A spectrometer based on grating filtering and superconducting detection

Abstract

The application provides a spectrometer based on grating filtering and superconducting detection, which can be applied to the technical field of quantum optics and superconducting detection equipment. The spectrometer comprises a first optical path device, a superconducting detector, a data acquisition card and a calculation processing card, the first optical path device comprises a first coupling lens, a first spectroscopic grating, a first focusing lens, a light transmission adjusting slit, a second focusing lens, a second spectroscopic grating and a second coupling lens arranged along an optical path; the incident end of the first coupling lens is communicated with the emitting end of the second optical path device through an optical fiber, and the emitting end of the second coupling lens is communicated with the incident end of the superconducting detector through an optical fiber. The measurement range is limited in the range near the target wavelength, which can effectively improve the detection sensitivity of the extremely weak fluorescent signal under the premise of ensuring the spectral resolution, and the corresponding specification of the grating can be flexibly selected according to the characteristic fluorescent wavelength of the target color center, so as to adapt to the spectral detection requirements of different solid-state fluorescent defect systems.

Description

Technical Field

[0001] This application relates to the field of quantum optics, specifically to the field of quantum optical devices based on grating filtering and superconducting detection, and more specifically to a spectrometer based on grating filtering and superconducting detection. Background Technology

[0002] The basic working principle of a spectrometer is that when a composite fluorescence signal containing multiple wavelength components is incident on a grating, due to the correspondence between the diffraction angle and the wavelength determined by the grating equation, light of different wavelengths will exit at different diffraction angles, thus being unfolded into a continuously distributed spatial spectrum in space.

[0003] In solid-state material systems, different fluorescent defect centers possess their own characteristic energy level structures. The energy difference between their ground and excited states determines the characteristic wavelength of the emitted fluorescent photons. Therefore, the type of defect can be identified and distinguished by measuring the wavelength of the fluorescence signal. However, the radiative transition processes of some fluorescent defects are constrained by quantum mechanical selection rules, exhibiting mechanisms such as forbidden transitions, resulting in low fluorescence quantum yield, long radiative lifetime, and extremely weak emission intensity. Under low-temperature conditions, some phonon-assisted transition channels are suppressed, further weakening the luminescence efficiency. Conventional spectrometers, limited by factors such as grating diffraction efficiency, detector dark count, and readout noise, have low sensitivity when faced with such ultra-weak fluorescence signals, making effective resolution and detection difficult. Summary of the Invention

[0004] In view of the above problems, embodiments of this application provide a spectrometer based on grating filtering and superconducting detection.

[0005] According to a first aspect of this application, a spectrometer based on grating filtering and superconducting detection is provided. The spectrometer includes: a first optical path device, a superconducting detector, a data acquisition card, and a computing processing card. The first optical path device includes: a first coupling lens arranged along the optical path for receiving collimated incident fluorescence signals; a first beam splitter, disposed on the outgoing optical path of the first coupling lens, for expanding the incident fluorescence signal into a spatial spectrum according to a preset wavelength; a first focusing lens, disposed on the outgoing optical path of the first beam splitter, for focusing the incident fluorescence signal to a preset spatial position on the focal plane; a light transmission adjustment slit, disposed on the common focal plane opposite to the first and second focusing lenses, for filtering fluorescence signals located at preset wavelengths at different spatial positions; a second focusing lens, disposed on the outgoing optical path of the light transmission adjustment slit, for focusing the outgoing fluorescence signal to a preset spatial position on the focal plane; and a second beam splitter, disposed on the outgoing optical path of the second focusing lens, for... The emitted fluorescence signal is expanded into a spatial spectrum according to a preset wavelength; a second coupling lens, disposed on the output optical path of the second beam splitter, is used to collect the emitted fluorescence signal; wherein, the input end of the first coupling lens is connected to the output end of the second optical path device through an optical fiber, and the output end of the second coupling lens is connected to the input end of the superconducting detector through an optical fiber, the superconducting detector is used to detect the fluorescence signal emitted after passing through the first optical path device; the light transmission adjustment slit is mounted on a stepping stage, the stepping stage is used to drive the light transmission adjustment slit to move in a one-dimensional direction within the common focal plane; the data acquisition card is electrically connected to the superconducting detector and the computing processing card respectively, the data acquisition card is used to acquire the fluorescence signal intensity detected by the superconducting detector and the fluorescence signal wavelength determined by the stepping stage; the computing processing card is electrically connected to the data acquisition card and the stepping stage respectively, the computing processing card is used to obtain the fluorescence signal intensity and the fluorescence signal wavelength to draw a light spectrum.

[0006] According to an embodiment of this application, the first coupling lens and the second coupling lens are fiber collimators, the focal length of the first coupling lens and the second coupling lens is 8 mm to 15 mm, and the numerical aperture of the first coupling lens and the second coupling lens is 0.20 to 0.30.

