Preparation method of optical fiber integrated single-photon detector and single-photon detector

Abstract

The invention discloses a preparation method of an optical fiber integrated single-photon detector and the single-photon detector. The method comprises the following steps: forming a first waveguide core in a first substrate by adopting a femtosecond laser direct writing technology; polishing and grinding the upper surface of the first substrate to obtain a second substrate comprising a second waveguide core; preparing a superconducting nanowire on the first surface; a second substrate containing the superconducting nanowire is installed on the detector integration platform, so that the two ends of the second waveguide core are connected with the first optical fiber and the second optical fiber on the detector integration platform respectively, and the superconducting nanowire is electrically connected with a metal polar plate on the detector integration platform through a lead. The optical fiber is adopted as a light guide carrier, physical limitation of a traditional detector on the wavelength of incident light is broken through, the bandwidth of the detector is expanded, meanwhile, efficient optical fiber-optical waveguide spot size conversion can be achieved, and therefore the detection efficiency is improved. The optical waveguide with the flat upper surface is formed through the precise polishing and grinding process, the flat interface enables the superconducting nanowire to be prepared by adopting a completely standard planar micro-nano process (such as lift-off), and the inherent problems that the uniformity is poor, the yield is low and the reliability is insufficient when the nanowire is integrated on the non-planar waveguide are fundamentally solved.

Description

Technical Field

[0001] This application relates to the field of quantum optoelectronics technology, and in particular to a method for fabricating an optical fiber integrated single-photon detector and the single-photon detector itself. Background Technology

[0002] Quantum information technology is not only crucial for the development of next-generation communication technologies but also relates to national defense strategy. Among the key performance bottlenecks of single-photon detectors, their detection efficiency, dark count, timing jitter, and integration are crucial factors limiting the scale, speed, and reliability of quantum information systems. Superconducting nanowire single-photon detectors (SNSPDs) are photodetectors with extreme sensitivity capable of detecting the energy of a single photon. When an incident photon is absorbed by the detector's active region, it disrupts the Cooper pairs of the superconducting nanowire, creating a localized "hot spot." This causes the nanowire to temporarily lose quench and generate a detectable resistance pulse. This single-photon-level detection capability makes it an indispensable core device in cutting-edge fields such as quantum key distribution, optical quantum computing, single-molecule fluorescence spectroscopy, and lidar.

[0003] Coupled photons from micro / nano waveguides into the active region of a detector via evanescent fields is a crucial method for achieving single-photon detection. However, this advanced waveguide integration scheme faces a key technical contradiction and challenge in its implementation: while traditional high-performance optical waveguides (such as silicon nitride or silicon waveguides) can efficiently generate and confine evanescent fields, they suffer from severe mode field mismatch with standard single-mode fibers. The mode field diameter of a standard single-mode fiber is approximately 10 micrometers, while the mode field size of a high-refractive-index-difference photonic integrated circuit waveguide is typically only on the sub-micrometer or 1-micrometer scale. This huge difference in mode field size results in significant coupling losses (typically several dB) when light is directly coupled from the fiber to such a waveguide, severely limiting the overall detection efficiency of the system. Although researchers have attempted to fabricate diffraction grating couplers above the waveguide, these methods suffer from inherent drawbacks such as narrow bandwidth, angle sensitivity, and selectivity to polarization states.

[0004] However, existing waveguide integration solutions (such as additively manufactured three-dimensional polymer waveguides) face a core technological bottleneck when integrating superconducting nanowire detectors: it is difficult to achieve high uniformity and high yield fabrication of superconducting nanowires on complex or irregular waveguide surfaces using standard planar micro / nano fabrication processes. This problem severely restricts the consistency and reliability of detector performance. Therefore, a waveguide-integrated single-photon detector with low coupling loss, high detection efficiency, and high stability is needed to solve these problems. Summary of the Invention

[0005] This application provides a method for fabricating an optical fiber integrated single-photon detector and a single-photon detector, in order to solve the problems of low detection efficiency and poor stability caused by uneven waveguide surfaces in the prior art.

