Silicon carbide color center laser processing and multi-mode real-time in-situ detection optical device

Abstract

The invention discloses a silicon carbide color center laser processing and multi-mode real-time in-situ detection optical device, and belongs to the field of quantum optics and quantum precision measurement. The system comprises a laser processing system, a confocal laser transmission and spectrum detection module, a single photon source detection module, a fluorescence imaging module and a data acquisition processing and control system. Monopulse laser emitted by a laser processing system is used for processing a preprocessed silicon carbide wafer, after silicon carbide is irradiated by femtosecond laser, a light source is switched to excite a defect position, and whether a color center is generated or not and whether the prepared color center is a single photon source or not are detected through a confocal laser transmission and spectrum detection module and a single photon source detection module; and the fluorescence imaging module monitors the forming process of the color center in real time and transmits an acquisition result to the upper computer for processing and analysis. The forming condition of the color center can be monitored in real time and in situ, the yield of the color center and the machining efficiency are improved, and meanwhile it is guaranteed that the finally machined color center is more likely to become a high-quality single photon source.

Description

Technical Field

[0001] The present invention relates to the fields of quantum optics and quantum precision measurement, and particularly to an optical device for laser processing and multimodal real-time in-situ detection of silicon carbide color centers, which is applicable to the processing and detection of silicon carbide color centers. Background Art

[0002] In today's era, with the accelerating process of social informatization, a vast amount of data has swept through human society like a tide, and the emerging discipline of quantum information science based on the quantum system has flourished. Fields such as quantum communication, quantum sensing, and quantum computing have become new battlefields for fierce international competition.

[0003] Constructing a quantum system with excellent performance, stability, and reliability is the foundation for the long-term development of quantum technology. Currently, there are many physical systems that can act as quantum information carriers, including superconducting systems, ion trap systems, and solid-state color center systems. Among these systems, the solid-state color center system combines the excellent optical and spin characteristics of the color center itself with the significant advantages of easy integration and strong scalability of the solid-state carrier, thus becoming one of the quantum platforms with great application potential at present.

[0004] Silicon carbide (SiC), as the third-generation wide-bandgap semiconductor, is widely used in industries such as microelectronics, aerospace, and high-power devices. The silicon carbide material has high-quality wafer manufacturing and epitaxial growth, as well as mature micro-nano processing technology. Its color center emission range is extremely wide, extending from the visible light region to the infrared band. It has a rich variety of color centers. Currently, more research has been conducted on silicon vacancy and divacancy color centers, which can achieve the polarization and readout of spin states using lasers at room temperature and perform spin manipulation using microwaves. These properties make it show unparalleled application prospects in many key fields such as quantum information technology, high-precision detection, and biological detection, and are expected to bring breakthrough changes and leaps to these fields.

[0005] Currently, the integration degree of the SiC color center processing and detection system is not high. In the past, the processing system and the detection system were independent, lacking means for processing and real-time in-situ detection, resulting in low efficiency. Moreover, due to the incompleteness of the system, the samples need to be continuously moved, which is likely to cause sample contamination. And once it is found that a batch of samples does not meet the requirements after processing and then detecting, this batch of materials will be wasted. The inability to provide real-time feedback will, to a certain extent, lead to a long and costly process of optimizing the processing technology. And due to the lack of real-time monitoring means, the understanding of the physical change process during the color center processing is limited. The low integration degree of the processing and detection system will cause problems such as low color center yield and processing efficiency. Summary of the Invention

[0006] To address the problems of uncontrollable processing quality, low color center yield, low processing and process optimization efficiency, and insufficient understanding of the microscopic formation mechanism of color centers caused by the ineffective correlation of existing color center processing and detection devices, the objective of the present invention is to provide an optical device for laser processing and multimodal real-time in-situ detection of silicon carbide color centers. Femtosecond laser is used to prepare color centers through the processing optical path, and the laser is connected to a computer for control operation, parameter setting, and dynamic adjustment. The EMCCD is synchronously triggered with the laser to continuously collect and observe the formation process of color centers in real time. The integration of the processing and detection system enables immediate detection of whether color centers are generated after processing and verification of whether they are single-photon sources. Based on the feedback results, the processing parameters are adjusted in real time to improve the yield and processing efficiency of color centers and avoid potential contamination of samples. Through fluorescence imaging combined with the fluorescence imaging system in the upper computer, image processing of the captured fluorescence signals can be performed to improve the color center resolution.