[0007] According to an embodiment of this application, the first beam splitter and the second beam splitter are transmission gratings, and the scribe line density of the first beam splitter and the second beam splitter is 300 lpmm to 1200 lpmm.

[0008] According to an embodiment of this application, the focal length of the first focusing lens and the second focusing lens is 80 mm to 120 mm, and the distance between the first focusing lens and the second focusing lens is 160 mm to 240 mm.

[0009] According to an embodiment of this application, the slit width adjustment range of the light-transmitting adjustment slit is 10 μm to 2 mm, and the single-step length of the stepping displacement stage is less than or equal to 10 μm.

[0010] According to an embodiment of this application, the second optical path device includes: a laser for emitting a laser signal of a preset wavelength arranged along the optical path; a beam splitter disposed on the incident optical path of the laser for separating the laser signal and a fluorescence signal; a galvanometer system disposed on the exit optical path of the beam splitter for controlling the laser signal to deflect and scan on the sample surface in a preset direction; a third focusing lens disposed on the incident and exit optical paths of the galvanometer system for focusing the incident laser signal and the exit fluorescence signal; an objective lens disposed on the exit optical path of the third focusing lens for focusing the incident laser signal and the exit fluorescence signal; and a cryogenic cavity disposed on the exit optical path of the objective lens for generating a cryogenic environment to accommodate the sample to be tested.

[0011] According to an embodiment of this application, the laser signal emitted by the laser passes sequentially through the beam splitter, the galvanometer system, the third focusing lens, and the objective lens and is focused onto the sample to be tested in the cryogenic cavity. The fluorescence signal generated by the sample after being excited passes sequentially through the objective lens, the third focusing lens, the galvanometer system, and the beam splitter and enters the first coupling lens of the first optical path device.

[0012] According to an embodiment of this application, the second optical path device further includes: a third coupling lens, disposed on the output optical path of the beam splitter, for collecting the output fluorescence signal; the output end of the third coupling lens is connected to the input end of the first optical path device through an optical fiber.

[0013] According to an embodiment of this application, the second optical path device further includes: a first filter disposed between the laser and the beam splitter for filtering out stray light in the incident laser signal.

[0014] According to an embodiment of this application, the second optical path device further includes: a second filter disposed between the beam splitter and the third coupling lens, used to filter out stray light in the emitted fluorescence signal.

[0015] The spectrometer based on grating filtering and superconducting detection provided in this application has at least the following advantages compared with related technologies:

[0016] The first optical path device of this application consists of conventional optical components, allowing for rapid assembly and debugging, and possesses high versatility and scalability. Before detection, the optical path is assembled on a breadboard, and the overall optical path efficiency is adjusted. After determining the wavelength-slit correspondence through light source calibration, the slit position is adjusted using a stepping stage, thereby filtering the spatial spectrum of the grating. The subsequently incident fluorescence signal enters the superconducting detector, data acquisition card, and computing processing card sequentially through the optical path, thus enabling the detection of fluorescence counting signals from the sample material. This limits the measurement range to the vicinity of the target wavelength, effectively improving the detection sensitivity to extremely weak fluorescence signals while maintaining spectral resolution. Furthermore, the grating specifications can be flexibly selected based on the characteristic fluorescence wavelength of the target color center, adapting to the spectral detection needs of different solid-state fluorescence defect systems. Attached Figure Description

[0017] The above-mentioned contents, other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0018] Figure 1 The schematic diagram illustrates the optical path principle of a spectrometer based on grating filtering and superconducting detection according to an embodiment of this application. Figure 1 ;

[0019] Figure 2 The schematic diagram illustrates the optical path principle of a spectrometer based on grating filtering and superconducting detection according to an embodiment of this application. Figure 2 ;

[0020] Figure 3 This schematic diagram illustrates the optical path principle of a first optical path device according to an embodiment of the present application.

[0021] Figure 4 A schematic diagram of the optical path of a second optical path device according to an embodiment of this application is shown.

[0022] Figure 5 This is a schematic diagram of the defect energy level structure of SiV0 in diamond.

[0023] Figure 6 The SiVO spectrum plotted using the spectrometer described in this application is shown below.

[0024] Figure 7 Photoluminescence spectrum plotted for scanning the reflected fluorescence of SiV0 sample;

[0025] Figure 8 The SiVO spectrum is plotted using an existing spectrometer.

[0026] Figure 9 The T-center spectrum is plotted using the spectrometer described in this application.

