluorescent photons that changes with time, and then obtain the spontaneous emission rate of the NV color center and the displacement of the diamond. At the same time, it is used to obtain the modulation information of the first acousto-optic modulator and the second acousto-optic modulator, so as to solve the physical quantity to be measured.

[0024] The present invention also provides a microwave-free acceleration sensing method based on NV color centers, which uses a microwave-free acceleration measurement device based on NV color centers, including the following steps:

[0025] S1. Turn on the trapping laser and adjust the trapping light to the appropriate power through the first acousto-optic modulator to form a light trap;

[0026] S2. Use piezoelectric vibration or atomization to vibrate the diamond particles, and wait for the light trap to capture the diamonds and bring them to the first equilibrium position, where the distance between the diamonds and the metal structure is denoted by x1.

[0027] S3. When the input force is applied, the captured light power is kept constant and the light is turned on for time t1, so that the diamond reaches a new second equilibrium position, where the distance between the diamond and the metal structure is recorded as x2;

[0028] S4. Turn off the trapping laser and then turn on the excitation laser for time t2 to polarize the NV color center spin to spin m. s =0 state;

[0029] S5. Turn off the excitation laser, and then measure the fluorescence photon count multiple times over a period of time using a photodetector to obtain the time-varying fluorescence photon count.

[0030] S6. The processor reads the number of fluorescence photons N(t) measured by the photon detector and performs fitting according to the following formula: Among them, C1 and C2 are fitting parameters, τ is the excited state lifetime obtained by fitting, and the reciprocal is the spontaneous emission rate

[0031] S7. Repeat steps S3 to S6 to reduce statistical errors by averaging multiple times, obtain the second equilibrium position x2 from the spontaneous radiation rate γ, and solve the displacement x of the diamond caused by the input force to satisfy x = x1-x2;

[0032] S8. The processor reads the displacement data of the diamond obtained in the previous step, and reads the power data of the captured light; the motion equation is Where m is the mass of the diamond, Γ is the damping coefficient determined by collisions with ambient gas molecules, k is the experimentally adjustable light trap stiffness, which depends on the wavelength and power of the trapped light, F is the input force, and a is the acceleration to be measured. By calculating experimental parameters such as k and Γ, the acceleration caused by the input force can be solved using F = ma and the equation of motion.

[0033] The beneficial effects of the present invention are:

[0034] The superiority of the present invention is reflected in three aspects: First, the sensing method of the present invention is based on the coupling effect of the spontaneous radiation process of the NV color center and the metal plasmon. The spontaneous radiation rate of the NV color center is obtained by detecting fluorescence, thereby obtaining the displacement of the mass block caused by the input force, and then solving the acceleration. The sensing principle is novel, and the detection accuracy and sensitivity are high; Second, compared with the traditional quantum sensing system based on NV color center spin readout, the sensing device of the present invention does not require the application of an external microwave field, reducing the system complexity and microwave field noise fluctuations; Third, compared with the traditional mechanical quantity sensing system based on photodynamic suspension, the sensing device of the present invention does not require a complex displacement detection optical path, reducing the system complexity and the degradation of sensing performance caused by optical path installation errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the microwave-free acceleration sensing device based on NV color centers in the present invention;

[0036] List of Figure Symbols:

[0037] 1. Capture laser, 2. First acousto-optic modulator, 3. Beam splitter, 4. Excitation laser, 5. Second acousto-optic modulator, 6. Objective lens, 7. Metal structure, 8. Diamond, 9. Lens, 10. Vacuum chamber, 11. Filter, 12. Photodetector, 13. Processor.

[0038] Figure 2 This is a flow chart of the microwave-free acceleration sensing method based on NV color centers in the present invention.

[0039] Figure 3 Schematic diagram of the time sequence of applying capture light, excitation light, and implementing photon number readout in the present invention.

