Diamond nitrogen vacancy color center thermometer excitation laser stabilization control device and method

Abstract

The present invention discloses a device and method for stabilizing the excitation laser of a diamond nitrogen vacancy color center thermometer, comprising an excitation laser, a laser stabilization closed-loop control module, an acousto-optic modulation module, and a fluorescence collection module. By integrating a light intensity stabilization closed-loop control design based on a liquid crystal phase retarder into an excitation laser optical path based on acousto-optic modulation, a full laser optical path power stabilization closed-loop control of the diamond NV color center thermometer is achieved. The present invention can significantly improve the long-term stability of the diamond NV color center thermometer and the anti-interference capability of the optical path, effectively suppress laser power fluctuations caused by changes in ambient temperature, and heating effect fluctuations caused by laser power fluctuations, achieve long-term stable fluorescence output and temperature, magnetic field, and other measurements, thereby facilitating the application of diamond NV color center thermometers in power systems, chip manufacturing, and other fields.

Description

Technical Field

[0001] The present invention relates to the technical field of diamond NV color center temperature measurement, and in particular to a device and method for stabilizing and controlling an excitation laser of a diamond nitrogen vacancy color center thermometer. Background Art

[0002] The diamond NV color center thermometer is a new type of high-precision, micro-nanoscale thermometer based on the solid-state quantum spin principle. It obtains the zero-field splitting energy D generated by the electron spin-spin dipole interaction through optical detection of magnetic resonance spectral lines, and establishes the relationship between D and temperature to achieve temperature measurement. It is expected to solve the problem of lack of high-precision micro-temperature observation methods in cutting-edge fields such as biomedicine and chip manufacturing.

[0003] Diamond NV color center temperature measurement primarily involves three key technologies: laser excitation, microwave manipulation, and fluorescence detection. Lasers polarize electron spins, while fluorescence is generated by the transition of polarized electron spins from an excited state back to the ground state. Therefore, fluctuations in laser power can cause fluctuations in the NV color center fluorescence intensity, increasing the noise in the ODMR (light-detected magnetic resonance) spectrum and reducing the accuracy of temperature measurements. Therefore, stable control of the laser power of the diamond NV color center thermometer is necessary. Currently, the main approach to suppressing the impact of laser power fluctuations on ODMR line measurements is to achieve normalized pulsed ODMR line measurements using pulsed lasers and microwaves, and then use a reference fluorescence signal to reduce the impact of laser fluctuations. This method cannot fundamentally suppress the impact of laser fluctuations on measurements, resulting in limited suppression effectiveness and leading to problems such as fluctuations in the laser-induced heating effect. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention aims to provide a device and method for stabilizing the excitation laser of a diamond nitrogen vacancy color center thermometer, which can achieve stable power control from the laser source incident on the diamond sample. By integrating the light intensity stabilization closed-loop control design based on the liquid crystal phase retarder with the excitation laser optical path based on acousto-optic modulation, the full laser optical path power stabilization closed-loop control of the diamond NV color center thermometer is realized, thereby suppressing the influence of laser fluctuations from the source and improving the temperature measurement accuracy and stability.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A diamond nitrogen vacancy color center thermometer excitation laser stabilization control device mainly includes an excitation laser, a laser stabilization closed-loop control module, an acousto-optic modulation module and a fluorescence collection module;

[0007] The excitation laser is used to provide a laser light source;

[0008] The laser stabilization closed-loop control module includes a first half-wave plate, a first polarization beam splitter prism, a first photodetector, a liquid crystal phase retarder, an analyzer, a second half-wave plate, a second polarization beam splitter prism, a second photodetector and a closed-loop control unit;

[0009] The acousto-optic modulation module includes a first convex lens, an acousto-optic modulator, a second convex lens, an aperture, an acousto-optic modulator driver and a pulse generator;

[0010] The fluorescence collection module includes an objective lens, a dichroic mirror, a filter and a third photodetector;