[0027] The above-mentioned figures include the following reference numerals: 1. First optical path device; 11. First coupling lens; 12. First beam splitter; 13. First focusing lens; 14. Light transmission adjustment slit; 15. Second focusing lens; 16. Second beam splitter; 17. Second coupling lens; 18. Stepping stage; 2. Superconducting detector; 3. Data acquisition card; 4. Computational processing card; 5. Second optical path device; 51. Laser; 52. Beam splitter; 53. Galvanometer system; 54. Third focusing lens; 55. Objective lens; 56. Cryogenic cavity; 57. Third coupling lens; 58. First filter; 59. Second filter. Detailed Implementation

[0028] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0030] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0031] Figure 1 The schematic diagram illustrates the optical path principle of a spectrometer based on grating filtering and superconducting detection according to an embodiment of this application. Figure 1 , Figure 2 The schematic diagram illustrates the optical path principle of a spectrometer based on grating filtering and superconducting detection according to an embodiment of this application. Figure 2 , Figure 3 The schematic diagram illustrates the optical path principle of the first optical path device 1 according to an embodiment of this application. Figure 4 The schematic diagram illustrates the optical path principle of the second optical path device 5 according to an embodiment of this application.

[0032] The embodiments of this application provide a spectrometer based on grating filtering and superconducting detection, which will be described below in conjunction with... Figures 1 to 4 The device is described in detail.

[0033] like Figures 1 to 4 As shown in the embodiments of this application, the spectrometer includes: a first optical path device 1, a superconducting detector 2, a data acquisition card 3, and a computing processing card 4. The first optical path device 1 includes a first coupling lens 11, a first beam splitter 12, a first focusing lens 13, a light transmission adjustment slit 14, a second focusing lens 15, a second beam splitter 16, and a second coupling lens 17 arranged along the optical path.

[0034] For example, the first coupling lens 11 is used to receive and collimate the fluorescence signal transmitted through the optical fiber to match the incident requirements of the subsequent grating. The first beam splitter grating 12 is disposed in the output optical path of the first coupling lens 11. Utilizing the correspondence between the diffraction angle and wavelength determined by the grating equation d(sinα±sinβ)=mλ, the incident fluorescence signal is spatially expanded into a continuously distributed spatial spectrum according to different wavelengths. The first focusing lens 13 is disposed in the output optical path of the first beam splitter grating 12 to converge the fluorescence signals emitted at different diffraction angles to a preset spatial position on its back focal plane, thereby completing the wavelength-to-position mapping conversion.

[0035] Furthermore, the light transmission adjustment slit 14 is disposed on the common focal plane opposite to the first focusing lens 13 and the second focusing lens 15, and is used to filter fluorescence signals of preset wavelengths located at different spatial positions, allowing only the fluorescence signal of the preset wavelength to pass through while blocking fluorescence signals of other wavelengths. The second focusing lens 15 is disposed in the outgoing light path of the light transmission adjustment slit 14, and is used to collimate and output the fluorescence signal exiting the light transmission adjustment slit 14.

[0036] Furthermore, the second beam splitter 16 is disposed in the output light path of the second focusing lens 15, and is used to perform secondary beam splitting on the filtered fluorescence signal, further compressing stray light and improving spectral purity. The second coupling lens 17 is disposed in the output light path of the second beam splitter 16, and is used to collect and couple the secondary beam splitting fluorescence signal to the photosensitive surface of the superconducting detector 2.

[0037] It should be noted that, in the embodiments of this application, the incident end of the first coupling lens 11 is connected to the output end of the second optical path device 5 via an optical fiber, and is used to receive fluorescence signals; the output end of the second coupling lens 17 is connected to the incident end of the superconducting detector 2 via an optical fiber, and is used to efficiently transmit the pure fluorescence signal after spectral splitting, filtering and secondary spectral splitting to the superconducting detector 2.

[0038] Furthermore, the light-transmitting adjustment slit 14 is mounted on the stepping stage 18. During detection, the light-transmitting adjustment slit 14 can be driven by the stepping stage 18 to move in a one-dimensional direction within the common focal plane. Through time-series scanning, fluorescence signals of different wavelengths pass through the light-transmitting adjustment slit 14 in sequence and are detected sequentially by the superconducting detector 2.

[0039] Furthermore, the data acquisition card 3 is electrically connected to the superconducting detector 2 and the computing processing card 4 integrated into a computer or other electronic device, respectively, for synchronously acquiring the photon pulse signal (corresponding to the fluorescence signal intensity) output by the superconducting detector 2 and the position feedback signal of the stepping stage 18 (corresponding to the fluorescence signal wavelength). The computing processing card 4 is electrically connected to the data acquisition card 3 and the stepping stage 18, respectively, and is equipped with wavelength mapping algorithm software based on calibration data. It can convert the position signal of the stepping stage 18 into the corresponding fluorescence signal wavelength, and correlate the fluorescence signal intensity with the wavelength to finally draw a complete spectral line graph.

[0040] It is understood that the spectrometer based on grating filtering and superconducting detection in the embodiments of this application can achieve high-sensitivity detection of weak fluorescence signals at specific wavelengths, thereby enabling the systematic detection of fluorescence signals of more types of materials (such as diamond NV centers, SiV centers, etc.) and more defect energy levels of a certain material (such as 946 nm of SiV0).

