KR20120035822A - Single photon detector and photon number resolving detector - Google Patents

Abstract

PURPOSE: A single photon detecting device and a photon number resolving detecting device are provided to detect an avalanche with smaller amplitude than an electrostatic capacity response. CONSTITUTION: A subsignal generating unit(103) generates a subsignal. A light receiving element(101) receives a photon. A synthesis unit(102) synthesizes an output signal of the light receiving element and the subsignal. An avalanche determining unit(104) receives a synthesized signal of the synthesis unit. The avalanche determining unit determines the reception of the photon.

Description

SINGLE PHOTON DETECTOR AND PHOTON NUMBER RESOLVING DETECTOR}

The present invention relates to a photon detection device, and more particularly to a single photon detection device and a photon decomposition detection device using an avalanche photodiode.

With the development of information and communication technology, including quantum cryptography, the importance of the photon detection technology is increasing. In particular, InGaAs is mostly used in a single photon detector used in a telecom band such as 1.3 μm to 1.5 μm and capable of detecting an optical signal having a weak signal intensity such as a single photon level. Avalanche Photo Diode (APD) is used. Avalanche photodiodes of the InGaAs / InP type are mostly used in gated Geiger mode.

When the avalanche photodiode is operated in gated geiger mode, some of the charge carriers generated during the avalanche generation are not immediately destroyed. Charge carriers that are not completely extinguished remain inside the avalanche photodiode and the remaining charge carriers generate avalanche when the next gate signal is applied to the avalanche photodiode. This phenomenon is called an after-pulsing effect, and the after pulse effect is one of the important causes of errors in photon detection.

A method for reducing the error caused by the after-pulse effect during photon detection, and a method in which a dead time is set long enough for the remaining charge carriers to disappear after the occurrence of the avalanche. There is this. That is, for a predetermined time after the avalanche is generated, a dead time in which the gate signal is not applied to the avalanche photodiode is set.

However, since a typical photon detector detects a relatively large avalanche, there are also a relatively large number of charge carriers that remain intact. As a result, a dead time sufficient for them to disappear must be set. After all, this after-pulse effect and dead time is an important factor in determining the limits of the gate signal frequency (Gating Frequency) and photon count rate (Photon Count Rate), the typical single-photon detector is a gate frequency of about 10 MHz or less It is working on.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a single photon detector and a photon decomposition detector capable of detecting an avalanche having an amplitude smaller than that of a capacitive response.

Another technical problem to be solved by the present invention is to provide a single photon detection device and a photon decomposition detection device in which the probability of generating an after pulse is reduced.

Another technical problem to be solved by the present invention is to provide a single photon detection device and photon number decomposition detection device with improved speed for detecting photons.

Another technical problem to be solved by the present invention is to provide a single photon detection device and a photon decomposition detection device having less influence on the waveform of the gate signal.

Another technical problem to be solved by the present invention is to provide a single photon detection device and a photon decomposition detection device capable of continuously changing the gate signal frequency.

A single photon detection device according to an embodiment of the present invention, the auxiliary signal generator for generating an auxiliary signal; A light receiving element that receives a photon and outputs an electrical signal; A synthesizer configured to receive and synthesize an output signal of the light receiving element and the auxiliary signal; And a determining unit which receives the synthesized signal of the combining unit and determines whether the photon is received.

In an embodiment, the light receiving element is an Avalanche Photo Diode, and the electrical signal includes an Avalanche signal.

In an embodiment, the determination unit includes an avalanche discriminator for determining whether avalanche is generated.

In an embodiment, the threshold of the avalanche discriminator is set at least higher than a predetermined amplitude of the capacitive response of the avalanche photodiode.

In example embodiments, the avalanche photodiode operates in a gated Geiger mode.

The gate signal generator may further include a gate signal generator configured to generate a gate signal and transfer the gate signal to the avalanche photodiode.

The apparatus may further include a time delay unit for temporally aligning the avalanche signal or the auxiliary signal.

The control apparatus may further include a controller configured to adjust the waveform and amplitude of the avalanche signal or the auxiliary signal.

