Waveguide integrated superconducting single photon detector, preparation method and testing device

Abstract

The disclosure provides a waveguide integrated superconducting single photon detector, which can be applied to the technical field of photoelectric detection, and the detector comprises a substrate, a lower cladding layer, a mode spot converter, a waveguide detector and an upper cladding layer; the lower cladding layer is located on the upper surface of the substrate; the mode spot converter and the waveguide detector are located between the lower cladding layer and the upper cladding layer; the mode spot converter comprises two symmetric narrow-end staggered taper mode spot converters; the waveguide detector comprises a waveguide core layer, a photon absorption layer and an electrode layer; the photon absorption layer is located on the upper surface of the waveguide core layer and is connected with the electrode layer; and the wide end of one of the taper mode spot converters is connected with the waveguide core layer. The detector provided by the disclosure has the advantages of realizing polarization independence and anti-stray light interference. The disclosure further provides a waveguide integrated superconducting single photon detector preparation method and a test device.

Description

A waveguide-integrated superconducting single-photon detector, its fabrication method, and testing device. Technical Field

[0001] This disclosure relates to the field of photoelectric detection technology, and more specifically, to a waveguide-integrated superconducting single-photon detector, its fabrication method, and testing device. Background Technology

[0002] Waveguide-integrated single-photon detectors (SPDs) are widely used in quantum computing, lidar, optical sensing, and optical communication due to their significant advantages such as miniaturization, high integration, good stability, and multifunctional expansion. The near-infrared band, in particular, exhibits low transmission loss and strong photon penetration, making it a key research area in modern optical communication, sensing, and quantum information processing. Despite the promising research prospects of waveguide SPDs, existing integrated waveguide SPDs still face numerous challenges in practical applications. Polarization dependence and stray light interference are significant factors affecting their detection performance. Polarization dependence manifests as the difference in response of waveguide SPDs to incident photons with different polarization states. Due to the inherent mode selectivity of waveguide structures, the propagation and absorption efficiencies of light signals with different polarizations differ within the waveguide, causing the detection efficiency to change with the polarization state. This leads to fluctuations in the device's response characteristics, thus affecting the detector's measurement stability. Furthermore, unavoidable stray light interference in the environment also impacts the performance of integrated waveguide SPDs, inducing key issues such as increased dark count rate and large time jitter. Summary of the Invention

[0003] In view of the above problems, this disclosure provides a polarization-independent waveguide integrated superconducting single-photon detector, its fabrication method and testing device.

[0004] According to a first aspect of this disclosure, a waveguide-integrated superconducting single-photon detector is provided, characterized in that it comprises: a substrate, a lower cladding layer, a mode converter, a waveguide detector, and an upper cladding layer; the lower cladding layer is located on the upper surface of the substrate; the mode converter and the waveguide detector are located between the lower cladding layer and the upper cladding layer; the mode converter comprises two symmetrically arranged tapered mode converters with staggered narrow ends; the waveguide detector comprises a waveguide core layer, a photon absorption layer, and an electrode layer; the photon absorption layer is located on the upper surface of the waveguide core layer and is in contact with the electrode layer; the wide end of one of the tapered mode converters is in contact with the waveguide core layer.

[0005] According to an embodiment of this disclosure, a light-absorbing layer is provided above the upper cladding layer.

[0006] According to an embodiment of this disclosure, a buffer layer is provided between the upper cladding layer and the light-absorbing layer.

[0007] According to an embodiment of this disclosure, the photon absorption layer is U-shaped, the electrode layer consists of two pieces, the curved portion of the U-shape is connected to the waveguide core layer, and the two ends of the U-shape are respectively connected to the two electrode layers.

[0008] According to embodiments of this disclosure, the upper surfaces of the two tapered mode converters are located in the same horizontal plane as the upper surface of the waveguide core layer, and the lower surfaces of the two tapered mode converters are located in the same horizontal plane as the lower surface of the waveguide core layer.

[0009] Another aspect of this disclosure provides a method for fabricating a waveguide-integrated superconducting single-photon detector, comprising the following steps:

[0010] S1 forms a lower cladding layer on the upper surface of the substrate.

