A single photon avalanche diode unit device two-dimensional scanning test system

Abstract

The application relates to a single-photon avalanche diode unit device two-dimensional scanning test system, which comprises an electric displacement table, a signal generator, a time delay device, a laser source and a beam splitter, an excitation light path, a quenching circuit, an optical power meter and a frequency meter, and is controlled by an upper computer. During work, the displacement table drives the device to step by step move, and a signal chain is triggered after each position: the signal generator outputs a square wave and a synchronous enable signal, the time delay device receives the square wave and the synchronous enable signal to generate a second enable signal for triggering the laser and a delayed quenching signal. After being split, the laser is focused and irradiated on the device through the excitation light path, and the other laser is monitored by the optical power meter. The quenching circuit outputs the photoelectric response of the device to the frequency meter for counting under the enablement of the quenching signal. The response characteristic value of the point can be calculated through the measured optical power and the response event number of each position, and the upper computer fuses all position data to form a two-dimensional response matrix, so that the position and shape of the photosensitive area are non-destructively, quickly and intuitively represented.

Description

Technical Field

[0001] This invention relates to the field of photosensitive area testing, and in particular to a two-dimensional scanning testing system for single-photon avalanche diode unit devices. Background Technology

[0002] Single-photon avalanche diodes (SPADs) are core components of modern optoelectronic systems, widely used in optical communication, lidar, quantum information, biofluorescence detection, and low-light imaging. The performance of these devices directly determines the sensitivity, accuracy, and reliability of the entire system.

[0003] The performance of a device depends not only on its average responsivity or gain, but more importantly on the uniformity of its photosensitive region's response. Response uniformity refers to the consistency of the photoelectric response signal at different locations within the photosensitive region under the same illumination conditions. Non-uniform response can lead to fixed-pattern noise in the image, reducing image quality; it can also decrease the system's signal-to-noise ratio and increase the bit error rate.

[0004] Traditional methods for detecting photoresponse uniformity include single-point scanning or sparse point measurement, wide-field uniform illumination comparison, and indirect inference based on electrical properties.

[0005] Among them, the single-point scanning or sparse point measurement method selects a limited number of points in the photosensitive area using only a single focused spot for measurement, and evaluates the overall uniformity by the difference in response of each point. Since the number of samples is extremely small, it is very easy to miss local defects in the photosensitive area, and the uniformity information given is unreliable.

[0006] Wide-field uniform illumination uses a uniform surface light source to illuminate the entire photosensitive area, measures the total response of the device, and indirectly judges the uniformity by moving the light spot or comparing different devices. However, this method only obtains an overall average response value and cannot determine the specific location of non-uniformity, thus failing to provide targeted feedback for process improvement.

[0007] Indirect inference methods based on electrical properties infer the uniformity of materials and mass by measuring electrical parameters such as dark current and breakdown voltage of devices. However, there is no one-to-one correspondence between the electrical parameters and the uniformity of optical response. Therefore, this method cannot directly characterize the optical response.

[0008] In summary, existing detection methods suffer from common technical challenges such as incomplete detection and low spatial resolution. They cannot meet the high-precision response uniformity evaluation requirements of current high-performance photodetectors, especially single-photon avalanche diode unit devices geared towards large-scale arraying and miniaturization. Therefore, there is an urgent need to develop a non-destructive, rapid, and intuitive testing method to obtain the precise position and shape of the photosensitive area on the surface of a photodetector chip. Summary of the Invention

[0009] The purpose of this invention is to provide a two-dimensional scanning test system for single-photon avalanche diode unit devices to address the aforementioned shortcomings of the prior art.