Photon number decomposition detection apparatus according to an embodiment of the present invention, the auxiliary signal generator for generating an auxiliary signal; A light receiving element that receives a photon and outputs an electrical signal; A synthesizer configured to receive and synthesize an output signal of the light receiving element and the auxiliary signal; And a photon number discriminating unit configured to receive the synthesized signal of the combining unit and determine the number of the photons received by the light receiving element.

In example embodiments, the photon number discriminator may determine the number of photons received by dividing the synthesized signal according to intensity.

In an embodiment, the number of photons determining unit has a plurality of thresholds, each of which is set at least higher than a predetermined amplitude of the capacitive response of the light receiving element, and N (N is a natural number) photons. It is set to be able to distinguish the synthesized signal generated by the according to the intensity.

The single photon detector or the photon decomposition detector according to an embodiment of the present invention may detect an avalanche having an amplitude smaller than that of the capacitive response.

In addition, the probability of generating an after pulse is reduced.

In addition, the speed of detecting photons is improved.

In addition, the waveform of the gate signal is less affected.

In addition, it is possible to continuously change the gate signal frequency.

1 is a view showing a single photon detection device according to a first embodiment of the present invention.
2 illustrates a signal input / output to a synthesis unit when no avalanche occurs.
3 is a diagram illustrating a signal input / output to a synthesis unit when an avalanche having an amplitude smaller than that of the capacitive response occurs.
4 is a view illustrating a concept of discriminating a synthesized signal and an avalanche signal of a photon detection device.
5 is a view showing a single photon detection device according to a second embodiment of the present invention.
6 illustrates a single photon detection device according to a third embodiment of the present invention.
7 is a view showing a single photon detection device according to a fourth embodiment of the present invention.
8 is a view showing a photon decomposition detection apparatus according to a first embodiment of the present invention.
FIG. 9 is a diagram illustrating a concept of determining a synthesized signal and a number of photons of a device for detecting a number of photons.
FIG. 10 is a diagram illustrating an apparatus for detecting photon decomposition according to a second exemplary embodiment of the present invention.
FIG. 11 is a view illustrating a photon decomposition detection apparatus according to a third exemplary embodiment of the present invention.
12 is a diagram illustrating an apparatus for detecting photon decomposition according to a fourth exemplary embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention.

When a gate signal is applied to operate an Avalanche Photo Diode (APD) in gated Geiger mode, a capacitive response inherent in the Avalanche Photo Diode is generated. Therefore, when photons are input to the avalanche photodiode and an avalanche occurs, the output of the avalanche photodiode becomes a signal in which the capacitive response and the avalanche signal are combined.

The capacitive response signal of a typical avalanche photodiode periodically oscillates, and the amplitude of the vibration gradually decreases with time, and disappears after sufficient time.

Since photon detection devices typically include avalanche photodiodes, this capacitive response should be taken into account when detecting photons. Therefore, the device for determining whether the avalanche included in the photon detection device has a threshold level set higher than the maximum amplitude of the capacitive response. As a result, the photon detecting device detects only the case where an avalanche signal having an amplitude higher than a set threshold value among the avalanche signals generated at the input of the photon is determined to determine whether to detect the photon. That is, the general photon detection apparatus can perform photon detection and photon counting only when an avalanche having an amplitude greater than the amplitude of the capacitive response occurs.

However, the large amplitude avalanche increases the probability of the occurrence of the after pulse, so that the dead time must also be set long. As a result, a large avalanche causes photon detection using an avalanche photodiode operated in gated Geiger mode to detect photons at high speed. In order for the photon detection device to detect photons at high speed, it is necessary to reduce the probability of occurrence of the after pulse and the dead time.

In order to reduce the probability of occurrence of after-pulse and dead time in a photon detection device, avalanine with small amplitude can be adjusted by adjusting the DC (direct current) bias voltage and gate signal size and width applied to the avalanche photodiode. Should be generated. In this case, however, an avalanche having a smaller amplitude than the capacitive response is very difficult to detect with a general photon detector. On the other hand, when the gate signal is made very short in order to operate the avalanche photodiode at high speed in gated Geiger mode, the amplitude of the generated avalanche is small, which reduces the probability of generating an after pulse. Since this small avalanche signal is difficult to detect with a conventional photon detection device as described above, high-speed operation of the photon detection device is impossible.