[0007] To achieve the above objective, the present invention is realized through the following technical solutions:

[0008] The optical device for laser processing and multimodal real-time in-situ detection of silicon carbide color centers disclosed in the present invention includes a laser processing system, a confocal laser transmission and spectral detection module, a single-photon source detection module, a fluorescence imaging module, and a data acquisition, processing, and control system. The single-pulse laser emitted by the laser processing system processes the pre-treated SiC wafer. Defects are generated in the SiC after femtosecond laser irradiation. The light source is switched to excite the defect position, and the material absorbs photon energy to produce electron transitions. The emitted fluorescence is detected by the confocal laser transmission and spectral detection module and the single-photon source detection module to determine whether color centers are generated and whether the prepared color centers are single-photon sources. The fluorescence imaging module monitors the formation process of color centers in real time and transmits the acquisition results to the upper computer for processing and analysis.

[0009] The laser processing system is used to process samples to generate defects. A 1030nm pulsed laser is generated by a femtosecond laser. The polarization state is adjusted by a half-wave plate, the beam is expanded by a beam expander, the laser energy is controlled by a diaphragm, and the scanning galvanometer and the electric displacement stage cooperate to achieve precise positioning for processing. The CCD monitors the surface morphology of the processing in real time.

[0010] The confocal laser transmission and spectral detection module is used to excite defects and perform fluorescence collection and spectral detection. A 780nm laser is generated by a pulsed laser. The short-pass dichroic mirror transmits the laser and reflects the fluorescence. The filter group filters out the light outside the fluorescence wavelength, and the fluorescence is transmitted to the spectrometer through a coupler and an optical fiber for fluorescence spectral characterization to determine whether color centers are generated.

[0011] The single-photon source detection module is used to detect whether the written color center is a single-photon source. The coupling lens couples the photon sequence into a 50:50 single-mode beam-splitting optical fiber, and the optical fiber is connected to two photon detectors for detection. The electrical pulses generated by the detectors are transmitted to the time-correlated single-photon counting card TCSPC. TCSPC respectively records the arrival time of each electrical pulse signal in the two paths. Finally, the autocorrelation information of the photon sequence is obtained by analyzing the measured time data. When the calculated second-order correlation function value is less than 0.5, it is considered a single-photon source.

[0012] The fluorescence imaging module is used to image the color center. The EMCCD is triggered synchronously with the pulsed laser to collect an image sequence of a single color center generated under each pulse excitation, and the formation process of the color center is monitored in real time.

[0013] The data acquisition, processing and control system is used to control the laser parameter setting and analyze and process the acquired signals. The upper computer controls the operation of each module, and is used to realize the laser parameter setting, acquisition of the spectral and photon sequence signals analysis, real-time monitoring of the fluorescence imaging process and acquisition of image processing.

[0014] Furthermore, during the processing of the laser processing system, according to the preset program or the real-time processing information of the sample fed back by the CCD, the power, repetition rate, focusing position and scanning speed of the femtosecond pulsed laser are dynamically adjusted to ensure the accuracy and stability of the color center induction.

[0015] Furthermore, in the confocal laser transmission and spectral detection module, the laser generated by the laser is transmitted through the dichroic mirror to the sample to excite fluorescence. The fluorescence is reflected by the dichroic mirror and then the light outside the fluorescence band is filtered by the filter, and then enters the spectrometer for detection through the coupling mirror. The confocal optical path ensures that the excitation light and the detection light are confocal, improving the accuracy and resolution of the spectral detection.

