Single-photon anti-bunching measurement system and method based on ADC acquisition card

Abstract

The invention provides a single-photon anti-bunching measurement method and system based on an ADC acquisition card. The single-photon anti-bunching measurement method and system are mainly used for acquiring and analyzing a second-order correlation function of a single-photon optical signal. Compared with a traditional single photon detection method, the high-speed ADC acquisition card in an intermediate trigger mode is adopted, redundant data are reduced, and meanwhile the data acquisition efficiency is improved. The system comprises a data acquisition unit, a data reading module, a data processing center and an algorithm execution module, and the data acquisition unit acquires a single photon signal through a confocal microscope system and converts an optical signal into an electric signal by using an SPAD detector. The ADC acquisition card adopts an intermediate trigger mode, so that sampling can be accurately triggered in a set effective sampling interval, and a large amount of redundant data existing in a traditional sampling mode is avoided; and the completeness of the time sequence is better ensured while the data is accurately acquired.

Description

Technical Field

[0001] The present invention relates to the technical field of ADC acquisition cards, and in particular to a single-photon antibunching measurement system and method based on an ADC acquisition card. Background Art

[0002] Currently, most commercial single-photon detection systems are scientific research-grade equipment. The commonly used single-photon detection method is to use a single-photon detector (Single-Photon Avalanche Diode, SPAD) to measure the second-order correlation function of the light field. The core idea is to measure the temporal correlation effect of the single-photon field measured by two detectors, thereby obtaining the statistical properties of single photons. The conventional path is to realize single-photon light source signal acquisition through an external confocal microscope system, and convert single photons into electron pulses through SPAD. Subsequently, the time difference is collected by a time-correlated single photon counting (TCSPC) device for statistical analysis to form an anti-bunching correlation statistical curve.

[0003] These control methods, systems, and devices have the following disadvantages:

[0004] 1) The time precision of TCSPC can reach the picosecond level, which is redundant for calculating the parameters of the second-order correlation function in non-scientific research situations;

[0005] 2) TCSPC usually directly outputs results, and the process processing lacks visibility and intuitiveness, which does not meet the needs in special environments such as education.

[0006] In response to the above problems, we propose a single-photon antibunching measurement system and method based on ADC acquisition card. Summary of the Invention

[0007] The object of the present invention is to provide a single-photon antibunching measurement system and method based on an ADC acquisition card to solve the problems raised in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] Single-photon antibunching measurement system based on ADC acquisition card, including:

[0010] A data acquisition unit, which collects single-photon light signals through a confocal microscope system;

[0011] In the data reading module, the SPAD converts the optical signal into an electrical signal, and the ADC uses the intermediate trigger mode;

[0012] The data processing center pre-processes the data through algorithms based on the nature of the intermediate trigger pattern;

[0013] An algorithm execution module determines the rising edge trigger point through a set threshold, obtains data by taking the difference of the relative timestamps of photons within two-channel trigger events, calculates the second-order correlation function from the statistical time difference, and normalizes it.

[0014] Preferably, the data acquisition unit includes:

[0015] A single photon detection module. The 520nm laser introduced by the optical fiber excitation group m is reflected by the mirror group l, and then the reflected light is introduced into the dichroic mirror group c, and the reflected light is introduced into the galvanometer group d, while the transmitted light is introduced into the beam scatterer.

[0016] The galvanometer group d adjusts the incident angle of the excitation light on the field lens group e by changing the angle. The field lens group e and the tube lens group g expand the excitation light and introduce it into the rear pupil of the objective lens through the mirror h. A change in the incident angle of the field lens group e will cause a change in the incident angle of the rear pupil of the objective lens. The parallel light with an inclined angle causes the position of the focused spot on the focal plane of the objective lens to shift, thereby realizing the horizontal scanning function of the focal plane of the objective lens.

[0017] The excited fluorescence and the reflected laser are collected by the objective lens together, and after being reflected by the mirror h, they are introduced into the tube lens group g.

[0018] The tube lens group g and the field lens group e reduce the collected light and then reflect it through the galvanometer d and introduce it into the dichroic mirror group c for primary filtering. The transmitted collected light is further filtered by the condenser group and focused on the optical fiber of the optical fiber acquisition group.

