Non-microwave acceleration sensing device and method based on NV color center

Abstract

The invention discloses a non-microwave acceleration sensing device and method based on an NV color center. The device comprises a capture module, an excitation module, a sensitive module and a detection module. The capture module is used for emitting capture light, generating a light trap and suspending diamond, the excitation module is used for emitting excitation light and polarizing an NV color center spin state to a 0 state, the sensitive module is used for coupling the NV color center spin and plasmons so as to convert different displacements into different spontaneous radiation rates of the NV color center, and the detection module is used for detecting the number of effective fluorescence emitted by the NV color center. And the input force and the acceleration to be measured are solved. According to the invention, on the basis of a luminous suspension mechanical quantity measurement system, the coupling effect of metal plasmons and NV color center spontaneous radiation process is utilized, the quantity of fluorescence is detected, the displacement of the mass block under the action of input force is obtained, and then the acceleration is calculated. An external microwave field of a traditional NV color center sensing system is not needed, a complex displacement detection light path of a traditional light force system is not needed, and the method 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] The NV center quantum platform in diamond is widely used in the field of quantum sensing due to its solid-state properties, easy control at room temperature and fluorescence stability. However, the traditional mechanical quantity measurement system based on the readout of the NV center spin state requires the application of a microwave field to achieve the manipulation of the spin state. On the one hand, the introduced microwave manipulation field noise will reduce its measurement accuracy, and on the other hand, the required microwave source increases the complexity of the measurement system. At the same time, the thermal effects introduced by the microwave field have an adverse effect on biomedical applications such as living 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 radiation rate of the NV center can be regulated under the wavelength resonance condition. The distance between the metal and the NV center will affect the speed of the NV center's spontaneous radiation rate, and it is reflected in the number of fluorescent photons emitted by the NV center. The photodynamic 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 required is usually difficult to balance 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 photodynamic sensing scheme of NV center fluorescence coupled plasmon 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 metal plasmons and NV color center spontaneous radiation processes is utilized to obtain the displacement of the mass block under the influence of input force by detecting the number of fluorescence, and then solve the acceleration. 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 sensor 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 capture laser is used to emit laser capture light with a wavelength of 1064nm or 1550nm;

[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 532nm or other wavelengths that can polarize the spin of the NV color center;

[0014] The second acousto-optic modulator is used to modulate the intensity of the laser emitted by the excitation laser and output it, 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 radiation process of the NV color center. Its resonance peak is in the NV color center fluorescence band and is used to regulate the spontaneous radiation 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 diamond and suppress measurement noise.

[0019] The detection module is used to detect the number of effective fluorescence emitted by the NV color center and resolve 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 650nm to 800nm ​​to distinguish negatively charged NV color centers;

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

[0023] The processor is used to process and obtain the number of fluorescent photons that varies 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, using a microwave-free acceleration measurement device based on NV color centers, comprising the following steps:

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

[0026] S2. Use piezoelectric vibration method or atomization method to vibrate diamond particles, wait 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;

[0027] S3. When the input force is applied, the captured light power is kept constant and the opening time is continued for 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 number of fluorescence by the photodetector multiple times within a period of time to obtain the number of fluorescence photons that changes with time;

[0030] S6. The processor reads the number of fluorescence photons N(t) measured by the photon detector that varies with time, and performs a 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 diamond, Γ is the damping coefficient determined by the collision of ambient gas molecules, k is the experimentally adjustable light trap stiffness, which depends on the wavelength and power of the captured 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 by 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 in the present invention is based on the coupling effect between 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 in the present invention does not need to apply an external microwave field, reducing the system complexity and microwave field noise fluctuations; third, compared with the traditional mechanical quantity sensing system based on photomechanical suspension, the sensing device in 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 a microwave-free acceleration sensor 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 It is a 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 when the metal structure is a triangular prism. Schematic diagram of the finite element simulation of the spontaneous emission rate (in arbitrary units) of the NV color center changing with the distance (in nanometers) as the distance between the diamond-metal structure changes. DETAILED DESCRIPTION