In order to solve the above problems of the conventional photon detection device, the gate signal applied to the avalanche photodiode is input in the form of a sine wave, and the capacitance of the output signal is included in the output signal by using a band elimination filter at the output terminal of the optical detection device. There is a way to remove the response. However, since this method has a sinusoidal gate signal, the gate width becomes very wide when the photon detection device operates at a low speed, and thus it is difficult to accurately measure the time of photon detection. It is difficult to separate the capacitive response from the output signal through. In addition, in order to detect photons while continuously changing the frequency of the gate signal, an appropriate band cancellation filter must be replaced in real time in response to the changed frequency.

As another method for solving the above problem of a conventional photon detection device, the output of the avalanche photodiode for two consecutively inputted gate signals is divided into two, and the time difference between the two branched signals Then, there is a method of detecting the avalanche signal from the difference between the two signals by inputting them to the differential circuit (Differencing Circuit). However, in this method, the adjustment of the time delay between the branched signals is generally dependent on the length of the wire, so it is difficult to control the time delay when the frequency of the gate signal is continuously changed. In addition, when avalanches occur simultaneously in two gate signals, photon detection errors may occur.

Single photon detector

1 is a view showing a single photon detection device according to a first embodiment of the present invention. Referring to FIG. 1, the single photon detection apparatus 100 includes an avalanche photodiode 101, an APD, a synthesis unit 102, an auxiliary signal generator 103, and an avalanche discriminator 104. do.

The avalanche photodiode 101 includes a light receiving element for receiving photons and outputting an electrical signal. The received and output electrical signal PS of the photon includes an avalanche signal, and the avalanche photodiode 101 transmits the output signal PS to the synthesis unit 102.

The auxiliary signal generator 103 generates an auxiliary signal AS to effectively detect a weak avalanche signal having a smaller amplitude than the capacitive response of the avalanche photodiode 101, and generates the auxiliary signal (AS). AS) is transmitted to the synthesis unit 102.

The synthesis unit 102 receives the output signal PS output from the avalanche photodiode 101 and receives the auxiliary signal AS output from the auxiliary signal generator 103. The synthesis unit 102 synthesizes the output signal PS and the auxiliary signal AS of the avalanche photodiode APD and transmits the synthesized signal MS to the avalanche discriminator 104. In the case where an avalanche is generated due to the input of photons, the amplitude of the composite signal MS becomes maximum at the part where the avalanche is generated.

The avalanche discriminator 104 receives the synthesized signal MS from the combining unit 102 to determine whether the avalanche photodiode 101, which is a light receiving element, has received photons.

2 is a view showing a signal input / output to the synthesis unit 102 of the single photon detection device 100 according to an embodiment of the present invention when no avalanche occurs. Referring to FIG. 2, the output signal PS of the avalanche photodiode 101 (see FIG. 1) shows only a capacitive response, and as described above, the capacitive response periodically oscillates. The point with the largest amplitude of the capacitive response is the point of the first peak 201. The auxiliary signal AS is a signal generated by the auxiliary signal generator 103, and is synthesized by the synthesizer 102 with the output signal PS of the avalanche photodiode 101. The synthesized signal MS is a signal obtained by synthesizing the two signals PS and AS, and the point 202 where the amplitude of the synthesized signal MS is maximized is the first peak at which the amplitude of the capacitive response is maximum. 201) Same as the point.

3 is a view showing a signal input / output to the synthesis unit 102 of the single photon detection apparatus 100 according to an embodiment of the present invention when an avalanche having an amplitude smaller than that of the capacitive response occurs.

Referring to FIG. 3, the output signal PS of the avalanche photodiode 101 (see FIG. 1) is a signal in which the avalanche signal generated by the capacitive response and the input of the photons is combined. As described above, the capacitive response shows a periodic oscillation shape, and the avalanche signal generated at the input of the photons is summed. The point with the largest amplitude of the avalanche photodiode output signal PS is the point of the first peak 302 of the capacitive response. The amplitude 301 of the avalanche signal generated at the input of the photons is less than the maximum amplitude of the capacitive response.