[0019] The optical fiber core diameter filters out stray light and introduces the fluorescence signal into the SPAD to be converted into an electrical signal and collected by the core board.

[0020] The control circuit of the core board generates a control signal to control the change of the galvanometer angle to achieve point scanning on the object surface and reconstruct the image; adjusts the scanning parameters and scans multiple times to gradually approach the optimal acquisition point.

[0021] The data at the best point is connected to an external ADC acquisition card using a coaxial cable. After collecting data for a period of time, the data is uploaded to the PC side.

[0022] The PC-side analysis software splits the input data into multiple groups according to the data format. Each group of data is the data of two channels with M points before and after the middle pulse of channel 1. The two channels are synchronized in time. The software sets a threshold to determine the timestamps corresponding to the photon pulses in each group of data, takes the difference between the two-channel timestamps, and the data satisfying -M < t < M is statistically counted.

[0023] Calculate the sum of the actual acquisition times of each group of data, draw the second-order correlation function image and normalize it to verify the single photon statistical properties.

[0024] A high-speed ADC module is used to convert analog signals into digital signals.

[0025] The data transmission module uses a PXIe 1GHz high-speed ADC acquisition card for data acquisition and transmits PXIe chassis data to a laptop computer via the Thunderbolt protocol.

[0026] Preferably, the intermediate trigger sampling is that the trigger point is located in the middle of the set effective sampling interval, that is, after the trigger signal arrives at the middle point, the data within a period of time before and after the trigger point is collected, rather than collecting data from the trigger point backward. This method comprehensively counts the before and after correlations of the trigger events to ensure the data integrity within the sampling window.

[0027] The measurement method of the single-photon antibunching measurement system based on the ADC acquisition card includes the following steps:

[0028] Step 1: Set the intermediate pulse trigger through ADC. When the pulse of channel 1 is triggered, collect M sampling points of data of channel 1 and channel 2, record them as one valid event, and continuously sample for 30 seconds as a set of data.

[0029] Step 2: Read the data. Based on the characteristics of intermediate trigger sampling, the data can be processed in groups, and the rising edge trigger point can be determined by the set threshold. The data is obtained by subtracting the relative timestamps of the photons in the trigger events of the two channels. The time difference is statistically calculated to calculate the second-order correlation function and normalize it.

[0030] Preferably, the single-photon second-order correlation function g is calculated based on the ADC sampling data (2) The steps of (τ) are as follows:

[0031] Step 21, data processing: extract the relative timestamp of each trigger event, calculate the time difference and make interval statistics;

[0032] Threshold detection: Set a threshold to determine the photon timestamp, and record the first time point when the signal exceeds the threshold as the timestamp;

[0033] Timestamp generation: Record the relative timestamp of each photon in each trigger event relative to the start time of the event. The ADC sampling interval is accurate to 1ns.

[0034] Time difference calculation: Based on the relative timestamps of each photon of each triggering event, traverse and calculate the time difference: τ = t 1i -t 2j ; where t 1i， t 2j The timestamps of each photon in channels 1 and 2 respectively;

[0035] Filtering and time difference statistics: Create statistics array G (2)(τ), set the threshold M to calculate whether the absolute value of τ exceeds M, and add 1 to the qualified group members if it does not exceed M:

[0036] G (2) (τ) = G (2) (τ)+1;

[0037] Step 22: Normalize to get g (2) (τ);

[0038] Total measurement time T and average counting rate R:

[0039]

[0040] Among them, N1 and N2 are the total number of photons detected by the two paths, and the detection time 0~T is discretized as: n t =1,2,...,N (N=T / Δt), Δt=1ns;

[0041] Since the sampling mode of the sample is intermediate trigger sampling:

[0042] T=Δt×M×Nc

[0043] M is the sampling width set by the acquisition card, and Nc is the number of trigger events present in the data;

[0044]

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The present invention currently rarely uses an ADC acquisition card to collect single-photon data, which is different from the conventional method; the 1GHz ADC sampling card sampling rate meets the requirement of g(0)<0.5 without excessive redundancy; the ADC sampling card supports the intermediate trigger mode, and can directly set the sampling interval of g2, reducing a large amount of redundant data, and is suitable for weak signal acquisition.