[0016] Furthermore, when the single-photon source detection module is detecting, the single-mode beam-splitting optical fiber precisely splits the light to two high-sensitivity photon detectors. The photon detectors convert the photon signals into electrical signals and transmit them to the TCSPC. By transmitting the photon sequence to the upper computer for calculating the photon second-order correlation function, it is judged whether the color center has the characteristics of a single-photon source.

[0017] Furthermore, during the imaging process of the fluorescence imaging module, the EMCCD is triggered synchronously with the pulsed laser to continuously collect the fluorescence images under each pulse. Under the control of the imaging parameter adjustment unit, parameters such as the exposure time and gain are adjusted according to the sample characteristics and imaging requirements. The fluorescence imaging optical path components ensure the stability of the imaging optical path, and clear and high-resolution images of the silicon carbide color center are obtained. The image data is transmitted to the data acquisition, processing and control module for storage, data processing and analysis.

[0018] Furthermore, the data acquisition, processing, and control system is used to control the laser parameter setting and analyze and process the acquired signals. The upper computer controls the operation of each module, including laser parameter setting, signal analysis such as acquisition of spectra and photon sequences, real-time monitoring of the fluorescence imaging process, and acquisition and image processing of images.

[0019] Beneficial effects:

[0020] 1. For the optical device for laser processing of silicon carbide color centers and multi-modal real-time in-situ detection disclosed in the present invention, since the detection optical path and the processing optical path are integrated, the processing parameters can be adjusted in real time according to the detection results, and the need to refocus to find the processing point during detection is avoided, improving the efficiency of color center processing and detection, preventing possible contamination of the sample by the test system after previous processing, and increasing the color center yield.

[0021] 2. For the optical device for laser processing of silicon carbide color centers and multi-modal real-time in-situ detection disclosed in the present invention, since the HBT interference method (the interference test scheme proposed by Hanbury Brown and Twiss) is integrated into the processing system, it is possible to determine whether the generated color centers are single-photon sources, which is more conducive to processing high-quality single-photon sources for integration with quantum devices.

[0022] 3. For the optical device for laser processing of silicon carbide color centers and multi-modal real-time in-situ detection disclosed in the present invention, due to the integrated fluorescence imaging module, the EMCCD is synchronously triggered to collect fluorescence images under each excitation pulse in real time, enabling the observation of the formation process of color centers, and the shape, size, and distribution of color centers can be visually presented, thereby enabling an in-depth understanding of the factors affecting the growth of color centers, such as the influence of laser processing parameters and material properties on the development of the microstructure of color centers.

[0023] 4. For the optical device for laser processing of silicon carbide color centers and multi-modal real-time in-situ detection disclosed in the present invention, the pulsed laser is used to synchronously collect fluorescence images under each pulse excitation. Due to the anti-bunching property of photons, the high-order resolution enhancement effect is achieved by using the correlation between the pixels of the collected fluorescence images. Combining with the fluorescence imaging system in the upper computer, the image processing of the captured fluorescence signals can improve the fluorescence imaging resolution. Description of the drawings

[0024] Figure 1 is a schematic diagram of the principle of the optical device for laser processing of silicon carbide color centers and multi-modal real-time in-situ detection of the present invention;

[0025] Figure 2 is the optical path diagram of the optical device for laser processing of silicon carbide color centers and multi-modal real-time in-situ detection of the present invention;

[0026] Wherein: 1 - femtosecond laser, 2 - half-wave plate, 3 - beam expander, 4 - aperture, 5 - beam splitter, 6 - CCD, 7 - flip mirror, 8 - mirror, 9 - scanning galvanometer, 10 - motorized displacement stage, 11 - pulsed laser, 12 - dichroic mirror, 13 - filter set, 14 - EMCCD, 15 - coupling mirror, 16 - single-mode fiber beam splitter, 17 - photon detector, 18 - TCSPC, 19 - spectrometer, 20 - host computer. Specific implementation mode

[0027] The main objective of the present invention is to solve the problems of low efficiency and low productivity caused by the separation of the processing system and the testing system, as well as the possible contamination caused by moving samples between systems. Additionally, it conducts detection on whether it can be integrated with quantum devices and observes the formation process of color centers and the improvement of resolution in fluorescence images. To make the objectives, technical solutions, and advantages of the present invention clearer, the following provides a further detailed description of the present invention in combination with specific embodiments and with reference to the accompanying drawings.

