Single photon avalanche diode temperature control system and method based on avalanche signal

Abstract

The invention relates to the technical field of quantum communication, in particular to a single-photon avalanche diode temperature control system and method based on an avalanche signal, and the system comprises a local instant refrigeration loop which is composed of a square-wave generator, a first current generator, a miniature semiconductor cooler and a single-photon avalanche diode. An environment temperature control circuit is formed by a temperature sensor, a controller, a second current generator and a second semiconductor cooler; the local instant refrigeration loop responds to the photon signal received by the single photon avalanche diode so as to carry out local instant refrigeration on the single photon avalanche diode receiving the photon signal; the environment temperature control circuit controls the interior of the sealing box to be always in a low-temperature environment based on a temperature signal in the sealing box. According to the invention, the miniature semiconductor cooler is introduced in single-photon detection, and a temperature feedback control mechanism is realized according to an avalanche signal, so that the problem of PN junction temperature drift caused by continuous reception of a plurality of photons by a single-photon avalanche diode is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the field of quantum communication technology, and in particular to a single-photon avalanche diode temperature control system and method based on an avalanche signal. Background Art

[0002] With the rapid development of quantum communication technology, Quantum Key Distribution (QKD) as its core application has become an important guarantee for information security in various fields with its high security given by the principles of quantum mechanics. QKD technology relies on single photons as the carrier of quantum signals. Efficient and accurate detection of these photons is the key to achieving secure communication. At present, InGaAs / InP single-photon avalanche diode (SPAD) is the mainstream single-photon detection element. It works in Geiger mode and shows extremely high sensitivity. When the photon is absorbed by the SPAD, the internal electron-hole pairs are generated and accelerated to collide, triggering the "self-sustaining avalanche" effect, thereby realizing the amplification and detection of the optical signal.

[0003] However, in practical applications, the performance stability of SPAD faces multiple challenges. First, even in the absence of photon incidence, SPAD will still generate dark current, which is particularly significant at room temperature. Although low temperature environment can effectively reduce dark current, maintaining the operating temperature of SPAD becomes another problem. Usually, a semiconductor cooler (TEC) is used for temperature control to ensure that SPAD is in the best working state. In addition, due to the randomness of photon arrival, SPAD will receive multiple photons in several consecutive gating cycles, causing its internal PN junction temperature to rise sharply; conversely, if there is no photon incidence for a long time, the PN junction temperature will drop. Both of these situations will cause temperature drift of SPAD, which will significantly affect its key performance indicators such as dark current, spike noise, sensitivity and post-pulse rate, and thus affect the performance of the quantum key distribution system.

[0004] In addition, existing technical solutions often ignore the dynamic temperature changes of SPAD when it continuously receives photons or is in a long-term silent state. This leads to unpredictable fluctuations in the performance parameters of SPAD in actual operation, seriously affecting the reliability and security of the quantum key distribution system. Therefore, how to effectively control the temperature changes of SPAD during the avalanche process and suppress the performance degradation caused by temperature drift has become a key issue that needs to be urgently solved in the current field of quantum communications. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a single photon avalanche diode temperature control system and method based on an avalanche signal.

[0006] In a first aspect, the present invention provides a temperature control system for a single-photon avalanche diode based on an avalanche signal, comprising a square-wave generator, a first current generator, a second current generator, a controller, and a single-photon avalanche diode, a micro thermoelectric cooler, a temperature sensor, and a second thermoelectric cooler disposed in a sealed box. Among them, the square-wave generator, the first current generator, the micro thermoelectric cooler, and the single-photon avalanche diode are sequentially connected to jointly form a local instant cooling circuit, and the temperature sensor, the controller, the second current generator, and the second thermoelectric cooler are connected in series to form an ambient temperature control circuit;

[0007] The local instant cooling circuit is configured to, in response to a photon signal received by the single-photon avalanche diode, generate an avalanche signal by the square-wave generator according to the difference in photon signals, and trigger the first current generator to generate a pulsed current through the avalanche signal, so as to drive the micro thermoelectric cooler to perform local instant cooling on the single-photon avalanche diode receiving the photon signal under the action of the pulsed current, and suppress the temperature drift generated when the single-photon avalanche diode continuously receives multiple photon signals;

[0008] The ambient temperature control circuit is configured to use the temperature sensor to continuously monitor the temperature signal in the sealed box, and based on the temperature signal, drive the second thermoelectric cooler through the second current generator to control the sealed box to always be in a low-temperature environment.

