CN202092781U - Balanced type active suppression circuit suitable for multi-pixel photon counter - Google Patents

Abstract

The utility model is a single photon detection technology, specifically a balanced active suppression circuit suitable for a multi-pixel photon counter (MPPC), which can be applied to weak light detection fields such as photon number distinguishable detection. It is composed of an active suppression module and a balance network. The active suppression circuit added with a delay can completely retain the amplitude information of the avalanche signal, and its balance network can effectively remove the interference of the suppression pulse, thereby extracting the photon An avalanche of digital information. The circuit not only maintains the advantages of high detection rate and continuous detection of the traditional active suppression circuit, but also overcomes the fatal defect that the traditional active suppression circuit cannot realize the photon number resolution detection, and realizes the high-speed MPPC photon number resolution detection.

Description

Balanced Active Suppression Circuit for Multi-Pixel Photon Counters

technical field

The utility model relates to a single photon detection technology, specifically a balanced active suppression circuit suitable for a multi-pixel photon counter (MPPC). Effectively improve the detection rate and efficiency of MPPC and reduce after-pulse.

Background technique

A multi-pixel photon counter (MPPC) is an M×N two-dimensional array of silicon-avalanche photodiodes (Si APDs) with common cathode and anode outputs. When the bias voltage of Si APD exceeds their breakdown voltage, these Si APDs work in Geiger mode, at this time, the carriers excited by a single photon can excite a self-sustaining avalanche current pulse, which can be detected by conventional current The circuit detects that the MPPC working in Geiger mode is a multi-pixel single-photon detector with M×N Si APDs. Because all Si APDs in MPPC have a common cathode and anode output, when multiple photons are incident on different Si APDs at the same time, the avalanche currents generated by these Si APDs are finally linearly superimposed on the output, and the avalanche pulse amplitude is the same as that of the Si APD that is self-sustained. The number of APDs is proportional, so by identifying the avalanche pulse amplitude of MPPC, the number of photons arriving on different Si APDs can be distinguished, and the number of photons can be resolved.

MPPC requires a special detection circuit, which needs to suppress the self-sustained avalanche generated in the Si APD to avoid device burnout. Due to the requirement to distinguish the number of photons, MPPC generally adopts a passive suppression circuit, that is, MPPC is connected in series with a large current-limiting resistor. When an avalanche occurs in any one or more Si APDs in MPPC, a large avalanche current will be generated, and the avalanche current will flow through the The current-limiting large resistor forms a voltage drop, which reduces the bias voltage loaded on both ends of the Si APD, thereby suppressing the continuous generation of avalanche. At this moment, the bias voltage is lower than the breakdown voltage of the Si APD, and all the Si APDs on the MPPC leave the Geiger mode, so MPPC cannot detect single photons during suppression. As the avalanche current continues to decrease, the voltage drop across the large resistor also decreases, and the bias voltage of the Si APD returns to the state before the avalanche, and single photons can be detected again. For the passive suppression mode, the recovery time of the Si APD is determined by the large current-limiting resistor and the junction capacitance and distributed capacitance of the Si APD. The larger the resistance, the better the avalanche suppression effect, but the longer the recovery time is. The value is on the order of tens of kiloohms, and the recovery time is on the order of microseconds. Therefore, the single-photon detection rate in passive mode is very low, usually lower than 1MHz. In addition, in the passive suppression circuit, because the avalanche lasts for a long time, the after-pulse effect of Si APD is more serious.

Another commonly used detection circuit is the gate mode circuit. When the photon arrives, a detection gate pulse is synchronously generated, which is AC-coupled to the cathode of the Si APD, and the DC bias voltage loaded on both ends of the Si APD is less than its breakdown voltage. In this mode, the gate pulse instantaneously increases the bias voltage of the Si APD to exceed the breakdown voltage, so the Si APD is in Geiger mode only during the gate pulse, and the Si APD is in linear detection mode at other times, not In response to single photons, the dark count rate and afterpulse probability are greatly reduced. Due to the equivalent junction capacitance of Si APD, the input gate pulse will generate charge and discharge pulses on the sampling resistor, which is usually called spike noise. The noise amplitude increases with the increase of repetition frequency, and the avalanche will be submerged in the spike noise. Among them, the peak noise needs to be suppressed in order to extract the avalanche signal. However, the gate mode requires a synchronous clock signal, which is suitable for occasions where the arrival time of photons is known in advance, and is not suitable for continuous detection of unknown signals.