[0040] Figure 4 This is a simulation example for a triangular prism-like metal structure. A finite element simulation shows how the spontaneous emission rate of the NV color center (in arbitrary units) varies with distance (in nanometers) as the distance between the diamond and metal structure changes. DETAILED DESCRIPTION

[0041] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0042] like Figure 1 As shown, the microwave-free acceleration sensing device based on NV color centers of the present invention includes a capture module, an excitation module, a sensing module, and a detection module. Specifically, wherein:

[0043] The capture module includes a capture laser 1, a first acousto-optic modulator 2, a beam splitter 3, and an objective lens 6. The capture laser 1 provides capture light with a wavelength of 1064 nm or 1550 nm. The first acousto-optic modulator 2 modulates the intensity of the laser light emitted by the capture laser 1 and outputs it. The beam splitter 3 aligns the two optical channels to the objective lens 6. In the capture module, it aligns the capture light output by the first acousto-optic modulator to the objective lens 6. The objective lens 6 focuses the two light beams, and in the capture module, it focuses the capture light to form a stable optical trap.

[0044] The excitation module, used to polarize the NV center spin state, includes an excitation laser 4 and a second acousto-optic modulator 5. The excitation laser 4 provides excitation light with a wavelength of 532 nm or other wavelength capable of polarizing the NV center spin. The second acousto-optic modulator 5 modulates the intensity of the laser light emitted by the excitation laser 4 and outputs it. The beam splitter 3 directs the laser light to the objective lens 6, which then focuses the light.

[0045] The sensitive module is used to couple the NV color center spin and plasmon to convert the displacement under different input forces into different spontaneous radiation rates of the NV color center, including metal structure 7, diamond 8 and vacuum chamber 10. Diamond 8 is suspended by the capture light emitted by the objective lens. Diamond 8 contains NV color centers, and the excitation light emitted by the objective lens 6 is polarized to spin m s =0 state, the metal structure 7 is used to generate plasmons and react to the spontaneous radiation process of the NV center. Its resonance peak is in the NV center fluorescence band, which is used to regulate the spontaneous radiation rate of the NV center. The position of the metal structure 7 remains unchanged. The vacuum chamber 10 is used to adjust the pressure at the position of the sensitive module, and the adjustment range is from atmospheric pressure to vacuum environment, so as to achieve stable capture of the diamond 8 and suppress measurement noise.

[0046] The detection module is used to detect the effective fluorescence emitted by the NV center and calculate the input force and acceleration. It includes a lens 9, a filter 11, a photodetector 12, and a processor 13. Lens 9 is used to collimate the fluorescence emitted by the NV center and pass it through the filter 11. The filter 11 is used to detect the fluorescence from 650nm to 800nm ​​to distinguish negatively charged NV centers. The photodetector 12 is used to detect the number of photons in real time and send it to the processor 13. The processor 13 is used to process the fluorescence photon number that varies with time, thereby determining the spontaneous emission rate of the NV center and the displacement of the diamond. At the same time, it is used to obtain the modulation information of the first and second acousto-optic modulators 2 and 5, thereby calculating the physical quantity to be measured.

[0047] The spontaneous emission process of NV color centers is affected by their inherent properties and the surrounding electromagnetic environment. According to the golden Fermi rule, the spontaneous emission rate of NV color centers under the coupling of NV color center spin and plasmon can be expressed as in, is the interaction Hamiltonian under the dipole approximation, and are the dipole operator and the electric field operator, ω e and ω f These represent the initial and final energy states of the entire NV-environment system, respectively. Therefore, diamond displacement changes the distance between the metal structure and the diamond, which in turn regulates the spontaneous emission rate of the NV color center. The diamond displacement can be inferred from the number of fluorescence photons. When the diamond is near equilibrium, the external input force causing the displacement can be inferred from the diamond displacement, and thus the acceleration.

