An integrated superconducting single-photon detector based on additive manufacturing and a method of manufacturing the same

Abstract

This invention discloses an integrated superconducting single-photon detector based on additive manufacturing and its fabrication method. This integrated superconducting single-photon detector includes a substrate, a transmission optical fiber, an integration platform, and a superconducting nanowire detector. The transmission optical fiber includes a silica optical fiber and a polymer waveguide, with the silica optical fiber located at both ends on the substrate and connected via the polymer waveguide. The superconducting nanowire detector is located on and tightly bonded to the polymer waveguide, and includes a superconducting nanowire and two sets of electrodes positioned at both ends of the superconducting nanowire. The integration platform is located on the substrate and has two sets of electrodes, which can fix the silica optical fiber and connect to external readout circuitry. This invention not only achieves efficient mode switching between fiber and polymer waveguide but also enables efficient single-photon detection between the polymer waveguide and the superconducting nanowire, improving detection efficiency while reducing optical coupling loss.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection technology, and in particular to an integrated superconducting single-photon detector based on additive manufacturing and its fabrication method. Background Technology

[0002] The continuous development of quantum technology has advanced research in various fields such as quantum communication and quantum optics. Among them, the superconducting nanowire single-photon detector (SNSPD) has achieved highly efficient single-photon detection. The working principle of the SNSPD is as follows: when the SNSPD is placed at a temperature below its superconducting critical temperature, when a photon comes into contact with the nanowire, the energy of the photon breaks the superconducting Cooper pairs within the nanowire, thereby disrupting its superconducting state. The detection of a single photon is then achieved by analyzing the electrical signal output by the detector at the test end.

[0003] Efficiently coupling single photons to a single-photon light-sensitive photodiode (SNSPD) is crucial for accurate detection. Current technologies commonly use spatial optical coupling; however, excessive divergence angles reduce coupling efficiency. With the continuous development of integrated micro / nano fabrication, single-photon detection can also be achieved by contacting the evanescent field of the optical waveguide surface with the SNSPD. While waveguide coupling allows for the integration of the entire detection component, significant coupling losses often occur during the coupling of the light source into the integrated waveguide. Therefore, researchers have proposed an SNSPD device based on micro / nano fibers (e.g., DOI: 10.1364 / OE.25.031221). This approach leverages the large evanescent field of micro / nano fibers to ensure sufficient contact between the SNSPD photosensitive surface and the light source, which propagates continuously within the fiber, thus reducing coupling losses. However, this approach suffers from significant instability due to the susceptibility of micro / nano fibers to damage.

[0004] Patent CN113204075A discloses a micro / nano fiber-waveguide-superconducting nanowire single-photon detector and its fabrication method. The micro / nano fiber fixed in a V-groove can achieve high-precision optical coupling alignment with the waveguide, and the transition section from thick to thin in the micro / nano fiber is suspended to prevent light leakage to the substrate, thereby reducing light transmission losses. The waveguide-type superconducting nanowire structure can achieve complete light absorption on-chip. The bend-angle waveguide design completely separates the optical coupling region of the micro / nano fiber-waveguide from the photodetection region of the waveguide-type superconducting nanowire structure, effectively reducing dark counts caused by background radiation propagating along the fiber and minimizing the impact of dark counts on photodetection. However, this invention does not specifically address how to reduce optical coupling losses within the integrated optical waveguide or how to achieve efficient single-photon detection.

[0005] Currently, how to achieve SNSPD devices with low coupling loss and high detection efficiency is a key technical issue that needs to be addressed by those skilled in the art. Summary of the Invention

[0006] Based on the above ideas, this application provides an all-fiber superconducting single-photon detector and its fabrication method. By fabricating a polymer optical waveguide, the integration of optical fiber, polymer optical waveguide, and superconducting nanowire is achieved, solving the problem of high optical coupling loss in existing single-photon detectors.

[0007] On one hand, this invention provides an integrated superconducting single-photon detector based on additive manufacturing. The integrated superconducting single-photon detector includes a substrate, a transmission optical fiber, an integration platform, and a superconducting nanowire detector, wherein:

[0008] The transmission optical fiber includes a quartz optical fiber and a polymer optical waveguide. There are two sets of quartz optical fibers, located at both ends of the substrate, and the two sets of quartz optical fibers are connected by a polymer waveguide.

[0009] The superconducting nanowire detector is located on the polymer optical waveguide and is closely attached to the polymer optical waveguide. The superconducting nanowire detector includes a superconducting nanowire and two sets of electrodes, which are disposed at both ends of the superconducting nanowire.

[0010] The integrated platform is located on the substrate, and the integrated platform has two sets, which can fix the quartz optical fiber and connect the external readout circuit.

