Single-photon Avalanche Photodiodes Research Articles

In-orbit dark count rate performance and radiation damage high-temperature annealing of silicon avalanche photodiode single-photon detectors of the Micius satellite.

Silicon avalanche photodiode (APD) single-photon detectors in space are continuously affected by radiation, which gradually degrades their dark count performance. From August 2016 to June 2023, we conducted approximately seven years (2507 days) of in-orbit monitoring of the dark count performance of APD single-photon detectors on the Micius Quantum Science Experimental Satellite. The results showed that due to radiation effects, the dark count growth rate was approximately 6.79 cps/day @ -24 °C and 0.37 cps/day @ -55 °C, with a significant suppression effect on radiation-induced dark counts at lower operating temperature. Based on the proposed radiation damage induced dark count annealing model, simulations were conducted for the in-orbit dark counts of the detector, the simulation results are consistent with in-orbit test data. In May 2022, four of these detectors underwent a cumulative 5.7 hours high-temperature annealing test at 76 °C, dark count rate shows no measurable changes, consistent with annealing model. As of now, these ten APD single-photon detectors on the Micius Quantum Science Experimental Satellite have been in operation for approximately 2507 days and are still functioning properly, providing valuable experience for the future long-term space applications of silicon APD single-photon detectors.

GHz photon-number resolving detection with high detection efficiency and low noise by ultra-narrowband interference circuits

We demonstrate the photon-number resolution (PNR) capability of a 1.25 GHz gated InGaAs single-photon avalanche photodiode (APD) that is equipped with a simple, low-distortion ultra-narrowband interference circuit for the rejection of its background capacitive response. Through discriminating the avalanche current amplitude, we are able to resolve up to four detected photons in a single detection gate with a detection efficiency as high as 45%. The PNR capability is limited by the avalanche current saturation, and can be increased to five photons at a lower detection efficiency of 34%. The PNR capability, combined with high efficiency and low noise, will find applications in quantum information processing technique based on photonic qubits.

CMOS-compatible self-quenched active recovery (SQUARE) single-photon detector

Current CMOS single-photon detectors operating in Geiger mode use passive quenching, yielding slow recovery due to the RC delay. Active quenching of CMOS photon detectors operating in the Geiger mode requires external quenching circuitry that occupies a large area, reducing the fill factor and spatial resolution. Here, we demonstrate a self-quenched active recovery (SQUARE) single-photon detector having its recovery accelerated by a secondary carrier multiplication process. The device consists of two gain regions, one giving rise to the photon response and the other quenching the device and amplifying the residual current for a speedy self-recovery. The first gain region is a crystalline silicon p/n junction fabricated through a commercial CMOS process, and the second gain region is a carbon-doped amorphous silicon layer deposited on the top metal layer of a completed CMOS wafer. The SQUARE single-photon detector shows a Geiger-mode gain greater than 100 000 and achieved <30 ns self-recovery time, much faster than self-quenched and passively quenched single-photon avalanche photodiodes reported to date.

Photo-Electric response of 4H-SiC APDs at High-Level incident flux

In many applications, the highest and lowest detectable flux are both important for single photon avalanche photodiodes (APDs). The photocurrent and single-photon-counting performance of 4H-SiC APDs are investigated under a wide-range incident flux. Experimental results show that the photocurrent is sub-linearly with the incident photon rate at high-level incident flux. In addition, the ratio of photon count rate to dark count rate is non-monotonic when the incident flux increases. The highest detectable flux of the 4H-SiC APD can be extended from 3 × 103 photons/s·μm2 to more than 4 × 104 photons/s·μm2 by reducing the threshold voltage and increasing the reverse voltage.

Ultra-narrowband interference circuits enable low-noise and high-rate photon counting for InGaAs/InP avalanche photodiodes.

Afterpulsing noise in InGaAs/InP single photon avalanche photodiodes (APDs) is caused by carrier trapping and can be suppressed successfully through limiting the avalanche charge via sub-nanosecond gating. Detection of faint avalanches requires an electronic circuit that is able to effectively remove the gate-induced capacitive response while keeping photon signals intact. Here we demonstrate a novel ultra-narrowband interference circuit (UNIC) that can reject the capacitive response by up to 80 dB per stage with little distortion to avalanche signals. Cascading two UNIC's in a readout circuit, we were able to enable a high count rate of up to 700 MC/s and a low afterpulsing of 0.5 % at a detection efficiency of 25.3 % for 1.25 GHz sinusoidally gated InGaAs/InP APDs. At a temperature of -30 ∘C, we measured an afterpulsing probability of 1 % at a detection efficiency of 21.2 %.