[0048] like Figure 2 As shown in FIG, a microwave-free acceleration sensing method based on NV color centers is described. The measurement process includes:

[0049] (1) Turn on the trapping laser 1 and adjust the first acousto-optic modulator 2 to an appropriate power to form a light trap;

[0050] (2) Using a piezoelectric vibration method or an atomization method to vibrate the diamond 8 particles, waiting for the light trap to capture the diamond 8 and bring it to a first equilibrium position, where the distance between the diamond 8 and the metal structure 7 is denoted as x1;

[0051] (3) When the input force is applied, the captured light power is kept constant and the open time is continued for t1, so that the diamond 8 reaches the second equilibrium position, where the distance between the diamond 8 and the metal structure 7 is recorded as x2;

[0052] (4) Turn off the trapping laser 1 and then turn on the excitation laser 4 for a period of time t2 to polarize the NV color center spin to spin m s =0 state;

[0053] (5) turning off the excitation laser 4, and then measuring the fluorescence number multiple times by the photodetector 12 over a period of time to obtain the fluorescence photon number;

[0054] (6) The processor reads the number of fluorescence photons N(t) measured by the photon detector 12 and performs fitting according to the following formula: Among them, C1 and C2 are fitting parameters, τ is the excited state lifetime obtained by fitting, and the reciprocal is the spontaneous emission rate

[0055] (7) Repeat steps (3) to (6) to reduce statistical errors by averaging multiple times. Apply capture light, excitation light, and implement the time series diagram of photon number readout. Figure 3As shown. The second equilibrium position x2 is obtained from the spontaneous radiation rate γ, and the displacement x of the diamond 8 is solved to satisfy x=x1-x2. As an example of obtaining the second equilibrium position x2 from the spontaneous radiation rate γ, when the metal structure 7 is a triangular prism structure, as the distance between the diamond 8 and the metal structure 7 changes, the finite element simulation diagram of the spontaneous radiation rate (in arbitrary units) of the NV color center changes with the distance (in nanometers) is shown as follows Figure 4 As shown;

[0056] (8) The processor 13 reads the displacement data x of the diamond 8 obtained in the previous step, and reads the power data of the captured light; the motion equation is Where m is the mass of diamond 8, Γ is the damping coefficient determined by collisions with ambient gas molecules, k is the experimentally adjustable light trap stiffness, which depends on the wavelength and power of the trapped light, F is the input force, and a is the acceleration to be measured. By calculating experimental parameters such as k and Γ, the acceleration caused by the input force can be solved using F = ma and the equation of motion.

[0057] It should be noted that the above content merely illustrates the technical idea of ​​the present invention and cannot be used to limit the scope of protection of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications all fall within the scope of protection of the claims of the present invention.

Claims

1. A microwave-free acceleration sensor device based on NV color centers, characterized by: The device includes a capture module, an excitation module, a sensitive module, and a detection module. The capture module is used to generate a light trap and suspend the diamond; The excitation module is used to polarize the NV color center spin state to m s =0 state; The sensitive module is used to couple the NV color center spin and plasmon to convert the diamond displacement under different input forces into different spontaneous radiation rates of the NV color center; The detection module is used to detect the effective fluorescence number emitted by the NV color center, thereby calculating the input force and acceleration.

2. The microwave-free acceleration sensor device based on NV color centers according to claim 1, characterized in that: The capture module includes a capture laser, a first acousto-optic modulator, a beam splitter, and an objective lens. The capture laser is used to emit laser capture light with a wavelength of 1064nm or 1550nm; the first acousto-optic modulator is used to modulate the laser intensity emitted by the capture laser and output it; the beam splitter is used to align the two optical channels to the objective lens. In the capture module, it is used to align the capture light output by the first acousto-optic modulator to the objective lens; the objective lens is used to focus the two light beams. In the capture module, it is used to focus the capture light to form a stable light trap.

3. The microwave-free acceleration sensor device based on NV color centers according to claim 1, characterized in that: The excitation module includes an excitation laser and a second acousto-optic modulator; The excitation laser is used to provide laser excitation light with a wavelength of 532nm or other polarized NV color center spins; the second acousto-optic modulator is used to modulate the laser intensity emitted by the excitation laser and output it, which is aligned to the objective lens by the beam splitter and then focused by the objective lens.

