CN100410636C - A circuit module for APD single photon detection - Google Patents

Abstract

The present invention relates to quantum security communication, and specifically relates to a circuit module for APD single-photon detection with capacitance-balanced narrow gate pulse suppression. The circuit module is mainly composed of a signal detection circuit, a signal amplification circuit, a balance suppression circuit and logic signal generation. The circuit structure, in which the balance suppression circuit, except for the variable capacitor C0, its circuit connection and the selection of the parameters of each component are completely consistent with the signal detection and amplification circuit, one-to-one correspondence, and its advantage is that it can realize the near infrared band single The detection of photons adopts a symmetrical circuit balance mode, which effectively offsets the oscillation and overcharge caused by the high-amplitude narrow pulse gate pulse, reduces noise, has high detection efficiency, low noise, and high detection time accuracy.

Description

A circuit module for APD single photon detection

technical field

The invention relates to quantum security communication, and in particular relates to a circuit module for APD single-photon detection with capacitive-balanced narrow gate pulse suppression to realize near-infrared band single-photon detection.

Background technique

Quantum secure communication is communication based on photons. Information is loaded on and transmitted by single photons. The unknown quantum state cannot be cloned. Measuring the quantum will change the quantum state, so that it is impossible for eavesdroppers to obtain information without being discovered. , so in quantum secure communication, single photon detection plays a very important role. The single-photon detectors used in quantum secure communication systems are mainly avalanche photodiodes (APDs). There are three main types of APDs currently used, namely silicon avalanche photodiode (Si-APD), germanium avalanche photodiode (Ge-APD) and indium gallium arsenic avalanche photodiode (InGaAs-APD), which respectively correspond to different wavelengths, Si- APD mainly works at 400nm to 1100nm, Ge-APD at 800nm to 1550nm, and InGaAs-APD at 900nm to 1700nm. For the part where the spectral response overlaps, InGaAs-APD has lower noise and higher frequency response characteristics, so it has basically replaced Ge-APD. The single photon detector made of Si-APD has a detection efficiency of more than 60% in the 700-800nm band under the condition of -20°C, and the noise is ^10-6-10-7 /ns; in the ^1310-1550nm band, Si -APD can no longer be used for single-photon detection; the single-photon detector made of InGaAs-APD has a detection efficiency of about 10% and a noise of 10 in the 1550nm band under the condition of -100℃～-60℃ ^-6 ~ 10 ^-5 /ns. Single-photon detectors made of Si-APD have gradually become mature.

In single-photon detection, the APD generally works in the so-called "Geiger mode". In this mode, the bias voltage across the avalanche photodiode is greater than the avalanche voltage, and when a photon signal reaches the APD, an avalanche is caused. In order to be able to respond to the next photon signal, it is necessary to adopt a certain suppression circuit, so that the avalanche is quickly suppressed after the occurrence, and the APD returns to the state of receiving photons. The methods usually adopted are: passive suppression, active suppression and gate-mode, in which the passive suppression mode has low detection efficiency and large noise; the active suppression mode is mainly used for the detection of optical signals with random arrival times, and can also be It is used for the detection of periodic signals, but it is related to the structure of the APD itself, and not all APDs are suitable; usually, the gate pulse suppression mode is used when detecting periodic optical signals. The gate pulse suppression mode has no requirements for the APD structure, and it is relatively easy to implement More convenient, effective and economical. In quantum secure communication, the gate pulse suppression mode is generally adopted, and its detection efficiency is relatively high, and the noise is relatively low.

The existing gate pulse suppression mode usually only adds a gate pulse at one end of the APD. When the gate pulse is relatively narrow, generally below 50ns, the charge and discharge signals of the APD are connected together, and there is no flat area between them. At this time, when photons arrive, The avalanche signal generated by the APD will be superimposed on its charge and discharge signal. Since the avalanche signal is much smaller than the charge and discharge signal, there is no way to identify it. At the same time, the oscillation and overshoot signal caused by the narrow pulse will affect the signal acquisition. ; Therefore, the gate width of the existing gate pulse suppression mode is relatively wide. When the gate pulse is relatively wide, there is a flat area between the charge and discharge signals of the APD. If photons arrive in this flat area, the avalanche signal generated by the APD will It can be detected, but the noise is relatively large, and the detection time accuracy is not accurate enough.