[0009] In a further embodiment, the single-photon avalanche diode at least includes an auxiliary single-photon avalanche diode and a main detection single-photon avalanche diode for detecting photon signals;

[0010] The square-wave generator is configured to generate an avalanche signal according to the difference in photon signals between the main detection single-photon avalanche diode and the auxiliary single-photon avalanche diode when the main detection single-photon avalanche diode receives a photon signal.

[0011] In a further embodiment, the single-photon avalanche diode only includes a main detection single-photon avalanche diode for detecting photon signals;

[0012] The square-wave generator is configured to generate an avalanche signal according to the difference in photon signals generated by the main detection single-photon avalanche diode in different periods when the main detection single-photon avalanche diode receives a photon signal.

[0013] In a further embodiment, the micro thermoelectric cooler is disposed around the main detection single-photon avalanche diode, and the cold end of the micro thermoelectric cooler is in direct contact with the PN junction of the main detection single-photon avalanche diode;

[0014] The micro thermoelectric cooler is used to locally and rapidly cool the main detection single-photon avalanche diode by receiving the pulsed current generated by the first current generator, so as to offset the heat generated during the avalanche process.

[0015] In a further embodiment, the refrigerating capacity generated by the micro thermoelectric cooler under the action of a single pulsed current is greater than the heat generated during a single avalanche process.

[0016] In a further embodiment, the refrigerating capacity generated by the micro thermoelectric cooler under the action of a single pulsed current is 1.2 times the maximum heat generated during a single avalanche process.

[0017] In a further embodiment, the controller is used to calculate the current value required to maintain the temperature inside the sealed box by using a proportional-integral-derivative control algorithm according to the temperature signal monitored by the temperature sensor, and generate an external control signal.

[0018] In a further embodiment, the second current generator is used to generate a low-temperature control working current according to the external control signal, so as to drive the second thermoelectric cooler to control the inside of the sealed box to always be in a low-temperature environment under the action of the low-temperature control working current.

[0019] In a further embodiment, the square-wave generator adopts a differential comparison and amplification circuit, and the differential comparison and amplification circuit includes a differential circuit and a comparison and amplification circuit connected in sequence;

[0020] The differential comparison and amplification circuit is used to extract the differential component of the input photon signal through the differential circuit, compare it with a reference voltage through the comparison and amplification circuit, and output an avalanche signal.

[0021] In a second aspect, the present invention provides a method for controlling the temperature of a single-photon avalanche diode based on an avalanche signal, and the method includes the following steps:

[0022] In response to the photon signal received by the single-photon avalanche diode, an avalanche signal is generated according to the difference of the photon signals, and a pulsed current is generated through the avalanche signal;

[0023] Under the action of the pulsed current, local and immediate cooling is performed on the single-photon avalanche diode that receives the photon signal, and the temperature drift generated when the single-photon avalanche diode continuously receives multiple photon signals is suppressed;

[0024] The temperature signal inside the sealed box for encapsulating the single-photon avalanche diode is monitored in real time, and the inside of the sealed box is controlled to always be in a low-temperature environment based on the temperature signal.