Free-Running Single-Photon Detection via GHz Gated InGaAs/InP APD for High Time Resolution and Count Rate up to 500 Mcount/s

Free-running InGaAs/InP single-photon avalanche photodiodes (SPADs) typically operate in the active-quenching mode, facing the problems of long dead time and large timing jitter. In this paper, we demonstrate a 1-GHz gated InGaAs/InP SPAD with the sinusoidal gating signals asynchronous to the incident pulsed laser, enabling free-running single-photon detection. The photon-induced avalanche signals are quenched within 1 ns, efficiently reducing the SPAD's dead time and achieving a count rate of up to 500 Mcount/s. However, the timing jitter is measured to be ~168 ps, much larger than that of the SPAD with synchronous gates. We adjust the delay between the gating signals and the incident pulsed laser to simulate the random arrival of the photons, and record the timing jitter, respectively, to figure out the cause of the jitter deterioration. In addition, the effects of the incident laser power and working temperature of the APD on the time resolution have been investigated, broadening the applications of the GHz gated free-running SPAD in laser ranging and imaging, fluorescence spectroscopy detection and optical time-domain reflectometry.

Simultaneous single-particle tracking and fluorescence lifetime measurement with a single-photon detector array.

Fluorescence single-particle tracking (SPT) techniques are a fundamental tool for providing information on the complex functions and interactions of individual particles in biological environments. The main concern about following single particles resides mostly in how to make registered photons informative and the solution is usually optimized only to better extrapolate either the temporal or the spatial information. This tradeoff ultimately reflects into the contraposition of wide-field camera-based techniques and real-time SMT, with the latter representing the state of the art, but at the cost of high technical complexity. Furthermore, fluorescence lifetime information, despite being accessible in many cases, has yet to be measured consistently. Within the context of the BrightEyes ERC-2018-COG project, we present a real-time three-dimensional SPT implementation based on a confocal laser-scanning microscope featuring a 5×5 single-photon avalanche photodiode (SPAD) array detector capable of overcoming the above limitations due to an hybrid approach. Briefly, each sensitive element of the detector acts as a confocal pinhole, and the recorded intensity distribution mirrors the position of the particle with respect to the center of the excitation volume. The estimation is then used as input for a real-time feedback tracking system. Notably, each pixel is an independent photon counting detector, allowing for concurrent measurement of the fluorescence lifetime. The system is capable of experimentally tracking single particles with localization precision up to 30 nm with 100 photons and microsecond time resolution. The same photon stream is used to perform fluorescence lifetime measurements. The technique has been validated by tracking 20 nm fluorescent beads moved along a predetermined path and by measuring the diffusion coefficient when freely diffusing in water-glycerol solutions. As application, the movement of lysosomes in living cells has been investigated while assessing the lifetime of the GFP marker.

InGaAs/InAlAs single photon avalanche photodiodes for X-ray detection

InGaAs/InAlAs single photon avalanche photodiodes for X-ray detection

Eye-safe photon counting LIDAR for magmatic aerosol detection

An eye-safe photon counting light detection and ranging (LIDAR) instrument has been developed for magmatic aerosol sensing in real time. The developed LIDAR was based on a pulsed diode laser (transmitter, 910 nm, 3 ns, <1 µJ cm−2) and a single-photon avalanche photodiode. The instrument was designed to fit the requirements of highly sensitive sensing of aerosol dynamics at distances up to 50 meters. The accuracy of the LIDAR instrument ranging was estimated as 18 cm. Field experiments inside the Baksan Neutrino Observatory tunnel above the volcano Elbrus chamber revealed a good correlation between the magmatic aerosol dynamics and the Earth’s crust deformation due to Moon and Sun tides quantified by a tiltmeter and a laser strainmeter.