[0028] In the embodiment, as Figure 2 shown, the optical device for laser processing and multimodal real-time in-situ detection of silicon carbide color centers disclosed in this embodiment is used to achieve the processing and multimodal detection of SiC color centers and is applied to many key fields such as quantum information technology, high-precision detection, and biological detection. The optical device for laser processing and multimodal real-time in-situ detection of silicon carbide color centers disclosed in this embodiment includes a femtosecond laser 1, a half-wave plate 2, a beam expander 3, an aperture 4, a beam splitter 5, a CCD 6, a flip mirror 7, a mirror 8, a scanning galvanometer 9, a motorized displacement stage 10, a continuous laser 11, a dichroic mirror 12, a filter set 13, an EMCCD 14, a coupling mirror 15, a single-mode fiber beam splitter 16, a photon detector 17, a TCSPC 18, a spectrometer 19, and a host computer 20. The optical device for laser processing and multimodal real-time in-situ detection of silicon carbide color centers operates as follows

[0029] In this implementation case, the processing flow is as follows: Place the SiC sample in the designated processing area of the motorized displacement stage 10 and adjust the Z-axis height of the sample stage so that the femtosecond laser can be focused on the surface of the SiC sample. The host computer 20 is connected to the femtosecond laser 1 to control it to generate a femtosecond laser at 1030 nm, with an average laser power of 1 mW - 5 W, a repetition rate of 1 MHz, and a maximum single-pulse energy of 10 μJ, generating a suitable femtosecond laser for precise processing of color centers.

[0030] In this implementation case, the laser emitted by the femtosecond laser 1 passes through the half-wave plate 2, the beam expander 3, and the aperture 4 to complete the beam expansion and energy adjustment operations, improving the laser quality so that it can be used for processing.

[0031] In this embodiment, the laser used for processing is split into two parts by a beam splitter 5. One part enters the CCD 6 for imaging, and the other part enters the subsequent optical path. The CCD 6 is connected to the host computer 20 and transmits the imaging data back to the host computer 20. The host computer 20 processes the imaging data to determine whether the processed laser beam can be used for the processing of color centers and the sample characterization during the processing, and adjusts the parameters of the femtosecond laser 1.

[0032] In this embodiment, if the processed laser can be used for the processing of color centers, it directly passes through the subsequent optical path. By means of the flip mirror 7 and the mirror 8, the optical path direction is changed so that it enters the scanning galvanometer 9. The scanning galvanometer 9 is connected to the host computer 20. Under the control of the host computer 20, the scanning galvanometer 9 can quickly change the direction of the laser beam, realize the rapid movement of the laser spot in the two-dimensional plane, and accurately position the laser at each point on the workpiece that needs to be processed, thereby completing the processing process.

[0033] In this embodiment, after the processing process is completed, the multi-modal detection of the color centers can be completed without replacing the system, avoiding possible contamination of the sample by the test system after processing. The multi-modal detection process is as follows: The pulsed laser 11 is connected to the host computer 20, and the host computer 20 controls the parameters of the pulsed laser 11 to make it output appropriate pulsed laser.

[0034] In this embodiment, the pulsed laser 11 outputs pulsed laser of 780 nm. Through the dichroic mirror 12, transmission occurs when the laser passes through the dichroic mirror 12. At the same time, the flip mirror 7 only participates in the processing during the processing. During the multi-modal detection process, the flip mirror 7 is electrically controlled to not participate in the detection optical path.

