A cascadable low-temperature and low-noise current pulse amplifier

Abstract

The present invention relates to a cascadable low-temperature and low-noise current pulse amplifier. The pulse amplifier includes an nTron device, an input coupling circuit, an output coupling circuit, and a bias circuit. The current signal to be detected is coupled to the gate terminal of the nTron through the input coupling circuit. The drain terminal of the nTron is connected to the signal output port V_out through the output coupling circuit. The bias current of the nTron is connected to the nTron through the bias circuit. The signal output port directly outputs the signal or is connected to the input coupling circuit in the next-stage pulse amplifier. The cascadable low-temperature and low-noise current pulse amplifier of the present invention operates in an extremely low-temperature environment, hardly introduces additional noise, amplifies weak current pulse signals to a certain extent, and improves the signal-to-noise ratio of weak current pulse signals. Moreover, the system has scalability and can achieve different amplification requirements through cascading.

Description

Technical Field

[0001] The present invention relates to the field of cryogenic amplification of output pulse signals of superconducting nanowire single-photon detectors, and particularly to a cascadable cryogenic low-noise current pulse amplifier. Background Art

[0002] SNSPD (superconducting nanowire single-photon detector) is a photon-counting detector that detects, analyzes, and processes optical signals at the photon scale. Its output signal cannot be directly detected and must be amplified using a low-noise amplifier. In the prior art, the conventional amplification method is to use a room-temperature low-noise amplifier, but the noise coefficient of the room-temperature amplifier limits the signal-to-noise ratio of its output and affects the reading of photon detection information. If a cryogenic semiconductor radio-frequency amplifier is used, the power consumption of the amplifier will increase the burden on the refrigeration system, which is not conducive to the integration of large-scale array devices. Therefore, it is necessary to find a current pulse amplifier with low power consumption, high gain, and low noise in a cryogenic environment. Summary of the Invention

[0003] To solve the existing technical problems, the present invention provides a cascadable cryogenic low-noise current pulse amplifier.

[0004] The specific content of the present invention is as follows:

[0005] A cascadable cryogenic low-noise current pulse amplifier, the pulse amplifier includes an nTron device, an input coupling circuit, an output coupling circuit, and a bias circuit. The current signal to be detected is coupled to the gate terminal of the nTron through the input coupling circuit. The drain terminal of the nTron is connected to the signal output port V_out through the output coupling circuit. The bias current of the nTron is connected to the nTron through the bias circuit. The signal output port directly outputs the signal or is connected to the input coupling circuit in the next-stage pulse amplifier.

[0006] Further, the input coupling circuit includes a resistor R1, a resistor R2, and an inductor L1. The resistor R1 and the resistor R2 are connected in series. One end of the inductor L1 is connected between the resistor R1 and the resistor R2, and the other end is grounded. The current signal to be detected is connected to the resistor R1, and the resistor R2 is connected to the gate terminal of the nTron.

[0007] Further, the bias current at the gate terminal of the nTron is connected to the gate terminal of the nTron through a resistor R3.

[0008] Further, the source terminal of the nTron is grounded, and the drain terminal of the nTron is connected to an external bias power supply. A resistor R4 and an inductor L2 are connected in series between the external bias power supply and the drain terminal of the nTron.

[0009] Further, an output coupling circuit is provided between the signal output port V_out and the drain end of the nTron. The output coupling circuit includes a resistor R5 and an inductor L3. The resistor R5 is connected between the resistor R4 and the inductor L2. One end of the inductor L3 is connected between the resistor R5 and the external readout circuit, and the other end is grounded.

[0010] Further, when the pulse amplifiers are cascaded, the output coupling circuit of the previous stage is omitted, and the resistor R1 in the input coupling circuit of the subsequent pulse amplifier is directly connected between the resistor R4 and the inductor L2 of the previous pulse amplifier.

[0011] Further, the narrowest part at the channel of the nTron is connected to the gate.

[0012] Further, the pulse amplifier is used to read the signal of the superconducting nanowire single photon detector, and the output signal of the superconducting nanowire single photon detector is connected to the resistor R1 of the pulse amplifier.