[0047] The single-photon data acquisition system with intermediate trigger sampling of the present invention needs to be combined with a high-speed ADC and is suitable for single-photon detection direction-dependent HBT experiments.

[0048] The ADC acquisition card uses an intermediate trigger mode, which accurately triggers sampling within the set effective sampling interval, avoiding the large amount of redundant data found in traditional sampling modes. Furthermore, compared to "window mode" data acquisition, intermediate trigger mode better ensures the integrity of the time series. Through algorithmic processing and time difference statistics, the system can more accurately calculate and normalize the second-order correlation function of photon events, verifying the statistical properties of single photons.

[0049] The core of the proposed single-photon antibunching measurement method and system lies in a high-speed ADC acquisition card and an innovative intermediate trigger mode for recording timestamps. This system aims to overcome the limitations of traditional methods and achieve complete, efficient, and accurate single-photon detection and verification. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic diagram of the intermediate trigger of the present invention;

[0051] Figure 2 The data waveform diagram collected by the present invention;

[0052] Figure 3 It is the flow chart of the algorithm of the present invention;

[0053] Figure 4 This is a diagram of the calculation results of the present invention;

[0054] Figure 5 This is a system diagram of the acquisition equipment of the present invention;

[0055] Figure 6 This is a physical diagram of the present invention. DETAILED DESCRIPTION

[0056] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0057] Example 1:

[0058] like Figure 1-6 As shown in FIG, the single-photon antibunching measurement system based on the ADC acquisition card includes:

[0059] Single-photon antibunching measurement system based on ADC acquisition card, including:

[0060] A data acquisition unit, which collects single-photon light signals through a confocal microscope system;

[0061] In the data reading module, the SPAD converts the optical signal into an electrical signal, and the ADC uses the intermediate trigger mode;

[0062] The data processing center pre-processes the data through algorithms based on the characteristics of intermediate trigger sampling;

[0063] The algorithm execution module determines the rising edge trigger point through the set threshold, obtains data by subtracting the relative timestamps of photons in the trigger events of the two channels, calculates the second-order correlation function based on the statistical time difference, and normalizes it.

[0064] The data acquisition unit includes:

[0065] A single-photon detection module. The 520nm laser introduced by the optical fiber excitation group m is reflected by the mirror group l and then introduced into the dichroic mirror group c. The reflected light is introduced into the galvanometer group d, and the transmitted light is introduced into the beam scatterer.

[0066] The galvanometer group d adjusts the incident angle of the excitation light on the field lens group e by changing the angle. The field lens group e and the tube lens group g expand the excitation light and introduce it into the rear pupil of the objective lens through the mirror h. The change in the incident angle of the field lens group e will cause a change in the incident angle of the rear pupil of the objective lens. The parallel light with an inclination angle causes the position of the focused spot on the focal plane of the objective lens to shift, thus realizing the horizontal scanning function of the focal plane of the objective lens.

[0067] The excited fluorescence and the reflected laser are collected by the objective lens together and introduced into the tube lens group g after being reflected by the mirror h.

[0068] The tube lens group g and the field lens group e reduce the collected light and then reflect it through the galvanometer d and introduce it into the dichroic mirror group c for primary filtering. The transmitted collected light is further filtered by the condenser group and focused on the optical fiber of the optical fiber acquisition group.

[0069] The optical fiber core diameter filters out stray light and introduces the fluorescence signal into the SPAD to be converted into an electrical signal and collected by the core board.

[0070] The control circuit of the core board generates a control signal to control the change of the galvanometer angle to achieve point scanning on the object surface and reconstruct the image; adjusts the scanning parameters and scans multiple times to gradually approach the optimal acquisition point.

[0071] Connect the data of the optimal point to the external ADC acquisition card using a coaxial cable. After collecting data for a period of time, upload the data to the PC side.

[0072] The PC-side analysis software splits the input data into multiple groups according to the data format. Each group of data is the data of two channels with M points before and after the middle pulse of channel 1. The two channels are synchronized in time. By setting the threshold in the software, the time stamps corresponding to the photon pulses in each group of data are judged. The time stamps of the two channels are subtracted from each other, and the data satisfying -M < t < M are counted.

