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

Abstract

The invention provides a waveguide integrated superconducting single-photon detector, which can be applied to the technical field of photoelectric detection, and comprises a substrate, a lower cladding, a spot size converter, a waveguide detector and an upper cladding, the lower cladding is located on the upper surface of the substrate; the spot size converter and the waveguide detector are located between the lower cladding and the upper cladding; the spot size converter comprises two conical spot size converters of which the symmetrical narrow ends are arranged in a staggered manner; the waveguide detector comprises a waveguide core layer, a photon absorption layer and an electrode layer; the photon absorption layer is positioned on the upper surface of the waveguide core layer and is connected with the electrode layer; and the wide end of one conical spot size converter is connected with the waveguide core layer. The detector provided by the invention has the advantages of polarization independence and stray light interference resistance. The invention further provides a preparation method and a testing device of the waveguide integrated superconducting single-photon detector.

Description

Technical Field

[0001] The present disclosure relates to the field of optoelectronic detection technology, and more specifically, to a waveguide integrated superconducting single photon detector, a preparation method and a test device. Background Art

[0002] Waveguide integrated single photon detectors are widely used in fields such as quantum computing, lidar, optical sensing and optical communication due to their significant advantages such as miniaturization, high integration, good stability and multi-functional expansion. Especially in the near-infrared band, the optical signal has low transmission loss and strong photon penetration ability, which is a key research band for modern optical communication, sensing and quantum information processing. Although waveguide single photon detectors have broad research prospects, existing waveguide integrated single photon detectors still face many challenges in practical applications. For example, polarization dependence and stray light interference are important factors affecting their detection performance. Among them, polarization dependence is mainly manifested as the response difference of waveguide single photon detectors to incident photons with different polarization states. Due to the inherent mode selectivity of the waveguide structure, the propagation and absorption efficiencies of optical signals with different polarizations in the waveguide are different, resulting in the detection efficiency changing with the change of the polarization state, thus causing fluctuations in the response characteristics of the device and further affecting the measurement stability of the detector. In addition, inevitable stray light interference in the environment will also affect the performance of waveguide integrated single photon detectors to a certain extent, inducing key problems such as an increase in the dark count rate of the detector and large time jitter. Summary of the Invention

[0003] In view of the above problems, the present disclosure provides a polarization-independent waveguide integrated superconducting single photon detector, a preparation method and a test device.

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

[0005] According to an embodiment of the present disclosure, an optical absorption layer is provided above the upper cladding.

[0006] According to an embodiment of the present disclosure, a buffer layer is provided between the upper cladding and the optical absorption layer.

[0007] According to an embodiment of the present disclosure, the photon absorption layer is U-shaped, the electrode layer is two pieces, the bent part 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 an embodiment of the present disclosure, the upper surfaces of the two tapered mode spot converters are in the same horizontal plane as the upper surface of the waveguide core layer, and the lower surfaces of the two tapered mode spot converters are in the same horizontal plane as the lower surface of the waveguide core layer.

[0009] Another aspect of the embodiments of the present disclosure provides a method for fabricating a waveguide integrated superconducting single-photon detector, including the steps of:

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

[0011] S2 Form a first growth layer, and form an electrode layer on the upper surface of the first growth layer in a first predetermined area.

[0012] S3 Etch the first growth layer to form a waveguide core layer with a predetermined structure and two tapered mode spot converters with symmetric narrow ends arranged in an interleaved manner.

[0013] S4 Form a second growth layer and etch it to form a photon absorption layer with a predetermined structure.

[0014] S5 Form an upper cladding.

[0015] S6 Etch in a second predetermined area to expose the electrode layer.

[0016] According to an embodiment of the present disclosure, after step S5, it includes the step of: S51 Form a light absorption layer above the upper cladding.

[0017] According to an embodiment of the present disclosure, S51 forming a light absorption layer above the upper cladding includes: S511 Form a buffer layer on the upper surface of the upper cladding; S512 Form a light absorption layer on the upper surface of the buffer layer.