[0041] Based on this, the spectrometer based on grating filtering and superconducting detection in this application embodiment differs from the traditional point-to-point optical path design of spectrometers, allowing for easy integration into various fiber-coupled optical path systems, significantly improving system compatibility and ease of use. Furthermore, the first optical path device 1 is composed of conventional optical components, enabling rapid assembly and debugging on a standard optical breadboard, exhibiting high versatility and scalability.

[0042] Understandably, before detection, the optical path is assembled on a breadboard and its overall efficiency is adjusted. After calibrating the light source to determine the correspondence between the wavelength and the light transmission adjustment slit 14, the position of the light transmission adjustment slit 14 is adjusted using a stepping stage 18. This filters the spatial spectrum of the grating. Subsequently, the incident fluorescence signal enters the superconducting detector 2, data acquisition card 3, and computing processing card 4 sequentially through the optical path, thereby realizing the detection of the fluorescence counting signal of the sample material. Thus, by limiting the measurement range to the vicinity of the target wavelength, the detection sensitivity to extremely weak fluorescence signals can be effectively improved while ensuring spectral resolution. Furthermore, the grating of the corresponding specification can be flexibly selected according to the characteristic fluorescence wavelength of the target color center, thus adapting to the spectral detection needs of different solid-state fluorescence defect systems.

[0043] Furthermore, the first coupling lens 11 and the second coupling lens 17 are fiber collimators, the focal length of the first coupling lens 11 and the second coupling lens 17 is 8 mm to 15 mm, and the numerical aperture of the first coupling lens 11 and the second coupling lens 17 is 0.20 to 0.30.

[0044] For example, the first coupling lens 11 and the second coupling lens 17 can be fiber collimators with a center wavelength of 633 nm, a focal length f of 10.99 mm, a numerical aperture NA of 0.25, and equipped with an FC / PC fiber connector. They are used to collimate the first-order diffraction spot of the incident laser through the grating and collect the corresponding outgoing first-order diffraction spot. They have the characteristics of low insertion loss and high beam quality, and can ensure efficient coupling of excitation light and fluorescence signal between the optical fiber and the spatial optical path.

[0045] Furthermore, the first beam splitter grating 12 and the second beam splitter grating 16 are transmission gratings, and the scribe line density of the first beam splitter grating 12 and the second beam splitter grating 16 is 300 lpmm to 1200 lpmm.

[0046] For example, the first beam splitter grating 12 and the second beam splitter grating 16 can be transmission gratings with a blaze wavelength of 900 nm and a grating density of 600 lpmm. They are used to split the collected fluorescence signal and accurately refract the signal of the corresponding wavelength into the collector. They have high diffraction efficiency in the near-infrared band and are suitable for the detection of fluorescence signals.

[0047] It should be noted that, in order to achieve efficient collection and detection of this spatial spectrum, a 4f optical system consisting of two confocal focusing lenses with the same focal length can be used to convert the outgoing light, which is angularly dispersed after being dispersed by the grating, into a straight optical path so that it can be collected uniformly. The light passes through a slit at the intermediate focal plane, and the fluorescence signals of different intensities collected at different positions are identified to match the fluorescence signal intensity of different wavelengths corresponding to each position.

[0048] Furthermore, the focal lengths of the first focusing lens 13 and the second focusing lens 15 are 80 mm to 120 mm, and the distance between the first focusing lens 13 and the second focusing lens 15 is 160 mm to 240 mm.

[0049] For example, the first focusing lens 13 and the second focusing lens 15 can be plano-convex lenses made of optical glass, with a diameter Ø of 1 inch and a focal length f of 100 mm. Their surfaces are coated with an anti-reflection film covering the main operating wavelengths from visible light to near-infrared, effectively reducing Fresnel reflection loss and improving light energy utilization. In the 4f system, the first focusing lens 13 is used to converge the parallel diffracted light from the grating to the focal plane, and the second focusing lens 15 is used to re-collimate the divergent light passing through the light-adjusting slit 14 into parallel light.

[0050] Based on this, in the spectrometer based on grating filtering and superconducting detection in this embodiment of the application, the focal length and spacing of the two focusing lenses in the 4f system are reasonably matched to ensure the accurate positioning of the common focal plane, so that fluorescence signals of different wavelengths are accurately separated according to their spatial positions on the focal plane. The light transmission adjustment slit 14 can complete the accurate screening of the target wavelength signal with high wavelength resolution. At the same time, the introduction of the fiber collimator enables low-loss connection between the optical path system and the fiber optic transmission system, which not only ensures the fidelity of the optical signal during transmission, but also makes it easy for users to flexibly adjust the optical path layout according to different experimental environments.

