Single-photon detector

Abstract

The present application relates to a single-photon detector. The single-photon detector includes: a driving unit, the driving unit includes a single-photon avalanche diode, and the single-photon avalanche diode is configured to generate an avalanche signal according to a single-photon signal when the bias voltage is greater than the avalanche breakdown voltage; a sampling unit, the sampling unit is connected to the driving unit and is used to perform random sampling and periodic sampling on the avalanche signal respectively according to a sampling clock signal to obtain a sampling signal; a processing unit, the processing unit is connected to the sampling unit; the processing unit is used to provide the sampling clock signal; the processing unit is further used to process the sampling signal and output a single-photon detection signal. The single-photon detector of the present application can be applicable to a variety of application scenarios.

Description

Technical Field

[0001] The present application relates to the technical field of optical signal detection, and particularly to a single-photon detector. Background Art

[0002] The single-photon detector uses a very low-noise avalanche photodiode to realize the conversion of single-photon optical pulse signals into electrical pulse signals. According to different application scenarios, the single-photon detector has two operating modes. One is the gated Geiger mode, and the other is the free-running mode. In the gated Geiger mode, a fixed-period gating signal is applied to the single-photon avalanche diode. Since the detector can only detect single-photon signals within the gating time range, the gated mode is mainly used in application scenarios where the arrival time of photons needs to be determined, such as quantum communication, etc. The free-running detector is always in the single-photon signal detection mode and can be applied to scenarios where the arrival time of photons is uncertain, such as single-photon laser ranging, quantum radar, etc.

[0003] For free-running single-photon detectors, currently, the method of comparator discrimination is mainly used to extract avalanche signals. To effectively discriminate avalanche current signals, a relatively high reverse bias voltage generally needs to be applied to the single-photon avalanche diode. Since the bias voltage applied to the single-photon avalanche diode is always higher than the avalanche voltage, this results in a large recovery time, a large afterpulse probability, and a low saturation count rate for free-running single-photon detectors, greatly limiting the scope of use of free-running detectors.

[0004] In the implementation process, the inventors found that at least the following problems exist in the traditional technology:

[0005] The current single-photon detection methods or traditional methods have problems such as large limitations in application scenarios. Summary of the Invention

[0006] Based on this, in view of the above technical problems, it is necessary to provide a single-photon detector that can be applied to a variety of application scenarios.

[0007] To achieve the above object, an embodiment of the present application provides a single-photon detector, including:

[0008] A driving unit, the driving unit includes a single-photon avalanche diode, and the single-photon avalanche diode is configured to generate an avalanche signal according to a single-photon signal when the bias voltage is greater than the avalanche breakdown voltage;

[0009] A sampling unit, the sampling unit is connected to the driving unit and is used to respectively perform random sampling and periodic sampling on the avalanche signal according to a sampling clock signal to obtain a sampling signal;

[0010] A processing unit, the processing unit is connected to a sampling unit; the processing unit is used to provide a sampling clock signal; the processing unit is also used to process the sampling signal and output a single-photon detection signal.

[0011] In one embodiment, it further includes:

[0012] A power distribution unit, the input end of the power distribution unit is connected to the driving unit, and is used to divide the avalanche signal into two paths, and respectively output a first signal to be processed and a second signal to be processed;

[0013] The processing unit is also used to respectively output a random sampling clock signal and a periodic sampling clock signal;

[0014] The sampling unit is connected to the output end of the power distribution unit; the sampling unit is used to randomly sample the first signal to be processed according to the random sampling clock signal; the sampling unit is also used to periodically sample the second signal to be processed according to the periodic sampling clock signal.

[0015] In one embodiment, it further includes:

[0016] A filtering unit, the input end of the filtering unit is connected to the driving unit, and is used to perform high-pass filtering on the avalanche signal; the output end of the filtering unit is connected to the input end of the power distribution unit.

[0017] In one embodiment, the anode of the single-photon avalanche diode is used to output the avalanche signal;

[0018] The driving unit further includes:

[0019] A protection resistor, one end of the protection resistor is used to access the bias voltage; the other end of the protection resistor is connected to the cathode of the single-photon avalanche diode;

[0020] A sampling resistor, one end of the sampling resistor is connected to the anode of the single-photon avalanche diode; the other end of the sampling resistor is used to ground.

[0021] In one embodiment, the processing unit is also used to output a control signal; the control signal is used to adjust the amplitude of the bias voltage.

[0022] In one embodiment, it further includes:

[0023] A power management unit, the input end of the power management unit is connected to the processing unit, and the output end of the power management unit is connected to one end of the protection resistor; the power management unit is used to output the bias voltage according to the control signal.