[0018] Another aspect of the embodiments of the present disclosure provides a testing device for a waveguide integrated superconducting single-photon detector, including: a waveguide integrated superconducting single-photon detector for receiving an optical signal and emitting an electrical signal; a refrigeration device for accommodating the waveguide integrated superconducting single-photon detector and making it in a superconducting state; a readout circuit for being electrically connected to the waveguide integrated superconducting single-photon detector, receiving its electrical signal and amplifying it to a readable state; an analysis device connected to the readout circuit for analyzing the electrical signal 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 according to the embodiments of the present disclosure designs two symmetric tapered mode spot converters. By utilizing their adiabatic coupling mechanism and according to the transverse coupled mode theory, under the action of the evanescent wave, the optical wave undergoes mode conversion, from the fundamental mode to the higher-order mode and then back to the fundamental mode. This enables the waveguide to achieve a stable power distribution in different polarization states. At the same time, through structural optimization, the TE and TM modes have similar effective refractive indices throughout the working wavelength range, reducing the relative propagation constant difference between the TE and TM modes, thereby reducing the polarization dependence.

[0021] A layer of material with high light absorption characteristics in the target band is coated on the surface of the waveguide integrated superconducting single-photon detector to effectively absorb the stray photons in the test environment, thereby reducing the influence of the optical signals in the non-target band on the dark count of the detector. This method can not only improve the stability of the waveguide integrated single-photon detector in a complex environment, ensure the high detection efficiency of the device, fundamentally suppress the dark count caused by environmental stray light, and provide a reliable guarantee for high-precision photon detection.

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

[0023] To clearly illustrate the structural technical solutions of the examples of the present invention, the drawings used in the description of the example structural technical solutions will be briefly introduced next. The drawing descriptions are only one example of the present invention, and those skilled in the relevant art can obtain other drawings based on these drawings.

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

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

[0026] Figure 3 Schematically shows according to Figure 2 The cross-sectional view of the waveguide integrated superconducting single-photon detector in the A-A direction in

[0027] Figure 4 Schematically shows the schematic diagram of the optical field transmission mode inside the waveguide of the waveguide integrated superconducting detector according to the embodiments of the present disclosure.

[0028] Figure 5 Schematically shows the comparison diagram of the normalized intensity of the optical field before and after setting the graphite layer for the waveguide integrated superconducting detector according to the embodiments of the present disclosure.

[0029] Figure 6Schematically shows the mode field distribution of two symmetric tapered mode spot converters in a waveguide integrated superconducting detector according to an embodiment of the present disclosure.

[0030] Figure 7 Schematically shows a flowchart of a method for fabricating a waveguide integrated superconducting detector according to an embodiment of the present disclosure.

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

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

[0033] Figure 10 Schematically shows a diagram of a test device for a waveguide integrated superconducting detector according to an embodiment of the present disclosure.

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

[0036] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the following detailed description, for the sake of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, obviously, one or more embodiments can also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present disclosure.

[0037] The terms used herein are merely for describing specific embodiments and are not intended to limit the present disclosure. The terms "including", "comprising", etc. used herein indicate the presence of the described 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 should be interpreted to have a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0039] Figures 1 - 3 FIG. shows a schematic diagram related to a waveguide-integrated superconducting single-photon detector according to an embodiment of the present disclosure. As shown in the figure, the waveguide-integrated superconducting single-photon detector according to an embodiment of the present disclosure can be generally divided into a mode spot conversion region and a waveguide detection region, and the mode spot conversion region and the waveguide detection region are adjacent and in contact. The waveguide-integrated superconducting single-photon detector includes a substrate 1, a lower cladding 4, a mode spot converter 2, a waveguide detector 3, and an upper cladding 9; the lower cladding 4 is located on the upper surface of the substrate 1; the mode spot converter 2 and the waveguide detector 3 are located between the lower cladding 4 and the upper cladding 9; the mode spot converter 2 is disposed in the mode spot conversion region and includes two tapered mode spot converters 5 with symmetric narrow ends arranged in an interleaved manner; 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 spot converters 5 is in contact with the waveguide core layer 6.

[0040] The wide end of one of the two tapered mode spot converters 5 with symmetric narrow ends arranged in an interleaved manner is used as an input end for receiving light input, and the wide end of the other tapered mode spot converter is in contact with 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 functions of the lower cladding 4 and the upper cladding 9 include ensuring the stable transmission of the optical field inside the mode spot converter 2 and the waveguide detector 3. In this embodiment, the substrate 1 can be made of Si, and the lower cladding 4 and the upper cladding 9 can be made of SiO2. The two tapered mode spot converters 5 and the waveguide core layer 6 can be made of silicon nitride material. The photon absorption layer 7 can be made of MoSi material.

[0042] The height of the upper surface of the electrode layer 8 can be relatively higher than the height of the upper surface of the waveguide core layer 6, and the lower surface of the electrode layer can be in the same horizontal plane as the upper surface of the waveguide core layer. The electrode layer 8 can include an Au layer. Further, the electrode layer can 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 is provided to increase the adsorption of the Au layer.

