Device and method for dynamically controlling dead time of single-photon detector

Abstract

The invention discloses a device and method for dynamically controlling the dead time of a single-photon detector, and the device comprises a drive circuit which is used for amplifying an input signal and then loading the amplified input signal to a cathode of an avalanche photodiode; the avalanche extraction and amplification circuit is used for filtering and amplifying the first avalanche analog signal and outputting a second avalanche analog signal; the multi-amplitude discriminating circuit is used for discriminating the amplitude of the second avalanche analog signal and respectively outputting a first avalanche digital signal to the dead time processing module and amplitude data to the dead time control module; the dead time control module outputs a dead time setting signal to the dead time processing module; the dead time processing module processes the first avalanche digital signal according to the dead time setting signal and then outputs a second avalanche digital signal. According to the amplitude of the avalanche current in the detection process, the setting of the dead time is dynamically adjusted, and the effect of improving the maximum counting rate can be achieved under the condition that the post-pulse probability is low.

Description

Technical Field

[0001] The present invention belongs to the field of quantum communication and weak light detection, and in particular relates to a device and method for dynamically controlling the dead time of a single-photon detector. Background Art

[0002] Single photon detector (SPD) is based on the photoelectric effect of avalanche photodiode. It is a highly sensitive detector that can detect only one photon under extremely weak light signals. Single photon detector is one of the key devices for realizing quantum communication. In quantum computing, single photon detector is used to monitor and operate the state of quantum bits and realize key tasks such as quantum gate operation. In laser radar, it can also significantly improve the sensitivity and detection distance of laser radar. In the biomedical field, single photon detector can be used for bioluminescence imaging, cell metabolism monitoring and other aspects. Single photon detector has important applications in optical measurement.

[0003] The dead time of a single-photon detector refers to the time it takes for the detector to recover to the state of receiving another photon after receiving a photon. The after-pulse probability refers to the probability of secondary or multiple detection signals caused by previous photon events after the single-photon detector recovers. There is a close relationship between the two. The dead time is a performance indicator to measure the dynamic range of the single-photon detector system. It is defined as the shortest interval between two adjacent detection events of the detector. The length of the dead time directly affects the after-pulse probability. A longer dead time helps the single-photon detector to fully recover and shield the secondary or multiple detection signals, thereby reducing the after-pulse probability, but it will limit the maximum detection count rate. Conversely, a shorter dead time may cause the single-photon detector to still have the influence of previous photon events during the recovery process, thereby increasing the after-pulse probability. Therefore, when setting the dead time, it is necessary to weigh the relationship between the after-pulse probability and the maximum count rate to meet the needs of specific application scenarios. Summary of the invention

[0004] The present invention discloses a device and method for dynamically controlling the dead time of a single-photon detector. The device and method adopt sampling and judgment of the amplitude of avalanche signal to obtain the intensity of avalanche carriers during each avalanche, and set the length of the dead time according to the intensity. In order to obtain a low after-pulse probability, the stronger the intensity, the longer the dead time is set, and vice versa. Through this method, the length of the dead time can be optimized and the value of the maximum counting rate can be improved under the condition of low after-pulse probability.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A device for dynamically controlling the dead time of a single-photon detector, the device comprising a driving circuit, a bias voltage source, a quenching resistor, an avalanche photodiode, a 50-ohm resistor, an avalanche extraction amplifier circuit, a multi-amplitude discrimination circuit, a dead time control module, and a dead time processing module, wherein:

[0007] The driving circuit is used to amplify the input signal and then load it to the cathode of the avalanche photodiode;

[0008] The bias voltage source is connected to the cathode of the avalanche photodiode via a quenching resistor, and is used to provide a bias voltage for the avalanche photodiode;

[0009] The 50-ohm resistor is connected to the anode of the avalanche photodiode and is used to perform impedance matching on the first avalanche analog signal output by the avalanche photodiode;

[0010] The avalanche extraction and amplification circuit is used to filter and amplify the first avalanche simulation signal and output a second avalanche simulation signal;

[0011] The multi-amplitude discrimination circuit is used to discriminate the amplitude of the second avalanche analog signal, and output the first avalanche digital signal to the dead time processing module and the amplitude data to the dead time control module respectively;

[0012] The dead time control module receives and processes the amplitude data, sets the dead time setting signal of this detection task according to the intensity of the avalanche carriers, and outputs the dead time setting signal to the dead time processing module;

[0013] The dead time processing module processes the first avalanche digital signal according to the dead time setting signal and outputs a second avalanche digital signal.