[0013] Further, the bias current of the SNSPD is connected to the SNSPD through a resistor.

[0014] The cascadeable cryogenic low-noise current pulse amplifier of the present invention operates in an extremely low-temperature environment, hardly introducing additional noise, achieving a certain amplification of weak signals, and improving the signal-to-noise ratio of weak signals; and the system has scalability and can achieve different amplification requirements through cascading. Description of the Drawings

[0015] The following further clarifies the specific implementation manners of the present invention with reference to the drawings.

[0016] Figure 1 is a schematic diagram of the cascadeable cryogenic low-noise current pulse amplifier of the present invention;

[0017] Figure 2 is a scanning electron beam microscope image of the nTron of the present invention;

[0018] Figure 3 is a schematic diagram of the pulse amplifier of the present invention measuring the signal of the superconducting nanowire single photon detector;

[0019] Figure 4 is Figure 3 's waveform diagram;

[0020] Figure 5 is a schematic diagram of the pulse amplifier of the present invention measuring the signal of the superconducting nanowire single photon detector after cascading;

[0021] Figure 6 is Figure 5 's waveform diagram. Detailed Description of the Invention

[0022] This embodiment discloses a cascadable low-temperature and low-noise current pulse amplifier. As Figure 1 shown, it includes an nTron device, an input coupling circuit, an output coupling circuit, and a bias circuit. The current signal to be detected is coupled to the gate terminal of the nTron through the input coupling circuit. The drain terminal of the nTron is connected to the signal output port V_out through the output coupling circuit. The bias current of the nTron is connected to the nTron through the bias circuit. The signal output port directly outputs the signal or is connected to the input coupling circuit in the next-stage pulse amplifier.

[0023] Figure 2 The following is the scanning electron microscope image of the nTron in this application. As shown in the figure, a single device nTron is a superconducting nanowire three-terminal device that uses an input gate current to control the change of the channel terminal resistance to achieve a logic switch with gating function. The gate terminal of the nTron receives the current signal, the source terminal is grounded, and the drain terminal is connected to the bias current. The nTron uses the formation of a small-range hot island to regulate the current of the superconducting wire perpendicular to it. The superconducting wire quickly turns into a resistive state so that it can drive a large-impedance load and has a strong fan-out ability at the same time. Its channel is biased slightly below the superconducting critical current. When the current pulse at the gate terminal reaches the choke of the device, since the width of the nanowire here is several times smaller than the channel, its critical current will also be correspondingly smaller. When the input current pulse is greater than the critical current here, it first causes the choke to lose superconductivity. Due to the effect of heat diffusion, a large-resistance area, that is, a hot island, is quickly formed in the channel. The formation of this hot island causes the bias current to flow to the load terminal to drive the load. Due to the cooling of the low-temperature environment, the hot island quickly disappears again under normal conditions, and the bias current gradually returns to the channel, and the nTron resumes its working state. Thus, the nTron completes one trigger.

[0024] As Figure 2The nTron scanning electron microscope image in this application is shown. Compared with the early nTron structure (A.N. McCaughan and K.K. Berggren, "A superconducting-nanowire three-terminal electrothermal device.", Nano Lett. 14(10), 5748–53(2014).), in this application, an optimized design is carried out at the connection between the gate and the channel. The narrowest part of the channel is connected to the gate to ensure that when the gate quenches, the position where the hot island forms is at the part connected to the nTron, thereby inducing the overall quenching of the channel and completing one operation of the nTron.

[0025] The superconducting nanowire single-photon detector (SNSPD) is a photon-counting detector, that is, each light detection outputs an electrical pulse, and the amplitude of the pulse does not carry additional information. What is concerned during measurement is the arrival time of the pulse. From the above description, the working principle of the nTron is a switch with gain, or can be regarded as a comparator, which can realize the reading of extremely small electrical pulse signals. In this embodiment, a pulse amplifier with an nTron is used to effectively read the SNSPD signal.