InGaAsP/InP Geiger-Mode Avalanche Photodiode Towards Sub-kHz Dark Count Rate at 20% Photon Detection Efficiency

Geiger-mode InGaAsP/InP single photon avalanche photodiode (SPAD) with a low dark count rate (DCR) of 870 Hz at a photon detection efficiency (PDE) of 20% at 1064 nm is achieved for a 40 micron diameter device at −30 °C. Extensively optimized and accurately controlled shallow/deep two-step pn junction and doping profiles are identified to play decisive roles for the performance improvement. While a state-of-the-art specific detectivity of 1.4×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> cm·Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> /W is realized for the optimized SPAD, a temperature coefficient of the breakdown voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">br</sub> ) of 139 mV/K, a dark current of 200 pA at 90%V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">br</sub> and a timing jitter of 280 ps at 20% PDE are also simultaneously attained. Thermal activation energies of approximate 0.5 eV are observed for both the dark current and the DCR at 253–293 K, indicates the dominant source of dark carriers is the mid-gap defect trapping states-related tunneling in the InGaAsP absorber.

ОЦЕНКА ВЛИЯНИЯ ФУНКЦИОНАЛЬНЫХ ЭЛЕМЕНТОВ НА ПАРАМЕТРЫ СИСТЕМЫ КВАНТОВОГО РАСПРЕДЕЛЕНИЯ КЛЮЧА НА ОСНОВЕ ПРОТОКОЛА B92

The influence of the parameters of functional elements on the energy, time and probabilisticcharacteristics of the quantum key distribution system (QKD) based on the B92 protocol is studied.The dependences of the probability of writing correct and erroneous bits into a raw quantumkey sequence are plotted for various lengths of a fiber-optic communication line (FOCL) and theuse of various lasers (EML-laser; DFB-laser; VCSEL-laser and FP-laser) and photodetectormodules (id201; id210; id220; id230). Thus, changes in the probability of writing a correct bit intoa raw quantum key sequence are much more significant than changes in the probability of writingan erroneous bit (50.9 times versus 3.3 times with FWHM=80 pm and a change in the length ofthe FOCL from 10 to 100 km). This is due to the fact that with an increase in the length of theFOCL, the probability of the absence of registration at the receiving station of photons or darkcurrent pulses (DCP) sharply increases. Numerical material indicates a direct proportional dependenceof the probability of writing an erroneous bit on the frequency of generation of noisepulses of single-photon avalanche photodiodes (SAPD). So, with an increase in the frequency ofoccurrence of DCP by 60 times (from 100 to 6000 Hz), the probability of recording an erroneousbit also increases by 60 times (for example, with a FOCL length of 100 km – 6.39 versus 383.3).It has been established that the root-mean-square deviation of the photon delay time is directly proportional to the length of the FOCL and the width of the laser spectrum. With a spectrum widthof FWHM=10 pm and an increase in the FOCL length from 10 to 100 km (by a factor of 10), thestandard deviation of the photon delay time also increases by a factor of 10 (from 4.16 to 41.6 ps).To achieve the best performance of the QKD system as a whole, it is advisable to use a laser witha minimum width of the radiation spectrum, for example, an EML-laser. However, EML-lasers areconsidered the most complex and expensive of all the considered types of lasers, so the use ofEML-lasers significantly increases the cost of the entire QKD system.

Dark current and single photon detection by 1550 nm avalanche photodiodes: dead time corrected probability distributions and entropy rates.

Single photon detectors have dark count rates that depend strongly on the bias level for detector operation. In the case of weak light sources such as novel lasers or single-photon emitters, the rate of counts due to the light source can be comparable to that of the detector dark counts. In such cases, a characterization of the statistical properties of the dark counts is necessary. The dark counts are often assumed to follow a Poisson process that is statistically independent of the incident photon counts. This assumption must be validated for specific types of photodetectors. In this work, we focus on single-photon avalanche photodiodes (SPADs) made for 1550 nm. For the InGaAs detectors used, we find the measured distributions often differ significantly from Poisson due to the presence of dead time and afterpulsing with the difference increasing with the bias level used for obtaining higher quantum efficiencies. We find that when the dead time is increased to remove the effects of afterpulsing, it is necessary to correct the measured distributions for the effects of the dead time. To this end, we apply an iterative algorithm to remove dead time effects from the probability distribution for dark counts as well as for the case where light from an external weak laser source (known to be Poisson) is detected together with the dark counts. We believe this to be the first instance of the comprehensive application of this algorithm to real data and find that the dead time corrected probability distributions are Poisson distributions in both cases. We additionally use the Grassberger-Procaccia algorithm to estimate the entropy production rates of the dark count processes, which provides a single metric that characterizes the temporal correlations between dark counts as well as the shape of the distribution. We have thus developed a systematic procedure for taking data with 1550 nm SPADs and obtaining accurate photocount statistics to examine novel light sources.