[0073] Calculate the sum of the actual acquisition times of each group of data, draw the second-order correlation function image and normalize it to verify the single-photon statistical properties.

[0074] A high-speed ADC module is used to convert analog signals into digital signals. In this example, a 1GHz high-speed acquisition card with a matching impedance of 50Ω is adopted.

[0075] Data transmission module: This example uses a PXIe 1GHz high-speed ADC acquisition card for data acquisition, and transmits data to a laptop via the Thunderbolt protocol through the PXIe chassis.

[0076] Example 2:

[0077] The measurement method of the single-photon antibunching measurement system based on the ADC acquisition card includes the following steps:

[0078] Step 1: Set the intermediate pulse trigger through ADC. When channel 1 triggers the pulse, collect data of channel 1 and channel 2 for M sampling points on each side, record it as a valid event, and continuously sample for 30 seconds as a set of data.

[0079] Step 2: Read the data. Based on the characteristics of intermediate trigger sampling, the data can be processed in groups, and the rising edge trigger point can be determined by the set threshold. The data is obtained by subtracting the relative timestamps of the photons in the trigger events of the two channels. The time difference is statistically calculated to calculate the second-order correlation function and normalize it.

[0080] Example 3:

[0081] The single-photon second-order correlation function g is calculated based on the ADC sampling data. (2) The steps of (τ) are as follows:

[0082] Calculation of single-photon second-order correlation function g based on ADC sampling data (2) The steps of (τ) are as follows:

[0083] Step 21, data processing: extract the relative timestamp of each trigger event, calculate the time difference and make interval statistics;

[0084] Threshold detection: Set a threshold to determine the photon timestamp. The first time point when the signal exceeds the threshold is recorded as the timestamp.

[0085] Timestamp generation: Record the relative timestamp of each photon in each trigger event relative to the start time of the event. The ADC sampling interval is accurate to 1ns.

[0086] Time difference calculation: Based on the relative timestamps of each photon of each triggering event, traverse and calculate the time difference: τ = t 1i -t 2j ; where t 1i， t 2j The timestamps of each photon in channels 1 and 2 respectively.

[0087] Filtering and time difference statistics: Create statistics array G (2) (τ), set the threshold M to calculate whether the absolute value of τ exceeds M, if not, add 1 to the qualified group members: G (2) (τ) = G(2) (τ)+1;

[0088] Step 22: Normalize to get g (2) (τ);

[0089] Total measurement time T and average counting rate R:

[0090]

[0091] Among them, N1 and N2 are the total number of photons detected by the two paths, and the detection time 0~T is discretized as: n t =1,2,...,N (N=T / Δt), Δt=1ns;

[0092] Since the sampling mode of the sample is intermediate trigger sampling:

[0093] T=Δt×M×Nc

[0094] M is the sampling width set by the acquisition card, and Nc is the number of trigger events present in the data.

[0095]

[0096] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. Single photon antibunching measurement system based on ADC acquisition card, characterized by: Comprising: A data acquisition unit that acquires optical signals through a confocal microscope system; A data reading module, where the SPAD converts the optical signal into an electrical signal, and the ADC uses an intermediate trigger mode; A data processing center that preprocesses the data through an algorithm according to the nature of the intermediate trigger mode; An algorithm execution module that determines the rising edge trigger point through a set threshold, obtains data by taking the difference of the relative timestamps of photons within two-channel trigger events, statistically calculates the time difference, calculates the second-order correlation function, and normalizes it.

