JP2012084877A - Single photon detector and photon number resolving detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single photon detector and a photon number detector which use an avalanche photodiode.SOLUTION: A single photon detector and a photon number detector which use an avalanche photodiode, include an auxiliary signal generator, a light receiving element, a mixer, and a determiner. The auxiliary signal generator generates an auxiliary signal. The light receiving element receives a photon to output an electric signal. The mixer receives and mixes an output signal of the light receiving element and the auxiliary signal. The determiner determines whether or not the photon is received or the number of received photons. The single photon detector or photon number resolving detector detects an avalanche of an amplitude less than the amplitude of a capacitive response. A probability that an after pulse is generated can be reduced. A photon detection rate is enhanced. The influence on the waveform of the gate signal can be decreased. The frequency of the gate signal can be continuously changed.

Description

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

  The importance of technology for detecting photons is increasing along with the development of information communication technology such as quantum cryptography. In particular, a single photon detection device (Single Photon) that is used in a communication wavelength band (telecom band) such as 1.3 μm to 1.5 μm and that can detect an optical signal having a weak signal strength such as a single photon level. In the detector, an InGaAs / InP type avalanche photodiode (APD) is mostly used. InGaAs / InP type avalanche photodiodes are mostly used in a gated Geiger mode.

  When the avalanche photodiode is operated in the gated Geiger mode, a part of the charge carriers generated in the avalanche generation process is not immediately lost. Charge carriers that are not completely extinguished remain inside the avalanche photodiode, and when the next gate signal is applied to the avalanche photodiode, the remaining charge carriers generate avalanche. Such a current situation is referred to as an after-pulsing effect, and the after-pulse effect is one of the important causes of errors during photon detection.

  In photon detection, as a method for reducing errors due to the after-pulse effect, dead time sufficient for the charge carriers remaining in the avalanche photodiode to disappear without being destroyed after the avalanche is generated (Dead Time) There is a way to set. That is, a dead time during which no gate signal is applied to the avalanche photodiode is set for a certain time after the avalanche is generated.

  However, since a typical photon detection device detects a relatively large avalanche, there are still relatively many charge carriers that remain undisappeared. Accordingly, the dead time sufficient for them to disappear must also be set long. Eventually, such after-pulse effect and dead time become important factors that determine the limits of the gate signal frequency (Gating Frequency) and the photon detection rate (Photon Count Rate), and this is a common single photon detection apparatus. Is operated at a gate frequency of about 10 MHz or less.

International Patent Publication No. WO2009 / 084744 International Patent Publication No. WO2007 / 102430

  The technical problem to be solved by the present invention is to provide a single photon detection device and a photon number resolution detection device capable of detecting an avalanche having an amplitude smaller than the amplitude of the capacitive response.

  Another technical problem to be solved by the present invention is to provide a single photon detection device and a photon number resolution detection device in which the probability that an after pulse is generated is reduced.

  Another technical problem to be solved by the present invention is to provide a single photon detection device and a photon number resolving detection device with an 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 number resolution detection device that have little 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 number resolution detection device capable of continuously changing the gate signal frequency.

  An apparatus for detecting a single photon according to an embodiment of the present invention includes an auxiliary signal generation unit that generates an auxiliary signal, a light receiving element that receives a photon and outputs an electrical signal, an output signal of the light receiving element, and the auxiliary signal A combining unit that receives and combines the signals; and a determination unit that receives the combined signal of the combining unit and determines whether the photons can be received.

  In the embodiment, the light receiving element is an avalanche photo diode, and the electrical signal includes an avalanche signal.

  In the embodiment, the discrimination unit includes an avalanche discriminator that discriminates whether or not avalanche is generated.

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

  In an embodiment, the avalanche photodiode operates in a gated Geiger mode.

  The embodiment further includes a gate signal generation unit that generates a gate signal and transmits the gate signal to the avalanche photodiode.

  The embodiment further includes a time delay unit that temporally aligns the avalanche signal or the auxiliary signal.

  The embodiment further includes an adjustment unit that adjusts the waveform and amplitude of the avalanche signal or the auxiliary signal.

  An apparatus for detecting the number of photons according to an embodiment of the present invention includes an auxiliary signal generating unit that generates an auxiliary signal, a light receiving element that receives a photon and outputs an electrical signal, an output signal of the light receiving element, and the auxiliary signal And a photon number discriminating unit for discriminating the number of the photons received by the light receiving element by receiving the synthesized signal of the synthesizing unit.