[0024] In one embodiment, the sampling unit includes:

[0025] An analog-to-digital converter, which is used to convert the sampling signal from an analog signal to a multi-bit digital signal and output it.

[0026] In one embodiment, the processing unit includes:

[0027] An FPGA, which is configured to process a multi-bit digital signal according to a plurality of preset thresholds and output a single-photon detection signal for characterizing the number of photons.

[0028] In one embodiment, the power distribution unit includes a power splitter.

[0029] In one embodiment, the material of the single-photon avalanche diode includes InGaAs and / or InP.

[0030] One of the above technical solutions has the following advantages and beneficial effects:

[0031] In the single-photon detector of the present application, the single-photon avalanche diode of the driving unit generates an avalanche signal according to a single-photon signal when the bias voltage is greater than the avalanche breakdown voltage; the sampling unit respectively performs random sampling and periodic sampling on the avalanche signal according to the sampling clock signal to obtain a sampling signal; the processing unit provides the sampling clock signal and processes the sampling signal to output a single-photon detection signal. By combining periodic sampling with random sampling, the single-photon detector of the present application can be applied to scenarios where the arrival time of photons is uncertain, such as quantum random number, quantum radar, single-photon laser ranging and other scenarios, to realize the measurement of the arrival time of photons. At the same time, the detection efficiency of the single-photon detector will not be reduced under low sampling conditions. The combination of periodic sampling and random sampling can also reduce the amplitude of the bias voltage to extract the avalanche signal from the avalanche signal with a small amplitude, which is beneficial to further reduce the dead time and after-pulse probability of the detector. The single-photon detector of the present application improves the performance indicators of the existing free-running single-photon detector and expands the application range of the single-photon detector. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 It is a structural block diagram of a single-photon detector in one embodiment;

[0034] Figure 2 It is a structural block diagram of a single-photon detector in another embodiment;

[0035] Figure 3 It is an application effect diagram of a single-photon detector in one embodiment;

[0036] Figure 4 Schematic diagram of the effect of combining periodic sampling and random sampling in one embodiment;

[0037] Figure 5 Block diagram of the structure of a single-photon detector in another embodiment;

[0038] Figure 6 Circuit principle block diagram of a single-photon detector in one embodiment;

[0039] Figure 7 Circuit principle block diagram of a single-photon detector in another embodiment. Specific implementation manners

[0040] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0042] It can be understood that the terms "first", "second", etc. used in this application can be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another.

[0043] Spatial relationship terms such as "under", "below", "lower", "beneath", "above", "upper", etc. can be used herein to describe the relationship between an element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relationship terms also include different orientations of the device during use and operation. For example, if the device in the drawing is flipped, the element or feature described as "under other elements" or "beneath it" or "under it" will be oriented "above" other elements or features. Therefore, the exemplary terms "under" and "below" can include both the upper and lower orientations. In addition, the device can also include other orientations (for example, rotated 90 degrees or other orientations), and the spatial description terms used herein are accordingly interpreted.

[0044] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediate element. In addition, in the following embodiments, "connection", if there is a transfer of electrical signals or data between the connected objects, should be understood as "electrical connection", "communication connection", etc.

[0045] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprises / include" or "has" etc. specify the presence of the stated features, wholes, steps, operations, components, parts or combinations thereof, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the related listed items.

[0046] In order to make the objectives, technical solutions and advantages of this application more clearly understood, the following further elaborates on this application in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0047] In one embodiment, as Figure 1 shown, a single-photon detector is provided, including:

[0048] A driving unit 110, the driving unit 110 includes a single-photon avalanche diode 112, and the single-photon avalanche diode 112 is configured to generate an avalanche signal according to a single-photon signal when the bias voltage is greater than the avalanche breakdown voltage;

[0049] A sampling unit 120, the sampling unit 120 is connected to the driving unit 110 and is used to respectively perform random sampling and periodic sampling on the avalanche signal according to a sampling clock signal to obtain a sampling signal;

[0050] A processing unit 130, the processing unit 130 is connected to the sampling unit 120; the processing unit 130 is used to provide a sampling clock signal; the processing unit 130 is also used to process the sampling signal and output a single-photon detection signal.