[0006] In a first aspect, this application provides a method for fabricating an optical fiber integrated single-photon detector, comprising: A first waveguide core is formed inside a first substrate using femtosecond laser direct writing technology; the first waveguide core extends along a first direction parallel to the upper surface of the first substrate; the first substrate has a first thickness; The upper surface of the first substrate is polished to obtain a second substrate containing a second waveguide core; the second substrate has a second thickness; the second thickness is less than the first thickness; the second waveguide core is a part of the first waveguide core; the second waveguide core has a first surface after polishing. Superconducting nanowires were fabricated on the first surface; The second substrate containing the superconducting nanowire is mounted on the detector integration platform, such that the two ends of the second waveguide core are respectively connected to the first optical fiber and the second optical fiber on the detector integration platform, and the superconducting nanowire is electrically connected to the metal electrode plate on the detector integration platform through leads.

[0007] In some embodiments, a superconducting nanowire detector is fabricated on the first surface, including: Superconducting nanowires were fabricated on the first surface using planar micro-nano technology.

[0008] In some embodiments, the second waveguide core, after polishing, is exposed to allow the light field leaking from the second waveguide core to couple with the superconducting nanowire.

[0009] In some embodiments, a first waveguide core is formed inside a first substrate using femtosecond laser direct writing technology, including: Multiple first waveguide cores are formed inside a first substrate using femtosecond laser direct writing technology; the multiple first waveguide cores are spaced apart along a second direction, which is parallel to the upper surface of the first substrate and perpendicular to the first direction.

[0010] In some embodiments, mounting the second substrate containing the superconducting nanowires onto a detector integration platform includes: Each second waveguide core obtained from the first waveguide core is connected at both ends to the corresponding first optical fiber and second optical fiber to form an optical path; Each of the superconducting nanowires corresponding to the second waveguide core is connected at both ends to the corresponding metal electrode to form an electrical path.

[0011] In some embodiments, before forming the first waveguide core inside the first substrate using femtosecond laser direct writing technology, the method further includes: The upper surface of the substrate to be processed is polished to obtain the first substrate.

[0012] In a second aspect, this application provides a single-photon detector fabricated using the method described in the first aspect, comprising: A detector integration platform; a first optical fiber and a second optical fiber are disposed opposite to each other on the detector integration platform; the extension directions of the first optical fiber and the second optical fiber are located on the same straight line; A second substrate is disposed on the detector integration platform; a second waveguide core is disposed inside the second substrate; the second waveguide core extends along a first direction parallel to the upper surface of the second substrate; the first top surface of the second substrate and the second top surface of the second waveguide core are coplanar, and the first top surface and the second top surface are polished planes; superconducting nanowires are attached to the second top surface; The two ends of the second waveguide core are respectively connected to the first optical fiber and the second optical fiber; the two ends of the superconducting nanowire are respectively connected to the metal electrode plate disposed on the detector integration platform.

[0013] In some embodiments, the superconducting nanowire is one of a spiral nanowire, a helical nanowire, or a fractal nanowire.

[0014] In some embodiments, the material of the second waveguide core is silicon dioxide.

[0015] In some embodiments, the second substrate has a plurality of second waveguide cores disposed therein, the plurality of second waveguide cores being spaced apart along a second direction, the second direction being perpendicular to the first direction.

[0016] Compared with the prior art, the beneficial effects of the present invention are: Fundamental process compatibility and high yield: This invention forms an optical waveguide with a flat upper surface through a precision polishing process. This flat interface allows superconducting nanowires to be fabricated using fully standard planar micro-nano processes (such as lift-off), fundamentally solving the inherent problems of poor uniformity, low yield, and insufficient reliability when integrating nanowires on non-planar waveguides.

[0017] Broadband detection and efficient mode conversion: This invention uses optical fiber as the light guide carrier, which breaks through the physical limitation of the incident light wavelength of traditional detectors, thereby broadening the bandwidth of the detector. At the same time, it can also realize efficient fiber-to-waveguide mode conversion, thereby improving detection efficiency.

[0018] Superior detection performance and consistency: The superconducting nanowires fabricated based on flat interfaces have highly uniform geometry and superconducting properties, ensuring stable coupling efficiency with the waveguide evanescent field, thus directly contributing to higher and more consistent system detection efficiency, lower dark count, and smaller time jitter.