[0025] The present invention provides a temperature control system and method for a single - photon avalanche diode based on avalanche signals. The system includes a local instant cooling loop formed by sequentially connecting a square - wave generator, a first current generator, a micro - semiconductor refrigerator, and a single - photon avalanche diode, and an ambient temperature control circuit formed by connecting a temperature sensor, a controller, a second current generator, and a second semiconductor refrigerator in series. The local instant cooling loop is used to respond to the photon signals received by the single - photon avalanche diode. The square - wave generator generates avalanche signals according to the differences in photon signals, and triggers the first current generator to generate pulsed current through the avalanche signals, so as to drive the micro - semiconductor refrigerator to locally and instantaneously cool the single - photon avalanche diode receiving the photon signals under the action of the pulsed current, and suppress the temperature drift generated when the single - photon avalanche diode continuously receives multiple photon signals. The ambient temperature control circuit is used to use the temperature sensor to continuously monitor the temperature signal in the sealed box, and control the second current generator to drive the second semiconductor refrigerator based on the temperature signal to keep the inside of the sealed box in a low - temperature environment all the time. Compared with the prior art, by introducing a micro - semiconductor refrigerator and a temperature feedback control mechanism in single - photon detection, etc., the system effectively reduces the temperature drift of the PN junction of the single - photon avalanche diode when continuously receiving multiple photons, significantly suppresses the performance change of the single - photon avalanche diode caused by temperature changes, and thus improves the reliability and stability of the key distribution system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FIG. is a structural diagram of a temperature control system for a single - photon avalanche diode based on avalanche signals provided by an embodiment of the present invention;

[0027] Figure 2 FIG. is a schematic structural diagram of a local instant cooling loop provided by an embodiment of the present invention;

[0028] Figure 3 FIG. is a schematic diagram showing the relationship between the current of the micro - semiconductor refrigerator and the avalanche signal changing with time provided by an embodiment of the present invention;

[0029] Figure 4 FIG. is a schematic structural diagram of an ambient temperature control circuit provided by an embodiment of the present invention;

[0030] Figure 5 FIG. is a temperature change diagram of the internal PN junction of a single - photon avalanche diode provided by an embodiment of the present invention;

[0031] Figure 6 FIG. is a schematic flow diagram of a temperature control method for a single - photon avalanche diode based on avalanche signals provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The embodiments of the present invention will be specifically described below in conjunction with the accompanying drawings. The examples are given only for illustrative purposes and should not be construed as limiting the present invention. The included drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0033] An embodiment of the present invention provides a temperature control system for a single-photon avalanche diode based on avalanche signals. The system includes a square-wave generator, a first current generator, a second current generator, a controller, and a single-photon avalanche diode, a micro thermoelectric cooler, a temperature sensor, and a second thermoelectric cooler placed in a sealed box. In some embodiments, as Figure 1 shown, two single-photon avalanche diodes are used in the single-photon avalanche diode temperature control system in this embodiment, namely, the main detection single-photon avalanche diode SPAD1 and the auxiliary single-photon avalanche diode SPAD2. Among them, the auxiliary single-photon avalanche diode SPAD2 is not used to receive photons. In this embodiment, it is set that only the main detection single-photon avalanche diode SPAD1 is responsible for receiving photons. In order to cool the main detection single-photon avalanche diode SPAD1 alone, a micro thermoelectric cooler (micro TEC) is installed around the main detection single-photon avalanche diode SPAD1 in this embodiment. The PN junction of the main detection single-photon avalanche diode SPAD1 is in direct contact with the cold end of the micro thermoelectric cooler to achieve an efficient cooling effect. At the same time, optical fiber 1 passes through the micro thermoelectric cooler and is in contact connection with the main detection single-photon avalanche diode SPAD1 to effectively transmit photon signals. In this embodiment, the main detection single-photon avalanche diode SPAD1 and the micro thermoelectric cooler are placed together in a sealed box. In order to maintain the low-temperature environment in the sealed box, a second thermoelectric cooler (second TEC) is used in this embodiment to further adjust the temperature in the box, ensure that the main detection single-photon avalanche diode SPAD1 and the micro thermoelectric cooler are in a stable operating temperature range, and indirectly cool the main detection single-photon avalanche diode SPAD1, so as to maintain the stable operation of the entire device.

[0034] In some embodiments, the square-wave generator, the first current generator, the micro thermoelectric cooler, and the single-photon avalanche diode are sequentially connected to jointly form a local instant cooling circuit, as Figure 2 shown. The local instant cooling circuit is used to respond to the photon signal received by the single-photon avalanche diode. The square-wave generator generates an avalanche signal according to the photon signal difference, and triggers the first current generator to generate a pulsed current I1 through the avalanche signal, so as to drive the micro thermoelectric cooler to perform local instant cooling on the single-photon avalanche diode that receives the photon signal, and suppress the temperature drift generated when the single-photon avalanche diode continuously receives multiple photon signals.