Unlike FIG. 2, the point 303 where the amplitude of the synthesized signal MS is maximum is the same as the point where the avalanche is generated, and the amplitude at that time is larger than the maximum amplitude 302 of the capacitive response. Accordingly, the photon detection apparatus according to an embodiment of the present invention detects whether an avalanche is generated even when the amplitude 301 of the avalanche signal generated at the input of the photon is smaller than the maximum amplitude 302 of the capacitive response. Then, the input of photons can be detected.

A general photon detection device has a threshold value set higher than the maximum amplitude of the capacitive response, making it difficult to detect whether a weak avalanche is generated.

On the other hand, the single photon detection device 100 according to an embodiment of the present invention, as shown in Figure 3 generates a composite signal (MS) using the auxiliary signal (AS), the generated composite signal (MS) The avalanche peak 303 can be detected from the. As a result, the single photon detection apparatus 100 according to the present invention can detect whether a weak avalanche is generated even though the threshold value is set higher than the maximum amplitude of the capacitive response.

FIG. 4 is a diagram illustrating a concept of discriminating a composite signal MS and an avalanche signal of a single photon detection apparatus 100 according to an exemplary embodiment of the present invention. Referring to FIG. 4, the synthesized signal MS is continuous over time, and the threshold 402 of the avalanche discriminator 104 is constant.

The synthesized signal MS is a signal input to the avalanche discriminator 104, and the avalanche discriminator 104 detects a case where a signal having an amplitude greater than the set threshold 402 is input. The threshold value 402 of the avalanche discriminator 104 is set higher than the maximum amplitudes 403 and 404 of the synthesized signal MS when no avalanche is generated because no photons are input.

As shown in FIGS. 2 and 3, the synthesized signal MS of the combiner 102 of FIG. 4 is a signal obtained by combining the auxiliary signal AS and the avalanche photodiode output signal PS. In FIG. 4, the synthesized signal MS includes three vibrational waveforms, and the amplitude of each of the waveforms gradually decreases with time. The maximum amplitude 403 of the first waveform with no input of photons is less than the threshold 402 of the avalanche discriminator 104, and the maximum amplitude 401 of the second waveform with input of photons. Is greater than the threshold 402 of the avalanche discriminator 104, and the maximum amplitude 404 of the third waveform, in the absence of input of photons, is greater than the threshold 402 of the avalanche discriminator 104. small.

In FIG. 4, the maximum amplitude 401 of the second waveform, which is the case where a weak avalanche smaller than the maximum amplitude of the capacitive response occurs at the input of the photon, is greater than the threshold 402 of the avalanche discriminator 104. As a result, the avalanche discriminator 104 determines that an avalanche due to the input of the photons is generated at the input of the second waveform, and the photon detection device detects the presence of the photons. And since the maximum amplitudes 403 and 404 of the remaining first and third waveforms are smaller than the threshold 402 of the avalanche discriminator 104, the avalanche discriminator 104 is caused by the input of photons. It is determined that there is no balance value, and thus the photon detection device detects that no photons exist.

5 is a diagram illustrating a single photon detection apparatus 500 according to a second embodiment of the present invention. Referring to FIG. 5, the single photon detector 500 includes an avalanche photodiode 101, a synthesizer 102, an auxiliary signal generator 103, an avalanche discriminator 104 and a gate signal generator. 501.

The single photon detector 500 of FIG. 5 includes the single photon detector 100 of FIG. 1 and further includes a gate signal generator 501. The avalanche photodiode 101, the synthesis unit 102, the auxiliary signal generator 103, and the avalanche discriminator 104, which are components other than the gate signal generator 501, are the same as those of FIG. 1. Since it has been described with reference to FIG. 1, a detailed description thereof will be omitted.

Since the avalanche photodiode 101 has a low quantum efficiency and a high probability of generating an after pulse, the avalanche photodiode 101 is generally used in a gated geiger mode.

The gate signal generator 501 generates a gate signal for operating the avalanche photodiode 101 in the gated geiger mode, and transfers the generated gate signal to the avalanche photodiode 101.