[0014] Furthermore, the quenching resistor is used to quench the avalanche photodiode by means of voltage division after the avalanche current is generated, so as to restore it to the initial detection state.

[0015] Furthermore, the dead time setting signal includes the length of the dead time.

[0016] Furthermore, the multi-amplitude discrimination circuit includes a power divider, a high-speed comparator and a high-speed analog-to-digital converter. The power divider divides the second avalanche analog signal into two, and outputs them to the high-speed comparator and the high-speed analog-to-digital converter respectively; the high-speed comparator discriminates the second avalanche analog signal to determine whether an avalanche signal is generated; the high-speed analog-to-digital converter samples the second avalanche analog signal to obtain amplitude data.

[0017] Furthermore, the multi-amplitude discrimination circuit includes a power divider and n high-speed comparators. The power divider divides the second avalanche analog signal into n parts and outputs them to the n high-speed comparators respectively. The n high-speed comparators correspond to n discrimination levels. The first high-speed comparator outputs a first avalanche digital signal. When the generated second avalanche analog signal is higher than the discrimination level, the first avalanche digital signal is output as a high level, and when it is lower than the discrimination level, the first avalanche digital signal is output as a low level. The dead time control module determines the amplitude data of the first avalanche digital signal according to the output levels of the n high-speed comparators.

[0018] Furthermore, the dead time control module includes a delay circuit, a D flip-flop, a digital potentiometer and a capacitor. The delay circuit is used to delay the first avalanche digital signal, and the delay time is not shorter than the time required for the dead time setting. The first avalanche digital signal after the delay is input to the clock input interface of the D flip-flop; the D flip-flop is used to receive the first avalanche digital signal and output a second avalanche digital signal; the digital potentiometer and the capacitor are connected in series to realize the dead time setting and the delay of the clearing end of the D flip-flop.

[0019] Furthermore, the dead time control module includes a first delay circuit, a D flip-flop, and a second delay circuit. The first delay circuit realizes the delay of the first avalanche digital signal, and the delay time is not shorter than the time required for the dead time setting. The first avalanche digital signal after the delay is input to the clock input interface of the D flip-flop; the D flip-flop is used to receive the first avalanche digital signal and output the second avalanche digital signal; the second delay circuit is used to realize the dead time setting and the delay of the clear end of the D flip-flop.

[0020] In another aspect, the present invention provides a method for dynamically controlling the dead time of a single-photon detector, the method comprising:

[0021] The input signal is amplified by the driving circuit and then loaded to the avalanche photodiode;

[0022] The avalanche photodiode obtains a bias voltage through a quenching resistor, generates an avalanche current signal, and then uses a 50-ohm resistor to match and convert it into a first avalanche analog signal;

[0023] The first avalanche simulation signal is extracted and amplified by the avalanche extraction and amplification circuit, and a second avalanche simulation signal is output;

[0024] The multi-amplitude discrimination circuit discriminates the amplitude of the second avalanche analog signal, and transmits the output first avalanche digital signal to the dead time processing module, and transmits the amplitude data to the dead time control module;

[0025] The dead time control module sets the dead time after this avalanche according to the amplitude data;

[0026] The dead time processing module receives the first avalanche digital signal and outputs a second avalanche digital signal according to the set dead time.