[0011] The first half-wave plate and the first polarization beam splitter prism are arranged in sequence along the optical path of the laser light emitted by the excitation laser. The first polarization beam splitter prism is used to split the laser light into two beams of linear polarized light. The first photodetector is located on the optical path of one of the beams of linear polarized light separated by the first polarization beam splitter prism. The liquid crystal phase retarder, the analyzer, the first convex lens, and the acousto-optic modulator are arranged in sequence on the optical path of the other beam of linear polarized light separated by the first polarization beam splitter prism. The laser light is divided into first-order diffracted light and zero-order diffracted light by the acousto-optic modulator. The second convex lens, the aperture, the second half-wave plate, and the second polarization beam splitter prism are arranged on the optical path of the first-order diffracted light. The optical path of the optical filter and the third photodetector are sequentially arranged on the optical path of the objective lens; the second polarization beam splitter prism is used to split the output light of the second half-wave plate into two beams of linear polarized light, the second photodetector is located on the optical path of one of the beams of linear polarized light separated by the second polarization beam splitter prism, and the dichroic mirror is located on the optical path of the other beam of linear polarized light separated by the second polarization beam splitter prism; the dichroic mirror is used to reflect the received light to the objective lens; the diamond sample stage is used to place a block or nano-particle diamond NV color center sample, and its position is opposite to the objective lens. The diamond NV color center sample emits fluorescence under the action of the laser, and the filter and the third photodetector are sequentially arranged on the optical path of the fluorescence;

[0012] The second photodetector and the liquid crystal phase retarder are both communicatively connected to the closed-loop control unit. The closed-loop control unit is configured to calculate a control result using a PID control algorithm after receiving an electrical signal fed back by the second photodetector and performing A / D conversion, and then output a control voltage through A / D conversion to act on the liquid crystal phase retarder to adjust the phase delay of the liquid crystal phase retarder.

[0013] The acousto-optic modulator driver is connected to a pulse generator and an acousto-optic modulator respectively. The pulse generator is used to generate a rectangular wave of a set frequency and apply it to the acousto-optic modulator driver, so that the acousto-optic modulator driver is used to output the high and low levels of the rectangular wave to control the on and off of the acousto-optic modulator, so that the laser incident on the diamond NV color center sample is pulsed, and the pulse frequency is the frequency of the rectangular wave.

[0014] Furthermore, the optical axis of the first polarization beam splitter is perpendicular to the optical axis of the analyzer and forms an angle of 45° with the fast axis of the liquid crystal phase retarder. The transmission axis of the analyzer is perpendicular to the crystal axis of the acousto-optic modulator.

[0015] Furthermore, the excitation laser generated by the excitation laser is parallel light, which passes through the first convex lens to converge the laser at its focus and enter the acousto-optic modulator. The first-order diffraction light generated after the exit becomes parallel light after passing through the second convex lens. The crystal in the acousto-optic modulator is located at the focus of the first convex lens and the second convex lens.

[0016] Furthermore, the modulation frequency generated by the pulse generator should be greater than the control frequency of the liquid crystal phase retarder by the closed-loop control unit.

[0017] The present invention also provides a method for exciting a laser stabilization control device using the diamond nitrogen vacancy color center thermometer described above, the specific process of which is as follows:

[0018] The excitation laser generated by the excitation laser is converted into two beams of linear polarized light after passing through the first half-wave plate and the first polarization splitting prism. One beam of linear polarized light separated by the first polarization splitting prism is incident on the first photodetector for monitoring the fluctuation of the original laser. The other beam of linear polarized light separated by the first polarization splitting prism is divided into two beams of linear polarized light, first-order diffraction and zero-order diffraction, after passing through the liquid crystal phase retarder, the analyzer, the first convex lens, and the acousto-optic modulator. The zero-order diffraction light is blocked by the aperture, and the first-order diffraction light is divided into two beams of linear polarized light after passing through the second convex lens, the aperture, the second half-wave plate, and the second polarization splitting prism. One of the linearly polarized beams separated by the second polarization beam splitter prism is incident on the second photodetector and converted into an electrical signal. This signal is then fed into a closed-loop control unit as a feedback signal for the excitation laser power. The PID control algorithm then outputs a control voltage that acts on the liquid crystal phase retarder to adjust the phase delay of the liquid crystal phase retarder in real time, ensuring that the power of the other linearly polarized beam separated by the second polarization beam splitter prism remains stable. The other linearly polarized beam separated by the second polarization beam splitter prism is then reflected by a dichroic mirror, converged by the objective lens, and incident on the diamond sample stage, causing the diamond NV color center sample to emit stable fluorescence.

[0019] Fluorescence is emitted from the diamond NV color center sample, passes through the objective lens, dichroic mirror, and filter in sequence, and is incident on the third photodetector and converted into an electrical signal for measuring the ODMR spectrum line.

