System and method for detecting avalanche photodiode

Abstract

The invention provides a detection system and method for an avalanche photodiode, and the system comprises an arbitrary signal generator, a laser, an adjustable attenuator, a time-to-digital converter and a test processor, the first output end of the arbitrary signal generator is connected with the laser, the laser is connected with the adjustable attenuator, and outputs a light pulse to the adjustable attenuator; the adjustable attenuator inputs the attenuated optical signal to the input end of the avalanche photodiode to be tested; a second output end of the arbitrary signal generator is connected with a time-to-digital converter; the time-to-digital converter receives an output signal of the avalanche photodiode to be tested; the test processor is connected with a to-be-tested avalanche photodiode and is used for debugging and configuring parameters of the to-be-tested avalanche photodiode; a to-be-detected avalanche photodiode is placed on the detection tool, and the detection tool and the semiconductor refrigerator are packaged together. According to the invention, the compatibility and integration degree of the system can be improved, the stability of the system is improved, and the sensitivity to detected photons is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of diode detection, and particularly relates to a detection system and method for an avalanche photodiode. Background Art

[0002] The statements in this part only provide background technical information related to the present invention, and do not necessarily constitute prior art.

[0003] Single-photon detectors are widely used in fields such as laser ranging, biomedicine, quantum communication, and quantum key distribution (QKD). Currently, the main single-photon detection devices include photomultiplier tubes, avalanche photodiodes (APDs), superconducting single-photon detectors, etc. Detection efficiency, dark count rate, and afterpulse are the main test indicators of silicon avalanche photodiodes, which directly affect key indicators such as the maximum communication distance, coding rate, maximum communication rate of quantum secure communication, and the measurement range of laser ranging.

[0004] Some research literatures have proposed the detection of avalanche photodiodes. For example, in the journal "Chinese Journal of Quantum Electronics", in an article named "Research on the Performance Test System of Avalanche Photodiodes", a set of test systems was designed for InGaAs avalanche photodiodes. The InGaAs avalanche photodiode performance test system was designed to test key parameters such as detection efficiency, dark count rate, and afterpulse probability when the APD operates in the Geiger mode. However, this system requires an external refrigeration box, and the airtightness of the refrigeration box will affect the refrigeration effect, thereby affecting the stability of the entire system.

[0005] In the journal "Acta Photonica Sinica", in an article named "Calibration System of Single-Photon Avalanche Diode Based on FPGA", FPGA was used to replace instruments such as function generators, pulse generators, and counters, and this system was used to calibrate silicon avalanche diodes operating in the active suppression mode and indium gallium arsenide / indium phosphide avalanche diodes operating in the gated Geiger mode. However, in the Si APD performance calibration experiment, the counting gate width was 200 ns, and the incident photon pulse intensity was 1.6 photons / pulse. The gate width and photon pulse intensity of this system are too large to be applicable to the detection of silicon avalanche photodiodes. Summary of the Invention

[0006] In order to solve the above problems, the present invention proposes a detection system and method for an avalanche photodiode. The present invention can improve the compatibility and integration level of the system, improve the system stability, and has high sensitivity to the detected photons.

[0007] According to some embodiments, the present invention adopts the following technical solutions:

[0008] An avalanche photodiode detection system includes an arbitrary signal generator, a laser, an adjustable attenuator, a time-to-digital converter, and a test processor, where:

[0009] The first output terminal of the arbitrary signal generator is connected to the laser, the laser is connected to the adjustable attenuator, and outputs optical pulses to the adjustable attenuator. The adjustable attenuator inputs the attenuated optical signal to the input terminal of the avalanche photodiode to be tested;

[0010] The second output terminal of the arbitrary signal generator is connected to the time-to-digital converter, and the time-to-digital converter receives the output signal of the avalanche photodiode to be tested;

[0011] The test processor is connected to the avalanche photodiode to be tested and is used to debug and configure the parameters of the avalanche photodiode to be tested;

[0012] The avalanche photodiode to be tested is placed on a detection fixture, and the detection fixture is encapsulated together with a semiconductor cooler.

[0013] As an alternative implementation, the laser is a picosecond laser.

[0014] As an alternative implementation, the test processor and the avalanche photodiode to be tested are connected by a serial cable.

[0015] As an alternative implementation, it further includes a dual-channel optical power meter for obtaining the output optical intensity of the laser and calculating the number of photons.

[0016] A test method based on the above system includes the following steps:

[0017] Determine the output optical intensity of the laser and the attenuation value of the adjustable attenuator, and calculate the calibrated number of photons of the avalanche photodiode to be tested;

[0018] Connect the test system, power on the avalanche photodiode to be tested, and configure the target temperature and bias voltage of the avalanche photodiode to be tested so that the count of the avalanche photodiode to be tested is less than the set value;

[0019] Turn on the time-to-digital converter, configure the test time and light source frequency, configure the number of photons to the calibrated number of photons, read the count of the time-to-digital converter when the laser is not working, and calculate the dark count rate value;

[0020] Configure the dark count rate parameter of the time-to-digital converter to the calculated dark count rate value, trigger the laser to emit light for testing, and record the detection data, including the total count rate and the optical count rate;

[0021] And calculate the detection efficiency and afterpulse probability according to the recorded data.