[0035] Specifically, in the temperature control system of the single-photon avalanche diode of this embodiment, two single-photon avalanche diodes are used (including the auxiliary single-photon avalanche diode SPAD2 that does not receive photons and the main detection single-photon avalanche diode SPAD1 for detecting photon signals). And when only the main detection single-photon avalanche diode SPAD1 is set to be responsible for receiving photons, when the single-photon avalanche diode SPAD1 receives a photon signal, an obvious signal difference will occur between the single-photon avalanche diode SPAD1 and the single-photon avalanche diode SPAD2. At this time, the square-wave generator will detect the signal difference between the two single-photon avalanche diodes (the main detection single-photon avalanche diode SPAD1 and the auxiliary single-photon avalanche diode SPAD2) and output a square-wave signal. This square-wave signal is the avalanche signal, indicating that a photon has been successfully detected.

[0036] In some other embodiments, the temperature control system of the single-photon avalanche diode provided in this embodiment is only provided with one single-photon avalanche diode, that is, the single-photon avalanche diode only includes the main detection single-photon avalanche diode for detecting photon signals. At this time, the square-wave generator adopts the self-differential detection technology. In the self-differential detection technology, when the main detection single-photon avalanche diode receives a photon signal, the square-wave generator generates an avalanche signal according to the photon signal difference generated by the main detection single-photon avalanche diode in different cycles. For example, if the main detection single-photon avalanche diode does not receive a photon in the previous cycle and receives a photon in the next cycle, then the signals output by the main detection single-photon avalanche diode in these two cycles will be different. The system delays the signal output in the previous cycle and then compares it with the signal output in the next cycle. The square-wave generator can also detect this signal difference and output a square-wave signal. This signal is also used as the avalanche signal, indicating that a photon has been detected.

[0037] Through the above two different implementation manners, this embodiment can effectively detect the signal change of the single-photon avalanche diode and output an avalanche signal through the square-wave generator, thereby realizing the precise control of the temperature of the single-photon avalanche diode. The square-wave generator in this embodiment adopts a differential comparison amplification circuit, and the differential comparison amplification circuit includes a differential circuit and a comparison amplification circuit connected in sequence; the differential comparison amplification circuit is used to extract the differential component of the input photon signal through the differential circuit and compare it with the reference voltage through the comparison amplification circuit to output an avalanche signal.

[0038] During the specific working process, the square wave generator is electrically connected to the first current generator, and the first current generator is electrically connected to the micro thermoelectric cooler. After the square wave generator outputs an avalanche signal, each time the first current generator detects an avalanche signal, it will generate a pulse current I1 and send the pulse current I1 to the micro thermoelectric cooler to control the working state of the micro TEC. The micro thermoelectric cooler receives the pulse current I1 generated by the first current generator and locally and rapidly cools the main detection single photon avalanche diode under the drive of the pulse current I1 to offset the heat generated during the avalanche process, realizing precise control of the temperature of the single photon avalanche diode (SPAD).

[0039] In some embodiments, the cooling capacity generated by the micro thermoelectric cooler under the action of a single pulse current is greater than the heat generated during a single avalanche process. Specifically, in this embodiment, the cooling capacity generated by the micro thermoelectric cooler under the action of a single pulse current is 1.2 times the maximum heat generated during a single avalanche process. This process depends on the photon reception situation of the single photon avalanche diode to generate the pulse current I1. Whenever the single photon avalanche diode detects a photon signal, it will trigger an avalanche signal and generate a pulse current accordingly.