  In the embodiment, the photon number discriminating unit discriminates the number of received photons by classifying the combined signal according to strength.

  In the embodiment, the photon number determination unit has a plurality of threshold values, and each of the threshold values is set to be higher than at least a predetermined amplitude of the capacitive response of the light receiving element, and N (N is a natural number) photons. Is set so that the synthesized signal generated by can be classified according to strength.

The single photon detection device or the photon number resolution detection device according to the embodiment of the present invention can detect an avalanche having an amplitude smaller than the amplitude of the capacitive response.
In addition, the probability that an after pulse is generated is reduced.
Also, the speed of detecting photons is improved.
In addition, there is little influence on the waveform of the gate signal.
In addition, the gate signal frequency can be continuously changed.

1 is a diagram illustrating a single photon detector according to a first embodiment of the present invention. It is a figure which shows the signal input / output to a synthetic | combination part when avalanche does not generate | occur | produce. It is a figure which shows the signal input / output to a synthetic | combination part when the avalanche with an amplitude smaller than the amplitude of a capacitive response generate | occur | produces. 4 is a diagram illustrating a concept of discriminating a combined signal and an avalanche signal of the single photon detection device according to the first embodiment of the present invention. 6 is a diagram illustrating a single photon detection device according to a second embodiment of the present invention. 6 is a diagram illustrating a single photon detector according to a third embodiment of the present invention. 7 is a diagram illustrating a single photon detection device according to a fourth embodiment of the present invention. 1 is a view showing a photon number decomposition detection apparatus according to a first embodiment of the present invention. It is drawing which shows the concept which discriminate | determines the synthetic signal and photon number of a photon number decomposition | disassembly detection apparatus. 5 is a view showing a photon number decomposition detection apparatus according to a second embodiment of the present invention. 6 is a view showing a photon number decomposition detection apparatus according to a third embodiment of the present invention. It is drawing which shows the photon number decomposition detection apparatus by 4th Embodiment of this invention.

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

  When a gate signal is applied to operate an avalanche photodiode (APD) in a gated Geiger mode, a capacitive response (capacitive response) unique to the avalanche photodiode is generated. Therefore, when a photon is input to the avalanche photodiode and avalanche is generated, the output of the avalanche photodiode is a signal obtained by combining the capacitive response and the avalanche signal.

  A capacitive response signal of a general avalanche photodiode shows a form of periodically oscillating (oscillation), and the amplitude of the vibration gradually decreases with time and disappears after a sufficient time has passed.

  Since a photon detection device generally includes an avalanche photodiode, such a capacitive response must be considered when detecting a photon. Therefore, the device for determining whether or not avalanche is included in the photon detection device has a threshold (Threshold Level) set higher than the maximum amplitude of the capacitive response. Eventually, such a photon detection device determines whether or not photons can be detected by sensing only when an avalanche signal having an amplitude higher than a set threshold is generated among avalanche signals generated by input of photons. That is, a general photon detection apparatus can perform photon detection and photon counting only when an avalanche having an amplitude larger than the amplitude of the capacitive response occurs.

  However, an avalanche having a large amplitude increases the probability of after-pulse generation, and the dead time must be set longer accordingly. Eventually, the avalanche having a large amplitude causes a photon detection device using an avalanche photodiode operated in a gated Geiger mode to be unable to detect photons at high speed. In order for the photon detector to detect photons at high speed, it is necessary to reduce the after-pulse generation probability and dead time.

  In order to reduce the after-pulse generation probability and dead time generation in a general photon detector, the DC (Direct Current) bias (Bias) voltage applied to the avalanche photodiode and the magnitude and width of the gate signal are adjusted. An avalanche with a small amplitude must be generated. However, in such a case, an avalanche having an amplitude smaller than that of the capacitive response is very difficult to detect with a general photon detector. On the other hand, when the width of the gate signal is made very short in order to operate the avalanche photodiode at high speed in the gated Geiger mode, the generated avalanche amplitude is small, so that the probability that an after pulse is generated is reduced. However, since an avalanche signal having a small amplitude is difficult to detect by a general photon detector as described above, it is impossible to operate the photon detector at high speed.

