Fluorescence enhancement measurement system and method based on silicon carbide silicon vacancy color center dielectric cavity

Abstract

The invention discloses a fluorescence enhancement measurement system and method based on a silicon carbide silicon vacancy color center dielectric cavity, and the measurement system comprises a confocal system and a dielectric cavity sample, the confocal system comprises a laser, a reflector, a dichroscope, a filter, a scanning galvanometer, a microscope objective, a lens, an optical fiber connector, a single-mode optical fiber, a single-photon detector, a counting card and a computer. The confocal system is used for excitation of a dielectric cavity sample, efficient collection of fluorescence, micron-sized fluorescence space distribution imaging and reading and processing of a fluorescence signal; the dielectric cavity sample is used to generate and enhance fluorescence counts. The invention has the advantages of easiness in assembly and debugging, high sensitivity, wide application range, simplicity in processing, low cost and the like, can improve the fluorescence intensity of the silicon vacancy color center, and is used for high-sensitivity magnetic field measurement and improvement of the performance of a quantum sensing technology.

Description

Technical Field

[0001] The present invention belongs to the field of optics and micro-nano manufacturing technology, and in particular to a fluorescence enhancement measurement system and method based on a silicon carbide silicon vacancy color center dielectric cavity. Background Art

[0002] High-sensitivity and high-performance sensing detection technology plays an important role in various scientific and technological research. Solid-state color center defects have gradually become a means of life science detection and applied physical detection due to their excellent properties such as photostability, biocompatibility, and chemical inertness at room temperature. At the same time, unlike traditional quantum dots and organic fluorescent molecules, it does not have the disadvantages of photobleaching and light flickering, and is an ideal light source. However, the low fluorescence count rate limits the sensitivity of detection and the performance of sensing technology.

[0003] In recent years, spin defects in diamond and silicon carbide have been applied by scientists to achieve spatially resolved detection at the nanoscale. However, the fluorescence of NV color centers in diamond is in the visible light range, which will lead to light absorption in living cells and limit its transmission distance in optical fibers. In addition, the disadvantages of high cost and difficulty in manufacturing limit the widespread application of sensing detection based on diamond color centers. In contrast, the fluorescence band of silicon carbide (SiC) is in the near-infrared range and has mature micro-nano manufacturing and inch-level growth technology. This makes the color centers in silicon carbide attract much attention in quantum technology. Among them, silicon vacancy color centers in silicon carbide have been widely studied by scientists because of their many excellent properties, such as: near-infrared fluorescence band, long coherence time and temperature-independent zero-field splitting constant.

[0004] Silicon vacancies have a ground state spin quantum number of 3 / 2 and are formed by the absence of a silicon atom in the 4H and 6H-SiC lattices. Since the missing silicon atom may be located at a hexagonal h lattice point or a quasi-cubic k lattice point, there are two types of silicon vacancies, V2 and V1. V2-type silicon vacancies have attracted great research interest from scientists because they can be read out at room temperature. However, the maximum count that can be achieved for a single silicon vacancy is only about 10 kcps, which limits its potential application in the field of quantum information. Recently, scientists have designed a variety of schemes to improve fluorescence counts. For example, a solid immersion lens with a diameter of 20 microns made by milling can increase the count by about 3 times; an 800-nanometer-high nanocolumn with a diameter of 400 to 1400 nanometers can increase the count by about 3 times; and a nanoscale photonic crystal cavity can enhance the zero phonon line of a silicon vacancy, achieving an 80-fold Purcell enhancement. However, these approaches require complex micro-nanofabrication techniques, and achieving the coupling of silicon vacancies to the optimal mode positions of photonic structures remains a challenging task. Summary of the invention