[0051] Understandably, the scheme of using a transmissive grating with a fiber collimator has high diffraction efficiency and light energy utilization in the near-infrared target band, avoiding the stray light problem caused by reflection loss and multiple reflections in reflective gratings. At the same time, the reasonably selected scribe line density and blaze wavelength allow the spatial spectrum near the target wavelength to be fully expanded, and the light transmission adjustment slit 14 can complete wavelength selection with a high signal-to-noise ratio.

[0052] Furthermore, the slit width adjustment range of the light-transmitting adjustment slit 14 is 10 μm to 2 mm, and the single-step length of the stepping displacement stage 18 is less than or equal to 10 μm.

[0053] For example, the stepping stage 18 is used to carry the light-transmitting adjustment slit 14 and obtain the correspondence between the position and the wavelength after spectral dispersion by moving the light-transmitting adjustment slit 14. By selecting the aforementioned type of grating, the spatial spectrum near the selected wavelength of 946 nm can be more fully broadened, resulting in higher sensitivity for subsequent detection and collection. This, combined with the light-transmitting adjustment slit 14, allows for the screening of fluorescence signals at different spatial positions corresponding to wavelengths after spectral dispersion by the grating.

[0054] Based on this, in the spectrometer based on grating filtering and superconducting detection in this application embodiment, the wide range of slit width adjustment capability, combined with the high-precision stepping stage 18 driving, can flexibly optimize the balance between spectral resolution and detection sensitivity according to different application scenarios during detection. When the signal is strong, a narrower slit width can be selected to obtain higher spectral resolution, and when the signal is extremely weak, the slit width can be appropriately widened to increase the light flux.

[0055] For example, the superconducting detector 2 can be a superconducting nanowire single-photon detector, which has the characteristics of high system detection efficiency and low dark count rate, and is used to detect the fluorescence signal after passing through the optical path of the spectrometer. It operates below the superconducting critical temperature, and the dark count at the corresponding wavelength is less than 10 counts / s. When a single photon is absorbed by the superconducting nanowire, it breaks the local Cooper pair and forms a normal-state hot spot, generating a voltage pulse signal.

[0056] Furthermore, the data acquisition card 3 is in counting mode, used to count the photon pulse signals output by the superconducting detector 2 according to the time sequence, and to synchronously match the photon count value with the position signal of the stepping displacement stage 18; the calculation and processing card 4 has a built-in matching program, used to match the read photon count with the displacement stage position, and convert the position into wavelength according to the pre-stored position and wavelength calibration data, and finally draw a spectral line graph.

[0057] Based on this, in the spectrometer based on grating filtering and superconducting detection in this embodiment of the application, the low dark count and high system detection efficiency of the superconducting nanowire single-photon detector can effectively extract photon count information from extremely weak fluorescence signals. Simultaneously, combined with time-series scanning operations, the data acquisition card 3 and the computational processing card 4 can accurately correlate each photon event with its corresponding wavelength position, ultimately generating a spectral polygon.

[0058] like Figures 1 to 4 As shown, in the embodiments of this application, the second optical path device 5 is an optical fiber coupled optical path system, including a laser 51, a beam splitter 52, a galvanometer system 53, a third focusing lens 54, an objective lens 55, and a cryogenic cavity 56 arranged along the optical path.

[0059] For example, laser 51 is used to emit a laser signal of a preset wavelength (e.g., 830 nm) as pump light to excite the sample to generate fluorescence. Beam splitter 52 is disposed in the output optical path of laser 51 to separate the laser signal and the fluorescence signal: in the excitation optical path, the laser signal is reflected (or transmitted) into the galvanometer system 53, and in the fluorescence collection optical path, the fluorescence signal is transmitted (or reflected) into the first optical path device 1.

[0060] Furthermore, the galvanometer system 53 is disposed in the output optical path of the beam splitter 52, including two independently controlled galvanometers arranged sequentially along the optical path, which oscillate around the X-axis and Y-axis respectively, to control the laser signal to perform two-dimensional deflection scanning on the sample surface in a preset direction, thereby realizing point-by-point excitation of different spatial positions of the sample. The third focusing lens 54 is disposed in the output optical path of the galvanometer system 53, and is used to focus the parallel beam deflected by the galvanometer onto the back focal plane of the objective lens 55.

[0061] Furthermore, objective lens 55 is positioned in the output optical path of the third focusing lens 54 to further focus the incident laser signal onto the surface of the sample under test, and simultaneously to focus the fluorescence signal emitted by the sample under test back into the optical path. The cryogenic cavity 56 is positioned in the output optical path of objective lens 55, containing the sample under test and providing a controllable cryogenic environment.

[0062] It should be noted that, in the embodiments of this application, the laser signal emitted by the laser 51 is focused onto the sample to be tested in the low-temperature cavity 56 after passing through the beam splitter 52, the galvanometer system 53, the third focusing lens 54 and the objective lens 55 in sequence. The fluorescence signal generated by the sample is excited and returns along the original optical path, passing through the objective lens 55, the third focusing lens 54, the galvanometer system 53 and the beam splitter 52 in sequence, and then enters the first coupling lens 11 of the first optical path device 1.