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

[0044] In this embodiment, two symmetric tapered mode spot converters are used. By utilizing their adiabatic coupling mechanism and according to the transverse coupled mode theory, mode conversion is generated under the action of evanescent waves. The optical wave is converted 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 in different polarization states and reducing the polarization dependence of the waveguide. At the same time, by further optimizing the structural parameters, the TE and TM modes can have similar effective refractive indices within the entire operating wavelength range, reducing the relative propagation constant difference between the TE and TM modes, thereby further reducing the polarization dependence. The optimization of the structural parameters specifically refers to adjusting the length, width, and thickness dimensions of the tapered mode spot coupler. Since mode spot converters with different dimensions have different effects on the transmission of the optical field, the polarization dependence is further reduced through the optimization of the structural parameters. Figure 6 Schematically shows the mode field distribution of two symmetric tapered mode spot converters in a waveguide integrated superconducting detector according to an embodiment of the present disclosure. As Figure 6 shown, the black boxes are the positions where two symmetric mode spot couplers are located. Figure 6 a shows the mode field conversion of the unoptimized structure, Figure 6 b shows the mode field conversion after the structure is optimized. It can be seen from the figure that, for example, the distance between two symmetric tapered mode spot converters is adjusted from about 2×10 -6 m to about 1×10 -6 m, the length is reduced from about 65×10 -6 m to about 60×10 -6 m, and the width dimension is reduced. After the x / y dimensions of the two symmetric tapered mode spot converters are optimized and adjusted, the optical fiber is incident through the left tapered mode spot converter, and energy exchange occurs in the coupling region and is transmitted to the other tapered mode spot converter, with a significant reduction in energy loss. As Figure 4 shown, the TE and TM modes of the internal optical field transmission 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 the present disclosure, an absorbing layer 10 is provided above the upper cladding 9. The upper surface of the upper cladding 9 and the lower surface of the absorbing layer 10 can be located in the same horizontal plane. The absorbing layer 10 is used to absorb stray light in 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 9, thereby reducing the influence of non-target optical signals on the dark count of the detector. The absorbing layer can be selected according to the optical wavelength band to be absorbed. For example, graphite material is used in the 1550 nm wavelength band, and other materials with appropriate absorption characteristics can be selected at other wavelengths. The absorption characteristics of the specific material can be judged according to the K value (extinction coefficient) measured using an ellipsometer. According to the magnitude of the K value of the material in different wavelength bands, the absorption characteristics of light in different wavelength bands during propagation in this material can be judged. Figure 5Schematically shows a comparison diagram of the normalized optical field intensity before and after setting the graphite layer of the waveguide integrated superconducting detector according to an embodiment of the present disclosure. The black box in the figure is the position where the waveguide is located. Figure 5 a is the optical field intensity distribution diagram without setting the graphite layer. Figure 5 b is the optical field intensity distribution diagram when the graphite layer is set. It can be seen from the comparison that Figure 5 After setting the graphite layer as the light absorption layer in b, it can effectively absorb the stray light in the environment outside the waveguide, thereby reducing the influence of non-target optical signals on the dark count of the detector.

[0046] In some embodiments of the present disclosure, a buffer layer is provided between the upper cladding layer and the light absorption layer for isolating the upper cladding layer and the light absorption layer as a buffer layer. For example, the buffer layer is an A12O3 layer. By setting the buffer layer, the mode mismatch during the waveguide transmission can be effectively prevented. If the A12O3 layer is not set, although the light absorption layer on the upper surface of the upper cladding layer can isolate the external stray light, it will interfere with the optical field transmission mode inside the waveguide, causing the mode mismatch problem during the waveguide transmission.

[0047] In some embodiments of the present disclosure, the electrode layer is two pieces, for example, it can be in a wing-shaped structure. The photon absorption layer 7 is a U-shaped nanowire. The bent part of the U-shaped nanowire is connected to the waveguide core layer 6, and the two ends of the U-shaped nanowire are respectively connected to the two electrode layers 8. As Figure 3 shown, since the photon absorption layer 7 is formed on the upper surfaces of the waveguide core layer 6 and the electrode layer 8, and 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 lower surfaces of the bent part and the two ends of the U-shaped nanowire when viewed from the side, and the height difference may not be obvious on the upper surfaces of the bent part and the two ends. By setting the U-shaped nanowire as the photon absorption layer, photons can be well absorbed for photoelectric conversion in the superconducting state.