[0051] Specifically, when the bias voltage is slightly greater than the avalanche breakdown voltage of the single-photon avalanche diode 112, under the action of the reverse bias voltage, the single-photon avalanche diode 112 can convert a single-photon signal into a single-photon avalanche signal, that is, the single-photon avalanche diode 112 is used for photoelectric conversion to convert the single-photon signal from an optical signal into an electrical signal and output an avalanche signal. Further, according to the sampling clock signal provided by the processing unit 130, the sampling unit 120 can perform analog sampling on the avalanche signal respectively, including random sampling and periodic sampling, extract the sampling signal and output it. The processing unit 130 processes the sampling signal and outputs a single-photon detection signal. The single-photon detection signal may include the arrival time of a single photon and the number of photons.

[0052] In some examples, an external input optical signal (including a single-photon signal) is coupled to the single-photon avalanche diode 112 through an optical fiber and converted into an avalanche current signal under the action of a reverse bias voltage. The driving unit 110 can further convert the avalanche current signal into an avalanche voltage signal for output, which is used for sampling by subsequent circuits.

[0053] It should be noted that for a free-running single-photon detector, the arrival time of a single-photon signal is uncertain. If only periodic sampling is performed, some photons may not be detected, resulting in a reduction in the detection efficiency of the detector. In the single-photon detector of the present application, through the single-photon avalanche diode of the driving unit, when the bias voltage is greater than the avalanche breakdown voltage, an avalanche signal is generated according to the single-photon signal; the sampling unit performs random sampling and periodic sampling on the avalanche signal respectively according to the sampling clock signal to obtain a sampling signal; the processing unit provides the sampling clock signal and processes the sampling signal to output a single-photon detection signal. By combining periodic sampling with random sampling, the single-photon detector of the present application can be applied to scenarios where the arrival time of photons is uncertain, such as quantum random numbers, quantum radar, single-photon laser ranging, etc., to measure the arrival time of photons. At the same time, the detection efficiency of the single-photon detector will not be reduced under low sampling conditions, which is beneficial to further reducing the dead time (recovery time) and noise count of the detector. The single-photon detector of the present application improves the performance indicators of the existing free-running single-photon detector and expands the application range of the single-photon detector.

[0054] In one embodiment, as Figure 2 shown, it further includes:

[0055] A power distribution unit 210, the input end of the power distribution unit 210 is connected to the driving unit 110, and is used to divide the avalanche signal into two paths and output a first signal to be processed and a second signal to be processed respectively;

[0056] The processing unit 130 is further used to output a random sampling clock signal and a periodic sampling clock signal respectively;

[0057] The sampling unit 120 is connected to the output end of the power distribution unit 210; the sampling unit 120 is configured to randomly sample the first signal to be processed according to a random sampling clock signal; the sampling unit 120 is further configured to periodically sample the second signal to be processed according to a periodic sampling clock signal.

[0058] Specifically, the power distribution unit 210 can divide the avalanche signal into two parts, where the first signal to be processed is used for random sampling and the second signal to be processed is used for periodic sampling. The sampling unit 120 randomly samples the first signal to be processed according to the random sampling clock signal output by the processing unit 130; the sampling unit 120 periodically samples the second signal to be processed according to the periodic sampling clock signal output by the processing unit 130.

[0059] It should be noted that, as Figure 3 shown, A is the curve of the amplitude of a traditional free-running single-photon detector changing with time, and B is the curve of the amplitude of the single-photon detector of the present application changing with time; for a traditional free-running single-photon detector, since the bias voltage applied to the single-photon avalanche diode is much higher than the avalanche voltage, this results in a relatively large dead time (recovery time), a relatively high afterpulse probability (about 10%), and a relatively low saturation count rate (about MHz) for the traditional free-running single-photon detector, greatly limiting the scope of use of the free-running detector; while the single-photon detector of the present application adopted in curve B can sample a relatively low avalanche current by simultaneously using a random sampling clock signal and a periodic sampling clock signal. Compared with the traditional free-running single-photon detector adopted in curve A, it does not require high-amplitude avalanche current information, and thus does not need to adopt a high-amplitude bias voltage, reducing the dead time, lowering the afterpulse probability, and increasing the saturation count rate.

[0060] Furthermore, as Figure 4 shown, S1 is the periodic sampling clock signal and S2 is the random sampling clock signal. When there is only the periodic sampling clock signal, problems such as signal loss and low-efficiency acquisition may occur during the acquisition process of the sampling unit 120; by adding the random sampling clock signal, during the acquisition process of the sampling unit 120 according to the periodic sampling clock signal, if signal loss or low-efficiency acquisition occurs, normal signal acquisition can be achieved by the random sampling clock signal; at the same time, during the process of the sampling unit 120 according to the random sampling clock signal, if signal loss occurs, normal signal acquisition can be achieved by the periodic sampling clock signal.