[0010] The objective of this invention can be achieved through the following technical solutions: A two-dimensional scanning test system for single-photon avalanche diode unit devices includes: An electric displacement stage, under the control of a host computer, drives a single-photon avalanche diode unit device to move stepwise along a first direction and / or a second direction, and outputs a first command after each stepwise movement to the position. The first direction and the second direction are perpendicular to each other, and the plane formed by the first direction and the second direction is parallel to or coincides with the base plane of the single-photon avalanche diode unit device. After receiving the first instruction, the signal generator outputs a first square wave signal through its first output terminal and outputs a first enable signal synchronized with the first square wave signal through its second output terminal. The delay device, upon receiving the first square wave signal, outputs a second enable signal through its first output terminal and a quenching signal with the same frequency as the second enable signal but delayed through its second output terminal, wherein the first square wave signal and the second enable signal have the same frequency. A laser source and a beam splitter, wherein the laser emitted by the laser source after receiving a second enable signal is split by the beam splitter to obtain a first beam and a second beam; The excitation optical path is used to focus the first beam onto the single-photon avalanche diode unit device. The quenching circuit outputs the photoelectric response generated by the single-photon avalanche diode unit device when enabled by the quenching signal. An optical power meter and a frequency meter are used. The optical power meter receives a second light beam and measures the optical power. The frequency meter receives the photoelectric response output by the quenching circuit to obtain the number of response events. Based on the measured optical power and the number of response events, the response characteristic value corresponding to a single location of the single-photon avalanche diode unit device is obtained. The response characteristic values ​​of each location are fused by the host computer into a response matrix of the single-photon avalanche diode unit device. Based on the response matrix, the location and range of the photosensitive area are obtained.

[0011] The excitation optical path includes an attenuation unit and a focusing microscope. After the first beam is attenuated by the attenuation unit, it is focused by the focusing microscope and then irradiates the single-photon avalanche diode unit device.

[0012] The attenuation unit includes multiple attenuators with fixed attenuation coefficients and an adjustable attenuator.

[0013] The first enable signal is the pulse signal corresponding to the rising edge of the first square wave signal.

[0014] The time that the quenching signal lags behind the second enabling signal is determined based on the response time of the laser source and the propagation time of the optical path through the beam splitter and the excitation optical path to the single-photon avalanche diode unit device.

[0015] The time interval between two consecutive step movements of the electric displacement stage is greater than the duration of the second enable signal.

[0016] The time interval between two consecutive step movements of the electric displacement stage is at least twice the duration of the second enable signal.

[0017] The beam splitter is a semi-reflective half-lens or an asymmetric beam splitter.

[0018] The single step movement of the electric displacement stage is to drive the single-photon avalanche diode unit device to move along a first direction or a second direction.

[0019] The host computer is a computer.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. On the one hand, by designing the excitation optical path to reduce the size of the light spot, a smaller response characteristic value can be obtained in a single measurement. On the other hand, by using an electric displacement stage to realize the step displacement of the single-photon avalanche diode unit device in the two-dimensional direction, and by combining the interrelationship between the first command, the first square wave signal, the first enable signal, the second enable signal and the quenching signal, the displacement measurement of the single-photon avalanche diode unit device can be realized, while protecting the single-photon avalanche diode unit device from the problem of response instability caused by long-term operation of the single-photon avalanche diode unit device during continuous measurement, thus effectively protecting the single-photon avalanche diode unit device.

[0021] 2. By focusing the first beam through a focusing microscope, the size of the spot illuminating the device under test can be significantly reduced, thereby obtaining response characteristic values ​​with higher spatial resolution in two-dimensional scanning and more accurately locating the boundary and internal response differences of the photosensitive area; the attenuation unit can control the light intensity reaching the device, preventing excessive laser power from damaging the sensitive single-photon avalanche diode unit device, and also allowing the intensity of the excitation light to be flexibly adjusted according to the test requirements.

[0022] 3. It provides a more refined and wider range of light intensity adjustment capabilities. By combining multiple attenuators with fixed attenuation coefficients and an adjustable attenuator, it is possible to set a wide range of attenuation ratios by changing the attenuators, and to make continuous and fine adjustments by adjusting the adjustable attenuator. This allows the system to adapt to the testing requirements of devices with different sensitivity and to find the optimal test light intensity point.