[0019] Excellent long-term stability and reliability: The planar optical waveguide, made of all inorganic materials (such as silicon dioxide), has extremely high thermal stability and mechanical strength. Its performance far exceeds that of organic polymer waveguides, which can ensure the long-term stable operation of the detector in the harsh low-temperature superconducting environment.

[0020] Strong scalability and industrialization prospects: The "laser direct writing-polishing-planar process" technology route adopted in this invention is highly compatible with mature semiconductor manufacturing processes, providing a solid technical foundation for building multi-channel, large-scale single-photon detection arrays, which is difficult to achieve with non-planar integration solutions. Attached Figure Description

[0021] Figure 1 A flowchart illustrating a method for fabricating an integrated fiber optic single-photon detector, as provided in this application embodiment; Figure 2 A schematic diagram illustrating the fabrication process of an optical fiber integrated single-photon detector provided in an embodiment of this application; Figure 3 A front view of a single-photon detector provided in an embodiment of this application; Figure 4 A top view of a single-photon detector provided in an embodiment of this application; Figure 5 A front view of another single-photon detector provided in an embodiment of this application; Figure 6 A top view of another single-photon detector provided in an embodiment of this application.

[0022] Wherein, 100-first substrate; 100'-second substrate; 200-first waveguide core; 101-Fiber cladding; 102-Fiber core; 103-Second waveguide core; 104-Superconducting nanowire; 105-Electrode; 106-Gold wire lead; 107-Metal plate; 108-Fiber clamp; 109-Substrate. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of this application.

[0024] In waveguide integration solutions in related technologies, additively manufactured polymer waveguides are commonly used. The main manufacturing process involves first creating a three-dimensional waveguide structure. To optimize optical performance, the upper surface of this waveguide structure is typically irregular, such as a curved or arc-shaped surface (e.g., a gradient cone). In contrast, the fabrication of superconducting nanowires employs standard planar micro / nano fabrication processes, which require a perfectly flat substrate. However, while theoretically feasible, existing methods are virtually impossible to reliably achieve in actual manufacturing. Even if the fabricated surface is close to planar, superconducting nanowires still suffer from stress, fracture risk, and performance inhomogeneity due to substrate unevenness, leading to low detector efficiency.

[0025] To address the aforementioned issues, this application provides a method for fabricating an optical fiber integrated single-photon detector based on a planar optical waveguide structure. This transforms the integration interface between the waveguide and the superconducting nanowire from an uncontrollable, irregular curved surface into a stable and controllable plane, thereby achieving perfect compatibility with nanowire photolithography.

[0026] See Figure 1 The flowchart below illustrates a method for fabricating an integrated fiber optic single-photon detector according to an embodiment of this application; see also... Figure 2 This is a schematic diagram illustrating the fabrication process of an optical fiber integrated single-photon detector provided in an embodiment of this application.

[0027] like Figure 1 and Figure 2 As shown in the embodiment of this application, a method for fabricating an optical fiber integrated single-photon detector includes: S100: A first waveguide core 200 is formed inside a first substrate 100 using femtosecond laser direct writing technology; the first waveguide core 200 extends along a first direction parallel to the upper surface of the first substrate 100; the first substrate 100 has a first thickness.

[0028] For details, see Figure 2 In embodiment (a) of this application, a substrate is first selected as the lower cladding of the optical waveguide and the mechanical support platform for the entire device. The substrate can be made of silicon dioxide.

[0029] In some embodiments, in order to ensure the accuracy of subsequent processing, the surface of the silicon dioxide substrate (substrate to be processed) can be polished before selecting the first substrate 100 to obtain the first substrate 100 with a polished surface, which makes it easier to control the size (e.g., thickness) of the first substrate 100.

[0030] After selecting the first substrate 100, see [link / reference] Figure 2 In section (b), a femtosecond laser direct writing system can be used to process the first substrate 100 to form a waveguide core with a higher refractive index along the scanning path. For details, see [link to documentation]. Figure 2 In section (c), a first waveguide core 200 extending along a first direction parallel to the upper surface of the first substrate 100 is formed inside the first substrate 100. Femtosecond laser direct writing technology features high precision and high resolution, enabling precise control of the position, shape, and size of the first waveguide core 200, thereby ensuring its performance. Furthermore, by adjusting the parameters of the femtosecond laser, such as power, pulse width, and repetition frequency, the refractive index distribution of the first waveguide core 200 can be flexibly adjusted to meet different optical performance requirements.