[0040] In a specific embodiment, when an avalanche occurs, the key parameters of the SPAD used in this embodiment may include a maximum working current of 2 mA, an avalanche voltage set to 72 V, a reverse bias voltage of 77 V, a gating frequency of 100 MHz, the maximum duration of a single avalanche is usually 5 ns, and the maximum heat generated during this period is 0.77 nJ. It should be noted that in most cases, the maximum time (actual duration) of a single avalanche is less than 5 ns, so the heat generated will also be lower than 0.77 nJ. These heats can increase the temperature of the PN junction of the single photon avalanche diode by about 0.55 degrees Celsius. In addition, the cooling efficiency of the micro thermoelectric cooler in this embodiment under the working environment is 0.44, its working voltage is 1.9 V. When the width of the pulse current is 5 ns, the intensity of the pulse current I1 reaches 0.221 A. At this time, the cooling capacity generated by a single pulse current is 0.924 nJ. The cooling capacity generated by the pulse current I1 is sufficient to effectively balance or exceed the heat generated by a single avalanche process (0.77 nJ). It should be noted that due to conduction in all directions, the cooling capacity generated by the pulse current must be greater than the heat generated by a single avalanche process to be able to effectively offset the heat generated during the avalanche process and thus maintain the temperature stability of the SPAD.

[0041] As Figure 3 shown, this embodiment adopts the above parameters to obtain a relationship diagram of the micro thermoelectric cooler current and the avalanche signal changing with time. From Figure 3It can be seen that when there is no avalanche, the current passing through the micro thermoelectric cooler in this embodiment is 0; when an avalanche signal occurs, this embodiment will correspondingly generate a pulsed current signal. Since the circuit itself requires a certain response time, the rising edge of the current pulse signal will be delayed compared to the rising edge of the avalanche signal. In addition, due to the influence of the distributed parameters (including capacitance and inductance, etc.) in the circuit, the rising edge of the current signal shows an inclined shape instead of rising instantaneously. After the avalanche signal ends, the current pulse signal will not disappear immediately but will gradually disappear after a certain delay. During this process, due to the effect of the distributed parameters in the circuit, the falling edge of the current signal also shows the characteristic of inclined decline instead of instantaneously returning to zero. This delay between the current and the avalanche signal and the inclined change of the current signal reflect the dynamic response characteristics of the circuit during actual operation.

[0042] In some embodiments, the temperature sensor, the controller, the second current generator, and the second thermoelectric cooler are connected in series to form an ambient temperature control circuit. As Figure 4 shown, the ambient temperature control circuit is used to use the temperature sensor to continuously monitor the temperature signal inside the sealed box, and based on the temperature signal, the controller generates a control signal, and drives the second thermoelectric cooler through the second current generator to keep the inside of the sealed box in a low-temperature environment all the time.

[0043] During the specific working process, the temperature sensor, the controller, the second current generator, and the second thermoelectric cooler (the second TEC) are electrically connected in sequence. The temperature sensor is used to continuously monitor the temperature signal inside the sealed box and feedback the temperature signal to the controller. At this time, the controller calculates the current value required to maintain the temperature inside the sealed box using the proportional-integral-derivative control algorithm, generates an external control signal, and the second current generator generates a low-temperature control working current I2 according to the external control signal to provide the required low-temperature control working current I2 for the second thermoelectric cooler, so that the second thermoelectric cooler controls the inside of the sealed box to be in a low-temperature environment all the time under the action of the low-temperature control working current, maintaining the low-temperature environment inside the sealed box. It should be noted that in most cases, the low-temperature control working current I2 remains relatively stable. However, when the external ambient temperature of the sealed box changes or the system starts, the low-temperature control working current I2 will show a relatively obvious fluctuation.

[0044] Regarding the specific selection parameters of the temperature control circuit structure, the following parameter settings are adopted in this embodiment: The temperature sensor uses a PT1000 thermistor, which has high precision and good temperature response characteristics and can monitor the temperature change inside the sealed box in real time; The controller uses a GD32F103 microcontroller to quickly generate a control signal according to the feedback signal of the temperature sensor; The core component of the first current generator is a high-frequency high-power transistor PD55015; The second current generator uses a field-effect transistor as the core device, and its continuous drain current can reach 10 A; The second semiconductor refrigerator selected is of the TEC1-12706 model; The square wave generator is implemented through a differential comparison amplification circuit, which consists of a differential circuit and a comparison amplification circuit built by a high-speed operational amplifier. Through the collaborative work of the above components, this embodiment can effectively maintain the temperature stability inside the sealed box and achieve precise temperature control of the single-photon avalanche diode.