[0023] 4. It provides a precise and simple synchronous triggering method, using the clear event of the rising edge of the square wave to generate an enable pulse, ensuring a strict and fixed timing relationship between the first enable signal output by the signal generator and the first square wave signal, simplifying the system synchronization logic and improving the reliability of timing control.

[0024] 5. It ensures precise timing matching of the laser excitation and quenching circuits. By incorporating the response time of the laser source and the propagation time of light in the beam splitter and excitation optical path into the lag time calculation, it can compensate for the inherent optical and electrical delays of the system. This allows the quenching signal to accurately enable the quenching circuit at the moment when the laser precisely irradiates the device and may generate a photoelectric response, thereby capturing an effective response event and improving measurement accuracy and signal quality.

[0025] 6. Ensure that measurement and motion do not interfere with each other. This design ensures that laser excitation and signal measurement will only begin during the second enable signal period after each step movement and stabilization of the displacement stage; and the displacement stage will only move again after the measurement is completely completed, avoiding errors introduced by the device measuring during movement, and preventing the displacement stage movement from interfering with precision optical alignment and signal acquisition.

[0026] 7. It provides a larger timing safety margin, and the longer interval time can further ensure that even if there are small timing fluctuations or system response delays, the measurement cycle and motion cycle will never overlap, which greatly enhances the stability and reliability of the system operation. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 The waveform diagrams are as follows: (a) is the waveform diagram of the first instruction, (b) is the waveform diagram of the quench signal, (c) is the waveform diagram of the first square wave signal, and (d) is the waveform diagram of the second enable signal. Among them: 1. Electric displacement stage, 2. Host computer, 3. Single-photon avalanche diode unit device, 4. Signal generator, 5. Delay unit, 6. Beam splitter, 7. Quenching circuit, 8. Optical power meter, 9. Frequency meter, 10. Attenuation unit, 11. Focusing microscope, 12. Laser controller, 13. Laser. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0029] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0030] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "proximal," "distal," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Physical quantities in formulas, unless otherwise specified, should be understood as basic quantities in the International System of Units (SI), or derived quantities derived from basic quantities through mathematical operations such as multiplication, division, differentiation, or integration.

[0031] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0032] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] A two-dimensional scanning test system for single-photon avalanche diode unit devices, such as Figure 1 As shown, it includes: The electric displacement stage 1, under the control of the host computer 2, drives the single-photon avalanche diode unit device 3 to move step by step along the first direction and / or the second direction, and outputs the first command after each step is in place. The first direction and the second direction are perpendicular to each other, and the plane formed by the first direction and the second direction is parallel to or coincides with the base plane of the single-photon avalanche diode unit device 3. After receiving the first instruction, the signal generator 4 outputs a first square wave signal through its first output terminal and outputs a first enable signal synchronized with the first square wave signal through its second output terminal. After receiving the first square wave signal, the delay unit 5 outputs a second enable signal through its first output terminal and a quenching signal with the same frequency as the second enable signal but delayed through its second output terminal. The first square wave signal and the second enable signal have the same frequency. The laser source and beam splitter 6: the laser emitted by the laser source after receiving the second enable signal is split by the beam splitter 6 to obtain the first beam and the second beam. The excitation optical path is used to focus the first beam onto the single-photon avalanche diode unit device 3; Quenching circuit 7 outputs the photoelectric response generated by single-photon avalanche diode unit device 3 to the outside when enabled by quenching signal; Optical power meter 8 and frequency meter 9 are used. Optical power meter 8 receives the second beam and measures the optical power. Frequency meter 9 receives the photoelectric response output by quenching circuit 7 and obtains the number of response events. Based on the measured optical power and the number of response events, the response characteristic value corresponding to a single position of single-photon avalanche diode unit device 3 is obtained. The response characteristic values ​​of each position are fused by host computer 2 into a response matrix of single-photon avalanche diode unit device 3. The position and range of photosensitive area are obtained based on the response matrix.