[0026] Specifically, the pulse amplifier includes four ports. Among them, the port V_in is the input signal port, that is, the output signal of the SNSPD to be detected passes through this port and triggers the nTron through coupling to generate an output pulse; the port I_gb is the adjustment port for the sensitivity of the input signal. By changing the current magnitude required to trigger the gate terminal of the nTron at the port I_gb, the detection of the input current amplitude is realized; the port I_cb provides power for the nTron and provides a bias current I-bias for the Channel of the nTron; the signal output port V_out outputs the signal, which can be either connected to the V_in port of the next-stage pulse amplifier or directly output the signal. In actual use, cascade or single-stage detection can be freely selected according to needs.

[0027] A resistor R1, a resistor R2, and an inductor L1 are arranged between the port V_in and the gate terminal of the nTron. The resistor R1 and the resistor R2 are in series. One end of the inductor L1 is connected between the resistor R1 and the resistor R2, and the other end is grounded. A typical value in this embodiment is that the resistor R1 and the resistor R2 are 20Ω, and the inductor L1 is 100nH. In actual use, the values of the resistor and the inductor can be adjusted according to needs.

[0028] Resistors R1 and R2 ensure the isolation of the circuit before the gate is triggered. Their sufficiently small values also ensure that the current pulse to be detected can be normally coupled to the gate port of nTron. Inductor L1 in the input part provides a current discharge path for the recovery after the gate is triggered, and at the same time shows a large impedance when the high-speed signal to be detected is input, so that the signal can be normally coupled to the gate of nTron.

[0029] A resistor R3 is provided between port I_gb and the gate of nTron. This port can provide a bias current for the gate of nTron, so as to realize the regulation of the input sensitivity of the pulse amplifier. When the input signal is large enough, the bias current of the gate can be cancelled. A typical value in this embodiment is that the resistance value of resistor R3 is 10 kΩ, and the resistance value can be adjusted according to needs in actual use.

[0030] A series-connected resistor R4 and inductor L2 are provided between port I_cb and the drain of nTron. The current I_bias provided by the external power supply of port I_cb is to provide a bias current for the Channel of nTron, and after nTron receives the current pulse to form a hot island, it flows to the signal output port V_out to realize the output of the signal. A typical value in this embodiment is that the resistance value of resistor R4 is 10 kΩ and the inductance of L2 is 300 nH. The resistance and inductance values can be adjusted according to needs in actual use.

[0031] After the signal is output, it passes through an output coupling circuit to reach the signal output port V_out. The output coupling circuit includes a series-connected resistor R5 and inductor L3. One end of resistor R5 is connected between resistor R4 and inductor L2, one end of inductor L3 is grounded, and the signal output port V_out is set between resistor R5 and inductor L3. Since the detection of SNSPD focuses on the arrival time of the pulse obtained at the rising edge, this output coupling circuit filters out the low-frequency components in the output signal, and can improve the working speed.

[0032] For a single pulse amplifier or a cascaded amplifier, the output port V_out can be directly connected to an oscilloscope for reading, or can be connected to a room temperature LNA (low noise amplifier) via a coaxial cable to realize further amplification of the signal.

[0033] When pulse amplifiers are cascaded, resistors R5 and inductor L2 can be removed because their functions are similar to those of resistor R1 and inductor L1. When cascaded, the resistor R1 and inductor L1 of the subsequent stage provide a current discharge path after the current is triggered at the output terminal of the nTron of the previous stage during direct output. Therefore, these two components can be omitted during cascading. A typical value in this embodiment is that resistor R5 is 20Ω and inductor L3 is 100nH. In actual use, the values of the resistor and inductor can be adjusted as needed.

[0034] As Figure 3 shown in the schematic diagram of measuring the SNSPD signal with a single pulse amplifier, the power supply of the SNSPD drives the SNSPD after passing through a 10kΩ resistor. Figure 4 This is its waveform diagram. Among them, the black line is the signal directly output by the SNSPD, and the gray line is the SNSPD signal read by the nTron. It can be seen that, with almost no additional noise introduced, compared with the signal obtained by directly connecting the output of the SNSPD to an external amplifier, the SNSPD signal read by the nTron has a 2.6-fold (8.3dB) amplification gain, improving the signal-to-noise ratio.