[0011] S2 forms a first growth layer, and an electrode layer is formed in a first predetermined region on the upper surface of the first growth layer.

[0012] S3 etches the first growth layer to form a waveguide core layer with a predetermined structure and two symmetrical narrow-end staggered tapered mode converters.

[0013] S4 forms a second growth layer and etches a photon absorption layer with a predetermined structure.

[0014] S5 forms the upper cladding.

[0015] S6 etches the electrode layer in the second predetermined area to expose it.

[0016] According to an embodiment of this disclosure, after step S5, the step S51 is to form a light-absorbing layer above the upper cladding layer.

[0017] According to an embodiment of the present disclosure, S51 forms a light-absorbing layer above the upper cladding layer, comprising: S511 forming a buffer layer on the upper surface of the upper cladding layer; and S512 forming a light-absorbing layer on the upper surface of the buffer layer.

[0018] Another aspect of this disclosure provides a waveguide-integrated superconducting single-photon detector testing apparatus, comprising: a waveguide-integrated superconducting single-photon detector for receiving optical signals and emitting electrical signals; a cooling device for housing the waveguide-integrated superconducting single-photon detector and placing it in a superconducting state; a readout circuit for being electrically connected to the waveguide-integrated superconducting single-photon detector, receiving its electrical signals and amplifying them to a readable state; and an analysis device connected to the readout circuit for analyzing the electrical signals output by the readout circuit.

[0019] The above one or more embodiments have the following beneficial effects:

[0020] The waveguide-integrated superconducting single-photon detector of this disclosure employs two symmetrical tapered mode converters. Utilizing their adiabatic coupling mechanism and based on transverse coupling mode theory, under the influence of evanescent waves, the light wave undergoes mode conversion, transitioning from the fundamental mode to a higher-order mode and then back to the fundamental mode. This enables the waveguide to achieve stable power distribution under different polarization states. Furthermore, structural optimization ensures that the TE and TM modes have similar effective refractive indices across the entire operating wavelength range, reducing the relative propagation constant difference between the TE and TM modes and thus lowering polarization dependence.

[0021] A layer of material with high light absorption characteristics in the target wavelength band is coated onto the surface of a waveguide-integrated superconducting single-photon detector. This effectively absorbs stray photons in the test environment, thereby reducing the influence of non-target wavelength light signals on the detector's dark count. This method not only improves the stability of the waveguide-integrated single-photon detector in complex environments and ensures high detection efficiency, but also fundamentally suppresses dark counts caused by environmental stray light, providing a reliable guarantee for high-precision photon detection.

[0022] By providing a buffer layer between the upper cladding and the light-absorbing layer, mode mismatch during waveguide transmission can be effectively prevented. Attached Figure Description

[0023] To clearly illustrate the structural technical solution of the present invention, the accompanying drawings used in the description of the exemplary structural technical solution will be briefly introduced below. The accompanying drawings are only one example of the present invention, and those skilled in the art can obtain other drawings based on these drawings.

[0024] Figure 1 schematically shows a three-dimensional perspective view of a waveguide-integrated superconducting single-photon detector according to an embodiment of the present disclosure.

[0025] Figure 2 schematically shows a two-dimensional top view of a waveguide-integrated superconducting single-photon detector according to an embodiment of the present disclosure.

[0026] Figure 3 schematically shows a cross-sectional view of the waveguide-integrated superconducting single-photon detector along the AA direction in Figure 2.

[0027] Figure 4 schematically illustrates the waveguide internal optical field transmission mode of a waveguide-integrated superconducting detector according to an embodiment of the present disclosure.

[0028] Figure 5 schematically illustrates a comparison of the normalized intensity of the optical field before and after the application of a graphite layer in a waveguide-integrated superconducting detector according to an embodiment of the present disclosure.

[0029] Figure 6 schematically illustrates the mode field distribution of two symmetrical conical mode converters in a waveguide-integrated superconducting detector according to an embodiment of the present disclosure.

[0030] Figure 7 schematically illustrates a flowchart of a waveguide-integrated superconducting detector fabrication method according to an embodiment of the present disclosure.

[0031] Figure 8 schematically illustrates a flowchart of a method for fabricating a waveguide-integrated superconducting detector according to another embodiment of the present disclosure.