[0005] To solve the above technical problems, the present invention provides a fluorescence enhancement measurement system and method based on a silicon carbide silicon vacancy color center dielectric cavity, wherein the confocal system is used for sample excitation and efficient fluorescence collection, as well as micron-level fluorescence spatial distribution imaging and fluorescence signal reading and processing; the dielectric cavity sample is used to generate and enhance fluorescence counts. The present invention can be used to enhance fluorescence counts and high-sensitivity sensor detection.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A fluorescence enhancement measurement system based on a silicon carbide silicon vacancy color center dielectric cavity includes a laser, a reflector, a short-pass filter, a dichroic mirror, a scanning galvanometer, a long-pass filter, a microscope objective, a lens, an optical fiber connector, a single-mode optical fiber, a single-photon detector, a counting card, a computer, and a dielectric cavity sample, wherein: The laser excites the silicon vacancy color center, generates a highly parallel incident laser and transmits it to the reflector; The reflector is located at the parallel end of the laser, and reflects the incident laser to the short-pass filter and then reaches the dichroic mirror. The short-pass filter is used to filter out the non-incident band stray light contained in the incident laser, and the dichroic mirror realizes the re-reflection of the incident laser. The re-reflected incident laser passes through a scanning galvanometer parallel to the dichroic mirror to achieve micrometer-level fluorescence spatial distribution imaging, and then is focused onto the dielectric cavity sample through a microscope objective to excite the sample fluorescence signal; The sample fluorescence signal passes through the dichroic mirror, filters out the non-sample fluorescence signal band through a long-pass filter, and then is coupled to the single-mode optical fiber through a lens and an optical fiber connector; The single-photon detector receives the sample fluorescence signal input by the single-mode optical fiber and converts it into an electrical signal; The counting card receives the electrical signal and converts it into a fluorescence counting signal; The computer receives the fluorescence counting signal from the counting card and reads the data; and the computer is also used to control the scanning range and scanning step of the scanning galvanometer; The dielectric cavity sample is used to generate a sample fluorescence signal and enhance the intensity of the sample fluorescence signal.

[0007] Furthermore, the central wavelength of the laser is 785 nm.

[0008] Furthermore, the short-pass filter is an 800nm ​​filter, and the long-pass filter is an 850nm filter.

[0009] Furthermore, an XY reflector is installed inside the scanning galvanometer, and the computer controls the scanning range and scanning step of the scanning galvanometer by controlling the angle and position of the XY reflector.

[0010] Furthermore, the single photon detector and the counting card, the counting card and the computer, and the computer and the scanning galvanometer are all connected via cables.

[0011] Furthermore, the dielectric cavity sample comprises a micron-sized 4H-SiC sample containing silicon vacancy color centers, a nano-sized SiO2 layer and a silver layer, wherein 10 1 10 2 A nanoscale SiO2 layer with a thickness of nm was plated on the 4H-SiC sample, and a silver layer with a thickness of 150 nm was plated on the nanoscale SiO2 layer.

[0012] On the other hand, the present invention also provides a fluorescence enhancement measurement method based on a silicon carbide silicon vacancy color center dielectric cavity, which is applied to the aforementioned measurement system, and the method comprises the following steps: Step S1: The laser emitted by the laser passes through a reflector and an 800nm ​​short-pass filter before entering a dichroic mirror. After being reflected again by the dichroic mirror, the direction and position of the laser are controlled by adjusting a scanning galvanometer mirror, and the laser is focused onto the surface of the dielectric cavity sample through a microscope objective lens to excite the sample fluorescence signal. Step S2: The excited sample fluorescence signal radiates and passes through the dichroic mirror, and enters the lens, fiber connector, and single-mode fiber in sequence through an 850nm long-pass filter. The single-mode fiber transmits the sample fluorescence signal to the single-photon detector to convert the sample fluorescence signal into an electrical signal, and then converts it into a fluorescence counting signal after passing through a counting card. The computer receives the fluorescence counting signal, records and analyzes the fluorescence counting data, and adjusts the scanning range and scanning step of the scanning galvanometer through a program; Step S3: Replace the dielectric cavity samples coated with nano-scale SiO2 layers of different thicknesses, implement fluorescence counting measurements of different dielectric cavity samples, compare the measured fluorescence counting data, and determine the optimal nano-scale SiO2 layer thickness.

[0013] Furthermore, the dielectric cavity sample is prepared according to the following steps: Step S1: Using ion implantation, a dose of 1 × 10 13 cm 2 30 keV carbon ions were implanted into high-purity 4H-SiC and annealed at 600 °C in vacuum for 2 hours to form silicon vacancy color centers in the sample. Step S2: using a magnetron sputtering system to prepare a nano-scale SiO2 film of a preset thickness on a 4H-SiC substrate through a plasma enhanced chemical vapor deposition process; Step S3: Depositing a silver layer with a thickness of 150 nm on the nano-scale SiO2 film by electron beam evaporation process.

[0014] The advantages of the present invention compared with the prior art are: The whole measurement system is simple and easy to debug, with high integration, small footprint, simple measurement method, and can conveniently and quickly optimize the fluorescence of different dielectric cavity samples. The preparation process and physical properties of the dielectric cavity based on nano-scale SiO2 / silver-SiC are simple to process, low cost, and have significant fluorescence enhancement effects compared to other micro-nano processing technologies (such as nano-pillars, bull's eye rings, solid immersion lenses, etc.), which can greatly improve the sensitivity of the sensing technology, with higher economy, flexibility, larger scale, and wider application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the fluorescence enhancement measurement system based on silicon carbide silicon vacancy color center dielectric cavity of the present invention; Figure 2 A schematic diagram of the dielectric cavity sample manufacturing process provided in an embodiment of the present invention.

