A new near-infrared single-photon detection system

Abstract

The present invention provides a novel near-infrared single-photon detection system. The system is characterized in that it is composed of a gated signal output circuit (1), a switch control signal circuit (2), a logic gate control circuit (3), a capacitor (4), a bias voltage generation circuit (5), a near-infrared single-photon avalanche photodiode (6) and a signal readout circuit (7), wherein the signal readout circuit is composed of an amplifier (71) and a resistor (72). The present invention can be used to solve the signal loss problem generated when the near-infrared single-photon avalanche diode collects light signals in a gated quenching mode; and can be widely used in the field of extremely weak light detection such as optical time domain reflectometry, laser radar detection and medical imaging.

Description

(I) Technical field

[0001] The present invention relates to a near-infrared single-photon detection system based on gated quenching, which solves the signal loss problem caused by the near-infrared single-photon avalanche diode when collecting light signals in the gated quenching mode, and belongs to the field of single-photon detection technology. (II) Background technology

[0002] A single-photon avalanche photodiode is a semiconductor optoelectronic device with internal photocurrent gain, which has the ability to detect weak signals at the single-photon energy level. Its avalanche effect is a mechanism that causes PN junction breakdown. It uses the impact ionization effect of photogenerated carriers in the diode depletion layer to obtain the avalanche multiplication of the photocurrent. When the bias voltage of a reverse-biased PN junction is high enough and the internal electric field in the space charge region is strong enough, the electron-hole pairs generated by the impact ionization can be continuously heated by the electric field and generate new hole-electron pairs. Then, these new hole-electron pairs will further impact ionize to generate more hole-electron pairs. Continuous impact ionization increases the number of carriers, and finally forms an avalanche current under the action of the electric field. At this time, the single-photon avalanche photodiode operates in Geiger mode (also called single-photon mode). In this mode, the internal gain of the single-photon avalanche photodiode can reach 10 6 above.

[0003] The responsivity of single-photon avalanche photodiodes made of different semiconductor materials to different wavelengths is also different. The most common types are silicon-based single-photon avalanche photodiodes and near-infrared single-photon avalanche photodiodes. Silicon-based single-photon avalanche photodiodes can respond to the spectrum in the band of 200nm-900nm, and its maximum quantum efficiency can reach more than 80%; near-infrared single-photon avalanche photodiodes can respond to the spectrum in the band of 1000nm-1700nm, and its maximum quantum efficiency is about 30%.

[0004] Near-infrared single-photon avalanche photodiodes usually work in gated mode, with their reverse bias voltage below the avalanche voltage, and a periodic gate pulse superimposed on the reverse bias voltage. Since the gate pulse has a certain voltage amplitude, during the time when the high voltage is present, the near-infrared single-photon avalanche photodiode is in an avalanche state and can perform single-photon detection; while during the time when the low voltage is present, the reverse bias voltage is below the avalanche voltage, and the near-infrared single-photon avalanche photodiode is quenched.

[0005] However, the near-infrared single-photon avalanche photodiode is in an avalanche state and can perform single-photon detection only when the gate signal is at a high voltage. During the low voltage period, the reverse bias voltage at both ends of the near-infrared single-photon avalanche photodiode is below the avalanche voltage, and the optical signal cannot be detected, resulting in signal loss problems.

[0006] In order to solve the problem that the near-infrared single-photon avalanche photodiode cannot detect the optical signal during the time when the system gate signal is at low voltage, resulting in signal loss. Ma Huaping et al. disclosed "A gated silicon-based visible near-infrared single-photon detection device" (Chinese patent: 202111000717.2) in 2021. The invention generates a large voltage gated pulse with a short rise and fall time, and effectively filters out the spike noise caused by the gated pulse before and after by controlling the width, amplitude and repetition frequency of the gated pulse, thereby realizing efficient counting of avalanche signals; Chen Huan et al. disclosed "A sampling-based adjustable frequency high-speed near-infrared single-photon detector" (Chinese patent: CN107843350B) in 2017. The invention uses a highly accurate analog-to-digital converter to sample the avalanche photodiode detection signal, and synchronizes the sampling clock with the avalanche photodiode gate signal, so that after the gate repetition frequency changes, the analog-to-digital converter can still sample the gated output signal, reducing the lack of detection signals in the system and improving the integrity of the system's acquisition signals.

[0007] Although the above inventions can effectively reduce the reverse bias voltage of the near-infrared single-photon avalanche photodiode to below the avalanche voltage to a certain extent, and fail to detect the optical signal, thus causing the problem of signal loss, they cannot fundamentally solve the problem of missing detection optical signals.

