Series nanowire detector

Abstract

The utility model provides a series nanowire detector, the series nanowire detector comprises a substrate and a detection structure formed on the substrate, the detection structure comprises M nanowires, 2M connecting wires and M resistors, the M nanowires are connected in series, the M resistors are respectively connected in parallel with two ends of the M nanowires through the 2M connecting wires, and M is a natural number greater than or equal to 2; wherein the nanowire and the connecting line are manufactured by adopting the same superconductive lamination layer, and the superconductive lamination layer sequentially comprises a first superconductive layer, a dielectric layer and a second superconductive layer from bottom to top. The series nanowire detector provided by the utility model solves the problem that there is no multi-photon resolution scheme capable of ensuring limit efficiency in the prior art.

Description

Technical Field

[0001] The utility model belongs to the technical field of detection, and particularly relates to a series-connected nanowire detector. Background Art

[0002] The optical quantum state is composed of the superposition of photon number states, and the PNR (high-fidelity photon number resolution) single-photon detector that can effectively distinguish and detect these states has always been a key goal of photon detection. It not only plays an important role in basic research, but also has been widely recognized in the applications of quantum optics and quantum information. For example, linear optical quantum computing, Gaussian boson sampling, quantum communication, and quantum metrology. So far, superconducting transition edge sensors have become a promising PNR single-photon detector, which can inherently resolve multi-photons, achieve a system detection efficiency of more than 90% at a wavelength of 1550 nm, and a maximum resolution of up to 20. However, the low count rate (usually below 1 MHz), moderate timing resolution (~ns), and the requirement for an ultra-low operating temperature (~100 mK) and other factors have hindered its deployment in high-repetition rate experiments and limited the scalability. Another implementation of the PNR single-photon detector includes using traditional single-photon detectors (SPDs) and spatial or temporal multiplexing techniques. Here, multiple incident photons are distributed over a series of spatial or temporal modes and then detected independently.

[0003] Superconducting nanowires have become promising candidates for detectors in quantum information systems due to their high sensitivity and fast response. The progress of quantum information technology has promoted the rapid development of superconducting single-photon detectors (SSPDs) based on superconducting nanowires in the past two decades, achieving nearly uniform system efficiency (≥98%), low timing jitter (≤20 ps), low dark count rate (≤100 Hz), and high count rate (≥10 MHz). Although SSPDs are traditionally considered "binary" detectors that can only distinguish between 0 and ≥1 photons, various methods have been proposed to improve the photon number resolution. For example, using traditional SSPD technology to directly calculate the number of hot spots generated under multi-photon illumination, using on-chip optical waveguide structures for temporal multiplexing, and using shunt resistors for spatial multiplexing. Among them, the first method can improve the signal-to-noise ratio by impedance matching tapers, low-timing jitter devices, and large inductance microstrips. However, the maximum resolvable photon number does not exceed 10. The second method can resolve up to 100 photons, but still faces challenges in achieving high-fidelity detection due to optical coupling losses and the limitation of the time distribution on the detection speed. The third method can increase the maximum resolvable photon number to 28 and the single-photon detection efficiency to 88%, but there is still a significant gap from the maximum efficiency of 99% that can be achieved by current SSPDs. All in all, there is currently no multi-photon resolution scheme that can guarantee the ultimate efficiency.

[0004] It should be noted that the above introduction of the technical background is only for the convenience of clearly and completely explaining the technical solution of the present invention and facilitating the understanding of those skilled in the art. It cannot be considered that the above technical solutions are well-known to those skilled in the art merely because these solutions are described in the background art part of the present invention. Summary of the Invention

[0005] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a series nanowire detector, which is used to solve the problem that there is no multi-photon resolution scheme that can ensure the ultimate efficiency in the prior art.

[0006] To achieve the above purpose and other related purposes, the present invention provides a series nanowire detector, and the series nanowire detector includes:

[0007] A substrate and a detection structure formed thereon, the detection structure includes M nanowires, 2M connection lines and M resistors. The M nanowires are connected in series, and the M resistors are respectively connected in parallel to both ends of the M nanowires through the 2M connection lines, where M is a natural number greater than or equal to 2; wherein, the nanowires and the connection lines are made of the same superconducting stack, and the superconducting stack includes a first superconducting layer, a dielectric layer and a second superconducting layer in sequence from bottom to top.

[0008] Optionally, the resistor is formed on the substrate and covers the resistive contact end of the connection line to be in electrical contact with at least the second superconducting layer in the connection line.

[0009] Optionally, the resistance value of the resistor is 30Ω - 60Ω.