The active suppression circuit can make the Si APD work in the continuous single photon detection mode. The active suppression circuit has an external feedback circuit, which uses the rising edge of the avalanche signal as a trigger signal to generate a voltage pulse, and then feeds the voltage pulse into the Si APD circuit. , the bias voltage across the Si APD is pulled down, so that the avalanche is suppressed in a short time, and then the Si APD is quickly charged, so that it quickly returns to the single-photon detection state. Due to the introduction of a fast turn-off circuit, the recovery time of Si APD is reduced a lot compared with that of passive circuit, the detection rate of Si APD single photon detector is improved, and the after-pulse effect of Si APD is also reduced. However, while the traditional active suppression circuit suppresses the avalanche current, it also overwhelms its original avalanche amplitude information. If it is directly applied to the MPPC, the number of photons cannot be distinguished. Therefore, how to improve the rate and detection efficiency of MPPC has become an urgent technical problem to be solved.

Contents of the invention

The purpose of this utility model is to aim at the deficiencies of the above-mentioned prior art, and propose a balanced active suppression circuit suitable for MPPC. The disadvantage that the active suppression circuit cannot realize the photon number-resolvable detection realizes the high-speed MPPC photon number-resolvable detection.

The realization of the utility model purpose is accomplished by the following technical solutions:

A balanced active suppression circuit suitable for multi-pixel photon counters, including an active suppression module, characterized in that the suppression circuit also includes a balanced network module, and the balanced network module is composed of a delay line circuit, a differential balance circuit, and an amplification circuit connected in series sequentially, wherein the active suppression module is connected in parallel with the balance network.

The active suppression module is composed of a delay line circuit, an avalanche discriminator circuit, a pulse shaping circuit, a suppression pulse generation circuit and a recovery pulse generation circuit, and the avalanche signal generated by the multi-pixel photon counter enters the avalanche discrimination through the delay line circuit The pulse shaping circuit is triggered after converting the identified avalanche signal into a digital signal, and the generated pulse signal simultaneously triggers the suppression pulse generation circuit and the recovery pulse generation circuit, wherein the suppression pulse generation circuit and the recovery pulse generation circuit are connected in parallel .

The suppressing pulse generating circuit is composed of an amplifier circuit and a beam splitting module, both of which are connected in series, wherein the beam splitting module divides the suppressing pulse into two paths, one path is provided to the MPPC for suppressing the avalanche process, and the other path is provided to the The balancing network of is used to balance the suppressed pulse component present in the avalanche signal.

The recovery pulse generating circuit is composed of a shaping circuit and a pull-down switch in series, wherein the shaping circuit is used to generate a very narrow recovery pulse to control the closing of the pull-down switch, so that the MPPC can be charged quickly.

The utility model has the advantage that a delay and balance network are added on the basis of the traditional active suppression circuit, so that the avalanche pulse information carrying the photon number information can be completely preserved. As shown in Figure 2, the gray curve is the avalanche signal, and the amplitude of the avalanche signal generated by it is different according to the number of incident photons. Because the peak time of various avalanche amplitudes is different, in order for the MPPC to retain the amplitude information of the avalanche pulse, a delay must be introduced so that the time for suppressing pulse loading is on the falling edge of the avalanche pulse and the amplitude information of the avalanche pulse is retained. In addition, since the amplitude of the suppression pulse is much higher than that of the avalanche signal, when extracting the avalanche signal, it is necessary to use a balanced method to differentially cancel the interference of the suppression pulse mixed on the avalanche signal. A balanced network is used here to complete this work. With the help of such a balanced active suppression circuit, the potential of the new MPPC photon number resolution counter can be fully explored, and high-speed photon number resolution detection can be realized.