[0041] The present invention will be further explained below in conjunction with 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 sensor device based on NV color center of the present invention comprises a capture module, an excitation module, a sensitive 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 is used to provide laser capture light with a wavelength of 1064nm or 1550nm; the first acousto-optic modulator 2 is used to modulate the laser intensity emitted by the capture laser 1 and output it; the beam splitter 3 is used to align the two optical channels to the objective lens 6, and in the capture module, it is used to align the capture light output by the first acousto-optic modulator to the objective lens 6; the objective lens 6 is used to focus the two light beams, and in the capture module, it is used to focus the capture light to form a stable light trap.

[0044] The excitation module is used to polarize the NV color center spin state, and includes an excitation laser 4 and a second acousto-optic modulator 5. The excitation laser 4 is used to provide a laser excitation light with a wavelength of 532nm or other laser excitation light that can polarize the NV color center spin. The second acousto-optic modulator 5 is used to modulate the laser intensity emitted by the excitation laser 4 and output it, which is aligned to the objective lens 6 by the beam splitter 3 and then focused by the objective lens 6.

[0045] 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 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 center, which is polarized to spin m by the excitation light emitted by the objective lens 6. 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 and 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 number of effective fluorescence emitted by the NV center and solve the input force and acceleration, including a lens 9, a filter 11, a photodetector 12 and a processor 13. The 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 pass the fluorescence from 650nm to 800nm ​​to distinguish the negatively charged NV center. 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 and obtain 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 2 and the second acousto-optic modulator 5, so as to solve 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 respectively, ω e and ω f They respectively characterize the energy of the initial state |e> and final state |f> of the entire NV-environment system. Therefore, the diamond displacement leads to a change in the distance between the metal structure and the diamond, which in turn regulates the spontaneous radiation rate of the NV color center. The diamond displacement can be inferred by detecting the number of fluorescence photons. When the diamond is near the equilibrium position, the external input force causing the displacement can be inferred from the diamond displacement, and then the acceleration can be inferred.

[0048] like Figure 2 As shown, a microwave-free acceleration sensing method based on NV color centers, the measurement method process includes:

[0049] (1) Turn on the capture laser 1 and adjust the first acousto-optic modulator 2 to a suitable 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 so that it is in a first equilibrium position, where the distance between the diamond 8 and the metal structure 7 is recorded as x1;

[0051] (3) When the input force is applied, the captured light power is kept constant and the opening 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 number of fluorescence by the photodetector 12 for a period of time to obtain the number of fluorescence photons;

[0054] (6) The processor reads the number of fluorescence photons N(t) measured by the photon detector 12 and changes with time, 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: Among them, m is the mass of diamond 8, Γ is the damping coefficient determined by the collision of ambient gas molecules, k is the experimentally adjustable light trap stiffness, which depends on the wavelength and power of the captured 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 by F=ma and the equation of motion.

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

Claims

1. A microwave-free acceleration sensor device based on NV color centers, characterized in that: The device comprises 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 number of effective fluorescence 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, and 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, and 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 radiation 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 a microwave-free acceleration measurement device based on NV color centers as described in 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 a suitable power to form a light trap; (2) Using piezoelectric vibration or atomization to vibrate 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 there is an input force, the captured light power is kept constant and the opening time is continued for 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 time t2 to polarize the NV color center 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 over time and performs a 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 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; (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 diamond, Γ is the damping coefficient determined by the collision of ambient gas molecules, k is the experimentally adjustable light trap stiffness, which depends on the wavelength and power of the captured 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 by F=ma and the equation of motion.

7. The microwave-free acceleration sensing method based on NV color centers according to claim 6 is characterized in that: Its working principle is: the diamond is displaced under the action of external input force, which affects the coupling of 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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