A device preparation method for regulating the speed of SNSPD on a chip

Abstract

The present invention discloses a method for fabricating a device for regulating the speed of an SNSPD on a chip. The device includes a nanowire in the electrode lead region and a nanowire in the photo-responsive region, and the two are connected in series. The superconducting nanowire single-photon detector structure proposed in this paper changes the width of the nanowire in the electrode lead region to be smaller than the width of the nanowire in the photo-responsive region. Thus, when the nanowire in the photo-responsive region normally responds to photons, the nanowire in the electrode lead region quenches superconductivity to form an on-chip series resistance, and further, the recovery speed of the superconducting nanowire single-photon detector after responding to a photon can be regulated.

Description

Technical Field

[0001] The present invention belongs to the technical field of single-photon detection, and specifically relates to a method for fabricating a device for on-chip regulating the speed of a SNSPD. Background Art

[0002] High-speed and high-efficiency superconducting nanowire single-photon detectors are urgently needed for applications such as quantum communication and deep-space optical communication. However, in order to achieve a high coupling efficiency with optical fibers, superconducting nanowire single-photon detectors generally need to wind a uniform nanowire back and forth to form a circular photosensitive surface with a diameter larger than the core diameter of the optical fiber. The long nanowire brings a large dynamic inductance L k , which further restricts the rapid recovery of the device after detecting photons, resulting in a certain mutual restriction relationship between efficiency and speed.

[0003] As Figure 1 shown, the circuit model of the SNSPD device is a series connection of a dynamic inductance L k and a dynamic resistance R n (t), where R n (t) is related to the photon detection event. When there is no signal photon, the device is in the superconducting state and R n (t) is 0; when the device absorbs a photon, the device changes from the superconducting state to the high-resistance state, and R n (t) is approximately equal to 5 kΩ and lasts for about several hundred ps. At this time, the current in the device quickly transfers to the load resistance Z0, corresponding to the time τ r =L k / (R n (t)+Z0). Subsequently, the device returns to the superconducting state, and the power supply starts to charge the device. The corresponding recovery time formula is τ f =L k / Z0, where L k is the dynamic inductance of the device and Z0 is the recovery resistance, generally 50 Ω. Since R n (t) is much larger than Z0, the recovery time corresponding to a general photon event is τ f .

[0004] Generally, in order to accelerate the recovery speed, it can be achieved by reducing the dynamic inductance L k or increasing the load resistance Z0. However, reducing the dynamic inductance generally reduces the coupling efficiency and thus leads to a decrease in the detection efficiency of the device. And increasing the load resistance can generally use off-chip resistors and on-chip resistors. The former requires changing the device packaging structure, and the latter requires adding additional process steps. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for fabricating a device for on-chip regulating the speed of a SNSPD to solve the problems raised in the above background art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for fabricating a device for on-chip regulating the speed of a SNSPD. First, the resistance of the nanowire, which is a constituent unit of the superconducting nanowire single-photon detector, can be regulated by the current flowing through the nanowire. Second, the nanowire is divided into two series-connected parts, one part serves as a photosensitive surface to respond to photons, and the other part serves as a series resistance to regulate the recovery speed.

[0008] As a further technical solution of the present invention: The nanowire in the electrode lead region is replaced with a narrower nanowire to form a series resistance.

[0009] Compared with the prior art, the beneficial effects of the present invention are:

[0010] The structure of the superconducting nanowire single-photon detector proposed in this paper changes the nanowire in the electrode lead region to a narrower nanowire, thereby forming a series resistance, which can effectively regulate the device recovery speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is the circuit diagram of the superconducting nanowire single-photon detector circuit.

[0012] Figure 2 is the structure diagram of a conventional superconducting nanowire single-photon detector.

[0013] Figure 3 is the structure diagram of the superconducting nanowire single-photon detector of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0015] Embodiment 1. A method for fabricating a device for on-chip regulating the speed of a SNSPD. First, the resistance of the nanowire, which is a constituent unit of the superconducting nanowire single-photon detector, can be regulated by the current flowing through the nanowire. Second, the nanowire is divided into two series-connected parts, one part serves as a photosensitive surface to respond to photons, and the other part serves as a series resistance to regulate the recovery speed.

[0016] The working principle is as follows: As Figure 2 shown, the structure of a conventional superconducting nanowire single-photon detector consists of an electrode lead region formed by a wider nanowire and a photon response region formed by a narrower nanowire. In this design, as Figure 3As shown, the nanowires in the electrode lead region are replaced with nanowires having a narrow width to form a series resistance and regulate the recovery speed.

[0017] Refer to the attached drawings Figure 1 As shown, the SNSPD circuit adopted in this design includes a power supply Vo, a resistor Rs, a resistor Zo, and a nanowire. The power supply Vo, the resistor Rs, and the resistor Zo are connected in series, and the nanowire is connected in parallel across the resistor Zo. The nanowire consists of an inductor Lk, a single-pole double-throw switch S, and a resistor Rn(t). The moving end of the single-pole double-throw switch S is connected to the inductor Lk, the other end of the inductor Lk is connected to the resistor Rs and the resistor Zo, one fixed end of the single-pole double-throw switch S is connected to the resistor Rn(t), the other fixed end of the single-pole double-throw switch S is grounded, and the other end of the resistor Rn(t) is grounded. The resistor Zo is a recovery resistor.

[0018] The nanowires in the electrode lead region are replaced from nanowires having a width greater than the photo-responsive region with nanowires having a width less than the photo-responsive region. The width of the nanowires in the photo-responsive region is w1, and the width w2 of the nanowires in the electrode region is set to be between 0.85w1 and 0.95w1.

[0019] The nanowires in the electrode lead region are replaced with nanowires having a narrow width to form a series resistance, and the counting rate can generally be increased by more than 6 times.

[0020] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed within the present invention.

[0021] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A device preparation method for regulating the speed of a superconducting nanowire single-photon detector, characterized in that, First, the resistance of the nanowire, which is the constituent unit of the superconducting nanowire single-photon detector, is regulated by the current flowing through the nanowire. Secondly, the nanowire is divided into two series-connected parts. One part acts as a photosensitive surface to respond to photons, and the other part acts as a series resistance to regulate the recovery speed. The nanowire in the electrode lead region is replaced with a nanowire having a width smaller than that of the light-responsive region from a nanowire having a width greater than that of the light-responsive region. The width w1 of the nanowire in the light-responsive region and the width w2 of the nanowire in the electrode region are between 0.85w1 and 0.95w1.

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