[0010] Optionally, the line width of the connection line is greater than the line width of the nanowire, and the line width of the connection line is an equidistant line width or a tapered line width.

[0011] Optionally, the line width of the nanowire is 30nm - 200nm, and the line pitch of the nanowire is 60nm - 400nm.

[0012] Optionally, the thickness of the first superconducting layer is 5nm - 10nm, the thickness of the dielectric layer is 2nm - 10nm, and the thickness of the second superconducting layer is 5nm - 10nm.

[0013] Optionally, the series nanowire detector further includes a reflection structure formed between the substrate and the detection structure.

[0014] Optionally, the reflection structure includes a Bragg reflector.

[0015] As described above, in the series nanowire detector of the present utility model, by connecting multiple nanowires in series and using the amplitude multiplexing of the series nanowires to read out, the number of distinguishable photons of the detector is expanded. At the same time, a superconducting stack with a sandwich structure is used to fabricate the nanowires, which can not only solve the restrictive relationship between photon absorption and photon response, making it easier for the detector to obtain a saturation efficiency close to the limit, but also increase the critical current of the detector to facilitate obtaining a higher signal-to-noise ratio. A higher signal-to-noise ratio is beneficial to further expanding the number of distinguishable photons of the detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It shows a schematic structural diagram of a series nanowire detector in an embodiment of the present utility model.

[0017] Figure 2 It shows another schematic structural diagram of a series nanowire detector in an embodiment of the present utility model.

[0018] Figures 3 to 5 It shows Figure 1 Schematic diagrams of the manufacturing steps when the cross-section of the shown detector along the AB direction, where Figure 3 is a schematic diagram of forming a superconducting stack, Figure 4 is a schematic diagram of forming nanowires and connection lines, Figure 5 is a schematic diagram of forming a resistor.

[0019] Figures 6 to 8 It shows Figure 1 Schematic diagrams of the manufacturing steps when the cross-section of the shown detector along the CD direction, where Figure 6 is a schematic diagram of forming a superconducting stack, Figure 7 is a schematic diagram of forming nanowires and connection lines, Figure 8 is a schematic diagram of forming a resistor.

[0020] Figure 9 It shows a schematic diagram of the system detection efficiency and dark count rate of a series nanowire detector in an embodiment of the present utility model.

[0021] Figures 10 to 14 It shows a schematic diagram of the output amplitude distribution of a series nanowire detector in an embodiment of the present utility model under different light intensities, where Figure 10 is a schematic diagram of the output amplitude distribution corresponding to an average number of photons per pulse equal to 5, Figure 11 is a schematic diagram of the output amplitude distribution corresponding to an average number of photons per pulse equal to 20, Figure 12 is a schematic diagram of the output amplitude distribution corresponding to an average number of photons per pulse equal to 100, Figure 13 is a schematic diagram of the output amplitude distribution corresponding to an average number of photons per pulse equal to 500, Figure 14 is a schematic diagram of the output amplitude distribution corresponding to an average number of photons per pulse equal to 5000.

[0022] Figure 15 It shows a schematic diagram of the counting ratio during the scanning measurement of the series nanowire detector in the embodiment of the present utility model.

[0023] Figure 16 It shows a schematic diagram of the IV curve of the series nanowire detector in the embodiment of the present utility model.

[0024] Description of component labels

[0025] 100 Series nanowire detector

[0026] 110 Substrate

[0027] 120 Superconducting stack

[0028] 121 First superconducting layer

[0029] 122 Dielectric layer

[0030] 123 Second superconducting layer

[0031] 130 Nanowire

[0032] 140 Connecting wire

[0033] 150 Metal layer

[0034] 160 Resistor

[0035] 170 Detection structure

[0036] 180 Reflection structure Detailed implementation manners

[0037] The following uses specific specific examples to illustrate the implementation manners of the present utility model. Those skilled in the art can easily understand other advantages and effects of the present utility model from the content disclosed in this specification. The present utility model can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present utility model.

[0038] Please refer to Figures 1 to 16 . It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present utility model in a schematic manner. Therefore, only the components related to the present utility model are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components during actual implementation. The form, quantity, and ratio of each component during actual implementation can be arbitrarily changed, and the layout form of its components may also be more complex.

[0039] Such as Figure 1 and Figure 2As shown, this embodiment provides a series nanowire detector 100, including a substrate 110 and a detection structure 170. Further, it further includes a reflection structure 180.