[0027] The beneficial effects of the present invention are:

[0028] Taking into account that when there are many avalanche carriers, the number of traps retained in the multiplication layer is large, and the probability of the retained carriers being released subsequently to cause after-pulses increases, while the number of single avalanche carriers is random, the present invention sets the length of the dead time according to the amplitude of the avalanche current signal, thereby solving the problem of limiting the maximum counting rate by conventionally adopting a fixed dead time in order to suppress the probability of after-pulses; by dynamically adjusting the dead time, the effect of increasing the maximum counting rate is obtained under low after-pulse probability conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of a device for dynamically controlling the dead time of a single-photon detector according to the present invention;

[0030] Figure 2 It is a schematic diagram of the structure of the multi-amplitude discrimination circuit of the present invention;

[0031] Figure 3 Another schematic diagram of the multi-amplitude discrimination circuit structure of the present invention;

[0032] Figure 4 This is a structural schematic diagram of a dead time control module of the present invention;

[0033] Figure 5 Another schematic diagram of the dead time control module structure of the present invention;

[0034] Figure 6 The present invention is a flow chart of a method for dynamically controlling the dead time of a single-photon detector. DETAILED DESCRIPTION

[0035] The present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0036] like Figure 1 As shown, it is a schematic diagram of a device for dynamic dead time control of a single photon detector of the present invention, including a driving circuit, a bias voltage source, a quenching resistor, an avalanche photodiode, a 50 ohm resistor, an avalanche extraction amplifier circuit, a multi-amplitude discrimination circuit, a dead time control module, and a dead time processing module. Among them,

[0037] The driving circuit is used to amplify the input signal and then load it to the cathode of the avalanche photodiode;

[0038] The bias voltage source is connected to the cathode of the avalanche photodiode via a quenching resistor to provide a bias voltage for the avalanche photodiode, and the bias voltage is higher than the breakdown voltage so that the avalanche photodiode operates in a Geiger mode;

[0039] The quenching resistor has one end connected to the cathode of the avalanche photodiode and one end connected to the bias voltage, and is used to quench the avalanche photodiode by voltage division after the avalanche current is generated, so as to restore it to the initial detection state;

[0040] The avalanche photodiode operates in Geiger mode to realize a high-sensitivity photodetector that detects single photon (the smallest quantum of light) signals;

[0041] The 50-ohm resistor has one end connected to the anode of the avalanche photodiode and one end connected to the ground potential to achieve impedance matching of the first avalanche analog signal output by the avalanche photodiode;

[0042] The avalanche extraction amplifier circuit has an input end connected to the anode of the avalanche photodiode and an output end connected to the input port of the multi-amplitude discrimination circuit, and is used to filter and amplify the first avalanche simulation signal and output a second avalanche simulation signal;

[0043] The multi-amplitude discrimination circuit has an input end connected to the avalanche extraction amplifier circuit, an output end connected to the dead time control module, and another output end connected to the dead time processing module, so as to discriminate the amplitude of the second avalanche analog signal, and output the first avalanche digital signal to the dead time processing module and the amplitude data to the dead time control module respectively;

[0044] The dead time control module has one end connected to the multi-amplitude discrimination circuit and one end connected to the dead time processing module to receive and process the amplitude data, set the dead time of this detection according to the intensity of the avalanche carrier, and output the dead time setting signal to the dead time processing module;

[0045] The dead time processing module is connected to the multi-amplitude discrimination circuit at one end and to the dead time control module at the other end, receives the first avalanche digital signal, configures the dead time of this detection task according to the dead time setting signal output by the dead time control module, and outputs the second avalanche digital signal.

[0046] A preferred implementation diagram of a multi-amplitude discrimination circuit is shown in FIG. Figure 2 As shown, it includes a power divider, a high-speed comparator and a high-speed analog-to-digital converter. The power divider divides the second avalanche analog signal into two and outputs them to the high-speed comparator and the high-speed analog-to-digital converter respectively; the high-speed comparator discriminates the second avalanche analog signal to determine whether an avalanche signal is generated, and the discrimination level is the avalanche signal threshold level. When it is higher than the discrimination level, the first avalanche digital signal is output as a high level, and when it is lower than the discrimination level, the first avalanche digital signal is output as a low level; the high-speed analog-to-digital converter samples the second avalanche analog signal and converts the analog signal into a digital signal, and outputs the amplitude data obtained based on the digital signal to the dead time control module.