[0034] On the one hand, the size of the light spot is reduced by designing the excitation optical path, thereby obtaining a smaller response characteristic value in a single measurement. On the other hand, the single-photon avalanche diode unit device 3 is moved in two dimensions using an electric displacement stage 1, such as... Figure 2 As shown, by combining the interrelationships between the first instruction, the first square wave signal, the first enable signal, the second enable signal, and the quenching signal, displacement measurement of the single-photon avalanche diode unit device 3 can be achieved while protecting the single-photon avalanche diode unit device 3 from response instability caused by long-term operation during continuous measurement, thus effectively protecting the single-photon avalanche diode unit device 3.

[0035] The excitation optical path includes an attenuation unit 10 and a focusing microscope 11. The first beam, after being attenuated by the attenuation unit 10, is focused by the focusing microscope 11 and then illuminates the single-photon avalanche diode unit device 3. In this embodiment, the attenuation unit 10 includes multiple attenuators with fixed attenuation coefficients and an adjustable attenuator. This provides a finer and wider range of intensity adjustment capabilities. By combining multiple attenuators with fixed attenuation coefficients and an adjustable attenuator, a wide range of attenuation settings with known ratios can be achieved by replacing the attenuators, while continuous and minute fine adjustments can be made using the adjustable attenuator. This allows the system to adapt to the testing requirements of devices with different sensitivity levels and find the optimal test intensity point.

[0036] In this embodiment, the first enable signal is the pulse signal corresponding to the rising edge of the first square wave signal, which provides a precise and simple synchronous triggering method. By using the clear event of the rising edge of the square wave to generate the enable pulse, it ensures that there is a strict and fixed timing relationship between the first enable signal output by the signal generator and the first square wave signal, which simplifies the system synchronization logic and improves the reliability of timing control.

[0037] Generally, the time that the quenching signal lags behind the second enabling signal is determined based on the response time of the laser source and the propagation time of the optical path through the beam splitter 6 and the excitation optical path to the single-photon avalanche diode unit device 3, thereby enabling the quenching circuit to quench the device in a timely manner.

[0038] Generally, the time interval between two consecutive step movements of the electric displacement stage 1 is greater than the duration of the second enable signal to ensure that no interference occurs between the two measurements and to reduce the difficulty of control. It is not necessary to ensure a high degree of synchronization between the first enable signal and the quench signal; instead, it is only necessary to synchronize the first enable signal with the first square wave signal. Furthermore, in some embodiments, the time interval between two consecutive step movements of the electric displacement stage 1 is at least twice the duration of the second enable signal.

[0039] Generally, beam splitter 6 is a semi-reflective mirror or an asymmetric beam splitter. In this embodiment, a 99:1 asymmetric beam splitter is used, with the first beam being 1 and the second beam being 99.

[0040] In addition, the single-step movement of the electric displacement stage 1 drives the single-photon avalanche diode unit device 3 to move along the first direction or the second direction, ensuring that the entire plane of the single-photon avalanche diode unit device 3 can be measured.

[0041] In this embodiment, the host computer is a computer, and the laser source includes a laser controller 12 and a laser 13. The signal generator 4, delay unit 5, frequency counter 9, and laser controller 12 all operate in external trigger mode. In this embodiment, the digital delay unit operates in external trigger mode. The electric displacement stage 1 has a movement accuracy of more than 1 micrometer. The frequency counter 9 records data according to the movement position. The computer generates a two-dimensional distribution map based on the data recorded by the frequency counter 9.

[0042] Compared with existing optoelectronic device characterization techniques, the two-dimensional scanning of this invention is an automatic scanning process, which is simple to operate and fast to test. It realizes two-dimensional photocounting image testing of single-photon avalanche diode unit device 3. The high light response area of ​​the device can be intuitively judged based on the count value. The quenching circuit 7 forcibly terminates avalanche within nanoseconds, realizing non-destructive testing of the device.