[0040] As Figure 1 shown, the substrate 110 is used to provide mechanical support for the series nanowire detector 100; in one embodiment, the material of the substrate 110 is silicon (Si). Of course, the substrate 110 can also be a substrate of other materials, which has no substantial impact on the implementation of the solution of this embodiment and is not limited thereto.

[0041] As Figure 1 shown, the detection structure 170 is formed on the substrate 110 and is used for multi-photon resolution detection. In one embodiment, the detection structure 170 includes M nanowires 130, 2M connection lines 140, and M resistors 160, where M is a natural number greater than or equal to 2. Among them, the M nanowires 130 are connected in series, and the M resistors 160 are respectively connected in parallel to both ends of the M nanowires 130 through the 2M connection lines 140; the M series-connected nanowires 130 constitute a complete photosensitive surface, so as to expand the resolvable photon number of the detector by using the amplitude multiplexing reading of the series nanowires, and each nanowire 130 is connected in parallel with a resistor 160 for signal reading.

[0042] In the above embodiment, the nanowires 130 and the connection lines 140 are made of the same superconducting stack 120. Among them, the superconducting stack 120 includes a first superconducting layer 121, a dielectric layer 122, and a second superconducting layer 123 in sequence from bottom to top; making the nanowires 130 with the superconducting stack 120 can not only solve the restrictive relationship between photon absorption and photon response, making it easier for the detector to obtain a saturation efficiency close to the limit, but also improve the critical current of the detector to obtain a higher signal-to-noise ratio, and a higher signal-to-noise ratio is beneficial to further expand the resolvable photon number of the detector. In an example, the material of the first superconducting layer 121 is niobium nitride (NbN) or niobium titanium nitride (NbTiN), the material of the dielectric layer 122 is silicon dioxide (SiO2) or aluminum nitride (AlN), and the material of the second superconducting layer 123 is niobium nitride (NbN) or niobium titanium nitride (NbTiN); in addition, the thickness of the first superconducting layer 121 is 5 nm to 10 nm, the thickness of the dielectric layer 122 is 2 nm to 10 nm, and the thickness of the second superconducting layer 123 is 5 nm to 10 nm.

[0043] In practical applications, the nanowire 130 is usually made into a meandering shape. Among them, the line width of the nanowire 130 is 30 nm to 200 nm, and the line pitch of the nanowire 130 is 60 nm to 400 nm. In addition, in order to avoid the connecting wire 140 from being photon-responsive, the line width of the connecting wire 140 is set to be greater than the line width of the nanowire 130; in one example, the line width of the connecting wire 140 is an equidistant line width, that is, the connecting wire 140 has a uniform line width; of course, in other examples, the line width of the connecting wire 140 can also be a tapered line width. At this time, the end of the connecting wire 140 close to the nanowire 130 is used as the nanowire contact end, and the end of the connecting wire 140 far from the nanowire 130 is used as the resistance contact end. Then, the line width of the connecting wire 140 gradually increases from the nanowire contact end to the resistance contact end. Using a tapered line width is beneficial to reducing the equivalent inductance of the connecting wire 140, thereby improving the signal response speed.

[0044] Specifically, the resistor 160 is formed on the substrate 110 and covers the resistance contact end of the connecting wire 140 to be electrically connected to at least the second superconducting layer 123 in the connecting wire 140; in one example, the resistor 160 is not electrically connected to both the first superconducting layer 121 and the second superconducting layer 123 in the connecting wire 140 at the same time, but is only electrically connected to the second superconducting layer 123 in the connecting wire 140 and is not electrically connected to the first superconducting layer 121 in the connecting wire 140. In practical applications, the material of the resistor 160 includes titanium (Ti), gold (Au), or titanium-palladium alloy (TiPd), and the resistance value of the resistor 160 is usually 30 Ω to 60 Ω.

[0045] As Figure 2 shown, the reflection structure 180 is formed between the substrate 110 and the detection structure 170 for photon reflection, avoiding photons passing through the nanowire 130 without being absorbed, thereby improving the photon absorption efficiency. In one implementation, the reflection structure 180 includes a Bragg reflector; among them, the Bragg reflector includes a plurality of stacked overlapping layers, and the overlapping layer includes a stacked high-refractive-index dielectric layer and a low-refractive-index dielectric layer; in practical applications, the number of stacked overlapping layers is related to the wavelength of the incident light and can be set according to the actual application scenario. Of course, in other implementations, the reflection structure 180 can also be implemented by other structures that can achieve the photon reflection function, which has no substantial impact on the implementation of the solution of this embodiment and is not limited thereto. It should be noted that when the series nanowire detector 100 includes the reflection structure 180, the nanowire 130, the connecting wire 140, and the resistor 160 in the detection structure 170 are all formed on the reflection structure 180, rather than on the substrate 110.