[0011] The working principle of the integrated superconducting single-photon detector provided by this invention is as follows:

[0012] A single-photon optical signal is transmitted via a silica optical fiber to a polymer optical waveguide, where efficient input optical coupling is achieved through mode switching. The single-photon signal propagates within the polymer optical waveguide. As the waveguide narrows, an evanescent field appears on its surface and further contacts the superconducting nanowire. Since the single photon disrupts the superconducting state of the nanowire, the optical signal is input to the superconducting nanowire detector. The single photon is then detected by the corresponding electrical signal generated by the detection electrodes.

[0013] Furthermore, the integrated platform includes an optical fiber clamp, a metal electrode plate, and gold wire leads. The optical fiber clamp is located outside the quartz optical fiber to tightly embed the quartz optical fiber in the optical fiber clamp. One end of the metal substrate is connected to an external readout circuit, and the other end is bonded to the electrode through the gold wire leads.

[0014] Furthermore, the quartz optical fiber includes an optical fiber cladding and an optical fiber core, the optical fiber cladding covering the outside of the optical fiber core, and the optical fiber core being connected to the polymer optical waveguide.

[0015] Furthermore, the polymer optical waveguide is made of one of epoxy resin, acrylate resin, or organic modified silicate. The polymer optical waveguide achieves mode conversion of single-photon optical signals within the quartz fiber by fabricating shapes such as semi-transparent lenses, and generates a large evanescent field by fabricating shapes such as graded cone regions.

[0016] Furthermore, the structure of the superconducting nanowire is one of the following: spiral nanowire, helical nanowire, fractal nanowire, hairpin type, or micron type.

[0017] Furthermore, the superconducting nanowires are made of one of the following materials: niobium nitride (NbN), niobium titanium nitride (NbTiN), tungsten silicide (WSi), molybdenum silicide (MoSi), magnesium boride (MgB2), iron-based superconducting materials, or cuprates.

[0018] On the other hand, the present invention also provides a method for fabricating an integrated superconducting single-photon detector based on additive manufacturing, which is used to fabricate the above-mentioned single-photon detector, comprising the following steps:

[0019] An integration platform is fabricated on a substrate, and two quartz optical fibers that have undergone end face cutting are fixed by optical fiber clamps in the integration platform.

[0020] A polymer is spin-coated onto a substrate between two sets of optical fiber clamps, and the polymer is exposed, developed, fixed, and baked to form a polymer optical waveguide.

[0021] Fabrication of superconducting nanowire detectors on polymer optical waveguides;

[0022] The electrodes in the superconducting nanowire detector are legally connected to the metal plates in the integrated platform via gold wire bonding.

[0023] Furthermore, the exposure method for exposing the polymer is one of femtosecond laser direct writing, two-photon polymerization, deep ultraviolet exposure, or electron beam exposure.

[0024] Furthermore, the method for fabricating a superconducting nanowire detector on a polymer optical waveguide involves directly integrating the superconducting nanowire detector onto the polymer optical waveguide using microfabrication techniques.

[0025] Furthermore, the microfabrication process is one of the following: lift-off integration process, micromechanical probe arm integration process, or nanofilm integration process.

[0026] Compared with the prior art, the beneficial effects of the present invention include:

[0027] This invention provides an integrated superconducting single-photon detector based on additive manufacturing, which integrates fiber, polymer waveguide, and superconducting nanowire by fabricating a polymer waveguide. Polymer waveguides have high optical coupling coefficients, low dielectric constants, low thermal losses, and are easy to integrate, thus effectively reducing optical coupling loss during single-photon detection. Furthermore, since the polymer waveguide is based on additive manufacturing, arbitrary structures can be fabricated. Therefore, this invention not only achieves efficient mode switching between fiber and polymer waveguide but also efficient single-photon detection using polymer waveguide-superconducting nanowires, improving detection efficiency while reducing optical coupling loss present in previous methods. Attached Figure Description

[0028] The following is a brief explanation of the content depicted in the accompanying drawings:

[0029] Figure 1 This is a front view of an integrated superconducting single-photon detector based on additive manufacturing provided in Embodiment 1 of the present invention;

[0030] Figure 2 This is a top view of an integrated superconducting single-photon detector based on additive manufacturing, provided in Embodiment 1 of the present invention.

[0031] Figure 3 This is a flowchart of a method for fabricating an integrated superconducting single-photon detector based on additive manufacturing, as provided in Embodiment 2 of the present invention.