[0035] In this embodiment, the laser passing through the previous optical path passes through the mirror 8, causing the light to be reflected into the scanning galvanometer 9. The scanning galvanometer 9 can accurately control the beam scanning to realize the excitation of fluorescence in the target area. The fluorescence is reflected back through the scanning galvanometer 9, the mirror 8, and reaches the dichroic mirror 12. When the fluorescence passes through the dichroic mirror, reflection occurs. After passing through the mirror group, it reaches the filter 13. The function of the filter 13 is to remove the laser component in the fluorescence for better subsequent detection.

[0036] In this embodiment, the beam passing through the filter 13 officially enters the multi-modal detection module. The multi-modal detection module is also connected to the host computer 20, and the data of the multi-modal detection can be transmitted to the host computer 20 in real time.

[0037] In this embodiment, the fluorescence entering the multimodal detection module first passes through the beam splitter 5. A part of it enters the EMCCD 14, which is connected to the host computer 20 and can transmit data to the computer in real time. Therefore, the generation of color centers can be observed in real time, which has advantages not possessed by other systems.

[0038] In this embodiment, the other part of the light enters the next beam splitter and is split into two again. One part of the light passes through the coupling mirror 15 and is efficiently coupled into the spectrometer 19 for detecting the fluorescence spectrum. At the same time, the spectrometer 19 is connected to the host computer 20 to transmit data to the host computer 20 in real time.

[0039] In this embodiment, the second part of the light split by the second beam splitter enters the coupling mirror 15. The coupling mirror 15 efficiently couples the light into the single-mode split fiber 16, and the light is split into two again. The single-mode split fiber 16 is respectively connected to the photon detectors 17. The detectors detect the electrical pulses generated by the fluorescence signal and send them to the time-correlated single-photon counting card (TCSPC). The TCSPC will record the arrival time of each electrical pulse signal in these two paths respectively. Finally, the autocorrelation information of the photon sequence can be obtained by analyzing the measured time data. When the value of the calculated second-order correlation function is less than 0.5, the color center is a single-photon source.

[0040] For the disclosed embodiments, under the ideal conditions of each component and when the optical path imaging is good, the present invention can achieve continuous processing and detection, all of which are precisely controlled by the computer.

[0041] For the disclosed embodiments, the present invention adjusts the processing parameters in real time to improve the efficiency of color center processing, and can immediately detect whether the color center is generated after processing and achieve fluorescence imaging.

[0042] For the disclosed embodiments, the present invention can detect the formation process of color centers in real time through the EMCCD.

[0043] For the disclosed embodiments, the present invention can perform fluorescence spectrum characterization in real time and detect the single-photon source in real time and feedback to adjust the processing parameters.