[0008] In order to solve the above problems, the present invention discloses a novel near-infrared single-photon detection system. It can be widely used in the field of extremely weak light detection such as optical time domain reflectometer, laser radar detection and medical imaging. The system uses a logic gate control circuit to divide the gated signal into two signals, one of which remains the same as the original signal, and the other uses an inverter to output a signal with the same frequency and opposite phase as the original signal. The switch control signal system outputs a signal with a lower frequency through the control logic gate circuit to make the two signals output in a loop, thereby ensuring that the system fully detects all signals, solving the signal loss problem caused by the near-infrared single-photon avalanche diode when collecting light signals in the gated quenching mode. (III) Summary of the invention

[0009] The purpose of the present invention is to provide a near-infrared single-photon detection system based on gated quenching.

[0010] A novel near-infrared single-photon detection system is characterized in that the system is composed of a gate signal output circuit (1), a switch control signal circuit (2), a logic gate control circuit (3), a capacitor (4), a bias voltage generation circuit (5), a near-infrared single-photon avalanche photodiode (6) and a signal readout circuit (7), wherein the signal readout circuit (7) is composed of an amplifier (71) and a resistor (72).

[0011] The present invention is implemented as follows: the bias voltage generating circuit (5) outputs a voltage so that the reverse bias voltage of the near-infrared single-photon avalanche photodiode (6) is below the avalanche voltage; the square wave signal output by the gate signal output circuit (1) is modulated by the logic gate control circuit (3) to form two square wave signals, namely, signal A and signal B; wherein the signal A is completely identical to the square wave signal output by the gate signal output circuit (1); after the signal B is modulated by the inverter (31), the output square wave signal is opposite in phase to the signal A and has the same amplitude; the switch control signal circuit (2) controls the signal A and signal B to cyclically output the signal D by outputting a signal C with a lower frequency; when the signal A is output to When a near-infrared single-photon avalanche photodiode (6) is used, since the A signal has a certain voltage amplitude, during the time when the A signal is at a high voltage, the near-infrared single-photon avalanche photodiode (6) is in a single-photon detection state, and the optical signal is detected and then read out by a signal readout circuit (7); after a period of detection, the C signal output by the switch control signal circuit (2) controls the B signal to be output to the near-infrared single-photon avalanche photodiode (6), and during the time when the A signal is at a high voltage, the optical signal not detected by the system is detected; the switch control signal circuit (2) ensures that the system fully detects all signals by controlling the cyclic output of the A signal and the B signal.

[0012] The function of the gate signal output circuit (1) in the system is to output a periodic square wave signal. The duty cycle and pulse width of the square wave signal can be set according to actual use.

[0013] In the system, the switch control signal system (3) controls the cyclic output of the A signal and the B signal by outputting the C signal with a lower frequency and a wider pulse, thereby ensuring that the system can fully detect all signals.

[0014] The logic gate control circuit (3) is composed of two signals, namely, an A signal and a B signal, wherein the A signal is completely identical to the square wave signal output by the gate control signal output circuit (1), and due to the action of the inverter (31), the B signal has an opposite phase to the square wave signal output by the gate control signal output circuit (1) but has the same amplitude; the switch control signal system (2) controls the output of the D signal by controlling the logic circuit in the logic gate control circuit (3).

[0015] In the system, the bias voltage generating circuit (5) is connected to the cathode of the near-infrared single-photon avalanche photodiode (6); its function is to realize voltage conversion, convert the input voltage into a DC voltage and output it to the near-infrared single-photon avalanche photodiode (6), so as to ensure that the bias voltage provided is stably below the avalanche voltage of the near-infrared single-photon avalanche photodiode (6); the bias voltage generating circuit (5) can be a DC-DC conversion circuit or an AC-DC conversion circuit.

[0016] The near-infrared single-photon avalanche photodiode (6) in the system is characterized in that the near-infrared single-photon avalanche photodiode (6) can be any one of near-infrared single-photon avalanche photodiodes made of indium gallium arsenide (InGaAs) or indium gallium arsenide / indium phosphide (InGaAs / InP) materials, and in specific use, the near-infrared single-photon avalanche photodiode with the best performance parameters can be selected according to use requirements.