In a typical photon detection device operating in gated Geiger mode, the after-pulse and dead time described above limit the frequency of the gate signal and the speed of detecting photons. However, in the photon detecting apparatus 500 according to the second exemplary embodiment of the present invention, even when the avalanche photodiode 101 is operated in the gated geiger mode, a weak avalanche signal is generated using the auxiliary signal AS. Since it can be detected, the frequency of the gate signal applied to the avalanche photodiode 101 is not limited low due to the after-pulse and dead time described above. That is, even when a weak avalanche having an amplitude smaller than the capacitive response is generated, the photon detection apparatus 500 of the present invention can be detected even in the gated Geiger mode because the photon can be detected by determining whether the avalanche is generated. Can operate at high speed.

6 illustrates a single photon detection device 600 according to a third embodiment of the present invention. Referring to FIG. 6, the single photon detection device 600 includes an avalanche photodiode 101, a synthesis unit 102, an auxiliary signal generator 103, an avalanche discriminator 104, and a gate signal generator. 501 and a time delay unit 601.

The single photon detector 600 of FIG. 6 includes the single photon detector 500 of FIG. 5 and further includes a time delay unit 601. The avalanche photodiode 101, the synthesis unit 102, the auxiliary signal generator 103, the avalanche discriminator 104, and the gate signal generator 501, which are components other than the time delay unit 601. ) Is the same as FIG. 5, and the detailed description is omitted since it has been described with reference to FIGS. 1 and 5.

The combining unit 102 receives the output signal PS and the auxiliary signal AS of the avalanche photodiode 101, combines the two signals, and outputs the combined signal MS. When the amplitude of the synthesized signal MS becomes maximum at the peak point of the avalanche signal, it is easier to determine whether the avalanche is generated. Therefore, when the two signals are synthesized, the position where the avalanche signal exists (the avalanche generating position) or the position of the auxiliary signal AS needs to be aligned in time.

The time delay unit 601 controls the synthesis unit 102 such that the output signal PS or the auxiliary signal AS of the avalanche photodiode 101 is aligned in time and synthesized. Due to the control of the time delay unit 601, the synthesized signal MS has a maximum amplitude at the point where the avalanche is generated, and the avalanche discriminator 104 receives the synthesized signal MS from the set threshold value. The synthesized signal MS having a large amplitude is determined. The photon detection device 600 detects the occurrence of avalanche and the input of the photon. In addition, the photon detector 600 may detect photons at high speed because the frequency of the gate signal is not limited in the gated Geiger mode similarly to the photon detector 500 of FIG. 5.

7 illustrates a single photon detection apparatus 700 according to a fourth embodiment of the present invention. Referring to FIG. 7, the single photon detector 700 includes an avalanche photodiode 101, a synthesizer 102, an auxiliary signal generator 103, an avalanche discriminator 104, and a gate signal generator. 501, a time delay unit 601, and an adjusting unit 701.

The single photon detector 700 of FIG. 7 includes the single photon detector 600 of FIG. 6 and further includes an adjusting unit 701. The avalanche photodiode 101, the synthesis unit 102, the auxiliary signal generator 103, the avalanche discriminator 104, and the gate signal generator 501 which are the remaining components except for the controller 701. The time delay unit 601 is the same as FIG. 6, and the detailed description is omitted since it has been described with reference to FIGS. 1, 5, and 6.

The synthesis unit 102 receives the output signal PS and the auxiliary signal AS of the avalanche photodiode 101, and combines the two signals PS and AS to output MS. When the amplitude of the synthesized signal MS becomes maximum at the peak point of the avalanche signal, it is easier to determine whether the avalanche is generated. Therefore, when the two signals PS and AS are synthesized, the position where the avalanche signal is present (the avalanche generating position) or the position of the auxiliary signal AS needs to be aligned in time. It is necessary to adjust the shape and amplitude of the output signal PS or the auxiliary signal AS of the avalanche photodiode 101 as well as the temporal alignment of the fields PS and AS.