[0022] As an alternative embodiment, it further includes changing the target temperature of the avalanche photodiode to be measured and repeating the above test process.

[0023] As an alternative embodiment, the dark count rate value is the count of the time-to-digital converter when the laser is not working divided by the test time.

[0024] As an alternative embodiment, the calculation process of the detection efficiency is as follows:

[0025]

[0026] where, μ - average number of photons per pulse, R ph - optical count rate, f L - light source frequency.

[0027] As an alternative embodiment, the afterpulse probability is:

[0028]

[0029] where R d - dark count rate, P ap - afterpulse probability, T d - dead time, R - total count rate, R ph - optical count rate.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] The present invention tests several key parameters of the avalanche photodiode through a test platform composed of an arbitrary signal generator, a picosecond laser, a detection tooling, a time-to-digital converter, a test processor, and corresponding test software.

[0032] The present invention can be used for the test of silicon avalanche photodiodes and can also be applied to the detection of other types of avalanche photodiodes.

[0033] The detection tooling of the present invention is packaged together with the semiconductor cooler, that is, the refrigeration device is integrated into the system, improving the compatibility and integration degree of the system and enhancing the system stability.

[0034] The detection system and the corresponding test method of the present invention can perform refined configuration management on multiple test parameters of the APD and the TDC, can truly reflect the relevant performance parameters of the APD, have high test result accuracy, and high test process automation.

[0035] The test method of the present invention has a gate width of only 800 ps and a photon pulse intensity of 0.1 photon / pulse, and has high sensitivity to the photons to be detected.

[0036] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides preferred embodiments in conjunction with the accompanying drawings and describes them in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The schematic diagrams of the drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0038] Figure 1 It is a schematic diagram of the detection system structure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The present invention will be further described below in conjunction with the drawings and embodiments.

[0040] It should be noted that the following detailed descriptions are all illustrative and are intended to provide a further description of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0041] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0042] Embodiment 1

[0043] As Figure 1 shown, a detection system for an avalanche photodiode includes an arbitrary signal generator, a laser, an adjustable attenuator, a time-to-digital converter, and a test computer, where:

[0044] The first output terminal (i.e., OUT1) of the arbitrary signal generator is connected to the laser, the laser is connected to the adjustable attenuator, and outputs optical pulses to the adjustable attenuator. The adjustable attenuator inputs the attenuated optical signal to the input terminal of the avalanche photodiode to be tested (in this embodiment, a silicon avalanche photodiode is taken as an example for illustration, and hereinafter it may also be simply referred to as an APD detector or APD);

[0045] The second output terminal (i.e., OUT2) of the arbitrary signal generator is connected to the time-to-digital converter (hereinafter simply referred to as TDC), and the time-to-digital converter receives the output signal of the avalanche photodiode to be tested;

[0046] The test computer and the avalanche photodiode to be tested are connected through a serial cable, and are used to debug and configure the parameters of the avalanche photodiode to be tested;

[0047] The avalanche photodiode to be measured is placed on a detection tooling, and the detection tooling is encapsulated together with a semiconductor cooler.

[0048] In this embodiment, a picosecond laser is selected. The picosecond laser is also connected to a dual-channel optical power meter.

[0049] Embodiment 2

[0050] A testing method based on the testing system provided in Embodiment 1 includes the following steps:

[0051] a) Connect the picosecond laser to the dual-channel optical power meter, power on the picosecond laser, and read the light intensity of the optical power meter; calculate the calibrated photon number of the Si APD detector according to the obtained output light intensity of the laser and the attenuation value of the adjustable attenuator.

[0052] b) Build a testing system. Refer to Figure 1 , install the APD detector on the detection tooling, and insert the USB-TTL serial cable into the main control board of the testing tooling.

[0053] c) Power on the detection tooling with a DC power supply (5V, 1.2A), open the APD debugging software on the testing computer, turn on the automatic query function, check items such as APD real-time temperature, APD target temperature, and detector count, set the APD threshold voltage to 2500 mV, the APD temperature control PI parameters P = 20, I = 100, and the APD temperature control target temperature = -35°C; after the APD real-time temperature is stable, adjust the APD bias voltage so that the detector count < 200 (observe for 30 s).

[0054] Of course, the specific values and types of the above parameter configurations can be adjusted or replaced in other embodiments or other testing processes, and are not limited to the above examples.