[0016] Reference numerals: 1. Laser, 2. Reflector, 3. Incident laser, 4. Short-pass filter, 5. Dichroic mirror, 6. Scanning galvanometer, 7. X-mirror, 8. Y-mirror, 9. Microscope objective, 10. Sample fluorescence signal, 11. Long-pass filter, 12. Lens, 13. Fiber connector, 14. Single-mode fiber, 15. Single-photon detector, 16. Cable, 17. Counting card, 18. Computer, 19. Dielectric cavity sample, 20. High-purity 4H-SiC sample, 21. Sample with carbon implantation to produce color center, 22. SiC sample with deposited SiO2 layer, 23. Complete dielectric cavity sample with evaporated silver layer. DETAILED DESCRIPTION

[0017] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0018] like Figure 1 As shown, it is a schematic diagram of the fluorescence enhancement measurement system based on the silicon carbide silicon vacancy color center dielectric cavity of the present invention, including: a laser 1, a reflector 2, a short-pass filter 4, a dichroic mirror 5, a scanning galvanometer 6, a microscope objective 9, a long-pass filter 11, a lens 12, an optical fiber connector 13, a single-mode optical fiber 14, a single-photon detector 15, a counting card 17, a computer 18, and a dielectric cavity sample 19, wherein: The laser 1 is located on the experimental table and fixed by bolts. It is used to excite the silicon vacancy color center, thereby achieving the effect of polarization quantum state and exciting fluorescence; The reflector 2 is located at the parallel end of the laser, mounted on a metal base and fixed on the experimental table by bolts. It is used to adjust the propagation direction of the optical path, reduce the experimental device space, and improve the integration; The dichroic mirror 5 is located on a metal platform, which is fixed on the experimental table. It reflects the incident laser 3 and transmits the sample fluorescence signal 10; The filter is located between the two propagation light paths, mounted on a metal base and fixed on the experimental table by bolts. The short-pass filter 4 filters the incident laser signal to improve the excitation efficiency, and the long-pass filter 11 filters the transmitted sample fluorescence signal 10 to enhance the signal-to-noise ratio of the sample fluorescence signal 10; The scanning galvanometer 6 is located on the metal platform and parallel to the dichroic mirror 5. It is used to realize micron-level fluorescence spatial distribution imaging; The microscope objective lens 9 is located directly below the scanning galvanometer 6 and fixed by a lens holder and a metal rod. It is used to focus the incident laser 3 reflected by the dichroic mirror 5 on the surface of the dielectric cavity sample 19, and to collect the sample fluorescence signal 10 radiated by the dielectric cavity sample 19; The lens 12 is located between the optical fiber connector 13 and the long-pass filter 11 and is used to focus the sample fluorescence signal 10 on the inner core of the single-mode optical fiber 14; The optical fiber connector 13 is located at the parallel end of the transmitted fluorescence, mounted on a matching metal base and fixed on the experimental table by bolts, and is used for coupling the single-mode optical fiber 14 and the lens 12; The single-mode optical fiber 14 is used to efficiently transmit the sample fluorescence signal 10; The single photon detector 15 is used to convert the input sample fluorescence signal 10 into an electrical signal; The counting card 17 receives the electrical signal and converts it into a fluorescence counting signal; The computer 18 is used to receive the fluorescence counting signal processed by the counting card 17, read the data, and control the scanning of the scanning galvanometer 6; The dielectric cavity sample 19 is used to generate a sample fluorescence signal 10 and enhance the intensity of the sample fluorescence, provide a fluorescence signal collected by the entire measurement system, and increase the fluorescence count of silicon vacancies.

[0019] Furthermore, the central wavelength of the laser 1 is 785 nm.

[0020] Furthermore, the short-pass filter 4 is an 800nm ​​filter, and the long-pass filter 11 is an 850nm filter.

[0021] Furthermore, the scanning galvanometer 6 is internally provided with an XY direction reflector ( Figure 1The X-mirror 7 and the Y-mirror 8 are shown in the figure. The angles and positions of the XY-mirrors are precisely controlled by a computer program, thereby controlling the scanning range and scanning step of the galvanometer 6.