Flexible X-ray imaging detectors using scintillating fibers

We present early design and simulation work on a novel X-ray imaging detector. The intent of the FleX-RAY project is to create a digital X-ray detector that is capable of producing high-resolution images, is flexible enough to produce an image on a curved surface, and is capable of self-reporting its final shape. The X-rays will be detected on a sheet of scintillating optical fibers, which will guide the scintillation light to single-photon avalanche photodiodes. This setup allows the electronics and hardware to be moved out of the path of the X-ray beam, limiting the need for additional shielding. Self-shape-reporting will be achieved using a flexible ultra-thin glass substrate with optical waveguides and Bragg gratings, processed by femtosecond laser point-by-point writing. The functionalized glass substrate allows precise measurement of strains, which can be used to calculate the shape.

Quantum non-Gaussianity certification of photon number-resolving detectors.

We report on direct experimental certification of the quantum non-Gaussian character of a photon number-resolving detector. The certification protocol is based on an adaptation of the existing quantum non-Gaussianity criteria for quantum states to quantum measurements. In our approach, it suffices to probe the detector with a vacuum state and two different thermal states to test its quantum non-Gaussianity. The certification is experimentally demonstrated for the detector formed by a spatially multiplexed array of ten single-photon avalanche photodiodes. We confirm the quantum non-Gaussianity of POVM elements Π^m associated with the m-fold coincidence counts, up to m = 7. The experimental ability to certify from the first principles the quantum non-Gaussian character of Π^m is for large m limited by low probability of the measurement outcomes, especially for vacuum input state. We find that the injection of independent Gaussian background noise into the detector can be helpful and may reduce the measurement time required for reliable confirmation of quantum non-Gaussianity. In addition, we modified and experimentally verified the quantum non-Gaussianity certification protocol employing a third thermal state instead of a vacuum to speed up the whole measurement. Our findings demonstrate the existence of efficient tools for the practical characterization of fundamental non-classical properties and benchmarking of complex optical quantum detectors.

Afterpulse effect in measurement-device-independent quantum key distribution.

There is no doubt that measurement-device-independent quantum key distribution (MDI-QKD) is a crucial protocol that is immune to all possible detector side channel attacks. In the preparation phase, a simulation model is usually employed to get a set of optimized parameters, which is utilized for getting a higher secure key rate in reality. With the implementation of high-speed QKD, the afterpulse effect which is an intrinsic characteristic of the single-photon avalanche photodiode is no longer ignorable, this will lead to a great deviation compared with the existing analytical model. Here we develop an afterpulse-compatible MDI-QKD model to get the optimized parameters. Our results indicate that by using our afterpulse-compatible model, we can get a much higher key rate than the prior afterpulse-omitted model. It is significant to take the afterpulse effect into consideration because of the improvement of the system working frequency.

Calibration and comparison of detection efficiency for free-space single-photon avalanche diodes at 850 nm.

A detection efficiency measurement system for free-space single-photon detectors has been established at the National Research Council (NRC) Canada. This measurement apparatus incorporates an 850 nm fiber laser source and utilizes a double-attenuation and substitution calibration technique. Detection efficiency calibrations of silicon single-photon avalanche photodiodes (SPADs) at incident photon rates in the range of 1.0×105 photon counts per second (Cts/s) (36 fW) to 2.1×106Cts/s (734 fW) are SI-traceable through the substitution configuration with a silicon transfer standard detector, calibrated directly using the NRC absolute cryogenic radiometer. The measurement approach taken by the NRC was compared with the SPAD calibration technique implemented at the National Institute of Standards and Technology (NIST) in the United States. The count-rate-dependent detection efficiency of a silicon SPAD was measured at NIST and compared with results from the same SPAD measured at NRC within the range of incident photon rates from 1×105Cts/s to 5×105Cts/s. Comparison of the calibration results shows agreement between the two laboratories within the combined measurement uncertainties.