[0017] The signal readout circuit (7) in the system is composed of an amplifier (71) and a resistor (72); the resistor (72) is connected to the anode of the near-infrared single-photon avalanche photodiode (6) and functions to reduce the bias voltage of the near-infrared single-photon avalanche photodiode (6) after an avalanche occurs, thereby achieving the purpose of avalanche quenching; the junction capacitance of the resistor (72) and the near-infrared single-photon avalanche photodiode (6) and the capacitor (4) determine the recovery time for the detector to return to the detection state; the amplifier (71) functions to amplify the electrical pulse output by the near-infrared single-photon avalanche photodiode (6); and the resistance value of the resistor (72) is selected according to actual use conditions. (IV) Description of the drawings

[0018] Figure 1 The system schematic diagram of the near-infrared single-photon detection system is shown in FIG. The system is composed of a gate signal output circuit (1), a switch control signal circuit (2), a logic gate control circuit (3), a capacitor (4), a bias voltage generation circuit (5), a near-infrared single-photon avalanche photodiode (6), and a signal readout circuit (7), wherein the signal readout circuit (7) is composed of an amplifier (71) and a resistor (72).

[0019] Figure 2 It represents the structure diagram of logic gate control circuit and the truth table of logic gate circuit.

[0020] Figure 3 The present invention is a schematic diagram of an embodiment of a near-infrared single-photon detection system for photon counting optical time domain reflectometer. The system is composed of a pulse laser (1), an optical fiber circulator (2), an optical fiber to be measured (3), a time-correlated single-photon counter (4), a near-infrared single-photon detector system based on gated quenching (5), a signal processing system (6) and a display system (7).

[0021] Figure 4 The system schematic diagram of the near-infrared single-photon detection system based on gated quenching in the embodiment is shown. The system is composed of a gated signal output circuit (51), a switch control signal circuit (52), a logic gate control circuit (53), a capacitor (54), a bias voltage generation circuit (55), a near-infrared single-photon avalanche photodiode (56) and a signal readout circuit (57), wherein the signal readout circuit (57) is composed of an amplifier (571) and a resistor (572).

[0022] Figure 5 The embodiment is a near-infrared single photon detection system in which the C signal output by the switch control signal circuit (53) is in a cyclic control relationship with the A signal and the B signal. The logic gate control circuit (52) modulates the gate pulse signal output by the gate control signal output circuit (51), and the A signal output by the logic gate control circuit (52) is completely consistent with the gate pulse signal output by the control signal circuit (1); the B signal of the logic gate control circuit (52) is due to the function of the inverter, and the output gate pulse signal is opposite in phase to the gate pulse signal output by the gate control signal circuit, but has the same amplitude. (V) Specific implementation methods

[0023] The present invention will be further described below in conjunction with specific embodiments.

[0024] Figure 4 An embodiment of a near-infrared single-photon detection system based on gated quenching for photon counting optical time domain reflectometry is provided. The system is composed of a pulsed laser (1), an optical fiber circulator (2), an optical fiber to be tested (3), a time-correlated single-photon counter (4), a near-infrared single-photon detector system based on gated quenching (5), a signal processing system (6) and a display system (7); the pulsed laser (1) outputs a synchronous electrical signal while outputting a pulsed optical signal to trigger the time-correlated single-photon counter (4) to start counting, the pulsed optical signal is injected into the optical fiber to be tested (3) through the optical fiber circulator (2), and the backscattered optical signal generated in the optical fiber to be tested (3) is output to the near-infrared single-photon detector system based on gated quenching (5) again through the optical fiber circulator (2). The structural schematic diagram of the near-infrared single-photon detector system based on gated quenching (5) is shown as follows: Figure 5As shown, the system is composed of a gated signal output circuit (51), a switch control signal circuit (52), a logic gate control circuit (53), a capacitor (54), a bias voltage generating circuit (55), a near-infrared single-photon avalanche photodiode (56), and a signal readout circuit (57), wherein the signal readout circuit (57) is composed of an amplifier (571) and a resistor (572), the bias voltage generating circuit (55) outputs a voltage so that the reverse bias voltage of the near-infrared single-photon avalanche photodiode (56) is below the avalanche voltage, and the square wave signal output by the gated signal output circuit (51) is modulated by the logic gate control circuit (52) to form two square wave signals, namely, a signal A and a signal B; wherein the signal A is completely identical to the square wave signal output by the gated signal output circuit (51), and the signal B is modulated by an inverter (521) to output a square wave signal that is identical to the signal A. The phases are opposite and the amplitudes are the same; the switch control signal circuit (3) controls the A signal and the B signal to output the D signal through the logic circuit by outputting the C signal with a lower frequency, and first outputs the A signal to the near-infrared single-photon avalanche photodiode (56). Since the A signal has a certain voltage amplitude, during the time when the A signal is at a high voltage, the near-infrared single-photon avalanche photodiode (56) is in a single-photon detection state, and the optical signal is detected and read out by the signal readout circuit (57); after a period of detection, the C signal output by the switch control signal circuit (53) controls the B signal to be output to the near-infrared single-photon avalanche photodiode (56), and during the time when the A signal is at a high voltage, the optical signal not detected by the system is detected; the switch control signal circuit (53) ensures that the system fully detects all signals by controlling the cyclic output of the A signal and the B signal. The near-infrared single-photon detector system (5) based on gated quenching outputs an electrical signal to the time-correlated single-photon counter (4) for stopping counting each time a light signal is detected. The time-correlated single-photon counter (4) records the time difference between the synchronous pulse electrical signal and the electrical signal output by the single-photon avalanche diode; on the other hand, the number of photons obtained after accumulating multiple pulse signals is counted to characterize the light intensity. The time-correlated single-photon counter (4) transmits the acquired photon counting data to the signal processing system (6), and after processing, a distance-photon number (light intensity) curve can be obtained.