[0063] like Figures 1 to 4 As shown, in an embodiment of this application, the second optical path device 5 further includes a third coupling lens 57.

[0064] For example, the third coupling lens 57 is disposed on the output optical path of the beam splitter 52 to collect the fluorescence signal transmitted (or reflected) by the beam splitter 52 and converge and couple it into the optical fiber. The output end of the third coupling lens 57 is connected to the input end of the first optical path device 1 (i.e., the input end of the first coupling lens 11) through the optical fiber.

[0065] Furthermore, in the embodiments of this application, the second optical path device 5 further includes a first filter 58 and a second filter 59.

[0066] For example, the first filter 58 is disposed between the laser 51 and the beam splitter 52 to filter out stray light in the incident laser signal. The second filter 59 is disposed between the beam splitter 52 and the third coupling lens 57 to filter out stray light in the emitted fluorescence signal.

[0067] It should be noted that the first filter 58 can be a bandpass filter or a notch filter, allowing only narrowband light near the main wavelength of the laser 51 (e.g., 830 nm) to pass through, effectively blocking stray light. The second filter 59 can be a longpass filter or a notch filter, with its cutoff wavelength set between the excitation wavelength and the fluorescence signal wavelength, effectively blocking the excitation light while allowing longer wavelength fluorescence signals to pass through.

[0068] Figure 5 This is a schematic diagram of the defect energy level structure of SiV0 in diamond. Figure 6 This is a broken-line plot of the SiVO spectrum generated using the spectrometer described in this application. Figure 7 The photoluminescence spectrum of the SiV0 sample was plotted to capture the reflected fluorescence. Figure 8 This is a line plot of the SiV0 spectrum generated using an existing spectrometer. Figure 9 The T-center spectrum is plotted using the spectrometer described in this application.

[0069] like Figures 5 to 9 As shown in the embodiments of this application, the basic working principle of the spectrometer is that when a composite fluorescence signal containing multiple wavelength components is incident on a beam splitter grating, due to the correspondence between the diffraction angle and wavelength determined by the grating equation d(sinα±sinβ)=mλ, light of different wavelengths will exit at different diffraction angles, thus being spatially expanded into a continuously distributed spatial spectrum. This application uses a 4f system to convert the angularly dispersed outgoing light after dispersion by the beam splitter into a parallel light path, so that different wavelength components are spatially separated and arranged on the intermediate focal plane. A light transmission adjustment slit 14 is set at this focal plane as a spatial filter. By adjusting the position and width of the light transmission adjustment slit 14, the selection of specific wavelength components is achieved. Subsequently, the fluorescence signal emitted from the light transmission adjustment slit 14 is re-collimated into parallel light output by a second plano-convex lens and finally collected by the superconducting detector 2. By driving the light-transmitting adjustment slit 14 to scan point by point in the focal plane using the stepping stage 18, light intensity information corresponding to different spatial positions can be obtained. Then, based on the pre-calibrated mapping relationship between position and wavelength, a spectral line graph can be finally drawn.

[0070] In solid-state material systems, different fluorescent defect centers possess their own characteristic energy level structures. The energy difference between their ground state and excited state determines the characteristic wavelength of the emitted fluorescent photons. Therefore, the type of defect can be identified and distinguished by measuring the wavelength of the fluorescence signal. The following section uses SiV in diamond as an example. 0 Let's take lust as an example to further illustrate this.

[0071] Figure 5 The SiV predicted by stress testing theory in the literature. 0Schematic diagram of defect energy level structure (Phys.Rev. B 99, 161112(R), 2019). SiV 0 The energy wavelengths corresponding to the ground and excited states in the energy level structure of the color center are 946 nm. When SiV is given... 0 When an 830 nm pump light is applied to the color center, the charge carriers in the valence band absorb photon energy and are excited from the ground state to the excited state. After a certain time (the excited state lifetime), they radiate back to the ground state and emit fluorescent photons. The energy of these fluorescent photons precisely corresponds to the energy level difference between the ground and excited states. Different solid-state fluorescent defects have different energy level structures and characteristic transition wavelengths. Therefore, it is necessary to identify the wavelength of the fluorescence signal emitted by solid-state fluorescent defects in order to distinguish different types of solid-state fluorescent defects.