[0046] The series nanowire detector 100 of this embodiment can have photon number resolution ability by only adding connection wires 140 and resistors 160 without changing the structure and parameters of the nanowire 130; for designs with special requirements for certain parameters, such as saturation, efficiency, etc., the photon number resolution ability can be improved by only changing the parameters of the nanowire 130 without changing the connection wires 140 and resistors 160.

[0047] This embodiment also provides a manufacturing method of the series nanowire detector 100, including the following steps; hereinafter, please refer to Figure 1 , and refer to Figures 3 to 8 for a detailed description of the manufacturing method of this embodiment.

[0048] Step S1, as shown in Figure 3 and Figure 6 , provide a substrate 110, and form a superconducting stack 120 on the substrate 110, wherein the superconducting stack 120 includes a first superconducting layer 121, a dielectric layer 122, and a second superconducting layer 123 in sequence from bottom to top. In an example, the material of the substrate 110 is silicon, the material of the first superconducting layer 121 is niobium nitride (NbN) or niobium titanium nitride (NbTiN), the material of the dielectric layer 122 is silicon dioxide (SiO2) or aluminum nitride (AlN), the material of the second superconducting layer 123 is niobium nitride (NbN) or niobium titanium nitride (NbTiN). Additionally, the thickness of the first superconducting layer 121 is 5 nm to 10 nm, the thickness of the dielectric layer 122 is 2 nm to 10 nm, and the thickness of the second superconducting layer 123 is 5 nm to 10 nm.

[0049] Of course, before forming the superconducting stack 120 in step S1, it may further include the step of forming a reflection structure 180 on the substrate 110 (not shown in the figure). At this time, the superconducting stack 120 is formed on the reflection structure 180, and the subsequent nanowire 130, connection wires 140, and metal layer 150 are all formed on the reflection structure 180. In an example, the reflection structure 180 includes a Bragg reflector; wherein, the Bragg reflector includes several stacked overlapping layers, and the overlapping layer includes a stacked high refractive index dielectric layer and a low refractive index dielectric layer; in practical applications, the number of stacked overlapping layers is related to the wavelength of the incident light and can be set according to the actual application scenario.

[0050] Step S2, as shown in Figure 4 and Figure 7As shown, the superconducting stack 120 is etched to form M nanowires 130 and 2M connection lines 140. Among them, the M nanowires 130 are connected in series, and the 2M connection lines 140 are correspondingly connected to both ends of the M nanowires 130; one end of the connection line 140 close to the nanowire 130 is used as the nanowire contact end, and the end of the connection line 140 far from the nanowire 130 is used as the resistor contact end. Since each nanowire 130 corresponds to two connection lines 140, the resistor regions can be defined by the resistor contact ends of the two connection lines 140, such as Figure 7 the region located between the two connection lines 140 in

[0051] Step S3, as Figure 5 and Figure 8 shown, in a vacuum or nitrogen environment, at least use an ion beam to bombard the resistor contact end of the connection line 140, and deposit a metal layer 150 on the resistor contact end of the connection line 140 and the substrate of the resistor region to fabricate the resistor 160. In one example, the material of the metal layer 150 includes titanium (Ti), gold (Au), or titanium-palladium alloy (TiPd), and the resistance value of the resistor 160 is 30Ω - 60Ω. In practical applications, the second superconducting layer 123 in the superconducting stack 120 is extremely easy to oxidize in the air, and an oxide insulating layer with a thickness of about 1nm will be formed on the surface. This oxide insulating layer will form a contact resistance and affect the resistance value design of the resistor 160; therefore, before depositing the metal layer 150, using an ion beam to bombard the surface of the resistor contact end of the connection line 140 in a vacuum or nitrogen environment can remove this oxide insulating layer, which is beneficial to accurately design the resistance value of the resistor 160. In one example, when bombarding the resistor contact end of the connection line 140 with an ion beam, the filament current is 7V - 12V, the emission current is 0.7A - -0.8A, and the time is 5min - 25min, so as to remove the oxide insulating layer without removing too much of the second superconducting layer 123.

[0052] Next, combined with specific examples, the performance of the series nanowire detector 100 of this embodiment will be described.