[0032] Figure 9 schematically illustrates a flowchart of a method for fabricating a waveguide-integrated superconducting detector according to another embodiment of the present disclosure.

[0033] Figure 10 schematically illustrates a test apparatus for a waveguide-integrated superconducting detector according to an embodiment of the present disclosure.

[0034] In the figure, 1 is the substrate; 2 is the mode converter; 3 is the waveguide detector; 4 is the lower cladding; 5 is the tapered mode converter; 6 is the waveguide core; 7 is the photon absorption layer; 8 is the electrode layer; 9 is the upper cladding; and 10 is the light-absorbing layer.

[0035] 101, Pulsed laser; 102, Polarization controller; 103, Tunable attenuator; 104, Beam splitter; 105, Power meter; 106, Cryogenic refrigerator; 107, Readout circuit; 108, Oscilloscope; 109, Counter; 110 Waveguide integrated superconducting single-photon detector sample. Detailed Implementation

[0036] The embodiments of the present disclosure 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 the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0037] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. 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.

[0038] 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.

[0039] Figures 1-3 illustrate schematic diagrams of a waveguide-integrated superconducting single-photon detector according to embodiments of the present disclosure. As shown, the waveguide-integrated superconducting single-photon detector according to embodiments of the present disclosure can be divided into a mode conversion region and a waveguide detection region, which are adjacent to each other. The waveguide-integrated superconducting single-photon detector includes a substrate 1, a lower cladding layer 4, a mode converter 2, a waveguide detector 3, and an upper cladding layer 9; the lower cladding layer 4 is located on the upper surface of the substrate 1; the mode converter 2 and the waveguide detector 3 are located between the lower cladding layer 4 and the upper cladding layer 9; the mode converter 2 is disposed in the mode conversion region and includes two symmetrically arranged tapered mode converters 5 with their narrow ends staggered; the waveguide detector 3 is disposed in the waveguide detection region and includes a waveguide core layer 6, a photon absorption layer 7, and an electrode layer 8; the photon absorption layer 7 is located on the upper surface of the waveguide core layer 6 in the waveguide detection region and is in contact with the electrode layer 8; the wide end of one of the tapered mode converters 5 is in contact with the waveguide core layer 6.

[0040] Two symmetrical tapered mode converters 5 with staggered narrow ends have their wide ends serving as the input end for receiving optical input, while the wide end of the other tapered mode converter is connected to the waveguide core layer 6 for outputting light to the waveguide core layer 6. The photon absorption layer 7 is used to convert the optical signal in the waveguide core layer 6 into an electrical signal and output it to the electrode layer 8.

[0041] In this embodiment, the lower cladding layer 4 and the upper cladding layer 9 serve to ensure stable transmission of the optical field within the mode converter 2 and the waveguide detector 3. In this embodiment, the substrate 1 can be made of Si, and the lower cladding layer 4 and the upper cladding layer 9 can be made of SiO2. The two tapered mode converters 5 and the waveguide core layer 6 can be made of silicon nitride. The photon absorption layer 7 can be made of MoSi.

[0042] The upper surface of electrode layer 8 can be at a height relatively higher than the upper surface of waveguide core layer 6, and the lower surface of electrode layer can be at the same horizontal plane as the upper surface of waveguide core layer. Electrode layer 8 may include an Au layer, and further, electrode layer may also include a Ti layer and an Au layer. The Ti layer is located on the lower surface of the Au layer, and the Ti layer can be used to increase the adsorption of the Au layer.

[0043] The lower surface of the lower cladding layer 4 is in contact with the upper surface of the substrate 1, and the upper surface of the lower cladding layer 4 is in contact with the lower surfaces of the mode converter 2 and the waveguide detector 3. The lower surface of the upper cladding layer 9 is in contact with the upper surfaces of the mode converter 2 and the waveguide detector 3.