[0031] In some embodiments, a cylindrical first waveguide core 200 can be formed in the first substrate 100 by controlling the femtosecond laser parameters, and the top surface of the first waveguide core 200 can be made as close as possible to the upper surface of the first substrate 100 (or in contact with the upper surface), so as to reduce the amount of subsequent polishing.

[0032] After the femtosecond laser direct writing process is completed, an embedded optical waveguide is formed inside the first substrate 100. This is the initial strongly confined optical waveguide, which needs to be further executed in step S200.

[0033] S200: Polish the upper surface of the first substrate 100 to obtain a second substrate 100' containing a second waveguide core 103; the second substrate 100' has a second thickness; the second thickness is less than the first thickness; the second waveguide core 103 is a part of the first waveguide core 200; the second waveguide core 103 has a first surface after polishing.

[0034] For details, see Figure 2 In step (d), the first substrate 100, which has undergone femtosecond laser direct writing, and the waveguide core therein, need to be precision polished as a whole. The polishing process can be precisely controlled to remove part of the substrate material (upper cladding) above the waveguide and cut into the waveguide core itself. When polishing reaches the polishing cutoff line, its cross-section changes from circular to D-shaped. During this process, the top surface area of ​​the waveguide core is continuously expanded.

[0035] See Figure 2In step (e), after the polishing process is completed, a polished surface is formed, and the original embedded waveguide is thinned, transforming it into a weakly confined planar optical waveguide. This structure greatly enhances the leakage of the optical mode field to the outside of the waveguide, generating a strong evanescent field. Step S300 will then be executed.

[0036] S300: Superconducting nanowires 104 are prepared on the first surface.

[0037] See Figure 2 In step (f), superconducting nanowires 104 can be fabricated on the exposed first surface of the second waveguide core 103 along its direction. The superconducting nanowires can be fabricated using planar micro / nano technology, which allows for precise control of key parameters such as the width, thickness, and length of the superconducting nanowires, ensuring high uniformity and high yield. During fabrication, optimizing process conditions, such as deposition temperature, deposition rate, and annealing, can further improve the performance of the superconducting nanowires, such as reducing resistance and increasing critical current.

[0038] In some embodiments, superconducting nanowires can be fabricated using lift-off micro / nano fabrication techniques. Specifically, a superconducting material film can be deposited on the first surface of the second waveguide core 103. The material of this film can be selected according to actual needs, such as niobium-titanium alloys or other materials with good superconducting properties. The deposition process must be carried out in a vacuum environment to ensure the purity and uniformity of the film. By precisely controlling the deposition rate and time, a superconducting material film with uniform thickness is obtained. Subsequently, a photoresist layer is coated on the superconducting material film. The photoresist coating should be uniform and of moderate thickness to ensure the accurate transfer of subsequent photolithography patterns. Next, the designed superconducting nanowire pattern is transferred onto the photoresist using photolithography. Through exposure and development steps, the photoresist forms a hollow structure corresponding to the superconducting nanowire pattern. Afterward, an etching process is used to etch the superconducting material film not protected by the photoresist, removing unwanted parts and leaving the superconducting nanowire structure consistent with the photoresist pattern. After etching, the photoresist is removed through a photoresist removal process to obtain the final superconducting nanowires with high uniformity and high yield.

[0039] In some embodiments, the superconducting nanowires fabricated by micro-nano processes include, but are not limited to, the use of one of niobium nitride (NbN), niobium titanium nitride (NbTiN), tungsten silicide (WSi), and molybdenum silicide (MoSi).

[0040] S400: The second substrate 100' containing the superconducting nanowire 104 is mounted on the detector integration platform so that both ends of the second waveguide core 103 are respectively connected to the optical fiber core 102 (including the first optical fiber and the second optical fiber) on the detector integration platform, and the superconducting nanowire is electrically connected to the metal electrode plate 107 on the detector integration platform through leads.