[0045] In some embodiments, the temperature sensor is used to convert the temperature inside the sealed box into an electrical signal. To eliminate interference signals and high-frequency signals, the output signal of the temperature sensor is subjected to low-pass filtering, and then the filtered signal is sent to the controller. The controller uses the PID algorithm to calculate the working current of the second TEC to maintain the temperature stability inside the sealed box, and then cool down the single-photon avalanche diode SPAD1 that receives the photon signal. It should be noted that using the PID algorithm to control the temperature in this embodiment is a known technology. For example, it is mentioned in master's theses such as "Software Design of the Temperature Control System for the Quantum Entanglement Source in the Optical Communication Band" published by Xie Jin in June 2023 and "Research and Development of the Digital Integrated Temperature Control System for the Entanglement Source in the Quantum Communication Band" published by Liang Wenzhe during the same period. These documents propose various PID algorithms to control the temperature of quantum devices.

[0046] Figure 5 Shows the comparison of the avalanche signal and the temperature change. Figure 5 Below is the avalanche signal, indicating that the single-photon avalanche diode SPAD has had three avalanches in a very short time. These avalanche signals are generated by the square wave generator. Figure 5Above is the temperature drift of the PN junction inside the SPAD in the traditional technical solution (temperature curve 1). When the first avalanche occurs, the temperature of the PN junction inside the SPAD rises rapidly, gradually decreases after reaching the peak, but the descent process is relatively long. Before the temperature drops to the system-set value, the second avalanche occurs, and the temperature rises again and reaches a new peak, which is higher than the previous one. When the third avalanche occurs, the temperature rises again. In the case where no photons are detected and no avalanches occur for a long time, the temperature of the PN junction inside the SPAD gradually drops below the system-set value. By adjusting the current of the semiconductor cooler through the PID algorithm, it takes a long time for the temperature to return to the system-set value again. In the traditional technical solution, when a single SPAD continuously receives multiple photons, multiple avalanches will occur in a short time, resulting in excessive temperature drift of the PN junction inside the SPAD, thereby affecting the performance of the SPAD, such as changes in parameters such as dark current, spike noise, sensitivity, and afterpulse rate, and ultimately leading to unstable performance of the key distribution system.

[0047] However, in Figure 5 The temperature drift of the SPAD under the control system provided by this embodiment is shown in the middle temperature curve 2. When each avalanche occurs, although the temperature of the PN junction inside the SPAD rises slightly, it can quickly drop below the system-set value after reaching the peak and return to the set temperature in a short time. This shows that even if the SPAD receives multiple photons and multiple avalanches occur in a short time, the solution of this embodiment can greatly reduce the temperature drift and suppress the performance changes of the SPAD caused by the temperature drift, thereby stabilizing important parameters such as the dark current, sensitivity, dark count, and afterpulse rate of the single-photon detector and maintaining the stable performance of the key distribution system.

[0048] In summary, the solution provided by this embodiment can not only adapt to the situation where a single SPAD continuously receives multiple photons, but also adapt to the situation where a single SPAD does not receive any photons in several consecutive gating cycles. At this time, there is no need to adjust the current of the semiconductor cooler to prevent the SPAD temperature from being too low. These advantages effectively reduce the temperature drift of the SPAD, suppress the performance changes caused by the temperature drift, avoid changes in important parameters of the single-photon detector, and thus ensure the stable performance of the key distribution system.