[0044] This embodiment utilizes two symmetrical tapered mode converters with an adiabatic coupling mechanism. Based on the transverse coupling mode theory, mode conversion occurs under the influence of evanescent waves. The light wave transforms from the fundamental mode to a higher-order mode and then back to the fundamental mode, enabling the waveguide to achieve a stable power distribution under different polarization states and reducing the waveguide's polarization dependence. Furthermore, by optimizing the structural parameters, the TE and TM modes can have similar effective refractive indices across the entire operating wavelength range, reducing the difference in relative propagation constants between the TE and TM modes, thereby further reducing polarization dependence. Structural parameter optimization specifically refers to adjusting the length, width, and thickness of the tapered mode converters. Since mode converters of different sizes have different effects on light field transmission, structural parameter optimization further reduces polarization dependence. Figure 6 schematically illustrates the mode field distribution of two symmetrical tapered mode converters in a waveguide-integrated superconducting detector according to an embodiment of this disclosure. As shown in Figure 6, the black box indicates the location of the two symmetrical mode converters. Figure 6a shows the mode field conversion without optimization, and Figure 6b shows the mode field conversion after optimization. As can be seen from the figure, for example, the spacing between two symmetrical conical mode converters is approximately 2 × 10. -6 m adjustment approximately 1×10 -6 m, with a length of approximately 65 × 10 m. -6 m is reduced to approximately 60 × 10 -6 m, and reduce the width dimension. After optimizing and adjusting the x / y dimensions of the two symmetrical tapered mode converters, the optical fiber is incident through the left tapered mode converter, energy exchange occurs in the coupling region, and the energy is transmitted to the other tapered mode converter, resulting in a significant reduction in energy loss. As shown in Figure 4, the internal optical field transmission TE and TM modes of the waveguide-integrated superconducting single-photon detector in this embodiment have similar effective refractive indices within the operating wavelength range.

[0045] In some embodiments of this disclosure, a light-absorbing layer 10 is provided above the upper cladding layer 9. The upper surface of the upper cladding layer 9 and the lower surface of the light-absorbing layer 10 can be located in the same horizontal plane. The light-absorbing layer 10 is used to absorb stray light from the external environment. Specifically, a material with high absorption characteristics in the target wavelength band can be coated on the upper surface of the upper cladding layer 9, thereby reducing the influence of non-target light signals on the dark count of the detector. The light-absorbing layer can be selected according to the light wavelength band to be absorbed. For example, graphite material is used in the 1550nm wavelength band, while other materials with suitable absorption characteristics can be selected for other wavelengths. The specific absorption characteristics of the material can be determined based on the K value (extinction coefficient) measured using an ellipsometer, etc. The absorption characteristics of light propagating in the material at different wavelengths are determined based on the K value of the material at different wavelengths. Figure 5 schematically shows a comparison of the normalized intensity of the light field before and after the graphite layer is set in the waveguide integrated superconducting detector according to an embodiment of this disclosure. The black box in the figure indicates the location of the waveguide. Figure 5a is the light field intensity distribution without the graphite layer, and Figure 5b is the light field intensity distribution with the graphite layer. As can be seen from the comparison in Figure 5b, after setting the graphite layer as the light-absorbing layer, it can effectively absorb stray light in the waveguide's surrounding environment, thereby reducing the impact of non-target light signals on the detector's dark count.

[0046] In some embodiments of this disclosure, a buffer layer is provided between the upper cladding and the light-absorbing layer to act as a buffer layer to isolate the upper cladding and the light-absorbing layer. For example, the buffer layer is an Al2O3 layer. By setting the buffer layer, mode mismatch during waveguide transmission can be effectively prevented. If the Al2O3 layer is not set, although the light-absorbing layer on the upper surface of the upper cladding can isolate stray light from the outside, it will interfere with the transmission mode of the optical field inside the waveguide, causing mode mismatch problems during waveguide transmission.

[0047] In some embodiments of this disclosure, the electrode layer consists of two layers, for example, a wing-shaped structure. The photon absorption layer 7 is a U-shaped nanowire, with the curved portion of the U-shaped nanowire connected to the waveguide core layer 6, and the two ends of the U-shaped nanowire connected to the two electrode layers 8 respectively. As shown in Figure 3, since the photon absorption layer 7 is formed on the upper surfaces of the waveguide core layer 6 and the electrode layers 8, and since the upper surface of the electrode layer 8 is higher than the upper surface of the waveguide core layer 6, there is a certain height difference between the curved portion of the U-shaped nanowire and the lower surfaces of its two ends when viewed from the side. This height difference may not be very noticeable between the curved portion and the upper surfaces of its two ends. By using U-shaped nanowires as the photon absorption layer, photons can be effectively absorbed and converted into photoelectric signals in a superconducting state.