[0025] In the embodiment, the pulse laser (1) outputs a synchronous electrical signal while outputting a pulse light signal to trigger a time-correlated single-photon counter (4) to start counting. The pulse light signal is injected into the optical fiber under test (3) through the optical fiber circulator (2). The backscattered light signal generated in the optical fiber under test (3) is output again through the optical fiber circulator (2) to a near-infrared single-photon detector system (5) based on gated quenching.

[0026] The gate pulse signal outputted by the gated signal output circuit (51) in the near-infrared single-photon detector system (5) based on gated quenching has a duty cycle of 50% and a pulse width of t. The logic gate control circuit (53) modulates the gate pulse signal outputted by the gated signal output circuit (1). The output A signal of the logic gate control circuit (53) is completely consistent with the gate pulse signal outputted by the gate control circuit (1). Due to the effect of the inverter, the output gate pulse signal of the B signal of the logic gate control circuit (2) is opposite in phase to the gate pulse signal outputted by the gated signal circuit, but has the same amplitude.

[0027] The DC voltage generated by the bias voltage generating circuit (55) makes the reverse bias voltage of the near-infrared single-photon avalanche photodiode below the avalanche voltage, and a periodic gate pulse is superimposed on the reverse bias voltage. Since the gate pulse signal has a certain voltage amplitude, during the time when the high voltage is present, the near-infrared single-photon avalanche photodiode is in an avalanche state and can perform single-photon detection; and during the time when the low voltage is present, the reverse bias voltage is below the avalanche voltage, and the near-infrared single-photon avalanche photodiode is quenched.

[0028] The pulse width of the C signal output by the switch control signal circuit (55) is t c , t in the embodiment c1 With t c2 When the system starts working, the pulse width of the C signal output by the switch control signal circuit (53) is t c1 When the A signal is output by the logic control circuit, the near-infrared single-photon avalanche photodiode is in an avalanche state, the photons are detected and converted into electrical signals, and then read out by the signal readout circuit (57).

[0029] When the pulse width of the C signal output by the switch control signal circuit (52) is t c2 When the signal A is detected, the logic control circuit outputs a B signal with the same amplitude and opposite phase as the A signal, so that the near-infrared single-photon avalanche photodiode is in an avalanche state, and the photons are detected and converted into electrical signals, which are read out by the signal readout circuit (57).

[0030] The switch control signal circuit (52) outputs a pulse with a width of t c The C signal controls the signal loop output of the A signal and the B signal, thereby ensuring the system's complete detection of all signals and solving the signal loss problem caused by the near-infrared single-photon avalanche diode when collecting optical signals in the gated quenching mode.

[0031] The near-infrared single-photon detector system (5) based on gated quenching outputs an electrical signal to the time-correlated single-photon counter (4) for stopping counting each time a light signal is detected. The time-correlated single-photon counter (4) records the time difference between the synchronous pulse electrical signal and the electrical signal output by the single-photon avalanche diode; on the other hand, the number of photons obtained after accumulating multiple pulse signals is counted to characterize the light intensity. The time-correlated single-photon counter (4) transmits the acquired photon counting data to the signal processing system (6), and after processing, a distance-photon number (light intensity) curve can be obtained and displayed by the display system (7).

[0032] The pulse laser (1) in the embodiment is responsible for adjusting the repetition frequency of the pulse light signal so that only one pulse light signal is transmitted in the optical fiber under test at the same time, and sends out a synchronous electrical signal to trigger the time-correlated single photon counter (4) to ensure the clock synchronization of the entire system.