  In order to solve the above problems of general photon detection devices, the gate signal applied to the avalanche photodiode is input in the form of a sine wave and output using a band elimination filter at the output end of the photo detection device. There are ways to remove the capacitive response contained in the signal. However, since the gate signal is a sine wave form in this method, the gate width becomes very wide when the photon detection device operates at low speed, which has the disadvantage that accurate time measurement of photon detection is difficult, However, it is difficult to separate the capacitive response from the output signal through a band elimination filter. In addition, in order to detect photons while continuously changing the frequency of the gate signal, there is a disadvantage that an appropriate band elimination filter must be replaced in real time corresponding to the changed frequency.

  As another method for solving the above-described problem of a general photon detection device, the output terminal of an avalanche photodiode for two consecutive gate signals periodically input is branched in two. There is a method in which a time difference is set between two branched signals and these signals are input to a differential circuit to detect an avalanche signal based on the difference between the two signals. However, since the adjustment of the time delay between signals branched in this way generally depends on the length of the electric wire, it is difficult to adjust the time delay when the frequency of the gate signal is continuously changed. Further, when avalanche occurs simultaneously with two gate signals, a photon detection error can occur.

(Single photon detector)

  FIG. 1 shows a single photon detection apparatus according to a first embodiment of the present invention. Referring to FIG. 1, the single photon detection apparatus 100 includes avalanche photodiodes APD and 101, a synthesis unit 102, an auxiliary signal generation unit 103, and an avalanche discriminator 104.

  The avalanche photodiode 101 includes a light receiving element that receives a photon and outputs an electrical signal. The electrical signal PS received and output from the photon includes an avalanche signal, and the avalanche photodiode 101 transmits the output signal PS to the combining unit 102.

  The auxiliary signal generation unit 103 generates an auxiliary signal AS in order to effectively detect a weak avalanche signal having an amplitude smaller than the capacitive response of the avalanche photodiode 101, and the generated auxiliary signal AS is sent to the synthesis unit 102. introduce.

  The synthesizer 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 synthesizer 102 synthesizes the output signal PS of the avalanche photodiode APD and the auxiliary signal AS and transmits the synthesized signal MS to the avalanche discriminator 104. When an avalanche is generated by the input of a photon, the amplitude of the composite signal MS becomes maximum at the portion where the avalanche is generated.

  The avalanche discriminator 104 receives the synthesized signal MS from the synthesizer 102 and discriminates whether or not the avalanche photodiode 101 which is a light receiving element has received a photon.

  FIG. 2 is a diagram illustrating signals input / output to / from the combining unit 102 of the single photon detector 100 according to the 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 shows a form that periodically oscillates. The point with the largest amplitude of the capacitive response is the first peak 201 point. The auxiliary signal AS is a signal generated by the auxiliary signal generating unit 103 and is combined with the output signal PS of the avalanche photodiode 101 by the combining unit 102. The synthesized signal MS is a signal obtained by synthesizing the above two signals PS and AS, and the point 202 where the amplitude of the synthesized signal MS is maximized is the same as the first peak 201 point where the amplitude of the capacitive response is maximized. .

  FIG. 3 is a diagram illustrating signals input / output to / from the combining unit 102 of the single photon detector 100 according to the 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 obtained by combining the capacitive response and the avalanche signal generated at the photon input. As described above, the capacitive response shows a form of periodically oscillating, and the avalanche signal generated by the input of the photon is matched. The point where the amplitude of the avalanche photodiode output signal PS is the largest is the first peak 302 point of the capacitive response. The amplitude 301 of the avalanche signal generated at the photon input is less than the maximum amplitude of the capacitive response.

  Unlike FIG. 2, the point 303 where the amplitude of the composite 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. Therefore, the photon detection device according to the embodiment of the present invention detects whether or not avalanche is generated even when the amplitude 301 of the avalanche signal generated by the input of the photon is smaller than the maximum amplitude 302 of the capacitive response, and Can be detected.

  It is difficult for a general photon detection device to detect whether or not a weak avalanche is generated by having a threshold value set higher than the maximum amplitude of the capacitive response.

  On the other hand, the single photon detection apparatus 100 according to the embodiment of the present invention generates the composite signal MS using the auxiliary signal AS as shown in FIG. 3, and detects the avalanche peak 303 from the generated composite signal MS. be able to. For this reason, the single photon detection apparatus 100 according to the present invention can detect whether or not a weak avalanche is generated even if the threshold value is set higher than the maximum amplitude of the capacitive response.