The adjusting unit 701 controls the combining unit 102 so that the shape and amplitude of the output signal PS or the auxiliary signal AS of the avalanche photodiode 101 are adjusted and synthesized. Under the control of the adjusting unit 701 and the time delay unit 601, the synthesized signal MS has a maximum amplitude at the point where the avalanche is generated, and the avalanche discriminator 104 inputs the synthesized signal MS. The synthesized signal MS having an amplitude greater than the set threshold is determined. The photon detection device 700 detects the occurrence of avalanche and the input of photons. In addition, like the photon detectors 500 and 600 of FIGS. 5 and 6, the photon detector 700 may detect photons at a high speed because the frequency of the gate signal is not limited in the gated Geiger mode.

Photon Decomposition Detector

8 is a view showing a photon decomposition detection apparatus according to a first embodiment of the present invention. Referring to FIG. 8, the photon decomposition detection apparatus 800 includes an avalanche photodiode 801 (APD), a synthesizer 802, an auxiliary signal generator 803, and a photon number discriminator 804. .

The avalanche photodiode 801 includes a light receiving element that receives photons and outputs an electrical signal. The output signal PS generated according to the photon reception includes an avalanche signal, and the avalanche photodiode 801 transmits the output signal PS to the combiner 802.

The auxiliary signal generator 803 generates an auxiliary signal AS and transmits the generated auxiliary signal AS to the combining unit 802.

The synthesis unit 802 receives the signal PS output from the avalanche photodiode 801 and receives the auxiliary signal AS output from the auxiliary signal generator 803. The combining unit 802 synthesizes the received output signal PS and the auxiliary signal AS, and transmits the synthesized signal MS to the photon number determining unit 804. In the case where an avalanche is generated due to the input of photons, the amplitude of the composite signal MS becomes maximum at the part where the avalanche is generated.

The photon number determining unit 804 determines the number of photons received by the avalanche photodiode 801, which is a light receiving element, by receiving the composite signal MS. The photon number discrimination unit 804 may determine the number of photons received by the avalanche photodiode 801 according to the strength of the synthesized signal MS, and synthesized as a classification method according to the intensity of the synthesized signal MS. A method of dividing according to the maximum amplitude of the signal MS may be used.

9 is a diagram illustrating a concept of determining a synthesized signal and a number of photons of an apparatus for detecting photon number according to an exemplary embodiment of the present invention. Referring to FIG. 9, the synthesized signal MS is a signal obtained by combining the auxiliary signal AS and the output signal PS of the avalanche photodiode 801, and the photon number discriminator 804 has three threshold values. 901a, 902a, 903a.

The amplitude of the weak avalanche signal has a discontinuous characteristic, which is directly related to the number of photons input to the avalanche photodiode 801. That is, the amplitude of the avalanche signal is proportional to the number of photons input to the avalanche photodiode 801, and thus, the output signal PS of the avalanche photodiode 801 including the avalanche signal. The amplitude is also proportional to the number of photons input to the avalanche photodiode 801. Accordingly, the maximum amplitudes 901, 902, 903 of the composite signal MS including the avalanche photodiode output PS are also proportional to the number of photons input to the avalanche photodiode 801. do.

In FIG. 9, the three thresholds 901a, 902a, and 903a are set to be distinguished according to the maximum amplitude of the composite signal MS proportional to the number of photons input to the avalanche photodiode 801. When the maximum amplitude of the composite signal MS is the lowest (903), the number of photons input to the avalanche photodiode 801 is one, and the maximum amplitude of the composite signal MS is a medium height ( 902 denotes a case where the number of photons input to the avalanche photodiode 801 is two, and when the maximum amplitude of the synthesized signal MS is the highest, 901 is input to the avalanche photodiode 801. The number of photons is three.

In the apparatus for dividing and detecting the number of photons by dividing according to the maximum amplitude of the synthesized signal MS, the number of counting units of photons can be adjusted to two, three, etc. as necessary. In order to decompose and detect the number of photons by adjusting the number of units, the thresholds of the photon number determination unit 804 may be adjusted.

A photon decomposition detection device that decomposes and detects the number of photons should be able to detect the occurrence of a weak avalanche having a smaller amplitude than the capacitive response. Therefore, in the photon decomposition detection apparatus according to the embodiment of the present invention, when an arbitrary number (natural number) of photons is input to the avalanche photodiode 801, not only the fact that the photons are input but also the number of input photons is easy. Detection is possible.