[0022] Furthermore, the single photon detector 15 and the counting card 17 , the counting card 17 and the computer 18 , and the computer 18 and the scanning galvanometer 6 are all connected via cables 16 .

[0023] Furthermore, the dielectric cavity sample comprises a micron-scale 4H-SiC sample containing silicon vacancy color centers, a nano-scale SiO2 layer and a silver layer, wherein the 4H-SiC sample is plated with 10 1 10 2 A SiO2 layer with a thickness of 100 nm and a silver layer with a thickness of 150 nm are plated on the SiO2 layer. The nanoscale SiO2 layer can be selected to be 20, 60, 100, 140, 180, and 220 nm, respectively, to prepare dielectric cavity samples including SiO2 layers with different thicknesses.

[0024] When the measurement system is working, a laser 1 with a central wavelength of 785nm is fixed on the experimental table by bolts to generate a highly parallel incident laser 3; a reflector 2 is mounted on a metal base and fixed on the experimental table by bolts, and the angle is adjusted to reflect the incident laser 3; an 800 nm short-pass filter 4 is mounted on a metal base and fixed on the experimental table by bolts to filter out stray light in non-incident bands; after being reflected by a dichroic mirror 5 fixed on a matching metal experimental platform, it reaches a scanning galvanometer 6, wherein an X-mirror 7 and a Y-mirror 8 are arranged inside the scanning galvanometer 6, which can be used to adjust the scanning position and angle; and then the light is focused on a dielectric cavity sample 19 through a microscope objective 9 to excite the sample fluorescence signal 10, wherein the microscope objective 9 is fixed by a lens holder and a metal rod, and has a numerical aperture of 0.65 Infrared objective lens; 850 nm long pass filter 11 is built in the direction of the dichroic mirror 5 through the sample fluorescence signal 10 to filter out the band of non-sample fluorescence signal. Lens 12 converges sample fluorescence signal 10 on the inner core of single-mode optical fiber 14; optical fiber connector 13 is installed on the matching metal base, fixed on the experimental table by bolts, coupling lens 12 and single-mode optical fiber 14; sample fluorescence signal 10 is collected by single-mode optical fiber 14 and enters single-photon detector 15, converting optical signal into electrical signal, and then converted into fluorescence counting signal through counting card 17. Single-photon detector 15, counting card 17 and computer 18 are connected by cable 16; computer 18 reads and processes the transmitted fluorescence counting signal to realize the measurement of fluorescence counting. At the same time, computer 18 adjusts the angle and position of X-mirror 7 and Y-mirror 8 inside scanning galvanometer 6 through program, controls the scanning range and scanning step, realizes micron-level fluorescence spatial distribution imaging so that the whole system reaches the best measurement state. By replacing dielectric cavity samples 19 of different thicknesses, the measurement of different fluorescence enhancement effects is realized. The dielectric cavity sample 19 is located directly below the microscope objective and is fixed on a metal base.

[0025] Figure 2 A schematic diagram of a dielectric cavity sample manufacturing process is provided for one embodiment of the present invention. In the present invention, a high-purity 4H-SiC epitaxial layer sample 20 (off-axis 4°, epitaxial layer thickness of about 7 μm, total sample thickness of about 350 μm, nitrogen doped with a concentration of 5.2×10 15 cm -3 First, ion implantation with a dose of 1 × 10 13 cm 2 30 keV carbon ions were implanted into high purity 4H-SiC sample 20 and annealed at 600 °C vacuum for 2 hours to form sample 21 with carbon implantation to generate color centers. Then SiO2 films of different thicknesses were prepared on SiC substrates by plasma enhanced chemical vapor deposition using a magnetron sputtering system to form SiC sample 22 with deposited SiO2 layer. Finally, the complete dielectric cavity sample 23 with evaporated silver layer was prepared by depositing a 150 nm thick silver layer on the SiO2 film by electron beam evaporation.