[0043] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

Claims

1. A two-dimensional scanning test system for single-photon avalanche diode unit devices, characterized in that, include: The electric displacement stage (1) drives the single-photon avalanche diode unit device (3) to move stepwise along the first direction and / or the second direction under the control of the host computer (2), and outputs the first command after each step is in place, wherein the first direction and the second direction are perpendicular to each other, and the plane formed by the first direction and the second direction is parallel or coincident with the base plane of the single-photon avalanche diode unit device (3). After receiving the first instruction, the signal generator (4) outputs a first square wave signal through its first output terminal and outputs a first enable signal synchronized with the first square wave signal through its second output terminal. After receiving the first square wave signal, the delay unit (5) outputs a second enable signal through its first output terminal and outputs a quenching signal with the same frequency as the second enable signal but delayed through its second output terminal. The first square wave signal and the second enable signal have the same frequency. The laser source and beam splitter (6) are used to split the laser emitted by the laser source after receiving the second enable signal into a first beam and a second beam. The excitation optical path is used to focus the first beam onto the single-photon avalanche diode unit device (3); The quenching circuit (7) outputs the photoelectric response generated by the single-photon avalanche diode unit device (3) to the outside when enabled by the quenching signal; Optical power meter (8) and frequency meter (9). The optical power meter (8) receives the second beam and measures the optical power. The frequency meter (9) receives the photoelectric response output by the quenching circuit (7) to obtain the number of response events. Based on the measured optical power and the number of response events, the response characteristic value corresponding to a single position of the single-photon avalanche diode unit device (3) is obtained. The response characteristic values ​​of each position are fused by the host computer (2) into the response matrix of the single-photon avalanche diode unit device (3). Based on the response matrix, the position and range of the photosensitive area are obtained.

2. The two-dimensional scanning test system for a single-photon avalanche diode unit device according to claim 1, characterized in that, The excitation optical path includes an attenuation group (10) and a focusing microscope (11). After the first beam is attenuated by the attenuation group (10), it is focused by the focusing microscope (11) and irradiates the single-photon avalanche diode unit device (3).

3. The two-dimensional scanning test system for a single-photon avalanche diode unit device according to claim 2, characterized in that, The attenuation unit (10) includes multiple attenuation plates with fixed attenuation coefficients and an adjustable attenuator.

4. The two-dimensional scanning test system for a single-photon avalanche diode unit device according to claim 1, characterized in that, The first enable signal is the pulse signal corresponding to the rising edge of the first square wave signal.

5. The two-dimensional scanning test system for a single-photon avalanche diode unit device according to claim 1, characterized in that, The time that the quenching signal lags behind the second enabling signal is determined based on the response time of the laser source and the propagation time of the optical path via the beam splitter (6) and the excitation optical path to the single-photon avalanche diode unit device (3).

6. The two-dimensional scanning test system for a single-photon avalanche diode unit device according to claim 1, characterized in that, The time interval between two consecutive step movements of the electric displacement stage (1) is greater than the duration of the second enable signal.

7. The two-dimensional scanning test system for a single-photon avalanche diode unit device according to claim 6, characterized in that, The time interval between two consecutive step movements of the electric displacement stage (1) is at least twice the duration of the second enable signal.

8. The two-dimensional scanning test system for a single-photon avalanche diode unit device according to claim 1, characterized in that, The beam splitter (6) is a semi-reflective half-lens or an asymmetric beam splitter.

9. The two-dimensional scanning test system for a single-photon avalanche diode unit device according to claim 1, characterized in that, The single step movement of the electric displacement stage (1) is to drive the single-photon avalanche diode unit device (3) to move along the first direction or the second direction.

10. A two-dimensional scanning test system for a single-photon avalanche diode unit device according to claim 1, characterized in that, The host computer is a computer.

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