Contents of the invention

The purpose of the present invention is to address the shortcomings of the above-mentioned prior art, and to provide a circuit module capable of detecting near-infrared single photons in a narrow gate pulse suppression mode. Under this condition, the charge and discharge, overcharge and ringing generated by the gate pulse can be effectively offset, and relatively weak avalanche signals can be identified more accurately.

The object of the present invention is realized by the following technical solutions:

The present invention is composed of a signal detection circuit, a signal amplification circuit, a balance suppression circuit and a logic signal generation circuit, wherein a logic signal generation circuit is connected between the combination circuit formed by the detection circuit and the signal amplification circuit and the balance suppression circuit, wherein the balance The suppression circuit, except for the variable capacitor C0, its circuit connection and the selection of the parameters of each component are exactly the same as the combined circuit composed of the signal detection and amplification circuit, one-to-one correspondence, corresponding in the combination circuit composed of the signal detection and amplification circuit An avalanche photodiode APD is used at the variable capacitor C0.

The invention has the advantages of being able to realize the detection of single photons in the near-infrared band, adopting a symmetrical circuit balance mode, effectively offsetting the oscillation and overcharging caused by the high-amplitude narrow gate pulse, reducing noise, high detection efficiency, and low noise. High detection time accuracy.

Figure overview

Accompanying drawing 1 is the circuit principle diagram of the single photon detection by the indium gallium arsenic avalanche photodiode InGaAs-APD of the embodiment 1 of the present invention;

Accompanying drawing 2 is the schematic circuit diagram of embodiment 2 of the present invention;

Specific technical solutions

The features of the present invention and other related features will be further described in detail below in conjunction with the accompanying drawings through embodiments, so as to facilitate the understanding of those skilled in the art:

Embodiment 1: As shown in Figure 1, this embodiment is made of signal detection circuit, signal amplification circuit, balance suppression circuit and logic signal generation circuit, wherein the detection circuit is connected to the signal amplification circuit, and the detection circuit and signal amplification circuit are formed A logic signal generation circuit is connected between the combination circuit and the balance suppression circuit.

The above-mentioned signal detection circuit is composed of capacitor C2, resistors R7, R8, and avalanche photodiode APD, wherein C2 is a coupling capacitor, one end of which is connected to the gate pulse, and the other end is connected to the APD cathode; one end of R7 is connected to the high voltage HV, and the other end is connected to The APD cathode is connected; R8 is a sampling resistor, one end of which is connected to the APD anode, and the other end is grounded. The main function of the signal detection circuit is to use the APD to detect the optical signal and convert the optical signal into an electrical signal.

Since the electrical signal converted by APD is relatively weak, it is necessary to add an amplifier circuit behind for comparison. The signal amplifier circuit is composed of resistors R5, R6 and transistor Q2, which is a common base amplifier circuit. One end of R5 is connected to the positive power supply, and the other end is connected to the collector of the triode Q2; the base of the triode Q2 is grounded, the emitter is connected to the negative power supply through R6, and the collector is connected to the positive end of the comparator while connected to R5.

The diode D2 is connected between the signal detection circuit and the signal amplifying circuit to play an isolation role, its anode is connected to the APD anode, and its cathode is connected to the emitter of Q2.

The balance suppression circuit is composed of resistors R1, R2, R3, R4, capacitors C0, C1, diode D1, and triode Q1. In addition to the variable capacitor C0, its circuit connection, selection of various component parameters, signal detection and amplification circuit The combined circuits of the two are completely consistent and correspond one-to-one. In the combined circuit formed by the signal detection and amplification circuit, the place corresponding to the variable capacitor C0 is an avalanche photodiode APD.

The generating circuit of the logic signal is composed of a comparator comp and a monostable flip-flop M. The comparator generates a logic signal by comparing the signals at the positive and negative input ends, and the signal triggers the monostable flip-flop to perform shaping and output.

The combined circuit composed of the balance suppression circuit and the signal detection amplifier circuit is completely symmetrical except for the variable capacitor C0. Its function is to generate a signal in common mode with the APD when there is no photon irradiation, that is, when the APD does not have an avalanche, to achieve balance suppression. Function: The signals generated by the balance suppression circuit and the signal detection amplifier circuit enter the negative and positive input terminals of the comparator respectively, and a logic signal is generated by comparison. When there is no light irradiation, it is a common mode signal, and there is no signal output. When there is light, the signal One end of the detection amplifier circuit has one more avalanche signal than the end of the balance suppression circuit. This signal is a differential mode signal, and a logic signal is output through the comparator, which is output after shaping by the monostable trigger, which is convenient for counting.