[0048] In some embodiments of the present disclosure, the upper surfaces of the two tapered mode spot converters 5 are in the same horizontal plane as the upper surface of the waveguide core layer 6, and the lower surfaces of the two tapered mode spot converters 5 are in the same horizontal plane as the lower surface of the waveguide core layer 6. Thus, the heights of the two tapered mode spot converters 5 are the same as the height of the waveguide core layer 6 of the waveguide detector 3. This structure is beneficial for the light output by the tapered mode spot converters 5 to be better received by the waveguide core layer 6.

[0049] Based on the above waveguide integrated superconducting single photon detector, the present disclosure also provides a method for manufacturing a waveguide integrated superconducting single photon detector. The following will be combined with Figures 7 - 9 to describe this manufacturing method in detail.

[0050] Figure 7 Schematically shows a flowchart of the method for manufacturing a waveguide integrated superconducting single photon detector according to an embodiment of the present disclosure.

[0051] As Figure 7 shown, 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 area on the upper surface of the first growth layer.

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

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

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

[0057] In operation S6, the electrode layer is etched and exposed in a second predetermined area

[0058] In this embodiment, in operation S1, on the Si substrate, a SiO2 layer can be grown by PECVD (Plasma Enhanced Chemical Vapor Deposition) process as the lower cladding layer.

[0059] In operation S2, a Si3N4 layer can be grown on the SiO2 layer in S1 by PECVD process as the first growth layer. Here, the thickness of Si3N4 is 400nm, obtained by simulation software, and the example wavelength band is the standard communication wavelength band of 1550nm. When designing for different communication wavelength bands, its thickness will fluctuate accordingly.

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

[0061] In operation S3, the structure of the waveguide core layer 6 of the waveguide detector 3 is fixed by EBL (Electron Beam Lithography) process, and the structures of two symmetrically staggered tapered mode spot converters 5 and the waveguide core layer 6 of the waveguide detector 3 are etched by RIE (Reactive Ion Etching) process. Here, the structures of the two tapered mode spot converters 5 and the waveguide core layer 6 of the waveguide detector 3 are all made of Si3N4 material.

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

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

[0064] In operation S6, after forming the upper cladding, a second mask plate is used to determine a second predetermined area, and the structure deposited in the second predetermined area above the electrode layer is etched away to expose the electrode layer for connection to the readout circuit during subsequent testing.

[0065] In some embodiments of the present disclosure, the method for fabricating a waveguide integrated superconducting single-photon detector includes: operation S51, forming an absorbing layer above the upper cladding. Specifically, a 160-nm graphite layer can be deposited on the upper surface of the upper cladding using a chemical vapor deposition process. In this embodiment, after operation S51, the steps of operation S6 are continued.

[0066] As Figure 8 shown, in some embodiments of the present disclosure, S51 forming an absorbing layer above the upper cladding includes:

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

[0068] In operation S512, an 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 upper cladding using a chemical vapor deposition process. Here, the thickness of the Al2O3 can be 50 nm, and the thickness of the graphite thin film can be 160 nm. In this embodiment, after operation S512, the steps of operation S6 are continued.

[0070] In some embodiments of the present disclosure, after operation S6, it further includes an etching operation according to the contour area of the predetermined waveguide integrated superconducting single-photon detector to obtain a separated waveguide integrated superconducting single-photon detector. As Figure 9 shown, the steps of this embodiment include:

[0071] Step 1: Obtain a Si substrate.

[0072] Step 2: Grow a SiO2 layer on the upper surface of the Si substrate using a PECVD process.

[0073] Step 3: Grow a 400 - nm Si3N4 layer on the upper surface of the SiO2 layer using the PECVD process.

[0074] Step 4: On the upper surface of the Si3N4 layer, use the first mask to determine the lithography area.

[0075] Step 5: Etch in the lithography area to form the electrode layer structure of the waveguide detector.

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

[0077] Step 7: Fix the waveguide core layer structure using the EBL process and etch to form the waveguide core layer structure using the RIE process.

[0078] Step 8: On the upper surface of the waveguide detection area, deposit a 5 - mm MoSi layer using the magnetron sputtering process.

[0079] Step 9: On the MoSi layer, fix the photon absorption layer structure of the waveguide detector using the EBL process and etch the photon absorption layer structure using the RIE process.

[0080] Step 10: Grow a 600 - nm SiO2 layer using the PECVD process.

[0081] Step 11: Above the SiO2 layer, deposit a graphite layer using the electron beam evaporation process.

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

[0083] Step 13: Etch in the lithography area to expose the electrode layer structure.

[0084] Step 14: Use the third mask to determine the lithography area of the contour of the waveguide integrated superconducting single - photon detector.