4. The microwave-free acceleration sensor device based on NV color centers according to claim 1, characterized in that: The sensitive module includes a metal structure, diamond and a vacuum chamber; The diamond is suspended by the trapped light emitted by the objective lens. The diamond contains NV color centers, which are polarized to spin m by the excitation light focused by the objective lens. s =0 state; the metal structure is used to generate plasmons and react to the spontaneous radiation process of the NV center, and its resonance peak is in the NV center fluorescence band, which is used to regulate the spontaneous radiation rate of the NV center; the position of the metal structure remains unchanged; the vacuum chamber is used to adjust the pressure at the position of the sensitive module, and the adjustment range is from atmospheric pressure to vacuum environment, so as to achieve stable capture of diamond and suppress measurement noise.

5. The microwave-free acceleration sensor device based on NV color centers according to claim 1, characterized in that: The detection module includes a lens, a filter, a photodetector and a processor; The lens is used to collimate the fluorescence emitted by the NV center and allow it to pass through the filter to reach the photodetector; the filter is used to pass the fluorescence from 650nm to 800nm ​​to distinguish the negatively charged NV center; the photodetector is used to detect the number of photons in real time and send it to the processor; the processor is used to process the number of fluorescence photons that changes with time, and then obtain the spontaneous emission rate of the NV center and the displacement of the diamond. At the same time, it is used to obtain the modulation information of the first acousto-optic modulator and the second acousto-optic modulator, so as to solve the physical quantity to be measured.

6. A microwave-free acceleration sensing method based on NV color centers, using the microwave-free acceleration measurement device based on NV color centers according to any one of claims 1 to 5, comprising the following steps: (1) Turn on the trapping laser and adjust the first acousto-optic modulator to an appropriate power to form a light trap; (2) Using the piezoelectric vibration method or the atomization method to vibrate the diamond particles, waiting for the light trap to capture the diamond and bring it to the first equilibrium position, where the distance between the diamond and the metal structure is recorded as x1; (3) When the input force is applied, the captured light power is kept constant and the light is kept on for a period of time t1, so that the diamond reaches a new second equilibrium position, where the distance between the diamond and the metal structure is recorded as x2; (4) Turn off the trapping laser and then turn on the excitation laser for a period of time t2, polarizing the NV color center spin to m s =0 state; (5) Turn off the excitation laser, and then measure the fluorescence number multiple times by the photodetector over a period of time to obtain the number of fluorescence photons that changes with time; (6) The processor reads the number of fluorescence photons N(t) measured by the photon detector and performs fitting according to the following formula: Among them, C1 and C2 are fitting parameters, τ is the excited state lifetime obtained by fitting, and the reciprocal is the spontaneous emission rate (7) Repeat steps (3) to (6) to reduce statistical errors by averaging multiple times; obtain x2 at the second equilibrium position from the spontaneous radiation rate γ, and solve the displacement x of the diamond caused by the input force to satisfy x = x1-x2; (8) The processor reads the displacement data of the diamond obtained in the previous step, and reads the power data of the captured light; the motion equation is Where m is the mass of the diamond, Γ is the damping coefficient determined by collisions with ambient gas molecules, k is the experimentally adjustable optical trap stiffness, which depends on the wavelength and power of the trapped light, F is the input force, and a is the acceleration to be measured. To calculate k and Γ, we use F = ma and the equation of motion to solve the acceleration caused by the input force.

7. The microwave-free acceleration sensing method based on NV color centers according to claim 6, characterized in that: Its working principle is: the diamond produces displacement under the action of external input force, which affects the coupling between the NV color center spin and plasmon, and is converted into a change in the NV spontaneous radiation rate; the spontaneous radiation rate is calculated by detecting the fluorescence intensity emitted by the NV color center, and then the diamond displacement and external input force are inferred, and the acceleration is calculated by solving the motion equation.

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