[0020] The beneficial effects of the present invention are as follows: the use of the present invention can significantly improve the long-term stability of the diamond NV color center thermometer and the anti-interference ability of the optical path, effectively suppress the laser power fluctuations caused by changes in ambient temperature, etc., and the heating effect fluctuations caused by laser power fluctuations, and achieve long-term stable fluorescence output and temperature, magnetic field and other measurements, thereby facilitating the application of diamond NV color center thermometers in power systems, chip manufacturing and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the diamond nitrogen vacancy color center thermometer excitation laser stabilization control device in Example 1 of the present invention.

[0022] Figure 1: Excitation laser 1, first half-wave plate 2, first polarization beam splitter prism 3, first photodetector 4, liquid crystal phase retarder 5, analyzer 6, first convex lens 7, acousto-optic modulator 8, second convex lens 9, aperture 10, second half-wave plate 11, second polarization beam splitter prism 12, second photodetector 13, dichroic mirror 14, objective lens 15, diamond sample stage 16, filter 17, third photodetector 18, closed-loop control unit 19, acousto-optic modulator driver 20 and pulse generator 21. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0024] Example 1

[0025] This embodiment provides a diamond nitrogen vacancy color center thermometer excitation laser stabilization control device, such as Figure 1 As shown, it includes an excitation laser 1, a laser stabilization closed-loop control module, an acousto-optic modulation module and a fluorescence collection module.

[0026] The excitation laser 1 is used to provide a laser light source. The wavelength of the laser can be 532 nm, and the coating of various optical devices in the subsequent optical path also needs to correspond to the wavelength of the laser.

[0027] The laser stabilization closed-loop control module includes a first half-wave plate 2, a first polarization beam splitter prism 3, a first photodetector 4, a liquid crystal phase retarder 5, an analyzer 6, a second half-wave plate 11, a second polarization beam splitter prism 12, a second photodetector 13 and a closed-loop control unit 19; the closed-loop control unit 19 is used to perform AD conversion, PID control and DA conversion.

[0028] The acousto-optic modulation module includes a first convex lens 7 , an acousto-optic modulator 8 , a second convex lens 9 , an aperture 10 , an acousto-optic modulator driver 20 and a pulse generator 21 .

[0029] The fluorescence collection module includes an objective lens 15, a dichroic mirror 14, a filter 17 and a third photodetector 18. It is used to collect fluorescence emitted by the diamond NV color center sample under laser polarization to obtain ODMR spectrum lines.

[0030] The first half-wave plate 2 and the first polarization splitter prism 3 are arranged in sequence along the optical path of the laser light emitted by the excitation laser 1. The first polarization splitter prism 3 is used to split the laser light into two beams of linear polarized light. The first photodetector 4 is located on the optical path of one of the beams of linear polarized light separated by the first polarization splitter prism 3. The liquid crystal phase retarder 5, the analyzer 6, the first convex lens 7, and the acousto-optic modulator 8 are arranged in sequence on the optical path of the other beam of linear polarized light separated by the first polarization splitter prism 3. The laser light is divided into first-order diffracted light and zero-order diffracted light by the acousto-optic modulator 8. The second convex lens 9, the aperture 10, the second half-wave plate 11 and the second polarization splitter prism 12 are arranged in sequence on the optical path of the first-order diffracted light. The second polarization beam splitter prism 12 is used to split the output light of the second half-wave plate 11 into two beams of linearly polarized light. The second photodetector 13 is located on the optical path of one of the linearly polarized light beams separated by the second polarization beam splitter prism 12. The dichroic mirror 14 is located on the optical path of the other linearly polarized light beam separated by the second polarization beam splitter prism 12. The dichroic mirror 14 is used to reflect the received light to the objective lens 15. The diamond sample stage 16 is used to place a block or nano-particle diamond NV color center sample. Its position is opposite to the objective lens 15. The diamond NV color center sample emits fluorescence under the action of the laser. The filter 17 and the third photodetector 18 are arranged in sequence on the optical path of the fluorescence.

[0031] The second photodetector 13 and the liquid crystal phase retarder 5 are both in communication with the closed-loop control unit 19. The closed-loop control unit 19 is configured to receive the electrical signal fed back by the second photodetector 13 and perform A / D conversion, calculate a control result using a PID control algorithm, and then output a control voltage through DA conversion to act on the liquid crystal phase retarder 5 to adjust the phase delay of the liquid crystal phase retarder 5.

[0032] The AOM driver 20 is connected to a pulse generator 21 and the AOM 8, respectively. The pulse generator 21 is used to generate a rectangular wave of a certain frequency and apply it to the AOM driver 20, so that the AOM driver 20 outputs the high and low levels of the rectangular wave to control the on and off of the AOM 8, so that the laser incident on the diamond NV color center sample is pulsed, and the pulse frequency is the frequency of the rectangular wave.