[0047] Another preferred implementation of the multi-amplitude discrimination circuit is shown in FIG. Figure 3 As shown, it includes a power divider and n-way high-speed comparators, and the power divider realizes dividing the second avalanche analog signal into n, and outputs them to the n-way high-speed comparators respectively. The n-way high-speed comparators correspond to n discrimination levels, where the discrimination level voltage value is set to the first minimum and increases in sequence. In principle, for the amplitude of the avalanche signal, the higher the discrimination level, the fewer the number of events of outputting a high level, and the lower the corresponding detection efficiency. However, the higher the amplitude of the avalanche signal, the larger the corresponding avalanche current. In order to reduce the dead time to be set for the back pulse, it is necessary to increase accordingly. For the n discrimination levels, the values ​​of n dead times are preset, and the first high-speed comparator outputs the first avalanche digital signal. When the generated second avalanche analog signal is higher than the discrimination level 1, the output of the first avalanche digital signal is a high level, and when it is lower than the discrimination level 1, the output of the first avalanche digital signal is a low level; the dead time control module determines the amplitude data of the first avalanche digital signal according to the output level of the n-way high-speed comparators.

[0048] A preferred implementation diagram of the dead time control module is shown in FIG. Figure 4 As shown, it includes a delay circuit, a D trigger, a digital potentiometer and a capacitor. The delay circuit realizes the delay of the first avalanche digital signal. The delay time is not shorter than the time required for the dead time setting. The first avalanche digital signal after the delay is input to the clock input interface of the D trigger; the D trigger realizes the reception of the first avalanche digital signal, outputs the second avalanche digital signal, and realizes that no other avalanche digital signals are output during the dead time. When the CLK in the D trigger receives a high-level jump, the Q port outputs a high level; the digital potentiometer and the capacitor realize the RC delay circuit. When the Q port in the D trigger jumps to a high level, the port outputs a low level. It is cleared to zero only after the time constant set by the RC delay circuit, during which the Q port remains at a high level.

[0049] Another preferred implementation of the dead time control module is shown in FIG. Figure 5 As shown, it includes a first delay circuit, a D trigger, and a second delay circuit. The first delay circuit realizes the delay of the first avalanche digital signal, and the delay time is not shorter than the time required for the dead time setting. The first avalanche digital signal after the delay is input to the clock input interface of the D trigger; the D trigger realizes the reception of the first avalanche digital signal, outputs the second avalanche digital signal, and realizes that no other avalanche digital signals are output during the dead time. When the CLK in the D trigger receives a high level jump, the Q port outputs a high level; the second delay circuit realizes the setting of the dead time. When the Q port in the D trigger jumps to a high level, The port output is low level. It is cleared to zero only after the time delay set by the second delay circuit, during which the Q port maintains a high level.

[0050] On the other hand, a flow chart of a method for dynamic control of dead time of a single photon detector is as follows: Figure 6 As shown, the input signal is amplified by the driving circuit and then loaded into the avalanche photodiode. The avalanche photodiode obtains the bias voltage through the quenching resistor. After the avalanche current signal is generated, a 50-ohm resistor is used to match and convert it into a first avalanche analog signal. The first avalanche analog signal passes through the avalanche extraction and amplification circuit to extract and amplify the avalanche signal and output a second avalanche analog signal; the multi-amplitude discrimination circuit performs amplitude discrimination on the second avalanche analog signal, and transmits the output first avalanche digital signal to the dead time processing module, and the amplitude data is transmitted to the dead time control module; the dead time control module sets the dead time after this avalanche according to the amplitude data; the dead time processing module receives the first avalanche digital signal, outputs the second avalanche digital signal according to the set dead time, and no longer outputs other detection signals.

[0051] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A device for dynamic control of dead time of a single photon detector, characterized in that: The device includes a driving circuit, a bias voltage source, a quenching resistor, an avalanche photodiode, a 50 ohm resistor, an avalanche extraction amplifier circuit, a multi-amplitude discrimination circuit, a dead time control module, and a dead time processing module, wherein: The driving circuit is used to amplify the input signal and then load it to the cathode of the avalanche photodiode; The bias voltage source is connected to the cathode of the avalanche photodiode via a quenching resistor, and is used to provide a bias voltage for the avalanche photodiode; The 50-ohm resistor is connected to the anode of the avalanche photodiode and is used to perform impedance matching on the first avalanche analog signal output by the avalanche photodiode; The avalanche extraction and amplification circuit is used to filter and amplify the first avalanche simulation signal and output a second avalanche simulation signal; The multi-amplitude discrimination circuit is used to discriminate the amplitude of the second avalanche analog signal, and output the first avalanche digital signal to the dead time processing module and the amplitude data to the dead time control module respectively; The dead time control module receives and processes the amplitude data, sets the dead time setting signal of this detection task according to the intensity of the avalanche carriers, and outputs the dead time setting signal to the dead time processing module; The dead time processing module processes the first avalanche digital signal according to the dead time setting signal and outputs a second avalanche digital signal.