Time-dependent POVM reconstruction for single-photon avalanche photo diodes using adaptive regularization

We report on the first realization of time-dependent quantum detector tomography for commercially available InGaAs avalanche photo detectors. For the construction of appropriate time-dependent POVMs from experimentally measured data, we introduce a novel scheme to calculate the weight of the regularization term based on the amount of measured data. We compare our POVM-based results with the theoretical predictions of the previously developed model by Gouzien et al (2018 Phys. Rev. A 98 013833). In contrast to our measurement-based construction of a time-dependent POVM for photon detectors, this previous investigation extends a time-independent POVM to a time-dependent one by including effects of detector timing jitter and dead time on the basis of particular model assumptions concerning the inner physical mechanisms of a photon detector. Our experimental results demonstrate that this latter approach is not sufficient to completely describe the observable properties of our InGaAs avalanche photo detectors. Thus, constructing the time-dependent POVM of a detector by direct quantum tomographic measurements can reveal information about the detector’s interior that may not easily be included in time-independent POVMs by a priori model assumptions.

A Mechanically Flexible, Implantable Neural Interface for Computational Imaging and Optogenetic Stimulation Over 5.4×5.4mm2 FoV.

Emerging optical functional imaging and optogenetics are among the most promising approaches in neuroscience to study neuronal circuits. Combining both methods into a single implantable device enables all-optical neural interrogation with immediate applications in freely-behaving animal studies. In this paper, we demonstrate such a device capable of optical neural recording and stimulation over large cortical areas. This implantable surface device exploits lens-less computational imaging and a novel packaging scheme to achieve an ultra-thin (250μm-thick), mechanically flexible form factor. The core of this device is a custom-designed CMOS integrated circuit containing a 160×160 array of time-gated single-photon avalanche photodiodes (SPAD) for low-light intensity imaging and an interspersed array of dual-color (blue and green) flip-chip bonded micro-LED (μLED) as light sources. We achieved 60μm lateral imaging resolution and 0.2mm3 volumetric precision for optogenetics over a 5.4×5.4mm2 field of view (FoV). The device achieves a 125-fps frame-rate and consumes 40 mW of total power.

Fluorescence detection of a trapped ion with a monolithically integrated single-photon-counting avalanche diode

We report on the demonstration of fluorescence detection from a trapped ion using single-photon avalanche photodiodes (SPADs) monolithically integrated with a microfabricated surface ion trap. The SPADs are located below the trapping positions of the ions and designed to detect 370 nm photons emitted from single 174Yb+ and 171Yb+ ions. We achieve an ion/no-ion detection fidelity for 174Yb+ of 0.99 with an average detection window of 7.7(1) ms. We report a dark count rate as low as 1.2 kcps for room temperature operation. The fidelity is limited by laser scatter, dark counts, and heating that prevents holding the ion directly above the SPAD. We measure count rates from each of the contributing sources and fluorescence as a function of ion position. We use the ion as a calibrated light source along with measurements of the active detector area to estimate a SPAD quantum efficiency of 24 ± 1%.

Design and implementation of silicon single-photon avalanche photodiode modeling tool for QKD systems

Single-photon detection concept is the most crucial factor that determines the performance of quantum key distribution (QKD) systems. In this paper, a simulator with time domain visualizers and configurable parameters using continuous time simulation approach is presented for modeling and investigating the performance of single-photon detectors operating in Gieger mode at the wavelength of 830 nm. The widely used C30921S silicon avalanche photodiode was modeled in terms of avalanche pulse, the effect of experiment conditions such as excess voltage, temperature and average photon number on the photon detection efficiency, dark count rate and afterpulse probability. This work shows a general repeatable modeling process for significant performance evaluation. The most remarkable result emerged from the simulated data generated and detected by commercial devices is that the modeling process provides guidance for single-photon detectors design and characterization. The validation and testing results of the single-photon avalanche detectors (SPAD) simulator showed acceptable results with the theoretical and experimental results reported in related references and the device's data sheets.