[0041] See Figure 2 In step (g), after obtaining the second substrate 100' containing the superconducting nanowire 104 through step S300, it can be placed on the detector integration platform, and the two ends of the superconducting nanowire 104 are aligned with the fiber cores 102 on both sides to form an optical path. Then, the electrodes connected to the superconducting nanowire 104 are connected to the metal electrode plate 107 through gold wires to form an electrical path. The metal electrode plate 107 can be connected to an external readout circuit to obtain the detection result of a single photon.

[0042] As can be seen from the above technical solution, the working principle of the single-photon detector prepared by the preparation method provided in this application embodiment is as follows: This application utilizes polishing to create a flat surface on the waveguide core. The evanescent field generated by polishing enhances the planar waveguide, thereby achieving efficient single-photon detection. The single-photon optical signal is transmitted to the planar waveguide via a quartz optical fiber, where efficient input optical coupling is achieved due to the uniformity of the materials. As the single-photon signal propagates within the planar waveguide, a strongly leaking evanescent field is generated in the polished waveguide region. This evanescent field further contacts the superconducting nanowires directly fabricated on the waveguide surface. Since the single photon disrupts the superconducting state of the nanowires, the single photon is detected by the corresponding electrical signal generated by the detection electrodes.

[0043] In the embodiments of this application, the superconducting nanowires prepared based on flat interfaces have highly uniform geometry and superconducting properties, ensuring stable coupling efficiency with the waveguide evanescent field, thereby directly contributing to higher and more consistent system detection efficiency, lower dark count, and smaller time jitter.

[0044] In some embodiments, when a first waveguide core 200 is formed inside a first substrate 100 using femtosecond laser direct writing technology, multiple first waveguide cores 200 can be formed inside the first substrate 100. The multiple first waveguide cores 200 are spaced apart along a second direction, which is parallel to the upper surface of the first substrate and perpendicular to the first direction. Correspondingly, after the polishing process is completed, multiple second waveguide cores 103 are formed. Corresponding superconducting nanowires are fabricated on each second waveguide core 103 to obtain independent waveguide structures. Each waveguide structure can then have independent input and output ports to achieve independent input of multiple optical signals and independent output of electrical signals.

[0045] In some embodiments, when multiple second waveguide cores are provided, step S400 specifically includes: S410: Connect both ends of each second waveguide core obtained from the first waveguide core to the corresponding first optical fiber and second optical fiber respectively to form an optical path; S420: Connect the two ends of the superconducting nanowire corresponding to each second waveguide core to the corresponding metal electrode to form an electrical path.

[0046] As can be seen from the above technical solutions, the preparation method provided in this application forms an optical waveguide with a flat upper surface through a precision polishing process. This flat interface enables the superconducting nanowires to be prepared using a fully standard planar micro-nano process (such as lift-off), fundamentally solving the inherent problems of poor uniformity, low yield, and insufficient reliability when integrating nanowires on non-planar waveguides.

[0047] Meanwhile, the single-photon detector prepared using the method provided in this application exhibits excellent long-term stability and reliability. The planar optical waveguide constructed from all-inorganic materials (such as silicon dioxide) possesses extremely high thermal stability and mechanical strength, with performance far exceeding that of organic polymer waveguides, ensuring long-term stable operation of the detector in harsh low-temperature superconducting environments.

[0048] See Figure 3 This is a front view of the single-photon detector provided in an embodiment of this application; see also... Figure 4 This is a top view of the single-photon detector provided in the embodiments of this application.

[0049] like Figure 3 and Figure 4 As shown, this application also provides a single-photon detector fabricated using the fabrication method of any of the foregoing embodiments, comprising: Detector integration platform; fiber optic cladding 101 is clamped on both sides of the detector integration platform by fiber optic clamps 108, and fiber optic cores 102 are arranged inside the fiber optic cladding 101 (e.g., Figure 3 An optical fiber core 102 is provided on each side (left and right), and the optical fiber cores 102 on both sides are located in a straight line. It should be noted that, in the embodiments of this application, optical fiber can refer to an optical fiber core or an optical fiber core with an optical fiber cladding.