[0049] An embodiment of the present invention provides a temperature control system for a single - photon avalanche diode based on avalanche signals. The system includes a local instant cooling loop formed by sequentially connecting a square - wave generator, a first current generator, a micro - semiconductor refrigerator, and a single - photon avalanche diode, and an ambient temperature control circuit formed by connecting a temperature sensor, a controller, a second current generator, and a second semiconductor refrigerator in series. The local instant cooling loop is used to respond to the photon signal received by the single - photon avalanche diode. The square - wave generator generates an avalanche signal according to the difference of the photon signals, and triggers the first current generator to generate a pulsed current through the avalanche signal, so as to drive the micro - semiconductor refrigerator to perform local instant cooling on the single - photon avalanche diode receiving the photon signal under the action of the pulsed current, and suppress the temperature drift generated when the single - photon avalanche diode continuously receives multiple photon signals. The ambient temperature control circuit is used to use the temperature sensor to continuously monitor the temperature signal in the sealed box, and control the second current generator to drive the second semiconductor refrigerator to keep the sealed box in a low - temperature environment all the time. Compared with the prior art, by introducing a micro - semiconductor refrigerator and a temperature feedback control mechanism in single - photon detection, etc., the system effectively reduces the temperature drift of the PN junction of the single - photon avalanche diode when continuously receiving multiple photons, significantly suppresses the performance change of the single - photon avalanche diode caused by temperature change, thus ensuring the stable performance of the key distribution system and guaranteeing the reliable operation of the key distribution system.

[0050] In one embodiment, as Figure 6 shown, an embodiment of the present invention provides a temperature control method for a single - photon avalanche diode based on avalanche signals. The method includes the following steps:

[0051] S1. Respond to the photon signal received by the single - photon avalanche diode, generate an avalanche signal according to the difference of the photon signals, and generate a pulsed current through the avalanche signal;

[0052] S2. Perform local instant cooling on the single - photon avalanche diode receiving the photon signal under the action of the pulsed current, and suppress the temperature drift generated when the single - photon avalanche diode continuously receives multiple photon signals;

[0053] S3. Continuously monitor the temperature signal in the sealed box for encapsulating the single - photon avalanche diode, and control the sealed box to be in a low - temperature environment all the time based on the temperature signal.

[0054] It should be noted that the magnitudes of the sequence numbers of the above - mentioned processes do not mean the order of execution. The order of execution of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0055] For the specific limitations on a temperature control method for a single-photon avalanche diode based on avalanche signals, reference can be made to the above limitations on a temperature control system for a single-photon avalanche diode based on avalanche signals, which will not be elaborated here. Those of ordinary skill in the art can realize that, in combination with the various modules and steps described in the embodiments disclosed in this application, they can be implemented in hardware, software, or a combination of both. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.

[0056] An embodiment of the present invention provides a temperature control method for a single-photon avalanche diode based on avalanche signals. The method includes: in response to a photon signal received by the single-photon avalanche diode, generating an avalanche signal according to the photon signal difference, and generating a pulsed current through the avalanche signal; locally and instantaneously cooling the single-photon avalanche diode that receives the photon signal under the action of the pulsed current to suppress the temperature drift generated when the single-photon avalanche diode continuously receives multiple photon signals; and real-time monitoring the temperature signal in the sealed box for packaging the single-photon avalanche diode, and controlling the sealed box to always be in a low-temperature environment based on the temperature signal. Compared with the prior art, by introducing a micro-semiconductor refrigerator and a temperature feedback control mechanism in single-photon detection, this method effectively reduces the temperature drift of the PN junction of the single-photon avalanche diode when continuously receiving multiple photons, significantly suppresses the performance change of the single-photon avalanche diode caused by temperature changes, thereby ensuring the stable performance of the key distribution system and guaranteeing the reliable operation of the key distribution system.

[0057] The above-described embodiments only represent several preferred implementation manners of this application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the technical field, without departing from the technical principle of the present invention, several improvements and substitutions can still be made, and these improvements and substitutions should also be regarded as the protection scope of this application. Therefore, the protection scope of the patent of this application shall be subject to the protection scope of the claimed rights.