[0026] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A fluorescence enhancement measurement system based on silicon carbide silicon vacancy color center dielectric cavity, characterized in that: Including laser, reflector, short pass filter, dichroic mirror, scanning galvanometer, long pass filter, microscope objective, lens, fiber connector, single mode fiber, single photon detector, counting card, computer, dielectric cavity sample, among which: The laser excites the silicon vacancy color center, generates a highly parallel incident laser and transmits it to the reflector; The reflector is located at the parallel end of the laser, and reflects the incident laser to the short-pass filter and then reaches the dichroic mirror. The short-pass filter is used to filter out the non-incident band stray light contained in the incident laser, and the dichroic mirror realizes the re-reflection of the incident laser. The re-reflected incident laser passes through a scanning galvanometer parallel to the dichroic mirror to achieve micrometer-level fluorescence spatial distribution imaging, and then is focused onto the dielectric cavity sample through a microscope objective to excite the sample fluorescence signal; The sample fluorescence signal passes through the dichroic mirror, filters out the non-sample fluorescence signal band through a long-pass filter, and then is coupled to the single-mode optical fiber through a lens and an optical fiber connector; The single-photon detector receives the sample fluorescence signal input by the single-mode optical fiber and converts it into an electrical signal; The counting card receives the electrical signal and converts it into a fluorescence counting signal; The computer receives the fluorescence counting signal from the counting card and reads the data; and the computer is also used to control the scanning range and scanning step of the scanning galvanometer; The dielectric cavity sample is used to generate a sample fluorescence signal and enhance the intensity of the sample fluorescence signal.

2. The fluorescence enhancement measurement system based on silicon carbide silicon vacancy color center dielectric cavity according to claim 1, characterized in that: The central wavelength of the laser is 785 nm.

3. The fluorescence enhancement measurement system based on silicon carbide silicon vacancy color center dielectric cavity according to claim 1 is characterized in that: The short-pass filter is an 800nm ​​filter, and the long-pass filter is an 850nm filter.

4. The fluorescence enhancement measurement system based on silicon carbide silicon vacancy color center dielectric cavity according to claim 1, characterized in that: The scanning galvanometer is internally provided with an XY reflector, and the computer controls the scanning range and scanning step of the scanning galvanometer by controlling the angle and position of the XY reflector.

5. The fluorescence enhancement measurement system based on silicon carbide silicon vacancy color center dielectric cavity according to claim 1, characterized in that: The single photon detector and the counting card, the counting card and the computer, and the computer and the scanning galvanometer are all connected through cables.

6. The fluorescence enhancement measurement system based on silicon carbide silicon vacancy color center dielectric cavity according to claim 1, characterized in that: The dielectric cavity sample comprises a micron-sized 4H-SiC sample containing silicon vacancy color centers, a nano-sized SiO2 layer and a silver (Ag) layer, wherein 10 1 10 2 A nanoscale SiO2 layer with a thickness of nm was plated on the 4H-SiC sample, and a silver layer with a thickness of 150 nm was plated on the nanoscale SiO2 layer.

7. A fluorescence enhancement measurement method based on a silicon carbide silicon vacancy color center dielectric cavity, applied to a fluorescence enhancement measurement system based on a silicon carbide silicon vacancy color center dielectric cavity as described in any one of claims 1 to 6, characterized in that: The steps include: Step S1: The laser emitted by the laser passes through a reflector and an 800nm ​​short-pass filter before entering a dichroic mirror. After being reflected again by the dichroic mirror, the direction and position of the laser are controlled by adjusting a scanning galvanometer mirror, and the laser is focused onto the surface of the dielectric cavity sample through a microscope objective lens to excite the sample fluorescence signal. Step S2: The excited sample fluorescence signal radiates and passes through the dichroic mirror, and enters the lens, fiber connector, and single-mode fiber in sequence through an 850nm long-pass filter. The single-mode fiber transmits the sample fluorescence signal to the single-photon detector to convert the sample fluorescence signal into an electrical signal, and then converts it into a fluorescence counting signal after passing through a counting card. The computer receives the fluorescence counting signal, records and analyzes the fluorescence counting data, and adjusts the scanning range and scanning step of the scanning galvanometer through a program; Step S3: Replace the dielectric cavity samples coated with nano-scale SiO2 layers of different thicknesses, implement fluorescence counting measurements of different dielectric cavity samples, compare the measured fluorescence counting data, and determine the optimal nano-scale SiO2 layer thickness.

8. The fluorescence enhancement measurement method based on silicon carbide silicon vacancy color center dielectric cavity according to claim 7, characterized in that: The dielectric cavity sample is prepared according to the following steps: Step S1: Using ion implantation, a dose of 1 × 10 13 cm 2 30 keV carbon ions were implanted into high-purity 4H-SiC and annealed at 600 °C in vacuum for 2 hours to form silicon vacancy color centers in the sample. Step S2: using a magnetron sputtering system to prepare a nano-scale SiO2 film of a preset thickness on a 4H-SiC substrate through a plasma enhanced chemical vapor deposition process; Step S3: Depositing a silver layer with a thickness of 150 nm on the nano-scale SiO2 film by electron beam evaporation process.

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