[0050] A second substrate 100' is provided at the middle position of the detector integration platform, and the bottom of the second substrate 100' is fixed on the substrate 109 of the detector integration platform; a second waveguide core 103 is provided inside the second substrate 100'; the second waveguide core 103 extends along a first direction parallel to the upper surface of the second substrate 100'; the first top surface of the second substrate 100' and the second top surface of the second waveguide core 103 are coplanar, and the first top surface and the second top surface are flat surfaces after polishing; a superconducting nanowire 104 is attached to the second top surface.

[0051] The two ends of the second waveguide core 103 are respectively connected to two optical fiber cores 102; the two ends of the superconducting nanowire 104 are connected to electrodes 105, and the electrodes 105 are connected to the metal electrode plate 107 set on the detector integration platform through gold wire leads 106.

[0052] In some embodiments, the superconducting nanowire 104 is made of, but is not limited to, one of niobium nitride (NbN), niobium titanium nitride (NbTiN), tungsten silicide (WSi), and molybdenum silicide (MoSi), all of which possess excellent superconducting properties and can meet the requirements of single-photon detection. In practical applications, a suitable superconducting material can be selected according to specific needs to further optimize the detector's performance. For example, niobium nitride (NbN) has a high critical temperature and critical current density, making it suitable for high-temperature superconducting environments; while niobium titanium nitride (NbTiN) has low resistance and high sensitivity, which helps improve the detector's detection efficiency. Tungsten silicide (WSi) and molybdenum silicide (MoSi) also have excellent superconducting properties and can maintain a stable superconducting state at low temperatures, providing reliable assurance for single-photon detection. By selecting a suitable superconducting material, the fabricated single-photon detector can achieve superior performance and meet the needs of different application scenarios.

[0053] In some embodiments, electrode 105 can be made of gold. Gold electrodes possess excellent conductivity and chemical stability, maintaining stable performance even at low temperatures. This allows for the effective transmission of weak electrical signals generated by single-photon detection in superconducting nanowires, reducing signal loss and interference during transmission. Furthermore, the gold electrode forms a good ohmic contact with the superconducting nanowires and gold wire leads, reducing contact resistance and further improving the efficiency and quality of electrical signal transmission.

[0054] In some embodiments, the superconducting nanowire 104 can be one of the following shapes: spiral nanowire, helical nanowire, or fractal nanowire. These different shapes can be optimized according to actual detection requirements. For example, spiral nanowires have a relatively simple structure, making high-precision control easier in fabrication processes. They can also ensure the overall uniformity of the superconducting nanowire to a certain extent, which is beneficial for stable detection of single-photon signals. Helical nanowires, through their unique helical structure, increase the contact path and contact area with the evanescent field, which can improve the detection sensitivity of single photons to a certain extent. Fractal nanowires, with their complex fractal structure, have a larger surface area and can interact more fully with the evanescent field, further enhancing the detector's ability to capture single photons and its detection efficiency. In practical applications, the appropriate shape of the superconducting nanowire can be flexibly selected based on different detection scenarios and specific requirements for detection performance to optimize the performance of the single-photon detector.

[0055] In some embodiments, the second waveguide core 103 can be made of silicon dioxide, which has extremely low optical loss, ensuring minimal attenuation of the optical signal during long-distance transmission. In practical applications, a suitable waveguide core material can be selected based on specific requirements such as detection wavelength, detection sensitivity, and integration level to achieve optimal performance of the single-photon detector.

[0056] See Figure 5 This is a front view of another single-photon detector provided in an embodiment of this application; see also Figure 6 This is a top view of another single-photon detector provided in an embodiment of this application.

[0057] like Figure 5 and Figure 6 As shown, in some embodiments, a discretely arranged multi-channel planar optical waveguide single-photon detector can be fabricated, wherein multiple second waveguide cores 103 can be fabricated inside the second substrate 100', the multiple second waveguide cores 103 are spaced apart, each second waveguide core 103 is connected to a set of optical fiber cores 102, and the superconducting nanowires 104 fabricated on each second waveguide core 103 are respectively connected to metal plates 107 through corresponding electrodes 105.

[0058] In this embodiment, multiple independent detection units are formed, which can realize independent input of multiple optical signals and independent acquisition of electrical signals.