[0061] The embodiment of the present application can provide a random sampling clock signal and a periodic sampling clock signal through the processing unit 130, enabling random sampling and periodic sampling of relatively low-amplitude avalanche signals simultaneously, while reducing the dead time, lowering the afterpulse probability, and increasing the saturation count rate.

[0062] In one embodiment, as Figure 5 shown, it further includes:

[0063] A filtering unit 310, the input end of the filtering unit 310 is connected to the driving unit 110, and is used for performing high-pass filtering on the avalanche signal; the output end of the filtering unit 310 is connected to the input end of the power distribution unit 210.

[0064] Specifically, the filtering unit 310 performs preliminary filtering on the avalanche signal output by the driving unit 110. A high-pass filtering method can be adopted to filter out low-frequency noise and reduce the influence of noise.

[0065] In one embodiment, the anode of the single-photon avalanche diode 112 is used to output the avalanche signal;

[0066] As Figure 6 shown, the driving unit 110 further includes:

[0067] A protection resistor 114, one end of the protection resistor 114 is used to access the bias voltage; the other end of the protection resistor 114 is connected to the cathode of the single-photon avalanche diode 112;

[0068] A sampling resistor 116, one end of the sampling resistor 116 is connected to the anode of the single-photon avalanche diode 112; the other end of the sampling resistor 116 is used to ground.

[0069] Specifically, under the action of the reverse bias voltage, the single-photon signal is converted into an avalanche current signal through the single-photon avalanche diode 112. Among them, the protection resistor 114 is a resistor with a relatively large resistance value, which is used to protect the single-photon avalanche diode 112 from being broken down; the sampling resistor 116 is a resistor with a relatively small resistance value, which is used to convert the avalanche photocurrent signal into a voltage signal and output it to an external sampling circuit. In some examples, the resistance value of the sampling resistor 116 includes 50Ω.

[0070] In one embodiment, the processing unit 130 is further used to output a control signal; the control signal is used to adjust the amplitude of the bias voltage.

[0071] Specifically, by outputting a control signal for adjusting the amplitude of the bias voltage, the processing unit 130 can realize the control of the avalanche signal generated by the single-photon avalanche diode 112.

[0072] In one embodiment, as Figure 7 shown, it further includes:

[0073] A power management unit 510, the input end of the power management unit 510 is connected to the processing unit 130, the output end of the power management unit 510 is connected to one end of the protection resistor 114; the power management unit 510 is used to output a bias voltage according to the control signal.

[0074] Specifically, the power management unit 510 is used to generate a low-noise and high-stability bias voltage required by the driving unit 110, and adjust the amplitude of the bias voltage according to the control signal of the processing unit 130, so as to control the generation of avalanche signals by the single-photon avalanche diode 112.

[0075] In one embodiment, the sampling unit 120 includes:

[0076] An analog-to-digital converter, which is used to convert the sampling signal from an analog signal into a multi-bit digital signal and output it.

[0077] Specifically, the analog-to-digital converter (ADC) is used to convert the sampling signal from an analog signal into a high-precision multi-bit digital signal, which is convenient for the subsequent processing unit 130 to process the multi-bit digital signal to realize the discrimination measurement of the number of photons. In some examples, the multi-bit digital signal is generally greater than 10 bits.

[0078] In one embodiment, the processing unit 130 includes:

[0079] An FPGA, which is used to process the multi-bit digital signal according to multiple preset thresholds and output a single-photon detection signal for characterizing the number of photons.

[0080] Specifically, the FPGA (Field Programmable Gate Array) is connected to the analog-to-digital converter to process the multi-bit digital signal. For example, when the output value of the analog-to-digital converter reaches a threshold each time, it is considered that the number of detected photons increases by one.

[0081] In some examples, for an n-bit analog-to-digital converter, the FPGA can set m judgment thresholds. When the output value N (N = 0, 1,..., 2 n -1) of the analog-to-digital converter is between N i and N i+1 (i = 0, 1, 2,..., m + 1; where, N0 = 1, N m = 2 n ), it is determined that the input optical pulse signal contains i photons. For example, for a threshold detector (which can only judge whether there are photons but cannot judge the number of photons), taking m = 1, the judgment interval is: if N0 = 0 ≤ N < N1, it is considered that there are no photons, and if N1 ≤ N ≤ N2 = 2 n -1, it is considered that there are photons.

[0082] In one embodiment, the power distribution unit 210 includes a power splitter.