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

  The composite signal MS is a signal input to the avalanche discriminator 104, and the avalanche discriminator 104 senses a case where a signal having an amplitude larger than the set threshold 402 is input. The threshold 402 of the avalanche discriminator 104 is set to be higher than the maximum amplitudes 403 and 404 of the combined signal MS when no avalanche is generated because there is no photon input.

  The combined signal MS of the combining unit 102 in FIG. 4 is a signal obtained by combining the auxiliary signal AS and the avalanche photodiode output signal PS as described with reference to FIGS. In FIG. 4, the synthesized signal MS includes waveforms of three vibration forms, and the amplitude of each waveform is gradually reduced according to time. The maximum amplitude 403 of the first waveform when there is no photon input is smaller than the threshold 402 of the avalanche discriminator 104, and the maximum amplitude 401 of the second waveform when there is a photon input is the threshold of the avalanche discriminator 104. The maximum amplitude 404 of the third waveform, which is greater than 402 and no photon input, is smaller than the threshold 402 of the avalanche discriminator 104.

  In FIG. 4, the maximum amplitude 401 of the second waveform, which is a case where a weak avalanche smaller than the maximum amplitude of the capacitive response is generated by the input of the photon, is larger than the threshold 402 of the avalanche discriminator 104, so that it is eventually Reference numeral 104 indicates that the avalanche is generated by the input of the photon at the input of the second waveform, and the photon detection device detects the presence of the photon. 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 discriminates that no avalanche is generated due to the input of photons, and this The photon detection device detects that no photon is present.

  FIG. 5 illustrates a single photon detector 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 combiner 102, an auxiliary signal generator 103, an avalanche discriminator 104, and a gate signal generator 501.

  A single photon detection apparatus 500 of FIG. 5 includes the single photon detection apparatus 100 of FIG. 1, and further includes a gate signal generation unit 501. The remaining components excluding the gate signal generation unit 501, which are the avalanche photodiode 101, the synthesis unit 102, the auxiliary signal generation unit 103, and the avalanche discriminator 104 are the same as those in FIG. Detailed description is omitted.

  Since the avalanche photodiode 101 has a low quantum efficiency and a high probability of after-pulse generation, it 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 transmits the generated gate signal to the avalanche photodiode 101.

  In a general photon detection apparatus operating in the gated Geiger mode, the frequency of the gate signal and the speed of detecting the photons are limited to be low by the after pulse and the dead time described above. However, the photon detection device 500 according to the second embodiment of the present invention can detect a weak avalanche signal using the auxiliary signal AS even when the avalanche photodiode 101 is operated in the gated Geiger mode. The frequency of the gate signal applied to the avalanche photodiode 101 is not limited by the after pulse and the dead time. That is, even when a weak avalanche having an amplitude smaller than that of the capacitive response is generated, it is possible to detect whether or not avalanche is generated and to detect the photons. it can.

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

  The single photon detection apparatus 600 of FIG. 6 includes the single photon detection apparatus 500 of FIG. 5 and further includes a time delay unit 601. The remaining components excluding the time delay unit 601 are the avalanche photodiode 101, the synthesis unit 102, the auxiliary signal generation unit 103, the avalanche discriminator 104, and the gate signal generation unit 501, which are the same as those in FIG. Since it demonstrated in 1 and FIG. 5, concrete description is abbreviate | omitted.

  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 a combined signal MS. When the amplitude of the synthesized signal MS becomes maximum at the peak point of the avalanche signal, it is further easier to determine whether or not avalanche is generated. Therefore, when the two signals are combined, the position where the avalanche signal exists (avalanche generation position) or the position of the auxiliary signal AS needs to be aligned in time.

  The time delay unit 601 controls the combining unit 102 so that the output signal PS or the auxiliary signal AS of the avalanche photodiode 101 is combined in time alignment. The composite signal MS has the maximum amplitude at the point where the avalanche is generated under the control of the time delay unit 601, and the avalanche discriminator 104 receives the composite signal MS and has a composite signal MS having an amplitude larger than a set threshold. Is determined. Therefore, the photon detector 600 detects the occurrence of avalanche and the input of photons. Further, like the photon detection device 500 of FIG. 5, the photon detection device 600 can detect photons at high speed because the frequency of the gate signal is not limited to be low in the gated Geiger mode.