[0033] The stabilization control device of this embodiment integrates the laser stabilization closed-loop control module and the acousto-optic modulation module optical path to achieve light intensity stabilization control under laser pulse modulation.

[0034] In this embodiment, the optical axis of the first polarization beam splitter prism 3 is perpendicular to the optical axis of the analyzer 6 and forms an angle of 45° with the fast axis of the liquid crystal phase retarder 5. The transmission axis of the analyzer 6 is perpendicular to the crystal axis of the acousto-optic modulator 8.

[0035] In this embodiment, the excitation laser generated by the excitation laser 1 is parallel light, which is converged at its focus by the first convex lens 7 and enters the acousto-optic modulator 8. The first-order diffraction light generated after the exit becomes parallel light after passing through the second convex lens 9. The crystal in the acousto-optic modulator 8 is located at the focus of the first convex lens 7 and the second convex lens 9.

[0036] In this embodiment, the modulation frequency generated by the pulse generator 21 should be greater than the control frequency of the liquid crystal phase retarder 5 by the closed-loop control unit 19 .

[0037] Example 2

[0038] This embodiment provides a method for exciting a laser stabilization control device using the diamond nitrogen vacancy color center thermometer described in Example 1. The specific process is as follows:

[0039] The excitation laser generated by the excitation laser 1 is converted into two beams of linear polarized light after passing through the first half-wave plate 2 and the first polarization beam splitter prism 3. One beam of linear polarized light separated by the first polarization beam splitter prism 3 is incident on the first photodetector 4 for monitoring the fluctuation of the original laser. The other beam of linear polarized light separated by the first polarization beam splitter prism 3 is divided into two beams of linear polarized light of first-order diffraction and zero-order diffraction after passing through the liquid crystal phase retarder 5, the analyzer 6, the first convex lens 7, and the acousto-optic modulator 8. The zero-order diffraction light is blocked by the aperture 10. The first-order diffraction light is divided into two beams of linear polarized light after passing through the second convex lens 9, the aperture 10, the second half-wave plate 11, and the second polarization beam splitter prism 12. One of the beams of linear polarized light separated by the second polarization beam splitter prism 12 is incident on the second photodetector 13 and converted into an electrical signal. It enters the closed-loop control unit 19 as a feedback signal of the excitation laser power and is then transmitted through the P The ID control algorithm outputs a control voltage that acts on the liquid crystal phase retarder 5 to adjust its phase delay in real time, ensuring that the power of the other beam of linearly polarized light separated by the second polarization beam splitter prism 12 remains stable. The other beam of linearly polarized light separated by the second polarization beam splitter prism 12 is reflected by the dichroic mirror 14 and converged by the objective lens 15 before being incident on the diamond sample stage 16, causing the diamond NV color center sample to emit stable fluorescence.

[0040] Fluorescence is emitted from the diamond NV color center sample, passes through the objective lens 15, the dichroic mirror 14, and the filter 17 in sequence, and is incident on the third photodetector 18 to be converted into an electrical signal for measuring the ODMR spectrum line.

[0041] Those skilled in the art can make various corresponding changes and modifications based on the above technical solutions and concepts, and all of these changes and modifications should be included in the scope of protection of the claims of the present invention.