Description of drawings

Fig. 1. system structural diagram of the utility model;

Figure 2. Schematic diagram of the signal of the MPPC anode;

Fig. 3. Circuit diagram of the utility model.

Detailed ways

The features of the utility model and other relevant features are further described in detail below in conjunction with the accompanying drawings through the embodiments, so as to facilitate the understanding of those skilled in the art:

The active suppression module of the utility model comprises a delay line circuit, an avalanche discriminator circuit, a pulse shaping circuit, a suppression pulse generation circuit and a recovery pulse generation circuit. The avalanche signal generated by MPPC enters the avalanche discriminator circuit after a certain delay is introduced by the delay line circuit. This circuit can distinguish the avalanche signal from the background electrical noise of the system, convert the avalanche signal into a digital signal, and then trigger the shaping circuit. A pulse signal with a width of about 10 ns is generated to trigger the suppression pulse generation circuit and the recovery pulse generation circuit. Wherein, the suppression pulse is used to rapidly raise the potential of the MPPC anode after an avalanche occurs in the MPPC, that is, to pull down the bias voltage at both ends of the MPPC, thereby suppressing the avalanche. Then, the anode of the MPPC is short-circuited to the ground instantaneously by the recovery pulse to complete the fast charging of the MPPC, so that the MPPC quickly returns to the state of single-photon detection.

The balance network module of the utility model includes a delay line circuit, a differential balance circuit, and an amplifier circuit. The avalanche signal generated by MPPC is mixed with the suppression pulse through the delay line circuit to adjust the delay to make it consistent with the time when the suppression pulse generated by the active suppression module reaches the differential circuit, and the suppression pulse can be offset by the differential balance circuit, thereby extracting pure avalanche signal

The features of the present utility model and other relevant features are further described in detail below in conjunction with the accompanying drawings by examples, so that those skilled in the art can understand:

The system block diagram of this embodiment is shown in Figure 1, and the circuit diagram is shown in Figure 3, which consists of an MPPC bias circuit, an active suppression module and a balance network.

In this system, the MPPC bias circuit is composed of MPPC, DC bias voltage V _bias , current limiting resistor R1, and sampling resistor R2 connected in series, wherein the DC bias source V _bias is about 50V, and the current limiting resistor R1 is about 10 kΩ .

The active suppression module is composed of delay line Delay Line 1, avalanche discrimination comparator U1, shaping circuit U2, suppression pulse generation circuits U4 and PS2, recovery pulse generation circuits U3 and Q1. The avalanche signal generated by MPPC passes through the delay line Delay Line 1, to ensure that the avalanche current pulse of the MPPC reaches the maximum, and then trigger the avalanche discrimination comparator U1. This delay circuit ensures that the avalanche signal will not be submerged by the suppression pulse just after it is generated, and the integrity of the avalanche signal is preserved. The comparator's inverting input reference level is controlled by an external precision voltage source and is set above the magnitude of the system background electrical noise. The identified avalanche signal is shaped into a control signal with a pulse width of about 10ns by the shaping circuit U2, which is used to trigger the suppression pulse and recovery pulse generation circuit, wherein the suppression pulse is a pulse with a width of about 10ns and an amplitude of 7V generated by the high-speed amplifier U4 , and divided into two equal paths through the power divider PS2, one path is sent to the MPPC as a suppression pulse, and the other path is provided to the balance network as a common mode signal for noise cancellation. The recovery pulse generation circuit is triggered by the reverse output signal of U2, and then shaped into a recovery pulse with a pulse width of about 3 ns. The recovery pulse is generated immediately following the falling edge of the suppression pulse, and is used to quickly turn off the MPPC after the MPPC suppresses the avalanche. The anode is pulled down to zero potential, so that the voltage difference between the two ends of the MPPC returns to above the breakdown voltage, and the MPPC is quickly charged to ensure that the MPPC can immediately return to the state of detecting single photons again, which is the key to improving the detection rate.