[0083] Specifically, a power divider is a device that divides the energy of an input signal into two or more output signals with equal or unequal energy. The power divider can divide the avalanche signal after high-pass filtering into two parts. One part of the signal is used for periodic sampling, and the other part of the signal is used for random sampling, that is, the first signal to be processed is used for random sampling, and the second signal to be processed is used for periodic sampling.

[0084] In one embodiment, the material of the single-photon avalanche diode 112 includes InGaAs and / or InP.

[0085] Specifically, the single-photon avalanche diode 112 can be an avalanche diode made of materials such as InGaAs / InP.

[0086] In a specific embodiment, an external input optical signal is coupled to the single-photon avalanche diode 112 through an optical fiber. Under the action of a reverse bias voltage, it is converted into an avalanche current signal. The sampling resistor converts the avalanche photocurrent signal into a voltage signal and outputs it to an external sampling circuit. The avalanche voltage signal is subjected to high-pass filtering by the filtering unit 310 to filter out low-frequency noise and then enters the power divider. The output signal of the power divider is divided into two parts. One part of the signal is used for periodic sampling of the ADC, and the other part of the signal is used for random sampling of the ADC. The ADC outputs a sampling signal. The FPGA analyzes and processes the sampling signal output by the ADC, analyzes the detected single-photon detection signal, and outputs it.

[0087] In the description of this specification, the description with reference to terms such as "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials or features described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0088] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0089] The above-described embodiments only represent several implementation manners of the present 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 art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A single-photon detector, characterized in that, Comprising: A driving unit, the driving unit includes a single-photon avalanche diode, and the single-photon avalanche diode is configured to generate an avalanche signal according to a single-photon signal when the bias voltage is greater than the avalanche breakdown voltage; A sampling unit, the sampling unit is connected to the driving unit and is used to respectively perform random sampling and periodic sampling on the avalanche signal according to a sampling clock signal to obtain a sampling signal; A processing unit, the processing unit is connected to the sampling unit; the processing unit is used to provide the sampling clock signal; the processing unit is also used to process the sampling signal and output a single-photon detection signal.

2. The single-photon detector according to claim 1, wherein, Further comprising: A power distribution unit, the input end of the power distribution unit is connected to the driving unit and is used to divide the avalanche signal into two paths and respectively output a first signal to be processed and a second signal to be processed; The processing unit is also used to respectively output a random sampling clock signal and a periodic sampling clock signal; The sampling unit is connected to the output end of the power distribution unit; the sampling unit is used to perform random sampling on the first signal to be processed according to the random sampling clock signal; the sampling unit is also used to perform periodic sampling on the second signal to be processed according to the periodic sampling clock signal.

3. The single-photon detector according to claim 2, wherein Further comprising: A filtering unit, the input end of the filtering unit is connected to the driving unit and is used to perform high-pass filtering on the avalanche signal; The output end of the filtering unit is connected to the input end of the power distribution unit.

4. The single-photon detector according to any one of claims 1 to 3, characterized in that, The processing unit is also used to output a control signal; the control signal is used to adjust the amplitude of the bias voltage.

5. The single-photon detector according to claim 1, characterized in that, The anode of the single-photon avalanche diode is used to output the avalanche signal; The driving unit further includes: A protection resistor, one end of the protection resistor is used to access the bias voltage; the other end of the protection resistor is connected to the cathode of the single-photon avalanche diode; A sampling resistor, one end of the sampling resistor is connected to the anode of the single-photon avalanche diode; the other end of the sampling resistor is used to ground.

6. The single-photon detector according to claim 5, wherein The processing unit is also used to output a control signal; the control signal is used to adjust the amplitude of the bias voltage.

7. The single-photon detector according to claim 6, characterized in that, Further comprising: A power management unit, the input end of the power management unit is connected to the processing unit, and the output end of the power management unit is connected to one end of the protection resistor; The power management unit is used to output the bias voltage according to the control signal.

8. The single-photon detector according to claim 1, characterized in that, The sampling unit includes: An analog-to-digital converter, which is used to convert the sampling signal from an analog signal into a multi-bit digital signal and output it.

9. The single-photon detector according to claim 8, wherein, The processing unit includes: An FPGA, which is used to process the multi-bit digital signal according to a plurality of preset thresholds and output the single-photon detection signal for characterizing the number of photons.

10. The single-photon detector according to claim 2 or 3, characterized in that, The power distribution unit includes a power splitter.

11. The single-photon detector according to claim 5, characterized in that, The material of the single-photon avalanche diode includes InGaAs and / or InP.

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