[0072] However, the radiative transitions of some fluorescent defects are constrained by quantum mechanical selection rules, exhibiting forbidden transition mechanisms. Specifically, SiV... 0 The excited state of SiV consists of two states with similar energy levels, where transitions from the lower energy level to the ground state are forbidden. This makes SiV... 0 At extremely low temperatures, luminescence weakens, meaning that charge carriers are confined to lower energy levels and cannot transition through forbidden channels. SiV 0 The maximum luminescence intensity exists around 70 K, at which point thermal excitation is sufficient to excite charge carriers from lower energy levels to higher energy levels, effectively activating the radiative transition channels. However, even at the optimal operating temperature of 70 K, SiV... 0 The luminescence intensity remains extremely weak and cannot be effectively measured using conventional commercial spectrometers. For example... Figure 8 As shown, under 830 nm pump light excitation, existing spectrometers can only observe a Raman peak near 933 nm (corresponding to the first-order Raman scattering signal of the 830 nm laser in the diamond lattice), while the SiV peak near 946 nm... 0 The characteristic fluorescence peaks are completely indistinguishable because existing spectrometers have low spectrometer diffraction efficiency and high dark count and readout noise in their detectors, resulting in a system noise floor generally exceeding 700 counts / s, far higher than that of SiV. 0 The intensity of the fluorescence signal.

[0073] It should be noted that the spectrometer used in this application needs to be calibrated beforehand.

[0074] For example, a 940 nm wavelength, 100 mW power laser 51 is used as the calibration laser and connected to the output fiber of the coupling lens. The preset angle between the coupling lens and the beam splitter is determined via the output fiber of another coupling lens. This wavelength laser 51 is closest to the target spectral wavelength (946 nm), which can reduce the optical range required after calibration and improve the detection accuracy.

[0075] After determining the preset angles of the beam splitter and coupling lens, a halogen incandescent lamp is used as a calibration light source to determine the position and wavelength relationship with the light-transmitting adjustment slit 14 on the stepping stage 18. This halogen incandescent lamp emits mixed light of the visible light band and wavelengths. By adjusting the slit width to make the emitted light intensity 70% of the incident light intensity, the peak value of the emitted fluorescence signal is detected by a spectrometer to obtain the corresponding wavelength position. The displacement coordinates are then obtained using the preset code program of the stepping stage 18, and a binary data set is established.

[0076] The above process is repeated multiple times. Based on the measured binary data sets, the slope and intercept of the linear function are calculated. The obtained slope and intercept are then filled into the corresponding parameter positions through a preset code program to obtain the light intensity information corresponding to different spatial positions. Finally, based on the pre-calibrated mapping relationship between position and wavelength, a spectral polygon is plotted.

[0077] For example, after determining the angle between the spectrometer and the coupling lens, a halogen incandescent lamp can be used as a calibration light source to calibrate the relationship between the position and wavelength of the light-transmitting adjustment slit 14 on the stepping stage 18 of the existing spectrometer. This is because the incandescent lamp is a mixed light of most wavelengths in the visible light band. By adjusting the slit width to make the outgoing light intensity 70% of the incident light intensity, the outgoing fluorescence signal is detected by the existing spectrometer to obtain the corresponding wavelength position. The binary data set is obtained by comparing the peak value with the displacement coordinates obtained by the built-in program of the stepping stage 18. This process is repeated five times. Then, the slope and intercept of the linear function are calculated from the five sets of binary data sets. By writing code to fill the obtained slope and intercept into the corresponding parameter positions, the spectrum can be measured by the position of the stepping stage 18.

[0078] Furthermore, the given SiV 0 The fluorescence signal emitted by the defect under 830 nm pump light excitation, with a laser power of 10 mW illuminating the sample material, was detected by both existing spectrometers and the spectrometer described in this application. The results were as follows: Figure 6 and Figure 7 As shown. The spectrometer of this application was used to study the same SiV. 0 When the sample was detected, a clear and distinguishable fluorescence signal peak was obtained at 946 nm, and a Raman peak consistent with that of existing spectrometers was also detected near 933 nm. This comparison result verifies that the spectrometer of this application can effectively detect extremely weak fluorescence signals.

[0079] For example, in another embodiment, when probing a silicon-based T-center, the characteristic wavelength of its fluorescence signal is 1326 nm, which falls within the near-infrared communication band. Scanning photoluminescence (PL) images show that the T-center sample exhibits ensemble luminescence characteristics, and the fluorescence signal count is extremely weak when spectrally probing at any arbitrary point. In existing spectrometers, apart from the Raman peak corresponding to the excitation light, no significant signal can be observed near 1326 nm. Figure 9 As shown, the characteristic fluorescence signal peak of the T color center can be clearly distinguished at 1326 nm using the spectrometer of this application. This further verifies the versatility and scalability of the spectrometer in different near-infrared bands. By simply replacing the spectrometer with a different blaze wavelength and recalibrating it, the detection range can be flexibly switched to any target wavelength, which is suitable for the spectroscopic characterization needs of different solid-state fluorescent defect systems.

[0080] Those skilled in the art will understand that the features described in the various embodiments of this application can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this application. In particular, the features described in the various embodiments of this application can be combined and / or combined in various ways without departing from the spirit and teachings of this application. All such combinations and / or combinations fall within the scope of this application.