FIG. 10 is a diagram illustrating an apparatus for detecting photon decomposition according to a second exemplary embodiment of the present invention. Referring to FIG. 10, the photon decomposition detection apparatus 1000 includes an avalanche photodiode 801, a synthesizer 802, an auxiliary signal generator 803, a photon number discriminator 804, and a gate signal generator. 1001.

The photon number decomposition detecting apparatus 1000 of FIG. 10 includes the photon number decomposition detecting apparatus 800 of FIG. 8, and further includes a gate signal generator 1001. The avalanche photodiode 801, the synthesis unit 802, the auxiliary signal generator 803, and the photon number discriminator 804, which are the remaining components except for the gate signal generator 1001, are the same as in FIG. 8. Since it has been described with reference to FIG. 8, a detailed description thereof will be omitted.

Since the avalanche photodiode 801 has a low quantum efficiency and a high probability of generating an after pulse, the avalanche photodiode 801 is generally used in a gated geiger mode.

The gate signal generator 1001 generates a gate signal for operating the avalanche photodiode 801 in the gated geiger mode, and transfers the generated gate signal to the avalanche photodiode 801.

In a typical photon decomposition detector operating in gated Geiger mode, the above-described after pulse and dead time limit the frequency of the gate signal and the speed of detecting photons. However, in the photon number decomposition detecting apparatus 1000 according to the second embodiment of the present invention, even when the avalanche photodiode 801 is operated in the gated geiger mode, a weak avalanche is generated by using the auxiliary signal AS. Since the signal can be detected, the frequency of the gate signal applied to the avalanche photodiode 801 is not limited low due to the after-pulse and dead time described above. That is, even when a weak avalanche having an amplitude smaller than the capacitive response is generated, it is possible to determine whether an avalanche is generated and detect the input of photons and the number of input photons. The photon decomposition detection apparatus 1000 may operate at a high speed.

FIG. 11 is a view illustrating a photon decomposition detection apparatus according to a third exemplary embodiment of the present invention. Referring to FIG. 11, the photon decomposition detection device 1100 includes an avalanche photodiode 801, a synthesizer 802, an auxiliary signal generator 803, a photon number discriminator 804, and a gate signal generator. 1001 and a time delay unit 1101.

The photon number decomposition detecting apparatus 1100 of FIG. 11 includes the photon number decomposition detecting apparatus 1100 of FIG. 10, and further includes a time delay unit 1101. The avalanche photodiode 801, the synthesis unit 802, the auxiliary signal generator 803, the number of photons determination unit 804, and the gate signal generator 1001, which are the remaining components except for the time delay unit 1101. 10 is the same as FIG. 10, and the detailed description thereof is omitted since it has been described with reference to FIGS. 8 and 10.

The combining unit 802 receives the output signal PS and the auxiliary signal AS of the avalanche photodiode 801, synthesizes the two signals, and outputs the combined signal MS. When the amplitude of the synthesized signal MS becomes maximum at the peak point of the avalanche signal, it is easier to determine whether the avalanche is generated. Therefore, when the two signals are synthesized, the position where the avalanche signal exists (the avalanche generating position) or the position of the auxiliary signal AS needs to be aligned in time.

The time delay unit 1101 controls the combiner 802 such that the output signal PS or the auxiliary signal AS of the avalanche photodiode 801 is aligned in time and synthesized. Due to the control of the time delay unit 1101, the synthesized signal MS has a maximum amplitude at the point where the avalanche is generated, and the photon number discriminator 804 receives the synthesized signal MS and is larger than the set threshold. The synthesized signal MS having an amplitude is determined. The photon decomposition detection device 1100 detects the occurrence of an avalanche, the input of photons, and the number of input photons.

Also, like the photon number decomposition detecting apparatus 1000 of FIG. 10, the photon number detecting apparatus 1100 can detect photons at a high speed because the frequency of the gate signal is not limited in the gated Geiger mode.

12 is a diagram illustrating an apparatus for detecting photon decomposition according to a fourth exemplary embodiment of the present invention. Referring to FIG. 12, the photon number decomposition detecting apparatus 1200 includes an avalanche photodiode 801, a synthesizer 802, an auxiliary signal generator 803, a photon number discriminator 804, and a gate signal generator. 1001, a time delay unit 1101 and an adjusting unit 1201.