[0085] Step 15: In the lithography area, etch the contour of the detector using the ICP - PECVD (Inductively Coupled Plasma - Enhanced Chemical Vapor Deposition) process.

[0086] Step 16: In the lithography area, etch the contour of the waveguide detector using the DRIE (Deep Reactive Ion Etching) process to obtain the waveguide detector.

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

[0088] It should be noted that some steps of the above - mentioned method can be executed alone or in combination, and can be executed in parallel or sequentially, not limited to the specific operation sequence shown in the figure.

[0089] Based on the above waveguide integrated superconducting single photon detector, the present disclosure also provides a test device for a waveguide integrated superconducting single photon detector. The device includes:

[0090] A waveguide integrated superconducting single photon detector, configured to receive an optical signal and emit an electrical signal.

[0091] A refrigeration device, configured to accommodate the waveguide integrated superconducting single photon detector and keep it in a superconducting state.

[0092] A readout circuit, electrically connected to the waveguide integrated superconducting single photon detector, configured to receive its electrical signal and amplify it to a readable state.

[0093] An analysis device, connected to the readout circuit, configured to analyze the electrical signal output by the readout circuit.

[0094] As Figure 10 shown, in some embodiments of the present disclosure, the test device for a 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 in 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. Among them, a part of the light enters a power meter 105 as a reference port, and the other part of the light enters the cryogenic refrigerator 106, and is coupled into the waveguide integrated superconducting single photon detector through a lens fiber for detection. After passing through the readout circuit 107, the incident photons are counted by the oscilloscope 108 or the counter 109.

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

[0096] The above describes the embodiments of the present disclosure. However, these embodiments are only for illustrative purposes and not for limiting the scope of the present disclosure. Although the embodiments are described separately above, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, and all such substitutions and modifications should fall within the scope of the present disclosure.

Claims

1. A waveguide-integrated superconducting single-photon detector, characterized in that, It includes: a substrate, a lower cladding, a mode spot converter, a waveguide detector, and an upper cladding; The lower cladding is located on the upper surface of the substrate; The mode spot converter and the waveguide detector are located between the lower cladding and the upper cladding; The mode spot converter includes two tapered mode spot converters with symmetric narrow ends arranged staggeredly; The waveguide detector includes 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 to the electrode layer; The wide end of one of the tapered mode spot converters is connected to the waveguide core layer.

2. The detector according to claim 1, wherein An 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 and the absorbing layer.

4. The detector according to claim 1, characterized in that, The photon absorption layer is U-shaped, the electrode layer is in two pieces, the bent part 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.

5. The detector according to claim 1, wherein The upper surfaces of the two tapered mode spot converters and the upper surface of the waveguide core layer are in the same horizontal plane, and the lower surfaces of the two tapered mode spot converters and the lower surface of the waveguide core layer are in the same horizontal plane.

6. A method for fabricating a waveguide-integrated superconducting single-photon detector, characterized in that, It includes steps: S1 Form a lower cladding on the upper surface of the substrate; S2 Form a first growth layer, and form an electrode layer on the upper surface of the first growth layer in a first predetermined area; S3 Etch the first growth layer to form a waveguide core layer with a predetermined structure and two tapered mode spot converters with symmetric narrow ends arranged staggeredly; S4 Form a second growth layer and etch it to form a photon absorption layer with a predetermined structure; S5 Form an upper cladding; S6 Etch in a second predetermined area to expose the electrode layer.

7. The method according to claim 6, wherein After step S5, it includes steps: S51 Form an absorbing layer above the upper cladding.

8. The method according to claim 7, wherein The step S51 of forming an absorbing layer above the upper cladding includes: S511 Form a buffer layer on the upper surface of the upper cladding; S512 Form an absorbing layer on the upper surface of the buffer layer.

9. The method according to claim 6, wherein The structure of the photon absorption layer is U-shaped, the electrode layer is in two pieces, and the two ends of the U-shaped photon absorption layer are respectively connected to the two electrode layers.

10. A waveguide integrated superconducting single photon detector test device, characterized in that, It includes: a waveguide integrated superconducting single-photon detector for receiving an optical signal and emitting an electrical signal; A refrigeration device for accommodating the waveguide integrated superconducting single-photon detector and keeping it in a superconducting state; A readout circuit for being electrically connected to the waveguide integrated superconducting single-photon detector, receiving its electrical signal and amplifying it to a readable state; An analysis device connected to the readout circuit for analyzing the electrical signal output by the readout circuit.

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