[0053] In a specific example, the series nanowire detector is a 32-pixel photon number-resolving device, which sequentially includes a substrate, a Bragg reflector, and a detection structure from bottom to top. Among them, the nanowires and connection wires are made of the same superconducting stack. The superconducting stack sequentially includes a 5.9-nm-thick niobium nitride layer, a 3-nm-thick silicon dioxide layer, and a 5.9-nm-thick niobium nitride layer from bottom to top. The central reflection band is located at 1550 nm. The line width of the nanowire is 80 nm, the line pitch of the nanowire is 160 nm, the area of the photosensitive surface is about 20 μm × 20 μm, and the resistance value of the resistor is 40 Ω.

[0054] The system detection efficiency and dark count rate of the above detector were tested, and the test results are as Figure 9 shown. It can be seen from the figure that at a dark count rate (DCR) of 20 cps, the single-photon SDE (system detection efficiency) of the detector is as high as 98%. The output amplitude distribution of the above detector was tested under different light intensities, and the test results are as Figures 10 to 14 shown. It can be seen from the figure that a total of 32 Gaussian peaks correspond to 32 photons.

[0055] The maximum amplitude output by the detector in this embodiment is linearly related to the number of incident photons. Therefore, the counter scanning measurement method can be used for detector calibration and performance characterization. By controlling the comparison voltage of the counter to scan the output, the counting ratio under different comparison voltages can be obtained, and the photon number distribution can be calculated based on this. Based on this, the above detector was scanned and measured, and the measurement results are as Figure 15 shown. In this way, the photon ratio of different photon numbers can be obtained.

[0056] When the detector is fabricated, the parameters of conventional devices are affected by multiple factors such as nanowire fabrication, film thickness, and film growth conditions. It is difficult to judge the problems that occur during the fabrication process through device parameters. The device in this embodiment adopts a structure with multiple nanowires in series. If some nanowires are poorly fabricated, it will cause the device to partially quench. As Figure 16 shown, curve 1 shows a device with normal preparation, and the quenching process is a straight line; curve 2 shows the situation where some nanowires are poorly prepared. When the bias current continues to increase, the device will partially quench in advance, causing the device to series a quenching resistance in a section, and then continue to quench.

[0057] In summary, for the series nanowire detector of the present utility model, by connecting multiple nanowires in series and using the amplitude multiplexing of the series nanowires to read out, the number of distinguishable photons of the detector is expanded. At the same time, a superconducting stack with a sandwich structure is used to fabricate the nanowires, which can not only solve the restrictive relationship between photon absorption and photon response, making it easier for the detector to obtain a saturation efficiency close to the limit, but also increase the critical current of the detector to facilitate obtaining a higher signal-to-noise ratio. A higher signal-to-noise ratio is beneficial for further expanding the number of distinguishable photons of the detector. Therefore, the present utility model effectively overcomes various drawbacks in the prior art and has high industrial utilization value.

[0058] The above embodiments are merely illustrative of the principles and effects of the present utility model and are not intended to limit the present utility model. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present utility model. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present utility model should still be covered by the claims of the present utility model.

Claims

1. A series nanowire detector, characterized in that The series nanowire detector includes: a substrate and a detection structure formed thereon. The detection structure includes M nanowires, 2M connection lines, and M resistors. The M nanowires are connected in series, and the M resistors are respectively connected in parallel to both ends of the M nanowires through the 2M connection lines, where M is a natural number greater than or equal to 2. Among them, the nanowires and the connection lines are made of the same superconducting stack, and the superconducting stack sequentially includes a first superconducting layer, a dielectric layer, and a second superconducting layer from bottom to top.

2. The series nanowire detector according to claim 1, characterized in that The resistor is formed on the substrate and covers the resistor contact end of the connection line to be electrically contacted with at least the second superconducting layer in the connection line.

3. The series nanowire detector according to claim 1 or 2, characterized in that The resistance value of the resistor is 30Ω - 60Ω.

4. The serial nanowire detector according to claim 1, characterized in that, The line width of the connection line is greater than the line width of the nanowire, where the line width of the connection line is an equal line width or a tapered line width.

5. The series nanowire detector according to claim 1 or 4, characterized in that, The line width of the nanowire is 30nm - 200nm, and the line pitch of the nanowire is 60nm - 400nm.

6. The series nanowire detector according to claim 1, wherein The thickness of the first superconducting layer is 5nm - 10nm, the thickness of the dielectric layer is 2nm - 10nm, and the thickness of the second superconducting layer is 5nm - 10nm.

7. The series nanowire detector according to claim 1, wherein The series nanowire detector further includes a reflection structure formed between the substrate and the detection structure.

8. The series nanowire detector according to claim 7, characterized in that, The reflection structure includes a Bragg reflector.

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