Claims

1. A novel near-infrared single-photon detection system, characterized by: It consists of a gated signal output circuit (1), a switch control signal circuit (2), a logic gate control circuit (3), a capacitor (4), a bias voltage generating circuit (5), a near-infrared single-photon avalanche photodiode (6), and a signal readout circuit (7), wherein the signal readout circuit (7) consists of an amplifier (71) and a resistor (72); in the system, the bias voltage generating circuit (5) outputs a voltage so that the reverse bias voltage of the near-infrared single-photon avalanche photodiode (6) is below the avalanche voltage; the square wave signal output by the gated signal output circuit (1) is modulated by the logic gate control circuit (3) to form two square wave signals, namely, a signal A and a signal B; wherein the signal A is completely identical to the square wave signal output by the gated signal output circuit (1); after the signal B is modulated by an inverter (31), the output square wave signal is in phase with the signal A. On the contrary, the amplitudes are the same; the switch control signal circuit (2) controls the A signal and the B signal to cyclically output the signal D by outputting the C signal with a lower frequency; when the A signal is output to the near-infrared single-photon avalanche photodiode (6), since the A signal has a certain voltage amplitude, during the time when the A signal is at a high voltage, the near-infrared single-photon avalanche photodiode (6) is in a single-photon detection state, and the optical signal is detected and then read out by the signal readout circuit (7); after a period of detection, the C signal output by the switch control signal circuit (2) controls the B signal to be output to the near-infrared single-photon avalanche photodiode (6), and during the time when the A signal is at a high voltage, the optical signal not detected by the system is detected; the switch control signal circuit (2) ensures that the system fully detects all signals by controlling the cyclic output of the A signal and the B signal.

2. The novel near-infrared single-photon detection system according to claim 1 is characterized in that: The function of the gate signal output circuit (1) is to output a periodic square wave signal. The duty cycle and pulse width of the square wave signal can be set according to actual use.

3. The novel near-infrared single-photon detection system according to claim 1 is characterized in that: The switch control signal circuit (2) outputs a C signal with a lower frequency and a wider pulse width to output a D signal by controlling the A signal and the B signal in the logic gate control circuit (3), thereby ensuring that the system fully detects all signals.

4. The novel near-infrared single-photon detection system according to claim 1 is characterized in that: The logic gate control circuit (3) is composed of two signals, namely, an A signal and a B signal, wherein the A signal is completely identical to the square wave signal output by the gate control signal output circuit (1), and the B signal has a phase opposite to that of the square wave signal output by the gate control signal output circuit (1) and has the same amplitude due to the action of the inverter (31); the switch control signal circuit (2) controls the output of the D signal by controlling the logic circuit in the logic gate control circuit (3).

5. The novel near-infrared single-photon detection system according to claim 1 is characterized in that: The bias voltage generating circuit (5) is connected to the cathode of the near-infrared single-photon avalanche photodiode (6); its function is to realize voltage conversion, convert the input voltage into a DC voltage and output it to the near-infrared single-photon avalanche photodiode (6), ensuring that the bias voltage provided is stably below the avalanche voltage of the near-infrared single-photon avalanche photodiode (6); the bias voltage generating circuit (5) can be a DC-DC conversion circuit or an AC-DC conversion circuit.

6. The novel near-infrared single-photon detection system according to claim 1 is characterized in that: The near-infrared single-photon avalanche photodiode (6) can be any one of a near-infrared single-photon avalanche photodiode made of indium gallium arsenide (InGaAs) or indium gallium arsenide / indium phosphide (InGaAs / InP) material. During specific use, a near-infrared single-photon avalanche photodiode with optimal performance parameters can be selected according to use requirements.

7. The novel near-infrared single-photon detection system according to claim 1 is characterized in that: The signal readout circuit (7) is composed of an amplifier (71) and a resistor (72); the resistor (72) is connected to the anode of the near-infrared single-photon avalanche photodiode (6) and functions to reduce the bias voltage of the near-infrared single-photon avalanche photodiode (6) after an avalanche occurs, thereby achieving the purpose of avalanche quenching; the junction capacitance of the resistor (72) and the near-infrared single-photon avalanche photodiode (6) and the capacitor (4) determine the recovery time for the detector to return to the detection state; the amplifier (71) functions to amplify the electrical pulse output by the near-infrared single-photon avalanche photodiode (6); and the resistance value of the resistor (72) is selected according to actual use conditions.

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