[0044] The above specific description further details the purpose, technical solution and beneficial effects of the invention. It should be understood that the above is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Optical device for laser processing of silicon carbide color centers and multi-modal real-time in-situ detection, characterized in that: It includes a laser processing system, a confocal laser transmission and spectrum detection module, a single-photon source detection module, a fluorescence imaging module, and a data acquisition, processing, and control system. The single-pulse laser emitted by the laser processing system processes the pre-treated SiC wafer, and the SiC is irradiated with a femtosecond laser to produce defects. The light source is switched to excite the defect position, and the material absorbs the photon energy to produce an electron transition. The emitted fluorescence is detected by the confocal laser transmission and spectrum detection module and the single-photon source detection module to determine whether a color center is generated and whether the prepared color center is a single-photon source. The fluorescence imaging module monitors the formation process of the color center in real time, and transmits the collected results to the host computer for processing and analysis. Laser processing system, used to process samples to produce defects, generates 1030nm pulsed laser through femtosecond laser, adjusts polarization state through half-wave plate, expands beam through beam expander, controls laser energy through aperture, coordinates scanning galvanometer and electric translation stage to achieve precise positioning processing, and CCD monitors processing surface morphology in real time; The confocal laser transmission and spectrum detection module is used to excite defects and perform fluorescence collection spectrum detection. The 780nm laser is generated by a pulsed laser, the short-pass dichroic mirror transmits the laser and reflects the fluorescence, the filter group filters out the light outside the fluorescence wavelength, and transmits it to the spectrometer through the coupler and optical fiber for fluorescence spectrum characterization, so as to determine whether a color center is generated; The single-photon source detection module is used to detect whether the written color center is a single-photon source. The coupling lens couples the photon sequence into a 50:50 single-mode beam splitting optical fiber, and the optical fiber is connected to two photon detectors for detection. The electric pulses generated by the detectors are transmitted to the time-correlated single-photon counting card (TCSPC). The TCSPC records the arrival time of each electric pulse signal in the two paths respectively. Finally, the self-correlation information of the photon sequence is obtained by analyzing the measured time data. When the second-order correlation function is calculated and the value is less than 0.5, it is considered to be a single-photon source; Fluorescence imaging module, used to image the color center. The EMCCD is triggered synchronously with the pulse laser to collect the image sequence of a single color center generated under each pulse excitation, and monitor the formation process of the color center in real time. The data acquisition, processing and control system is used to control the laser parameter settings and analyze and process the collected signals. The host computer controls the operation of each module and is used to realize laser parameter settings, collect spectrum and photon sequence signal analysis, real-time monitoring of the fluorescence imaging process and collected image processing.

2. The optical device for laser processing and multi-modal real-time in-situ detection of silicon carbide color centers according to claim 1, characterized in that: During the processing, the laser processing module dynamically adjusts the power, repetition rate, focus position and scanning speed of the femtosecond pulse laser according to a preset program or according to the real-time processing information of the sample fed back by the CCD to ensure the accuracy and stability of color center induction.

3. The optical device for laser processing and multi-modal real-time in-situ detection of silicon carbide color centers according to claim 1, characterized in that: In the confocal laser transmission and spectrum detection module, the laser generated by the laser is transmitted to the sample through a dichroic mirror to excite fluorescence. The fluorescence is reflected by the dichroic mirror and then filtered out of the fluorescence band through a filter. The fluorescence then enters the spectrometer for detection through a coupling mirror. The confocal optical path ensures that the excitation light and the detection light are co-focused, thereby improving the accuracy and resolution of spectral detection.

4. The optical device for laser processing and multi-modal real-time in-situ detection of silicon carbide color centers according to claim 1, characterized in that: When the single-photon source detection module is detecting, the single-mode beam-splitting optical fiber accurately splits the light into two high-sensitivity photon detectors. The photon detectors convert the photon signals into electrical signals and transmit them to the TCSPC. The photon sequence is transmitted to the host computer to calculate the second-order correlation function of the photons to determine whether the color center has the characteristics of a single-photon source.

5. The optical device for laser processing and multi-modal real-time in-situ detection of silicon carbide color centers according to claim 1, characterized in that: During the imaging process of the fluorescence imaging module, the EMCCD is synchronously triggered with the pulse laser to continuously collect the fluorescence image under each pulse. Under the control of the imaging parameter adjustment unit, the exposure time, gain and other parameters are adjusted according to the sample characteristics and imaging requirements. The fluorescence imaging optical path component ensures the stability of the imaging optical path, obtains a clear and high-resolution image of the silicon carbide color center, and the image data is transmitted to the data acquisition processing and control module for storage, data processing and analysis.

6. The optical device for laser processing and multi-modal real-time in-situ detection of silicon carbide color centers according to claim 1, characterized in that: The data acquisition processing and control system is used to control the laser parameter settings and analyze and process the collected signals. The host computer controls the operation of each module, including laser parameter settings, signal analysis of collected spectra and photon sequences, real-time monitoring of the fluorescence imaging process, and collected image processing.

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