[0032] In the picture:

[0033] 101 - Includes fiber cladding, 102 - Fiber core, 103 - Polymer waveguide, 104 - Superconducting nanowire, 105 - Electrode, 106 - Gold wire lead, 107 - Metal electrode plate, 108 - Fiber clamp, 109 - Substrate. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] To reduce the optical coupling loss in existing single-photon detection technologies, this invention provides a fiber-polymer waveguide-superconducting nanowire single-photon detector, comprising a substrate 109, a transmission fiber, an integrated platform, and a superconducting nanowire detector, wherein:

[0036] The transmission optical fiber includes a quartz optical fiber and a polymer optical waveguide 103. There are two sets of quartz optical fibers, which are located at both ends of the substrate, and the two sets of quartz optical fibers are connected by the polymer optical waveguide 103.

[0037] The superconducting nanowire detector is located on the polymer optical waveguide 103 and is closely attached to the polymer optical waveguide 103. The superconducting nanowire detector includes a superconducting nanowire 104 and two sets of electrodes 105, which are disposed at both ends of the superconducting nanowire 104.

[0038] The integrated platform is located on the substrate 109. The integrated platform has two sets, which can fix the quartz optical fiber and connect the external readout circuit.

[0039] Furthermore, the integrated platform includes an optical fiber clamp 108, a metal electrode plate 107, and a gold wire lead 106. The optical fiber clamp 108 is located outside the quartz optical fiber so that the quartz optical fiber is tightly embedded in the optical fiber clamp. One end of the metal substrate 107 is connected to an external readout circuit, and the other end is bonded to the electrode 105 through the gold wire lead 106.

[0040] Furthermore, the quartz optical fiber includes an optical fiber cladding 101 and an optical fiber core 102. The optical fiber cladding 101 covers the outside of the optical fiber core 102, and the optical fiber core 102 is connected to the polymer optical waveguide 103.

[0041] When the single-photon detector is in operation, the single-photon optical signal is transmitted through a silica optical fiber to a polymer optical waveguide. The polymer optical waveguide achieves efficient input optical coupling through mode switching. The single-photon signal propagates within the polymer optical waveguide. As the polymer optical waveguide narrows, an evanescent field appears on its surface and further contacts the superconducting nanowire. Because the single photon disrupts the superconducting state of the superconducting nanowire, the optical signal is input to the superconducting nanowire detector, and the single photon is detected by the corresponding electrical signal generated by the detection electrodes.

[0042] The process of the above preparation method will be specifically described below with reference to specific embodiments.

[0043] Example 1

[0044] This embodiment provides a structure for an integrated superconducting single-photon detector based on additive manufacturing, such as... Figure 1 Front view and Figure 2 As shown in the top view, the single-photon detector includes an optical fiber cladding 101, an optical fiber core 102, a polymer optical waveguide 103, a superconducting nanowire 104, an electrode 105, a gold wire lead 106, a metal electrode plate 107, an optical fiber clamp 108, and a substrate 109.

[0045] Two sets of optical fiber cladding 101, optical fiber core 102, electrode 105, gold wire lead 106, metal electrode plate 107 and optical fiber clamp 108 are respectively installed on the substrate 109 at the bottom.

[0046] Fiber optic clamps 108 and metal electrodes 107 are mounted at both ends above the substrate 109. The quartz fiber cladding 101, which encloses the quartz fiber core 102, is fixed by the fiber optic clamps 108. The two sets of quartz fibers are connected by a polymer optical waveguide 103. The quartz fiber core 102 is of type SMF-28, and the polymer optical waveguide 103 is made of epoxy resin SU-8.

[0047] The connection between the converging waveguide 103 and the optical fiber core 102 is designed as a semi-transparent lens to increase the mode conversion efficiency.

[0048] The superconducting nanowire 104 and two sets of electrodes 105 are located above and in close contact with the polymer optical waveguide 103. The two sets of electrodes 105 are located at both ends of the superconducting nanowire 104. The superconducting nanowire 104 is made of niobium nitride and uses a loop-shaped superconducting wire structure; the electrodes 105 are made of gold.

[0049] The coupling region between the polymer waveguide 103 and the superconducting nanowire 104 is designed as a tapered shape to increase the evanescent field intensity of the optical signal.

[0050] A metal substrate 107 is disposed on a substrate, with one end connected to an external readout circuit and the other end bonded to an electrode 105 via a gold wire lead 106.

[0051] Example 2

[0052] This embodiment provides a method for fabricating an integrated superconducting single-photon detector based on additive manufacturing, the process of which is as follows: Figure 3 As shown, the specific steps include the following:

[0053] Step 201: Fabricate an integration platform on the substrate, and fix two quartz optical fibers that have undergone end face cutting through the optical fiber clamps in the integration platform. The quartz optical fibers are of type SMF-28.