[0035] As Figure 5 shown in the schematic diagram of measuring the SNSPD signal with two cascaded pulse amplifiers, the power supply of the SNSPD drives the SNSPD after passing through a 10kΩ resistor. Figure 6 This is its waveform diagram, where the light gray line is the waveform diagram after cascading, and it is Figure 4 compared. It can be seen that the cascaded pulse amplifier achieves further amplification, and the total amplification gain reaches 7.6 times (17.6dB).

[0036] Compared with the current readout scheme that generally uses a low-noise amplifier to amplify the signal and then operates at room temperature, the current detection discriminator designed by us operates in an extremely low-temperature environment, hardly introducing additional noise, achieving a certain amplification of weak signals, and improving the signal-to-noise ratio of weak signals; and the system has scalability and can achieve different amplification requirements through cascading. At the same time, during the development of SNSPD towards arrayization, it is necessary to integrate amplification, multiplexing technology, etc. onto the chip. In these applications, nTron is very conducive to large-scale integration due to its low power consumption, small size, and being a superconducting material, that is, each signal of the SNSPD in the array is amplified by the SNSPD. Therefore, the pulse amplifier in this embodiment has high economic benefits.

[0037] Numerous specific details have been set forth in the foregoing description in order to provide a thorough understanding of the present invention. However, the above description is only a preferred embodiment of the present invention, and the present invention can be implemented in many other ways different from those described herein. Therefore, the present invention is not limited by the specific implementations disclosed above. At the same time, any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes. All modifications, equivalent changes and decorations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A cascadeable low-temperature and low-noise current pulse amplifier, characterized in that: The pulse amplifier includes an nTron device, an input coupling circuit, an output coupling circuit, and a bias circuit. The current signal to be detected is coupled to the gate terminal of the nTron through the input coupling circuit. The drain terminal of the nTron is connected to the signal output port V_out through the output coupling circuit. The bias current of the nTron is connected to the nTron through the bias circuit. The signal output port directly outputs the signal or is connected to the input coupling circuit in the next-stage pulse amplifier. The input coupling circuit includes a resistor R1, a resistor R2, and an inductor L1. The resistor R1 and the resistor R2 are connected in series. One end of the inductor L1 is connected between the resistor R1 and the resistor R2, and the other end is grounded. The current signal to be detected is connected to the resistor R1, and the resistor R2 is connected to the gate terminal of the nTron. The source terminal of the nTron is grounded. An external bias power supply is connected to the drain terminal of the nTron. A resistor R4 and an inductor L2 are connected in series between the external bias power supply and the drain terminal of the nTron. An output coupling circuit is provided between the signal output port V_out and the drain terminal of the nTron. The output coupling circuit includes a resistor R5 and an inductor L3. The resistor R5 is connected between the resistor R4 and the inductor L2. One end of the inductor L3 is connected between the resistor R5 and the external readout circuit, and the other end is grounded. When the pulse amplifiers are cascaded, the output coupling circuit of the previous stage is omitted. In the input coupling circuit of the next-stage pulse amplifier, the resistor R1 is directly connected between the resistor R4 and the inductor L2 of the previous-stage pulse amplifier.

2. The cascadable low-temperature and low-noise current pulse amplifier according to claim 1, wherein: The bias current at the nTron gate terminal is connected to the gate terminal of the nTron through the resistor R3.

3. The cascadeable low-temperature and low-noise current pulse amplifier according to claim 1, wherein: The narrowest part at the channel of the nTron is connected to the gate.

4. The cascadable low-temperature and low-noise current pulse amplifier according to claim 1, characterized in that: The pulse amplifier is used to read the signal of the superconducting nanowire single-photon detector. The output signal of the superconducting nanowire single-photon detector is connected to the resistor R1 of the pulse amplifier.

5. The cascadeable low-temperature and low-noise current pulse amplifier according to claim 4, wherein: The bias current of the SNSPD is connected to the SNSPD through a resistor.

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