[0048] In some embodiments of this disclosure, the upper surfaces of the two tapered mode converters 5 are located in the same horizontal plane as the upper surface of the waveguide core layer 6, and the lower surfaces of the two tapered mode converters 5 are located in the same horizontal plane as the lower surface of the waveguide core layer 6. Thus, the height of the two tapered mode converters 5 is the same as the height of the waveguide core layer 6 of the waveguide detector 3. This structure facilitates better reception of the light output from the tapered mode converters 5 by the waveguide core layer 6.

[0049] Based on the aforementioned waveguide-integrated superconducting single-photon detector, this disclosure also provides a method for fabricating such a detector. The fabrication method will be described in detail below with reference to Figures 7-9.

[0050] Figure 7 schematically illustrates a flowchart of a method for fabricating a waveguide-integrated superconducting single-photon detector according to an embodiment of the present disclosure.

[0051] As shown in Figure 7, the preparation method includes:

[0052] In operation S1, a lower cladding layer is formed on the upper surface of the substrate.

[0053] In operation S2, a first growth layer is formed, and an electrode layer is formed in a first predetermined region on the upper surface of the first growth layer.

[0054] In operation S3, a waveguide core layer with a predetermined structure and two symmetrical narrow-end staggered tapered mode converters are etched in the first growth layer.

[0055] In operation S4, a second growth layer is formed and a photon absorption layer with a predetermined structure is etched.

[0056] In operation S5, the upper cladding is formed.

[0057] In operation S6, the electrode layer is etched out in the second predetermined region.

[0058] In this embodiment, during operation S1, a SiO2 layer can be grown on the Si substrate using PECVD (plasma-enhanced chemical vapor deposition) as the lower cladding layer.

[0059] In operation S2, a Si3N4 layer can be grown on the SiO2 layer in S1 using PECVD as the first growth layer. The thickness of the Si3N4 layer here is 400nm, which is obtained from simulation software. The example band is the standard communication band 1550nm. When designing for different communication bands, its thickness will vary to some extent.

[0060] On the upper surface of the Si3N4 layer, a first mask is used to define a first predetermined area as the photolithography area. Here, the mask is mainly used to determine the structure of the electrode layer 8 of the waveguide detector 3. The electrode layer structure 8 of the waveguide detection area is etched in the photolithography area. The electrode layer structure can be a wing-shaped structure; however, the structure of the electrode layer 8 can be designed according to factors such as device integration density, and the wing-shaped structure is not the only possible structure. Specifically, a Ti layer and an Au layer can be deposited sequentially in the photolithography area using an electron beam evaporation process. Here, the deposited Ti layer has a thickness of 10 nm and the Au layer has a thickness of 80 nm to increase the adsorption of the Au layer.

[0061] In operation S3, the waveguide core layer 6 structure of the waveguide detector 3 is fixed using EBL (electron beam lithography), and the structure of the waveguide core layer 6 of the waveguide detector 3 is etched using RIE (reactive ion etching). Here, both tapered mode converters 5 and the waveguide core layer 6 structure of the waveguide detector 3 are made of Si3N4 material.

[0062] In operation S4, a second growth layer is deposited on the upper surface of the waveguide core layer 6 using magnetron sputtering. The waveguide detector 3 is then etched using RIE to obtain the photon absorption layer 7 structure. Specifically, a 5nm MoSi material layer can be deposited using magnetron sputtering and then etched using RIE to obtain a photon absorption layer made of MoSi. Here, the photon absorption layer 7 can have a U-shaped nanowire structure with a thickness of 5nm, a spacing of 60nm, a nanowire width of 130nm, and a length of 70µm.

[0063] In operation S5, the upper cladding layer is grown using the PECVD process. The upper cladding layer can be a 600nm thick SiO2 layer.

[0064] In operation S6, after the upper cladding is formed, the second predetermined region is determined using the second mask, and the structure deposited in the second predetermined region above the electrode layer is etched away to expose the electrode layer for subsequent testing and connection to the readout circuit.