[0054] Step 202: Spray a polymer onto the substrate between the two sets of fiber clamps, so that it is evenly distributed between the two quartz optical fibers. The polymer material is epoxy resin SU-8.

[0055] Step 203: Expose the polymer on the integrated platform according to the designed polymer optical waveguide structure. The exposure process uses a two-photon polymerization instrument.

[0056] Step 204: The polymer optical waveguide is formed on the integration platform through processes such as developing, fixing, and baking.

[0057] Step 205: Fabricate a superconducting nanowire detector on a polymer optical waveguide using microfabrication technology.

[0058] Step 206: Connect the electrodes to the metal plates on the superconducting nanowire detector using gold wire bonding technology.

[0059] In the embodiments of this invention, the connection between the polymer optical waveguide and the optical fiber core is designed as a semi-transparent lens to increase the mode conversion efficiency. In other embodiments, the shapes of other polymer optical waveguides based on the solutions provided by this invention are also applicable to this application.

[0060] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An integrated superconducting single-photon detector based on additive manufacturing, characterized in that, The integrated superconducting single-photon detector includes a substrate, a transmission optical fiber, an integration platform, and a superconducting nanowire detector, wherein... The transmission optical fiber includes a quartz optical fiber and a polymer optical waveguide. There are two sets of quartz optical fibers, located at both ends of the substrate, and the two sets of quartz optical fibers are connected by the polymer optical waveguide. The superconducting nanowire detector is located on the polymer optical waveguide and is closely attached to the polymer optical waveguide. The superconducting nanowire detector includes a superconducting nanowire and two sets of electrodes, which are disposed at both ends of the superconducting nanowire. The integrated platform is located on the substrate, and the integrated platform is provided in two sets for fixing the quartz optical fiber and connecting the external readout circuit. The integrated platform includes an optical fiber clamp, a metal electrode plate, and gold wire leads. The optical fiber clamp is located outside the quartz optical fiber to tightly embed the quartz optical fiber in the optical fiber clamp. One end of the metal electrode plate is connected to an external readout circuit, and the other end is bonded to the electrode through the gold wire leads.

2. The integrated superconducting single-photon detector based on additive manufacturing according to claim 1, characterized in that, The quartz optical fiber includes an optical fiber cladding and an optical fiber core. The optical fiber cladding covers the outside of the optical fiber core, and the optical fiber core is connected to the polymer optical waveguide.

3. The integrated superconducting single-photon detector based on additive manufacturing according to claim 1, characterized in that, The polymer optical waveguide is made of one of epoxy resin, acrylate resin, or organic modified silicate.

4. The integrated superconducting single-photon detector based on additive manufacturing according to claim 1, characterized in that, The structure of the superconducting nanowire is one of the following: spiral nanowire, fractal nanowire, hairpin type, or micron type.

5. An integrated superconducting single-photon detector based on additive manufacturing according to claim 1, characterized in that, The superconducting nanowires are made of one of the following materials: niobium nitride, titanium niobium nitride, tungsten silicide, molybdenum silicide, magnesium boride, iron-based superconducting materials, or cuprates.

6. A method for fabricating an integrated superconducting single-photon detector based on additive manufacturing, used to fabricate the integrated superconducting single-photon detector based on additive manufacturing as described in any one of claims 1 to 5, characterized in that, Includes the following steps: An integration platform is fabricated on a substrate, and two quartz optical fibers that have undergone end face cutting are fixed by optical fiber clamps in the integration platform. A polymer is spin-coated onto a substrate between two sets of optical fiber clamps, and the polymer is exposed, developed, fixed, and baked to form a polymer optical waveguide. Fabrication of superconducting nanowire detectors on polymer optical waveguides; The electrodes in the superconducting nanowire detector are legally connected to the metal plates in the integrated platform via gold wire bonding.

7. The method for fabricating an integrated superconducting single-photon detector based on additive manufacturing according to claim 6, characterized in that, The exposure method for exposing the polymer is one of femtosecond laser direct writing, two-photon polymerization, deep ultraviolet exposure, or electron beam exposure.

8. The method for fabricating an integrated superconducting single-photon detector based on additive manufacturing according to claim 6, characterized in that, The method for fabricating superconducting nanowire detectors on polymer optical waveguides involves directly integrating the superconducting nanowire detectors onto the polymer optical waveguides using microfabrication processes.

9. The method for fabricating an integrated superconducting single-photon detector based on additive manufacturing according to claim 8, characterized in that, The microfabrication process is one of the following: peel-and-strip integration process, micromechanical probe arm integration process, or nanofilm integration process.

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