[0059] Each detection unit can be connected to an external readout circuit via independent electrode leads to support independent operation and signal processing of each detection unit.

[0060] As can be seen from the above technical solutions, the "laser direct writing-polishing-planar process" technical route used in the single-photon detector prepared by the preparation method provided in this application embodiment is highly compatible with mature semiconductor manufacturing processes, providing a solid technical foundation for building multi-channel, large-scale single-photon detector arrays.

[0061] The above detailed embodiments further illustrate the purpose, technical solution, and beneficial effects of the embodiments of this application. It should be understood that the above are merely specific embodiments of the embodiments of this application and are not intended to limit the protection scope of the embodiments of this application. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solutions of the embodiments of this application should be included within the protection scope of the embodiments of this application.

Claims

1. A method of fabricating a fiber-integrated single-photon detector, comprising: The method comprises: forming a first waveguide core inside a first substrate by femtosecond laser direct writing technology; the first waveguide core extends along a first direction parallel to the upper surface of the first substrate; the first substrate has a first thickness; polishing the upper surface of the first substrate to obtain a second substrate containing a second waveguide core; the second substrate has a second thickness; the second thickness is less than the first thickness; the second waveguide core is part of the first waveguide core; the second waveguide core has a first surface after polishing; preparing a superconducting nanowire on the first surface; mounting the second substrate containing the superconducting nanowire on a detector integration platform, so that the two ends of the second waveguide core are respectively connected with a first optical fiber and a second optical fiber on the detector integration platform, and the superconducting nanowire is electrically connected with a metal plate on the detector integration platform through a lead.

2. The method of claim 1, wherein the method further comprises: The method for preparing a superconducting nanowire detector on the first surface comprises: preparing a superconducting nanowire on the first surface by plane micro-nano process.

3. The method of claim 1, wherein the method further comprises: The second waveguide core after polishing is in a bare state, so that the light field leaked from the second waveguide core is coupled with the superconducting nanowire.

4. The method of claim 1, wherein the method further comprises: The method for forming a first waveguide core inside a first substrate by femtosecond laser direct writing technology comprises: forming a plurality of first waveguide cores inside the first substrate by femtosecond laser direct writing technology; the plurality of first waveguide cores are arranged at intervals along a second direction, the second direction is parallel to the upper surface of the first substrate, and the second direction is perpendicular to the first direction.

5. The method of claim 4, wherein the method further comprises: The method for mounting the second substrate containing the superconducting nanowire on a detector integration platform comprises: connecting the two ends of each second waveguide core obtained from the first waveguide core with a corresponding first optical fiber and a second optical fiber respectively to form an optical path; connecting the two ends of each superconducting nanowire corresponding to the second waveguide core with a corresponding metal plate respectively to form an electrical path.

6. The method of claim 1, wherein the method further comprises: Before forming a first waveguide core inside a first substrate by femtosecond laser direct writing technology, the method further comprises: polishing the upper surface of a to-be-processed substrate to obtain the first substrate.

7. A single photon detector prepared by the method of any one of claims 1 to 6, characterized in that, It comprises: a detector integration platform; a first optical fiber and a second optical fiber are oppositely arranged on the detector integration platform; the extension directions of the first optical fiber and the second optical fiber are on the same straight line; a second substrate is arranged on the detector integration platform; the second substrate is internally provided with a second waveguide core; the second waveguide core extends along a first direction parallel to the upper surface of the second substrate; the first top surface of the second substrate and the second top surface of the second waveguide core are coplanar, and the first top surface and the second top surface are planes after polishing; a superconducting nanowire is attached to the second top surface; the two ends of the second waveguide core are respectively connected with the first optical fiber and the second optical fiber; the two ends of the superconducting nanowire are respectively connected with metal plates arranged on the detector integration platform.

8. The single photon detector of claim 7, wherein, The superconducting nanowire is one of a meander nanowire, a spiral nanowire, and a fractal nanowire.

9. The single photon detector of claim 7, wherein, The material of the second waveguide core is silicon dioxide.

10. The single photon detector of claim 7, wherein, The second substrate is internally provided with a plurality of second waveguide cores, and the plurality of second waveguide cores are arranged at intervals along a second direction, wherein the second direction is perpendicular to the first direction.

Images