[0065] In some embodiments of this disclosure, the method for fabricating a waveguide-integrated superconducting single-photon detector includes: operation S51, forming a light-absorbing layer above the upper cladding. Specifically, this can be achieved by depositing a 160 nm graphite layer on the upper surface of the upper cladding using a chemical vapor deposition process. In this embodiment, after operation S51, step S6 is performed.

[0066] As shown in Figure 8, in some embodiments of this disclosure, S51 forms a light-absorbing layer above the upper cladding layer, comprising:

[0067] During operation S511, a buffer layer is formed on the upper surface of the upper cladding layer;

[0068] During operation S512, a light-absorbing layer is formed on the upper surface of the buffer layer.

[0069] Specifically, an Al2O3 layer and a graphite layer can be deposited on the upper surface of the cladding using a chemical vapor deposition process. Here, the Al2O3 thickness can be 50 nm, and the graphite film thickness can be 160 nm. In this embodiment, after operation S512, operation S6 is performed.

[0070] In some embodiments of this disclosure, after operation S6, an etching operation is further performed along the contour region of a predetermined waveguide-integrated superconducting single-photon detector to obtain a separated waveguide-integrated superconducting single-photon detector. As shown in FIG9, the steps of this embodiment include:

[0071] Step 1: Obtain the Si substrate.

[0072] Step 2: A SiO2 layer is grown on the surface of the Si substrate using a PECVD process.

[0073] Step 3: A 400 nm Si3N4 layer is grown on the surface of the SiO2 layer using PECVD process.

[0074] Step 4: On the upper surface of the Si3N4 layer, the photolithography area is determined using the first mask.

[0075] Step 5 involves etching the electrode layer structure of the waveguide detector in the photolithography area.

[0076] Step 6: In the photolithography area, a 10nm Ti layer and an 80nm Au layer are deposited sequentially using an electron beam evaporation process.

[0077] Step 7: The waveguide core structure is fixed using the EBL process and then etched using the RIE process to form the waveguide core structure.

[0078] Step 8: A 5 mm MoSi layer is deposited on the upper surface of the waveguide detection area using a magnetron sputtering process.

[0079] Step 9: On the MoSi layer, the photonic absorption layer structure of the waveguide detector is fixed using the EBL process, and the photonic absorption layer structure is etched using the RIE process.

[0080] Step 10: A 600 nm SiO2 layer is grown using PECVD process.

[0081] Step 11: Deposit a graphite layer on top of the SiO2 layer using an electron beam evaporation process.

[0082] Step 12: On the graphite layer, use a second mask to determine the photolithographic area of ​​the electrode layer.

[0083] Step 13 involves etching the photolithography area to expose the electrode layer structure.

[0084] Step 14 uses a third mask to determine the lithographic region for the waveguide-integrated superconducting single-photon detector profile.

[0085] Step 15: In the photolithography area, the detector outline is etched using ICP-PECVD (Inductively Coupled Plasma Enhanced Chemical Vapor Deposition) process.

[0086] Step 16: In the photolithography area, the waveguide detector outline is etched using DRIE (deep reactive ion etching) process to obtain the waveguide detector.

[0087] The first, second, and third masks used in this embodiment are determined according to the required structure and are not the same.

[0088] It should be noted that some steps of the above method can be executed individually or in combination, and can be executed in parallel or sequentially, and are not limited to the specific order of operations shown in the figure.

[0089] Based on the aforementioned waveguide-integrated superconducting single-photon detector, this disclosure also provides a testing apparatus for the waveguide-integrated superconducting single-photon detector. The apparatus includes:

[0090] Waveguide-integrated superconducting single-photon detectors are used to receive optical signals and emit electrical signals.

[0091] A cooling device is used to house the waveguide-integrated superconducting single-photon detector and to put it in a superconducting state.

[0092] The readout circuit is used to electrically connect to the waveguide-integrated superconducting single-photon detector, receive its electrical signal, and amplify it to a readable state.

[0093] An analysis device, connected to a readout circuit, is used to analyze the electrical signals output by the readout circuit.