Claims

1. A diamond nitrogen vacancy color center thermometer excitation laser stabilization control device, characterized in that: It includes an excitation laser, a laser stabilization closed-loop control module, an acousto-optic modulation module, and a fluorescence collection module; The excitation laser is used to provide a laser light source; The laser stabilization closed-loop control module includes a first half-wave plate, a first polarization beam splitter prism, a first photodetector, a liquid crystal phase retarder, an analyzer, a second half-wave plate, a second polarization beam splitter prism, a second photodetector and a closed-loop control unit; The acousto-optic modulation module includes a first convex lens, an acousto-optic modulator, a second convex lens, an aperture, an acousto-optic modulator driver and a pulse generator; The fluorescence collection module includes an objective lens, a dichroic mirror, a filter and a third photodetector; The first half-wave plate and the first polarization beam splitter prism are arranged in sequence along the optical path of the laser light emitted by the excitation laser, the first polarization beam splitter prism is used to split the laser light into two beams of linear polarized light, the first photodetector is located on the optical path of one of the beams of linear polarized light separated by the first polarization beam splitter prism, and the liquid crystal phase retarder, the analyzer, the first convex lens, and the acousto-optic modulator are arranged in sequence on the optical path of the other beam of linear polarized light separated by the first polarization beam splitter prism; the laser light is divided into first-order diffracted light and zero-order diffracted light by the acousto-optic modulator, the second convex lens, the aperture, the second half-wave plate, and the second polarization beam splitter prism are arranged in sequence on the optical path of the first-order diffracted light; the second polarization beam splitter prism is used to split the output light of the second half-wave plate into two beams of linear polarized light, the second photodetector is located on the optical path of one of the beams of linear polarized light separated by the second polarization beam splitter prism, and the dichroic mirror is located on the optical path of the other beam of linear polarized light separated by the second polarization beam splitter prism; the dichroic mirror is used to reflect the received light to the objective lens; The diamond sample stage is used to place a block or nano-particle diamond NV color center sample, and its position is opposite to the objective lens. The diamond NV color center sample emits fluorescence under the action of laser, and the filter and the third photodetector are arranged in sequence on the optical path of the fluorescence; The second photodetector and the liquid crystal phase retarder are both communicatively connected to the closed-loop control unit. The closed-loop control unit is configured to calculate a control result using a PID control algorithm after receiving and performing A / D conversion on the electrical signal fed back by the second photodetector, and then output a control voltage through DA conversion to act on the liquid crystal phase retarder to adjust the phase delay of the liquid crystal phase retarder. The acousto-optic modulator driver is connected to a pulse generator and an acousto-optic modulator respectively. The pulse generator is used to generate a rectangular wave of a set frequency and apply it to the acousto-optic modulator driver, so that the acousto-optic modulator driver is used to output the high and low levels of the rectangular wave to control the on and off of the acousto-optic modulator, so that the laser incident on the diamond NV color center sample is pulsed, and the pulse frequency is the frequency of the rectangular wave.

2. The device according to claim 1, characterized in that The optical axis of the first polarization beam splitter is perpendicular to the optical axis of the analyzer and forms an angle of 45° with the fast axis of the liquid crystal phase retarder. The transmission axis of the analyzer is perpendicular to the crystal axis of the acousto-optic modulator.

3. The device according to claim 1, characterized in that The excitation laser generated by the excitation laser is parallel light. It passes through the first convex lens to converge the laser at its focus and enter the acousto-optic modulator. The first-order diffraction light generated after exiting becomes parallel light after passing through the second convex lens. The crystal in the acousto-optic modulator is located at the focus of the first and second convex lenses.

4. The device according to claim 1, characterized in that The modulation frequency generated by the pulse generator should be greater than the control frequency of the liquid crystal phase retarder by the closed-loop control unit.

5. A method for exciting a laser stabilization control device using the diamond nitrogen vacancy color center thermometer according to any one of claims 1 to 4, characterized in that: The specific process is as follows: The excitation laser generated by the excitation laser is converted into two beams of linear polarized light after passing through the first half-wave plate and the first polarization splitting prism. One beam of linear polarized light separated by the first polarization splitting prism is incident on the first photodetector for monitoring the fluctuation of the original laser; the other beam of linear polarized light separated by the first polarization splitting prism is divided into two beams of linear polarized light of first-order diffraction and zero-order diffraction after passing through the liquid crystal phase retarder, the analyzer, the first convex lens, and the acousto-optic modulator. The zero-order diffraction light is blocked by the aperture, and the first-order diffraction light is divided into two beams of linear polarized light after passing through the second convex lens, the aperture, the second half-wave plate, and the second polarization splitting prism. One of the linearly polarized beams separated by the two polarization beam splitters is incident on the second photodetector and converted into an electrical signal. This signal then enters the closed-loop control unit as a feedback signal for the excitation laser power. The PID control algorithm then outputs a control voltage that acts on the liquid crystal phase retarder to adjust the phase delay of the liquid crystal phase retarder in real time, ensuring that the power of the other linearly polarized beam separated by the second polarization beam splitter remains stable. The other linearly polarized beam separated by the second polarization beam splitter is reflected by the dichroic mirror and enters the objective lens. After convergence, it is incident on the diamond sample stage, causing the diamond NV color center sample to excite stable fluorescence. Fluorescence is emitted from the diamond NV color center sample, passes through the objective lens, dichroic mirror, and filter in sequence, and is incident on the third photodetector and converted into an electrical signal for measuring the ODMR spectrum line.

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