Claims

1. A single photon avalanche diode temperature control system based on avalanche signals, characterized in that: The invention comprises a square wave generator, a first current generator, a second current generator, a controller, and a single-photon avalanche diode, a micro-semiconductor refrigerator, a temperature sensor and a second semiconductor refrigerator placed in a sealed box, wherein the square wave generator, the first current generator, the micro-semiconductor refrigerator and the single-photon avalanche diode are connected in sequence to form a local instant refrigeration circuit, and the temperature sensor, the controller, the second current generator and the second semiconductor refrigerator are connected in series to form an environmental temperature control circuit; The local instant cooling circuit is used to respond to the photon signal received by the single-photon avalanche diode, generate an avalanche signal by the square wave generator according to the difference of the photon signal, and trigger the first current generator to generate a pulse current through the avalanche signal, so as to drive the micro semiconductor refrigerator to perform local instant cooling on the single-photon avalanche diode receiving the photon signal under the action of the pulse current, so as to suppress the temperature drift generated by the single-photon avalanche diode when receiving multiple photon signals continuously; The ambient temperature control circuit is used to use the temperature sensor to monitor the temperature signal in the sealed box in real time, and based on the temperature signal, drive the second semiconductor refrigerator through the second current generator to control the sealed box to always be in a low temperature environment.

2. A single photon avalanche diode temperature control system based on an avalanche signal as claimed in claim 1, characterized in that: The single photon avalanche diode at least includes an auxiliary single photon avalanche diode and a main detection single photon avalanche diode for detecting photon signals; The square wave generator is used to generate an avalanche signal according to the difference in photon signals between the main detection single photon avalanche diode and the auxiliary single photon avalanche diode when the main detection single photon avalanche diode receives a photon signal.

3. A single photon avalanche diode temperature control system based on an avalanche signal as claimed in claim 1, characterized in that: The single photon avalanche diode only includes a main detection single photon avalanche diode for detecting photon signals; The square wave generator is used to generate an avalanche signal according to the difference in photon signals generated by the main detection single-photon avalanche diode in different periods when the main detection single-photon avalanche diode receives a photon signal.

4. A single photon avalanche diode temperature control system based on an avalanche signal as claimed in claim 2 or 3, characterized in that: The micro semiconductor refrigerator is arranged around the main detection single photon avalanche diode, and the cold end of the micro semiconductor refrigerator is in direct contact with the PN junction of the main detection single photon avalanche diode; The micro semiconductor refrigerator is used to perform local rapid cooling on the main detection single photon avalanche diode by receiving the pulse current generated by the first current generator, so as to offset the heat generated by the avalanche process.

5. A single photon avalanche diode temperature control system based on avalanche signals as claimed in claim 4, characterized in that: The cooling capacity generated by the micro semiconductor refrigerator under the action of a single pulse current is greater than the heat generated in a single avalanche process.

6. A single photon avalanche diode temperature control system based on avalanche signals as claimed in claim 5, characterized in that: The cooling capacity generated by the micro semiconductor refrigerator under the action of a single pulse current is 1.2 times the maximum heat generated by a single avalanche process.

7. A single photon avalanche diode temperature control system based on avalanche signal as claimed in claim 1, characterized in that: The controller is used to calculate the current value required to maintain the temperature in the sealed box according to the temperature signal monitored by the temperature sensor, using a proportional-integral-differential control algorithm to generate an external control signal.

8. A single photon avalanche diode temperature control system based on avalanche signals as claimed in claim 7, characterized in that: The second current generator is used to generate a low-temperature control working current according to the external control signal to drive the second semiconductor refrigerator to control the sealed box to always be in a low-temperature environment under the action of the low-temperature control working current.

9. A single photon avalanche diode temperature control system based on an avalanche signal as claimed in claim 1, characterized in that: The square wave generator adopts a differential comparison amplifier circuit, and the differential comparison amplifier circuit includes a differential circuit and a comparison amplifier circuit connected in sequence; The differential comparison amplifier circuit is used to extract the differential component of the input photon signal through the differential circuit, compare it with the reference voltage through the comparison amplifier circuit, and output an avalanche signal.

10. A single photon avalanche diode temperature control method based on an avalanche signal, characterized in that: The method comprises the following steps: In response to a photon signal received by the single-photon avalanche diode, an avalanche signal is generated according to a difference in the photon signal, and a pulse current is generated through the avalanche signal; Under the action of the pulse current, the single-photon avalanche diode receiving the photon signal is locally and instantly cooled to suppress the temperature drift of the single-photon avalanche diode when it continuously receives multiple photon signals; The temperature signal in the sealing box for packaging the single-photon avalanche diode is monitored in real time, and the sealing box is controlled to be in a low-temperature environment all the time based on the temperature signal.

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