[0055] d) Turn on the time-to-digital converter (TDC), set the test time to 60 s, the light source frequency to 1 MHz, the photon number to the photon number calculated in step a, the dead time to 650 ns through the configuration parameter interface of the upper computer software (not shown in the figure), switch to the interface of Channel 1 (i.e., the channel connected to the APD detector), click RUN, so that an arbitrary signal generator sends a 1 MHz square wave signal to the TDC. After the working indicator light goes out, read the total count in Channel 1, then the dark count rate = total count / test time, and make a record.

[0056] Similarly, the specific values and types of the above parameter configurations can be adjusted or replaced in other embodiments or other testing processes, and are not limited to the above examples.

[0057] e) Open the configuration parameter column, input the dark count value obtained from the previous step of the test into Dark Count 1. Switch to Channel 1 column, open the OUT1 button of the trigger source, so that any signal generator sends a 1 MHz square wave signal to the picosecond laser. Click the Run button to start the test. After waiting for a certain period of time (one minute in this step), obtain detection data such as the total count rate and the optical count rate. Close the OUT1 button and save the original data table.

[0058] f) Substitute the data into the silicon detector calculation formula to calculate the detection efficiency:

[0059]

[0060] where μ is the average number of photons per pulse, R ph is the optical count rate, and f L is the frequency of the weak coherent pulsed light (i.e., the light source frequency).

[0061] g) Calculate the afterpulse probability:

[0062]

[0063] where R d is the dark count rate, P ap is the afterpulse probability, T d is the dead time, R is the total count rate, and R ph is the optical count rate.

[0064] h) When testing other APD target temperatures, set the corresponding APD target temperature through the APD debugging software, and repeat the above steps d, e, f, and g.

[0065] Similarly, the specific values and types of the above parameter configurations can be adjusted or replaced in other embodiments or other test processes, and are not limited to the above examples.

[0066] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program codes.

[0067] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices produce a means for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or a means for implementing the functions specified in one or more of the blocks.

[0068] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including an instruction means that implements the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or a means for implementing the functions specified in one or more of the blocks.

[0069] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operational steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or a means for implementing the functions specified in one or more of the blocks.

[0070] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art without creative efforts within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A detection system for an avalanche photodiode, characterized in that, It includes an arbitrary signal generator, a laser, an adjustable attenuator, a time-to-digital converter, and a test processor, where: The first output terminal of the arbitrary signal generator is connected to the laser, the laser is connected to the adjustable attenuator, and outputs optical pulses to the adjustable attenuator, and the adjustable attenuator inputs the attenuated optical signal to the input terminal of the avalanche photodiode under test; The second output terminal of the arbitrary signal generator is connected to the time-to-digital converter, and the time-to-digital converter receives the output signal of the avalanche photodiode under test; The test processor is connected to the avalanche photodiode under test and is used to debug and configure the parameters of the avalanche photodiode under test; The avalanche photodiode under test is placed on a detection tooling, and the detection tooling is encapsulated together with a semiconductor cooler.

2. The detection system of an avalanche photodiode according to claim 1, characterized in that, The laser is a picosecond laser.

3. The detection system of an avalanche photodiode according to claim 1, characterized in that, The test processor and the avalanche photodiode under test are connected by a serial cable.

4. The detection system of an avalanche photodiode according to claim 1, characterized in that, It further includes a dual-channel optical power meter for obtaining the output optical intensity of the laser and calculating the number of photons.

5. A testing method for the system according to any one of claims 1-4, characterized in that, It includes the following steps: Determine the output optical intensity of the laser and the attenuation value of the adjustable attenuator, and calculate the calibrated number of photons of the avalanche photodiode under test; Connect the test system, power on the avalanche photodiode under test, and configure the target temperature and bias voltage of the avalanche photodiode under test so that the count of the avalanche photodiode under test is less than the set value; Turn on the time-to-digital converter, configure the test time and light source frequency, configure the number of photons as the calibrated number of photons, read the count of the time-to-digital converter when the laser is not working, and calculate the dark count rate value; Configure the dark count rate parameter of the time-to-digital converter as the calculated dark count rate value, trigger the laser to emit light for testing, and record the detection data, including the total count rate and the optical count rate; And calculate the detection efficiency and the afterpulse probability according to the recorded data.

6. The test method according to claim 5, characterized in that, It further includes changing the target temperature of the avalanche photodiode under test and repeating the above test process.

7. The testing method according to claim 5, characterized in that, The dark count rate value is the count of the time-to-digital converter when the laser is not working / the test time.

8. The test method according to claim 5, characterized in that, The calculation process of the detection efficiency is: Among them, μ is the average number of photons per pulse, R ph is the optical counting rate, and f L is the light source frequency.

9. The test method according to claim 5, characterized in that, The afterpulse probability is: where R d - dark count rate, P ap - afterpulse probability, T d - dead time, R - total count rate, R ph - optical count rate.

10. The test method according to claim 5, characterized in that, The state where the count of the avalanche photodiode under test is less than the set value is maintained for a set duration.

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