2. The single-photon antibunching measurement system based on the ADC acquisition card according to claim 1, characterized in that: The data acquisition unit includes: A single-photon detection module. The 520nm laser introduced by the fiber excitation group m is reflected by the mirror group l, and then the reflected light is introduced into the dichroic mirror group c, and the reflected light is introduced into the galvanometer group d, while the transmitted light is introduced into the beam scatterer; The galvanometer group d adjusts the incident angle of the excitation light on the field lens group e by changing the angle. The field lens group e and the tube lens group g expand the excitation light beam and introduce it into the rear pupil of the objective lens through the mirror h. A change in the incident angle of the field lens group e will cause a change in the incident angle of the rear pupil of the objective lens. The parallel light with an inclined angle causes the focal spot position on the objective focal plane to shift, thereby realizing the horizontal scanning function of the objective focal plane; The excited fluorescence and the reflected laser are collected by the objective lens together, and after being reflected by the mirror h, they are introduced into the tube lens group g; The tube lens group g and the field lens group e reduce the collected light beam and then reflect it through the galvanometer d and introduce it into the dichroic mirror group c for primary filtering. The transmitted collected light is then secondarily filtered through the condenser lens group and focused on the optical fiber of the optical fiber acquisition group; The optical fiber core diameter filters out stray light and introduces the fluorescence signal into the SPAD to be converted into an electrical signal and collected by the core board; The control circuit of the core board generates a control signal to control the change of the galvanometer angle to achieve point scanning on the object surface and reconstruct the image; adjusts the scanning parameters and scans multiple times to gradually approach the optimal acquisition point; Connects the data of the optimal point to an external ADC acquisition card using a coaxial cable. After collecting data for a period of time, the data is uploaded to the PC side; The PC-side analysis software splits the input data into multiple groups according to the data format. Each group of data is the data of two channels with M points before and after the intermediate pulse of channel 1. The two channels are synchronized in time. By setting a threshold in the software, the timestamps corresponding to the photon pulses in each group of data are judged, and the timestamps of the two channels are subtracted from each other. The data satisfying -M < t < M is statistically counted; Calculates the actual acquisition time sum of each group of data, plots the second-order correlation function image and normalizes it to verify the single-photon statistical properties; A high-speed ADC module for converting analog signals into digital signals; A data transmission module that uses a 1GHz high-speed ADC acquisition card of PXIe to collect data and transmits the data of the PXIe chassis and the laptop computer through the Thunderbolt protocol.

3. The single-photon antibunching measurement system based on the ADC acquisition card according to claim 1, characterized in that: The intermediate trigger sampling means that the trigger point is located in the middle of the set effective sampling interval. That is, after the trigger signal arrives at the middle point, the data within a period of time before and after the trigger point is collected, rather than starting from the trigger point and collecting backward. This method comprehensively statistically analyzes the front and back correlations of the trigger events to ensure the data integrity within the sampling window.

4. The measurement method of the single-photon antibunching measurement system based on the ADC acquisition card according to any one of claims 1 to 3, characterized in that: Including the following steps: Step 1: Set the intermediate pulse trigger through ADC. When the pulse of channel 1 is triggered, collect M sampling points of data of channel 1 and channel 2, record them as one valid event, and continuously sample for 30 seconds as a set of data. Step 2: Read the data. Based on the characteristics of intermediate trigger sampling, the data can be processed in groups, and the rising edge trigger point can be determined by the set threshold. The data is obtained by subtracting the relative timestamps of the photons in the trigger events of the two channels. The time difference is statistically calculated to calculate the second-order correlation function and normalize it.

5. The measurement method of the single-photon antibunching measurement system based on the ADC acquisition card according to claim 4, characterized in that: The single-photon second-order correlation function g is calculated based on the ADC sampling data. (2) The steps of (τ) are as follows: Step 21, data processing: extract the relative timestamp of each trigger event, calculate the time difference and make interval statistics; Threshold detection: Set a threshold to determine the photon timestamp, and record the first time point when the signal exceeds the threshold as the timestamp; Timestamp generation: Record the relative timestamp of each photon in each trigger event relative to the start time of the event. The ADC sampling interval is accurate to 1ns. Time difference calculation: Based on the relative timestamps of each photon of each triggering event, traverse and calculate the time difference: τ = t 1i -t 2j ; where t 1i， t 2j The timestamps of each photon in channels 1 and 2 respectively; Filtering and time difference statistics: Create statistics array G (2) (τ), set the threshold M to calculate whether the absolute value of τ exceeds M, and add 1 to the qualified group members if it does not exceed M: G (2) (τ)=G (2) (t)+1; Step 22: Normalize to get g (2) (τ); Total measurement time T and average counting rate R: Among them, N1 and N2 are the total number of photons detected by the two paths, and the detection time 0~T is discretized as: n t =1,2,...,N (N=T / Δt), Δt=1ns; Since the sampling mode of the sample is intermediate trigger sampling: T=Δt×M×Nc M is the sampling width set by the acquisition card, and Nc is the number of trigger events present in the data;

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