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

  The single photon detection device 700 of FIG. 7 includes the single photon detection device 600 of FIG. 6 and further includes an adjustment unit 701. The remaining components excluding the adjustment unit 701, which are the avalanche photodiode 101, the synthesis unit 102, the auxiliary signal generation unit 103, the avalanche discriminator 104, the gate signal generation unit 501, and the time delay unit 601, are the same as in FIG. Since it was previously described with reference to FIGS. 1, 5, and 6, a detailed description thereof will be omitted.

  The synthesizer 102 receives the output signal PS and the auxiliary signal AS of the avalanche photodiode 101, synthesizes the two signals PS and AS, and outputs MS. When the amplitude of the synthesized signal MS becomes maximum at the peak point of the avalanche signal, it is further easier to determine whether or not avalanche is generated. Therefore, when the two signals PS and AS are combined, the position where the avalanche signal exists (avalanche generation position) or the position of the auxiliary signal AS needs to be aligned in time, and the two signals PS, In addition to the temporal alignment of AS, the pattern and amplitude of the output signal PS or auxiliary signal AS of the avalanche photodiode 101 need to be adjusted.

  The adjusting unit 701 controls the combining unit 102 so that the pattern and amplitude of the output signal PS or the auxiliary signal AS of the avalanche photodiode 101 are adjusted and combined. The combined signal MS has the maximum amplitude at the point where the avalanche is generated under the control of the adjusting unit 701 and the time delay unit 601, and the avalanche discriminator 104 receives the combined signal MS and has a larger amplitude than the set threshold. The signal MS is discriminated. Therefore, the photon detection device 700 detects avalanche generation and photon input. In addition, the photon detection device 700 can detect photons at high speed because the frequency of the gate signal is not limited to a low value in the gated Geiger mode, similarly to the photon detection devices 500 and 600 of FIGS.

(Photon number resolution detector)

  FIG. 8 is a view showing a photon number decomposition detection apparatus according to the first embodiment of the present invention. Referring to FIG. 8, the photon number resolution detection apparatus 800 includes avalanche photodiodes APD and 801, a synthesis unit 802, an auxiliary signal generation unit 803, and a photon number determination unit 804.

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

  The auxiliary signal generation unit 803 generates the auxiliary signal AS and transmits the generated auxiliary signal AS to the synthesis unit 802.

  The synthesizer 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 combines the received output signal PS and auxiliary signal AS, and transmits the combined signal MS to the photon number determining unit 804. When an avalanche is generated by the input of a photon, the amplitude of the composite signal MS is maximized at the portion where the avalanche is generated.

  The photon number discriminating unit 804 receives the composite signal MS and discriminates the number of photons received by the avalanche photodiode 801 as a light receiving element. The photon number discriminating unit 804 can discriminate the number of photons received by the avalanche photodiode 801 according to the strength of the synthesized signal MS, and classify according to the maximum amplitude of the synthesized signal MS as a sorting method according to the strength of the synthesized signal MS. Can be used.

  FIG. 9 is a view showing a concept of discriminating the composite signal and the number of photons of the photon number decomposition detection apparatus according to the embodiment of the present invention. Referring to FIG. 9, the synthesized signal MS is a signal obtained by synthesizing the auxiliary signal AS and the output signal PS of the avalanche photodiode 801, and the photon number discriminating unit 804 has three threshold values 901a, 902a, and 903a.

  The amplitude of a weak avalanche signal has a discontinuous characteristic, and such a discontinuous characteristic 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 eventually the amplitude of the output signal PS of the avalanche photodiode 801 including the avalanche signal is also equal to the number of photons input to the avalanche photodiode 801. Proportional. Therefore, the maximum amplitudes 901, 902, and 903 of the combined signal MS that finally include the avalanche photodiode output PS are also proportional to the number of photons input to the avalanche photodiode 801.

  In FIG. 9, the three threshold values 901a, 902a, and 903a are set so that they can be classified according to the maximum amplitude of the combined 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 is when the number of photons input to the avalanche photodiode 801 is one, and when the maximum amplitude of the composite signal MS is an intermediate height, 902 is This is a case where the number of photons input to the avalanche photodiode 801 is two. When the maximum amplitude of the composite signal MS is the highest, 901 is a case where the number of photons input to the avalanche photodiode 801 is three. It is.