The photon number decomposition detecting apparatus 1200 of FIG. 12 includes the photon number decomposition detecting apparatus 1100 of FIG. 11, and further includes an adjusting unit 1201. The avalanche photodiode 801, the synthesis unit 802, the auxiliary signal generator 803, the number of photons determination unit 804, the gate signal generator 1001, and the other components except for the adjuster 1201, and The time delay unit 1101 is the same as that of FIG. 11 and has been described above with reference to FIGS. 8, 10, and 11, and thus a detailed description thereof will be omitted.

The combining unit 802 receives the output signal PS and the auxiliary signal AS of the avalanche photodiode 801, synthesizes the two signals, and outputs the combined signal MS. When the amplitude of the synthesized signal MS becomes maximum at the peak point of the avalanche signal, it is easier to determine whether the avalanche is generated. Therefore, when two signals are synthesized, the position where the avalanche signal exists (the avalanche generating position) or the position of the auxiliary signal AS needs to be aligned in time, and in addition to the temporal alignment of the two signals, The shape and amplitude of the output signal PS or the auxiliary signal AS of the avalanche photodiode 801 need to be adjusted.

The adjusting unit 1201 controls the synthesizing unit 802 such that the shape and amplitude of the output signal PS or the auxiliary signal AS of the avalanche photodiode 801 are adjusted and synthesized. Under the control of the adjusting unit 1201 and the time delay unit 1101, the synthesized signal MS has a maximum amplitude at the point where the avalanche is generated, and the photon number determining unit 804 receives the synthesized signal MS. The synthesized signal MS having an amplitude greater than the set threshold is determined. The photon decomposition detection device 1200 detects the occurrence of avalanche, input of photons and the number of input photons. Also, like the photon decomposition detection apparatuses 1000 and 1100 of FIGS. 10 and 11, the photon decomposition detection apparatus 1200 detects photons at high speed since the frequency of the gate signal is not limited in the gated Geiger mode. can do.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. For example, the detailed circuit configuration of the avalanche photodiode, the synthesis unit, the auxiliary signal generator, the avalanche discriminator, and the number of photons, and the connection relationship between the front and rear ends may vary depending on the usage environment or use. It may change. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined by the equivalents of the claims of the present invention as well as the following claims.

Claims (11)

An auxiliary signal generator for generating an auxiliary signal;
A light receiving element that receives a photon and outputs an electrical signal;
A synthesizer configured to receive and synthesize an output signal of the light receiving element and the auxiliary signal; And
And a discriminating unit which receives the synthesized signal of the combining unit and determines whether the photon is received. The method of claim 1,
The light receiving element is an avalanche photo diode,
Wherein said electrical signal comprises an avalanche signal. The method of claim 2,
The determination unit includes a single photon detection device for determining whether the avalanche generation. The method of claim 3, wherein
And the threshold value of said avalanche discriminator is set at least higher than a predetermined amplitude of the capacitive response of said avalanche photodiode. The method of claim 4, wherein
The avalanche photodiode operates in a gated geiger mode. The method of claim 5, wherein
And a gate signal generator for generating a gate signal and transferring the gate signal to the avalanche photodiode. The method according to claim 6,
And a time delay unit for temporally aligning the avalanche signal or the auxiliary signal. The method according to claim 6,
And a control unit for adjusting the waveform and amplitude of the avalanche signal or the auxiliary signal. An auxiliary signal generator for generating an auxiliary signal;
A light receiving element that receives a photon and outputs an electrical signal;
A synthesizer configured to receive and synthesize an output signal of the light receiving element and the auxiliary signal; And
And a photon number determining unit configured to receive the combined signal of the combining unit and determine the number of the photons received by the light receiving element. The method of claim 9,
And the photon number determination unit classifies the synthesized signal according to the intensity to determine the number of the received photons. The method of claim 10,
The photon number discriminating unit has a plurality of thresholds, each of which is set at least higher than a predetermined amplitude of the capacitive response of the light receiving element and is generated due to N photons (N is a natural number). A photon number decomposition detection device configured to distinguish a synthesized signal according to an intensity.

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