The balance network is composed of delay line Delay Line 2 and differential operational amplifier U5. Among them, the delay line Delay Line 2 compensates the time difference of the two signals, so that the suppression pulse component in the signal output by the power divider PS1 reaches U5 at the same time as the suppression pulse output by PS2. By adjusting the adjustable resistor R15 at the input end of U5, the amplitudes of the two suppression pulse signals are adjusted to be equal. Therefore, U5 can exert its maximum common-mode signal suppression ability to offset the suppression pulse component in the MPPC anode, thereby extracting the avalanche signal containing photon number information.

This embodiment uses a new type of active suppression circuit with a balanced network, not only using the active suppression technology to achieve rapid avalanche suppression for each Si APD in the MPPC, quickly recovering the single-photon detection capability of the Si APD, but also avoiding the suppression of avalanche pulses in the pulse team. Influence, through the balance network to counteract the interference of the suppression pulse on the output signal of the MPPC, so that the MPPC finally outputs an avalanche signal containing photon number information, realizing high-speed photon number-resolvable detection.

The components used can be selected as follows:

R1: 10kΩ R2: 50Ω R3: 22Ω

R4: Adjustable resistor R5: 75Ω R6: 75Ω

R7: 100Ω R8: 390Ω R9: 390Ω

R10: 390Ω R11: 390Ω R12: 100Ω

R13: 287Ω R14: 1.14kΩ R15: adjustable resistor

R16: 1kΩ R17: 25Ω R18: 1kΩ

R19: 100Ω R20: 1kΩ R21: 1kΩ

C1: 10uF C2: 0.1uF C3: 0.01uF

C4: 10uF C5: 0.1uF C6: 0.01uF

C7: 10uF C8: 0.1uF C9: 0.01uF

C10: 0.1uF C11: 30pF C12: 10pF

C13: 100pF C14: 100pF C15: 100pF

MPPC: S10362-11

D1: BAS125

Q1: BFG591

PS1, PS2: ZFRSC-42-S+

U1: ADCMP572 U2: MC10EL31D

U3: MC10EL31D U4: THS3201

U5: AD8351.

Claims (4)

1. a balanced type that is applicable to many pixels photon counter initiatively suppresses circuit, comprise and initiatively suppress module, it is characterized in that this inhibition circuit also comprises balanced network module, described balanced network module is connected in series successively by delay line circuit, difference balancing circuitry and amplifying circuit and constitutes, and wherein saidly initiatively suppresses module and described balancing network is connected in parallel.

2. a kind of balanced type of many pixels photon counter that is applicable to according to claim 1 initiatively suppresses circuit, it is characterized in that the described module that initiatively suppresses is by the delay line circuit, the snowslide discriminator circuit, pulse shaping circuit, suppressor pulse produces circuit and recovers pulse-generating circuit and constitutes, the avalanche signal that described many pixels photon counter produces enters the snowslide discriminator circuit through the delay line circuit, to identify and trigger described pulse shaping circuit again after avalanche signal is converted into digital signal, the pulse signal that produces triggers suppressor pulse simultaneously and produces circuit and recover pulse-generating circuit, wherein, suppressor pulse produces circuit and recovers pulse-generating circuit and is connected in parallel.

3. a kind of balanced type of many pixels photon counter that is applicable to according to claim 2 initiatively suppresses circuit, it is characterized in that described suppressor pulse produces circuit and is made up of amplifying circuit and beam splitting module, both are connected in series, wherein beam splitting module is divided into two-way with suppressor pulse, one the tunnel offers MPPC is used to suppress avalanche process, another road offers described balancing network, is used for the suppressor pulse composition that the balance avalanche signal exists.

4. a kind of balanced type of many pixels photon counter that is applicable to according to claim 2 initiatively suppresses circuit, it is characterized in that described recovery pulse-generating circuit is by shaping circuit and pulls down switch and be composed in series, wherein shaping circuit is used to produce a very narrow recovery pulse, in order to the closure that control pulls down switch, make MPPC to charge rapidly.

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