[0094] As shown in Figure 10, in some embodiments of this disclosure, the testing apparatus for the waveguide-integrated superconducting single-photon detector includes a waveguide-integrated superconducting single-photon detector sample 110, a cryogenic refrigerator 106, a readout circuit 107, and an analysis device. Specifically, the waveguide-integrated superconducting single-photon detector sample 110 is placed in the cryogenic refrigerator 106. The cryogenic refrigerator 106 can be a 2K refrigerator, capable of providing a 2K low-temperature environment. The analysis device specifically includes an oscilloscope 108 and a counter 109. In this embodiment, light of the target wavelength band is generated by a pulsed laser 101 and sequentially enters a polarization controller 102, a tunable attenuator 103, and a beam splitter 104 with a 1:1 splitting ratio. A portion of the light enters a power meter 105 as a reference port, while the other portion enters the cryogenic refrigerator 106, is coupled via a lens fiber to the waveguide-integrated superconducting single-photon detector for detection, and is then counted by the oscilloscope 108 or the counter 109 after passing through the readout circuit 107.

[0095] Those skilled in the art will understand that the features described in the various embodiments of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0096] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A waveguide-integrated superconducting single-photon detector, characterized in that, It comprises: a substrate, a lower cladding layer, a mode converter, a waveguide detector, and an upper cladding layer; the lower cladding layer is located on the upper surface of the substrate; the mode converter and the waveguide detector are located between the lower cladding layer and the upper cladding layer; the mode converter comprises two symmetrically arranged, narrow-end staggered, tapered mode converters of the same height; the waveguide detector comprises a waveguide core layer, a photon absorption layer, and an electrode layer; the photon absorption layer is located on the upper surface of the waveguide core layer, the photon absorption layer is U-shaped, the electrode layer consists of two pieces, the curved portion of the U-shape is connected to the waveguide core layer, and the two ends of the U-shape are respectively connected to the two electrode layers; the wide end of one of the tapered mode converters is connected to the waveguide core layer.

2. The detector according to claim 1, characterized in that, A light-absorbing layer is provided above the upper cladding.

3. The detector according to claim 2, characterized in that, A buffer layer is provided between the upper cladding layer and the light-absorbing layer.

4. The detector according to claim 1, characterized in that, The upper surfaces of the two tapered modulus converters are located in the same horizontal plane as the upper surface of the waveguide core layer, and the lower surfaces of the two tapered modulus converters are located in the same horizontal plane as the lower surface of the waveguide core layer.

5. A method for fabricating a waveguide-integrated superconducting single-photon detector, characterized in that, The process includes the following steps: S1 forming a lower cladding layer on the upper surface of a substrate; S2 forming a first growth layer, and forming an electrode layer in a first predetermined region on the upper surface of the first growth layer, wherein the electrode layer consists of two pieces; S3 etching the first growth layer to form a waveguide core layer with a predetermined structure and two symmetrical narrow-end staggered tapered mode converters of the same height; S4 forming a second growth layer and etching to form a photon absorption layer with a predetermined structure, wherein the photon absorption layer has a U-shaped structure and the two ends of the U-shaped photon absorption layer are respectively connected to the two electrode layers; S5 forming an upper cladding layer; and S6 etching the second predetermined region to expose the electrode layer.

6. The method according to claim 5, characterized in that, After step S5, the following step is included: S51 Forming a light-absorbing layer above the upper cladding layer.

7. The method according to claim 6, characterized in that, S51 forms a light-absorbing layer above the upper cladding layer, comprising: S511 forming a buffer layer on the upper surface of the upper cladding layer; and S512 forming a light-absorbing layer on the upper surface of the buffer layer.

8. A waveguide-integrated superconducting single-photon detector testing device, characterized in that, The device comprises: the waveguide-integrated superconducting single-photon detector of claim 1, for receiving optical signals and emitting electrical signals; a cooling device for housing the waveguide-integrated superconducting single-photon detector and placing it in a superconducting state; a readout circuit for being electrically connected to the waveguide-integrated superconducting single-photon detector, receiving its electrical signals and amplifying them to a readable state; and an analysis device connected to the readout circuit for analyzing the electrical signals output by the readout circuit.

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