  The number of units for counting photons by a device that decomposes and detects the number of photons by dividing according to the maximum amplitude of the combined signal MS can be adjusted to 2, 3 or the like as necessary. It is sufficient to adjust the threshold value of the photon number discriminating unit 804 in order to adjust the unit number and detect the number of photons.

  A photon number resolving detection apparatus that decomposes and detects the number of photons must be able to detect the occurrence of a weak avalanche having an amplitude smaller than that of the capacitive response. Therefore, in the photon number resolving and detecting apparatus according to the embodiment of the present invention, when an arbitrary number (natural number) of photons are input to the avalanche photodiode 801, not only the number of photons input but also the number of input photons. It can be easily detected.

  FIG. 10 is a view illustrating a photon number resolution detection apparatus according to a second embodiment of the present invention. Referring to FIG. 10, the photon number resolution detection apparatus 1000 includes an avalanche photodiode 801, a synthesis unit 802, an auxiliary signal generation unit 803, a photon number determination unit 804, and a gate signal generation unit 1001.

  10 includes the photon number decomposition detection apparatus 800 of FIG. 8 and further includes a gate signal generation unit 1001. The remaining components excluding the gate signal generation unit 1001, which are the avalanche photodiode 801, the synthesis unit 802, the auxiliary signal generation unit 803, and the photon number determination unit 804, are the same as those in FIG. Therefore, a specific description is omitted.

  Since the avalanche photodiode 801 has a low quantum efficiency and a high probability of after-pulse generation, it is generally used in a gated Geiger mode.

  The gate signal generation unit 1001 generates a gate signal for causing the avalanche photodiode 801 to operate in the gated Geiger mode, and transmits the generated gate signal to the avalanche photodiode 801.

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

  FIG. 11 illustrates a photon number resolution detection apparatus according to a third embodiment of the present invention. Referring to FIG. 11, the photon number resolution detection apparatus 1100 includes an avalanche photodiode 801, a synthesis unit 802, an auxiliary signal generation unit 803, a photon number determination unit 804, a gate signal generation unit 1001, and a time delay unit 1101.

  A photon number decomposition detection apparatus 1100 in FIG. 11 includes the photon number decomposition detection apparatus 1100 in FIG. 10, and further includes a time delay unit 1101. The remaining components excluding the time delay unit 1101, which are the avalanche photodiode 801, the synthesis unit 802, the auxiliary signal generation unit 803, the photon number determination unit 804, and the gate signal generation unit 1001, are the same as those in FIG. Since it demonstrated in FIG.8 and FIG.10, specific description is abbreviate | omitted.

  The combiner 802 receives the output signal PS and the auxiliary signal AS of the avalanche photodiode 801, combines the two signals, and outputs a combined signal MS. When the amplitude of the synthesized signal MS becomes maximum at the peak point of the avalanche signal, it is further easier to determine whether or not avalanche is generated. Therefore, when the two signals are combined, the position where the avalanche signal exists (avalanche generation position) or the position of the auxiliary signal AS needs to be aligned in time.

  The time delay unit 1101 controls the combining unit 802 so that the output signal PS or the auxiliary signal AS of the avalanche photodiode 801 is combined in time. The composite signal MS has the maximum amplitude at the point where the avalanche is generated under the control of the time delay unit 1101, and the photon number discriminating unit 804 receives the composite signal MS and receives the composite signal MS having an amplitude larger than a set threshold. Determine. Accordingly, the photon number resolution detection apparatus 1100 detects avalanche generation, photon input, and the number of input photons.

  In addition, the photon number resolution detection apparatus 1100 can detect photons at high speed because the frequency of the gate signal is not limited to a low value in the gated Geiger mode, similar to the photon number resolution detection apparatus 1000 of FIG.

  FIG. 12 is a view illustrating a photon number resolution detection apparatus according to a fourth embodiment of the present invention. Referring to FIG. 12, a photon number resolution detection apparatus 1200 includes an avalanche photodiode 801, a synthesis unit 802, an auxiliary signal generation unit 803, a photon number determination unit 804, a gate signal generation unit 1001, a time delay unit 1101, and an adjustment unit 1201. Including.

