The invention is related to phase detection in lidar systems using single photon detectors (SPDs). The frequency at which the SPDs are time gated is related to but not an integer multiple of the frequency of the transmitted optical pulses. Each return optical pulse arrives with a particular temporal position with respect to the nearest gate, and thus is detected with a related detection efficiency. The SPD output can be segmented into multiple time-multiplexed signals whose relative detection efficiency reveals the phase of the optical return pulses, and no such phases have negligible detection efficiency for all the time-multiplexed signals. To mitigate the impact of afterpulsing and other saturation effects, when a first optical pulse is detected with high detection efficiency the next optical pulse that is detected with high detection efficiency is separated by a time period about equal to or greater than the detector dead time.

System and method for measuring the phase of a modulated optical signal

A single-photon receiver and method for detecting a single-photon are presented. The receiver comprises a SPAD that receives a gating signal having a fundamental frequency in the 100 MHz to multiple GHz range. The receiver further comprises a two-stage frequency filter for filtering the output of the SPAD, wherein the filter has: (1) a notch filter response at the fundamental frequency; and (2) a low-pass filter response whose cutoff frequency is less than the first harmonic of the fundamental frequency. As a result, the frequency filter removes substantially all the frequency components in the SPAD output without significant degradation of the signal quality but with reduced complexity, cost, and footprint requirement relative to receivers in the prior art.

High-repetition-rate single-photon receiver and method therefor

An exemplary photodetector includes a SPAD and a capacitor. The capacitor is configured to be charged, while the SPAD is in a disarmed state, with a bias voltage by a voltage source. The capacitor is further configured to supply, when the SPAD is put in an armed state, the bias voltage to an output node of the SPAD such that a voltage across the SPAD is greater than a breakdown voltage of the SPAD.

Fast-gated photodetector architectures comprising dual voltage sources with a switch configuration

Provided is a photo detector. The photo detector includes: an avalanche photodiode; a bias circuit supplying a bias voltage to one end of the avalanche photodiode; a detection circuit connected to the other end of the avalanche photodiode and detecting a photoelectric current occurring in the avalanche photodiode; and a coupling capacitor connected to the one end or the other end of the avalanche photodiode and supplying a coupling voltage to drive the avalanche photodiode in a Geiger mode.

Photo detector having coupling capacitor

An apparatus and method for revealing both attack attempts performed on the single- photon detector(s) of a quantum cryptography system and Trojan horse attack attempts performed on quantum cryptography apparatus containing at least one single photon detector. The attacks detection relies on both the random modification of the setting parameters of the said single-photon detector(s) and the comparison of the measured detection probability values for each setting parameter with the expected detection probability values. The modified parameter of the single-photon detector can be its efficiency or its timing of activation for example.

Apparatus and method for the detection of attacks taking control of the single photon detectors of a quantum cryptography apparatus by randomly changing their efficiency

In order to operate a single photon detector in communication wavelength band at a high speed, a DC bias voltage 2 lower than the breakdown voltage is applied to an InGaAs/InP avalanche photodiode (APD) 1. A 500 MHz sine wave gating signal 3 is superimposed with the DC bias voltage 2 and applied to the APD so as to exceed the breakdown voltage by about 4V in a fractional time of each period. The sine wave gating signal 3 passed through the APD 1 is substantially completely removed by a filter 4, thereby improving S/N and enabling to detect a single photon even if the avalanche multiplication time is shortened to reduce the after pulse and the detection period. As a result, it achieves to detect a single photon in the 1550 nm communication band at a high speed.

High-speed single-photon detector in telecommunication wavelength band

In order to operate a single photon detector in communication wavelength band at a high speed, a DC bias voltage 2 lower than the breakdown voltage is applied to an InGaAs/InP avalanche photodiode (APD) 1. A 500MHz sine wave gating signal 3 is superimposed with the DC bias voltage 2 and applied to the APD 1 so as to exceed the breakdown voltage by about 4V in a fractional time of each period. The sine wave gating signal 3 passed through the APD 1 is substantially completely removed by a filter 4, thereby improving S/N and enabling to detect a single photon even if the avalanche multiplication time is shortened to reduce the after pulse and the detection period. As a result, it achieves to detect a single photon in the 1550nm communication band at a high speed.

Optical communication wavelength band high speed single photon detector

La presente invention concerne un detecteur monophotonique fonctionnant a grande vitesse dans une bande de longueur d'onde de communication optique. Une tension de polarisation continue (2) inferieure a la tension de claquage est appliquee a une photodiode a avalanche InGaAs/InP (1). Un signal de gâchette sinusoidal (3) ayant une frequence de 500 MHz est superpose a la tension de polarisation continue (2) et applique a la photodiode a avalanche (1) afin de depasser la tension de claquage d'environ 4 V dans une partie d'une periode. Le signal de gâchette sinusoidal (3) transmis a la photodiode (1) est supprime au moyen d'un filtre (4). Le rapport signal/bruit est ameliore, car le signal de gâchette (3) combine a un signal de detection (5) peut etre supprime sensiblement dans sa totalite, et il est possible de detecter un photon unique meme en cas de duree d'avalanche courte. En consequence, la post-impulsion peut etre reduite et la periode de detection raccourcie. Il est donc possible de detecter un photon unique dans la bande de longueur d'onde de communication de 1550 nm a grande vitesse.

Shinji Sasamori

Papers

High-speed single-photon detector in telecommunication wavelength band

Optical communication wavelength band high speed single photon detector

Detecteur monophotonique a bande de longueur d'onde de communication optique a grande vitesse