In this embodiment, near-infrared single-photon detection is realized by using an avalanche photodiode single-photon detector in the capacitive balance gate pulse suppression mode, and the components used can be selected as follows:

C1: 100pF C2: 100pF

R1: 20kΩ R2: 100Ω R3: 3.3kΩ R4: 4.7kΩ

R5: 3.3kΩ R6: 4.7kΩ R7: 20kΩ R8: 100Ω

D1: IN4148 D2: IN4148

Q1: 2SD601 Q2: 2SD601

comp high-speed comparator: AD96685

M monostable trigger: MC10198

Embodiment 2: As shown in Figure 2, the principle of this embodiment is the same as that of Embodiment 1. It is composed of a signal detection circuit, a signal amplification circuit, a balance suppression circuit and a logic signal generation circuit, wherein the detection circuit is connected to the signal amplification circuit, and the detection circuit A logic signal generating circuit is connected between the combined circuit formed by the sum signal amplifying circuit and the balance suppressing circuit.

The connection composition of the signal detection circuit and the generation circuit of the logic signal is the same as that of embodiment 1, the difference is that its signal amplifying circuit adopts an integrated operational amplifier ampl2 instead of the triode Q2, the anode of the diode D2 is connected with the APD anode, and the cathode is connected with the APD anode. The input end of the integrated operational amplifier ampl2 is connected.

The balance suppression circuit is composed of resistors R1, R2, R3, R4, capacitors C0, C1, diode D1, and integrated operational amplifier ampl1. In addition to the variable capacitor C0, its circuit connection, selection of component parameters and signal detection and amplification The combined circuits formed by the circuits are completely consistent and correspond one-to-one. In the combined circuit formed by the signal detection and amplifying circuits, an avalanche photodiode APD is used at the position corresponding to the variable capacitor C0.

Those skilled in the art can obviously realize that the signal amplifying circuit is not limited to the above-mentioned content here, as long as the amplification can be realized, a transistor or an operational amplifier integrated block (such as opa300, opa842, etc.) can be used; the same is true for the logic signal generating circuit The comparator in the circuit, as long as its frequency can meet the experimental requirements, it can be an ECL component or a TTL component, such as max913, max9685, etc.

The working conditions adopted in the above-mentioned embodiment are: working temperature -60°C; the high voltage (HV) added in the circuit is slightly lower than the avalanche voltage of the avalanche photodiode (APD); the variable capacitor C0 is adjusted to make its capacitance just equal to the junction of the APD Capacitance; the gate pulse is 10Vp-p, the pulse width is 10ns (or narrower such as 2ns, here only 10ns is taken as an example) and the repetition frequency is 100kHz.

The above embodiments are divided into two working states: static state and avalanche state.

When the gate pulse is not added to the circuit, the voltage across the APD is lower than the avalanche voltage, no avalanche occurs, and the circuit is in a static working state. At this time, the signals of A (R2 and C0 connection point) and B (APD anode) are capacitance The charging signal, since C0 is equal to the APD junction capacitance, so the two points have the same level, and then amplified by Q1 (or ampl1) and Q2 (or ampl2), where Q1 and Q2 are high-frequency transistors of the same type with very consistent characteristics. Ampl1 and ampl2 are high-frequency operational amplifiers of the same type with the same characteristics. The two signals enter the negative and positive input terminals of the comparator respectively after the same amplification. Since the signals at both ends of the input comparator are completely consistent at this time, they belong to common mode signals, so The comparator has no signal output at this time.

When a gate pulse arrives in the circuit, during the 10ns duration of the gate pulse, the signals at points A and B are a 10ns charge and discharge signal. At this moment, the voltage across the APD exceeds the avalanche voltage, and it works in the "Geiger mode" and responds to single photons. Assuming that a photon is incident on the APD at this moment, since it is working in the "Geiger mode", the photon triggers an avalanche, and an avalanche current flows through the resistor R8. At this time, there is a weak avalanche signal superimposed on the original charge and discharge signal at point B Above, it is amplified by Q2 (or ampl2) and enters the comparator; the signal at point A is only a charge and discharge signal, which is amplified by Q1 (or ampl1) and enters the comparator; since the gate pulses added at both ends are the same, the amplified charge and discharge signals at both ends The discharge signals are the same, common-mode signals, which cancel each other out, and the amplified avalanche signal is unique to the APD side. It is a differential-mode signal, so a logic signal is generated by the comparator, and then passed through the monostable trigger. Output after shaping, counted by the counter.