  12 includes the photon number resolution detection apparatus 1100 of FIG. 11 and further includes an adjustment unit 1201. The remaining components excluding the adjustment unit 1201, which are the avalanche photodiode 801, the synthesis unit 802, the auxiliary signal generation unit 803, the photon number determination unit 804, the gate signal generation unit 1001, and the time delay unit 1101 are the same as those in FIG. Yes, since it was previously described with reference to FIGS. 8, 10, and 11, a detailed description thereof will be omitted.

  The combiner 802 receives the output signal PS and the auxiliary signal AS of the avalanche photodiode 801, combines the two signals, and outputs a combined signal MS. When the amplitude of the synthesized signal MS becomes maximum at the peak point of the avalanche signal, it is further easier to determine whether or not avalanche is generated. Therefore, when the two signals are combined, the position where the avalanche signal exists (avalanche generation position) or the position of the auxiliary signal AS needs to be aligned in time, and only the time alignment of the two signals together with this. Instead, the pattern 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 combining unit 802 so that the pattern and amplitude of the output signal PS or the auxiliary signal AS of the avalanche photodiode 801 are adjusted and combined. The combined signal MS controlled by the adjusting unit 1201 and the time delay unit 1101 has a maximum amplitude at the point where the avalanche is generated, and the photon number determining unit 804 has an amplitude larger than a threshold set by receiving the combined signal MS. The composite signal MS is determined. Therefore, the photon number resolution detection apparatus 1200 detects the occurrence of avalanche, the input of photons, and the number of input photons. In addition, the photon number resolution detection apparatus 1200 can detect photons at high speed because the frequency of the gate signal is not limited to a low level in the gated Geiger mode, similar to the photon number resolution detection apparatuses 1000 and 1100 of FIGS. .

  On the other hand, while the detailed description of the present invention has been described with respect to specific embodiments, various modifications can be made without departing from the scope of the present invention. For example, detailed circuit configurations such as avalanche photodiodes, combining units, auxiliary signal generating units, avalanche discriminators, and photon number discriminating units, and the connection relationship between the front and rear ends can be changed or modified in various ways according to the usage environment and usage. . Therefore, the scope of the present invention should not be defined by being limited to the above-described embodiments, and should be determined not only by the claims described below but also by the equivalents of the claims of this invention. .

102, 802 Synthesizer 103, 803 Auxiliary signal generator 104 Avalanche discriminator 501, 1001 Gate signal generator 701, 1201 Adjuster 804 Photon number discriminator 1101 Time delay unit PS APD output signal AS Auxiliary signal MS Composite signal

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 combining unit that receives and combines the output signal of the light receiving element and the auxiliary signal; and
A single-photon detection device including: a determination unit that receives a combined signal of the combining unit and determines whether the photon can be received; The light receiving element is an avalanche photodiode (Avalanche Photo Diode),
The single-photon detection device according to claim 1, wherein the electrical signal includes an avalanche signal.   The single-photon detection device according to claim 2, wherein the discrimination unit includes an avalanche discriminator that discriminates whether or not avalanche is generated.   4. The single photon detection device according to claim 3, wherein the threshold value of the avalanche discriminator is set to be higher than at least a predetermined amplitude of the capacitive response of the avalanche photodiode.   The single photon detection device according to claim 4, wherein the avalanche photodiode operates in a gated Geiger mode.   The single photon detection device according to claim 5, further comprising a gate signal generation unit that generates a gate signal and transmits the gate signal to the avalanche photodiode.   The single photon detection apparatus according to claim 6, further comprising a time delay unit that temporally aligns the avalanche signal or the auxiliary signal.   The single photon detection apparatus according to claim 6, further comprising an adjustment unit that adjusts a waveform and an 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 combining unit that receives and combines the output signal of the light receiving element and the auxiliary signal; and
A photon number resolving and detecting device, comprising: a photon number determining unit that receives a combined signal of the combining unit and determines the number of photons received by the light receiving element.   The photon number resolving and detecting apparatus according to claim 9, wherein the photon number determining unit determines the number of the received photons by classifying the combined signal according to strength.   The photon number discriminating unit has a plurality of threshold values, and each of the threshold values is set higher than a predetermined amplitude of at least the capacitive response of the light receiving element and is generated by N (N is a natural number) photons. The photon number resolution detection device according to claim 10, wherein the combined signal is set so as to be classified according to intensity.

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