Claims

1. A spectrometer based on grating filtering and superconducting detection, characterized in that, The spectrometer includes: a first optical path device, a superconducting detector, a data acquisition card, and a computing processing card. The first optical path device comprises components arranged along the optical path: The first coupling lens is used to receive the collimated incident fluorescence signal; The first beam splitter is disposed in the outgoing light path of the first coupling lens and is used to expand the incident fluorescence signal into a spatial spectrum according to a preset wavelength. The first focusing lens is disposed on the outgoing light path of the first beam splitter and is used to focus the incident fluorescence signal to a preset spatial position on the focal plane. A light-transmitting adjustment slit is set on the common focal plane opposite to the first focusing lens and the second focusing lens, and is used to filter fluorescence signals of preset wavelengths located at different spatial positions; The second focusing lens is disposed on the outgoing light path of the light transmission adjustment slit and is used to focus the outgoing fluorescence signal to a preset spatial position on the focal plane. The second beam splitter is disposed in the output light path of the second focusing lens and is used to expand the output fluorescence signal into a spatial spectrum according to a preset wavelength; The second coupling lens is disposed in the output light path of the second beam splitter and is used to collect the output fluorescence signal; The first coupling lens is connected to the output end of the second optical path device via an optical fiber, and the output end of the second coupling lens is connected to the input end of the superconducting detector via an optical fiber. The superconducting detector is used to detect the fluorescence signal emitted after passing through the first optical path device. The light-transmitting adjustment slit is mounted on a stepping displacement stage, which is used to drive the light-transmitting adjustment slit to move in a one-dimensional direction within the common focal plane. The data acquisition card is electrically connected to the superconducting detector and the computing card, respectively. The data acquisition card is used to acquire the fluorescence signal intensity detected by the superconducting detector and the fluorescence signal wavelength determined by the stepping displacement stage. The computing processing card is electrically connected to the data acquisition card and the stepping displacement stage, respectively. The computing processing card is used to acquire the fluorescence signal intensity and the fluorescence signal wavelength to draw a light spectrum.

2. The spectrometer according to claim 1, characterized in that, The first coupling lens and the second coupling lens are fiber collimators, the focal length of the first coupling lens and the second coupling lens is 8 mm to 15 mm, and the numerical aperture of the first coupling lens and the second coupling lens is 0.20 to 0.

30.

3. The spectrometer according to claim 1, characterized in that, The first and second beam splitters are transmission gratings, and the grating density of the first and second beam splitters is 300 lpmm to 1200 lpmm.

4. The spectrometer according to claim 1, characterized in that, The focal lengths of the first focusing lens and the second focusing lens are 80 mm to 120 mm, and the distance between the first focusing lens and the second focusing lens is 160 mm to 240 mm.

5. The spectrometer according to claim 1, characterized in that, The slit width of the light-transmitting adjustment slit is adjustable from 10 μm to 2 mm, and the single-step length of the stepping displacement stage is less than or equal to 10 μm.

6. The spectrometer according to claim 1, characterized in that, The second optical path device includes: arranged along the optical path: A laser is used to emit laser signals of a preset wavelength. A beam splitter is disposed in the incident light path of the laser to separate the laser signal and the fluorescence signal; A galvanometer system is set in the output optical path of the beam splitter to control the laser signal to deflect and scan on the sample surface in a preset direction; The third focusing lens is disposed on the incident and outgoing optical paths of the galvanometer system and is used to focus the incident laser signal and the outgoing fluorescence signal. An objective lens is positioned in the output optical path of the third focusing lens to focus the incident laser signal and the output fluorescence signal. The low-temperature cavity is located in the exit light path of the objective lens and is used to generate a low-temperature environment to accommodate the sample to be tested.

7. The spectrometer according to claim 6, characterized in that, The laser signal emitted by the laser passes sequentially through the beam splitter, the galvanometer system, the third focusing lens, and the objective lens before being focused onto the sample to be tested in the cryogenic cavity. The fluorescence signal generated by the sample after being excited passes sequentially through the objective lens, the third focusing lens, the galvanometer system, and the beam splitter before entering the first coupling lens of the first optical path device.

8. The spectrometer according to claim 6, characterized in that, The second optical path device further includes: The third coupling lens is disposed in the output optical path of the beam splitter to collect the output fluorescence signal; The exit end of the third coupling lens is connected to the entrance end of the first optical path device via an optical fiber.

9. The spectrometer according to claim 6, characterized in that, The second optical path device further includes: The first filter is placed between the laser and the beam splitter to filter out stray light in the incident laser signal.

10. The spectrometer according to claim 6, characterized in that, The second optical path device further includes: The second filter, located between the beam splitter and the third coupling lens, is used to filter out stray light in the emitted fluorescence signal.

Images