2. The device for dynamic control of dead time of a single photon detector according to claim 1, characterized in that: The quenching resistor is used to quench the avalanche photodiode by voltage division after the avalanche current is generated, so as to restore the avalanche photodiode to its initial detection state.

3. The device for dynamic control of dead time of a single photon detector according to claim 1, characterized in that: The dead time setting signal includes the length of the dead time.

4. The device for dynamic control of dead time of a single photon detector according to claim 1, characterized in that: The multi-amplitude discrimination circuit includes a power divider, a high-speed comparator and a high-speed analog-to-digital converter. The power divider divides the second avalanche analog signal into two and outputs them to the high-speed comparator and the high-speed analog-to-digital converter respectively; the high-speed comparator discriminates the second avalanche analog signal to determine whether an avalanche signal is generated; the high-speed analog-to-digital converter samples the second avalanche analog signal to obtain amplitude data.

5. The device for dynamic control of dead time of a single photon detector according to claim 1, characterized in that: The multi-amplitude discrimination circuit includes a power divider and n-way high-speed comparators. The power divider divides the second avalanche analog signal into n and outputs them to the n-way high-speed comparators respectively. The n-way high-speed comparators correspond to n discrimination levels. The first high-speed comparator outputs the first avalanche digital signal. When the generated second avalanche analog signal is higher than the discrimination level, the first avalanche digital signal is output as a high level, and when it is lower than the discrimination level, the first avalanche digital signal is output as a low level. The dead time control module determines the amplitude data of the first avalanche digital signal according to the output levels of the n-way high-speed comparators.

6. The device for dynamic control of dead time of a single photon detector according to claim 1, characterized in that: The dead time control module includes a delay circuit, a D flip-flop, a digital potentiometer and a capacitor. The delay circuit is used to delay the first avalanche digital signal. The delay time is not shorter than the time required for the dead time setting. The first avalanche digital signal after the delay is input to the clock input interface of the D flip-flop. The D flip-flop is used to receive a first avalanche digital signal and output a second avalanche digital signal; the digital potentiometer and the capacitor are connected in series to achieve dead time setting and delay of the reset end of the D flip-flop.

7. The device for dynamic control of dead time of a single photon detector according to claim 1, characterized in that: The dead time control module includes a first delay circuit, a D flip-flop, and a second delay circuit. The first delay circuit realizes the delay of the first avalanche digital signal. The delay time is not shorter than the time required for the dead time setting. The first avalanche digital signal after the delay is input to the clock input interface of the D flip-flop. The D flip-flop is used to receive a first avalanche digital signal and output a second avalanche digital signal; the second delay circuit is used to implement dead time setting and delay of the reset end of the D flip-flop.

8. A method for dynamically controlling the dead time of a single-photon detector, characterized in that: The method comprises: The input signal is amplified by the driving circuit and then loaded to the avalanche photodiode; The avalanche photodiode obtains a bias voltage through a quenching resistor, generates an avalanche current signal, and then uses a 50-ohm resistor to match and convert it into a first avalanche analog signal; The first avalanche simulation signal is extracted and amplified by the avalanche extraction and amplification circuit, and a second avalanche simulation signal is output; The multi-amplitude discrimination circuit discriminates the amplitude of the second avalanche analog signal, and transmits the output first avalanche digital signal to the dead time processing module, and transmits the amplitude data to the dead time control module; The dead time control module sets the dead time after this avalanche according to the amplitude data; The dead time processing module receives the first avalanche digital signal and outputs a second avalanche digital signal according to the set dead time.

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