The comparison between this embodiment and the passive suppression mode circuit is as follows: T=-60°C, f=100kHz,

Detection efficiency Noise (per nanosecond) Passive suppression mode 9.58% 4.0×10^-5 Gate Suppression Mode 10.6% 6.3×10^-6

Claims (6)

1. the circuit module of the APD single photon detection of a gate pulse balanced mode, comprise signal detection circuit, the generation circuit of signal amplification circuit and logical signal, it is characterized in that also comprising that balance suppresses circuit, this balance suppresses circuit and uses identical gate pulse with signal detection circuit, wherein detection circuit connects signal amplification circuit, combinational circuit that detection circuit and signal amplification circuit constituted and balance suppress to be connected with between the circuit generation circuit of logical signal, described balance suppresses circuit, except that variable capacitance C0, choosing with the combinational circuit of acquisition of signal and amplifying circuit formation of its circuit connection and each component parameter is in full accord, and corresponding to the use of variable capacitance C0 place in the combinational circuit of acquisition of signal and amplifying circuit formation is avalanche photodide APD.

2. the circuit module of the APD single photon detection of a kind of gate pulse balanced mode according to claim 1, it is characterized in that described balance suppresses circuit by resistance R 1, R2, R3, R4, capacitor C 0, C1, diode D1, triode Q1 constitutes, signal enters described balance from C1 and suppresses circuit, the other end of C1 connects high-voltage power supply by R1, join with C0 simultaneously, C0 and R2 polyphone ground connection, D1 is by drawing in the middle of C0 and the R2, and its other end connects negative supply through R4, connect the emitter of Q1 simultaneously, the base earth of Q1, the collector of Q1 connects positive supply through R3, connects the negative input end of comparer comp simultaneously, except that variable capacitance C0, choosing with the combinational circuit of acquisition of signal and amplifying circuit formation of circuit connection and each component parameter is in full accord, corresponding one by one.

3. the circuit module of the APD single photon detection of a kind of gate pulse balanced mode according to claim 1, it is characterized in that described balance suppresses circuit by resistance R 1, R2, R3, R4, capacitor C 0, C1, diode D1, integrated operational amplifier amp11 constitutes, signal enters described balance from C1 and suppresses circuit, the other end of C1 connects high-voltage power supply by R1, join with C0 simultaneously, C0 and R2 polyphone ground connection, D1 is by drawing in the middle of C0 and the R2, the positive input terminal of its another termination amp11, the negative input end of amp11 is through R3 ground connection, simultaneously connect its output terminal through R4, the negative input end of its output termination comparer comp is except that variable capacitance C0, and choosing with the combinational circuit of acquisition of signal and amplifying circuit formation of its circuit connection and each component parameter is in full accord, corresponding one by one.

4. the circuit module of the APD single photon detection of a kind of gate pulse balanced mode according to claim 1, it is characterized in that described signal detection circuit is by capacitor C 2, resistance R 7, R8, avalanche photodide APD constitutes, and wherein C2 is a coupling capacitance, the one end is connected with gate pulse, an other end is connected with the APD negative electrode, links to each other with R7 simultaneously, and the R7 other end links to each other with high pressure HV, the APD anode links to each other with sample resistance R8, the other end ground connection of R8.

5. the circuit module of the APD single photon detection of a kind of gate pulse balanced mode according to claim 1, it is characterized in that described signal amplification circuit is made of resistance R 5, R6, triode Q2, diode D2, be common-base amplification circuit, wherein the anode of diode D2 links to each other with the APD anode, the negative electrode of D2 connects negative supply by R6, connect the emitter of triode Q2 simultaneously, the base earth of Q2, the collector of triode Q2 is connected with positive supply through R5, links to each other with the anode of comparer in the generation circuit of logical signal simultaneously.

6. the circuit module of the APD single photon detection of a kind of gate pulse balanced mode according to claim 1 is characterized in that described signal amplification circuit is made of an integrated operational amplifier amp12, resistance R 5, R6, diode D2.Wherein the anode of diode D2 links to each other with the APD anode, and the negative electrode of D2 connects the positive input terminal of amp12, and the negative input end of amp12 connects output terminal through R6 simultaneously through R5 ground connection, the positive input terminal of its output termination comparer comp.

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