High Dark Count Rate Research Articles

Room Temperature Single Photon Detection at 1550 nm Using van der Waals Heterojunction

AbstractSingle‐photon detectors (SPDs) are crucial in applications ranging from space, biological imaging to quantum communication and information processing. The SPDs that operate at room temperature are of particular interest to broader application space as the energy overhead introduced by cryogenic cooling can be avoided. Although silicon‐based single photon avalanche diodes (SPADs) are well‐matured and operate at room temperature, the bandgap limitation restricts their operation at telecommunication wavelength (1550 nm) and beyond. InGaAs‐based SPADs, on the other hand, are sensitive to 1550 nm photons but suffer from relatively lower efficiency, high dark count rate, afterpulsing probability, and pose hazards to the environment from the fabrication process. In this work, the properties of nanomaterials that can be leveraged to address these challenges are demonstrated and a room‐temperature single‐photon detector capable of operating at 1550 nm is realized. This is achieved by coupling a low bandgap (≈ 350 meV) absorber (black phosphorus) to a sensitive van der Waals probe that is capable of detecting discrete electron fluctuation. The device is optimized for operation at 1550 nm and demonstrates an overall quantum efficiency of 21.4% (estimated as 42.8% for polarized light), and a minimum dark count of ≈ 720 Hz at room temperature.

Dual-Frequency Lidar for Compressed Sensing 3D Imaging Based on All-Phase Fast Fourier Transform

Lidar, with its advantages of high measurement accuracy, fine angular resolution, and strong anti-interference capability, plays a pivotal role in the field of scene depth information acquisition. Traditional approaches to achieving lateral spatial resolution in imaging include raster scanning and array detectors. The former necessitates frequent scanning to acquire depth maps, resulting in time consumption and instability. The latter encounters challenges such as high dark count rates, pixel crosstalk, and excessive costs for obtaining high-resolution images using array detectors. The introduction of compressed sensing (CS) offers a novel perspective on realizing non-scanning three-dimensional imaging. In this context, we propose a novel three-dimensional imaging system that combines CS with coherent dual-frequency continuous-wave lidar and utilizes the all-phase fast Fourier transform to extract both amplitude and phase information. This system requires only M measurements, and through a reconstruction algorithm, it achieves the inversion of depth information for N-pixel scenes (M << N). Integrating cost-effective components such as digital micromirrors and single-point detectors, this affordable system accomplishes three-dimensional imaging of a single target. Notably, it significantly reduces the required number of measurements while concurrently ensuring enhanced eye safety and signal-to-noise ratio.

Quantitative analysis of silicon photomultipliers for thermoluminescence measurement

The employment of silicon photomultipliers (SiPMs) in photon detection systems facilitates the reduction of detection module size, enhances portability and ruggedness, and lowers product costs. This study investigated the potential of SiPM in thermoluminescence (TL) measurements, focusing on its detection limits, temperature dependency, and dose responses. A 3 × 3 mm2 multi-pixel photon counter (MPPC, Hamamatsu MPPC) composed of 50 μm single-photon avalanche diodes (SPADs) was utilized in single-photon counting mode as the detector. This experimental setup was compared with a conventional photomultiplier tube (PMT) in TL readout case. To ensure comparable light exposure between the two detectors, a 3-mm diameter pinhole was positioned in front of the PMT. By using a thermoelectric (TE) cooling module to maintain the sensor temperature at −20 °C, signal reproducibility was achieved with a fluctuation of less than 1.2%, and a detection limit ranging from 30 to 300 μGy was assessed for four dosimeters: LiF:Mg,Ti, LiF:Mg,Cu,P, LiF:Mg,Cu,Si, and Al2O3:C. The dose response of the system was limited by significant signal saturation due to pile-up effects. We introduced a correction model with a 50 ns paralyzable deadtime, which enhanced the signal response by more than 20-fold. Furthermore, this model also correlated well with the observed count rates under high dark count rate (DCR) conditions up to 1.67 MHz. The findings from this study further contributes to the discussion regarding the perspective of SiPM as TL detectors.

A versatile photon counting system with active afterpulse suppression for free-running negative-feedback avalanche diodes.

InGaAs/InP-based negative-feedback avalanche diodes (NFADs) have been demonstrated to be an excellent option for photon detection at telecom wavelengths in quantum communication applications, where photon arrival times are random. However, it is well-known that the operation of NFADs at low temperatures (193K or below) is crucial to minimize the effects of afterpulsing and high dark count rates (DCRs). In this work, we present a new versatile readout electronics system with active afterpulse suppression that also offers flexible cooling options. Through the characterization of two NFAD detectors from Princeton Lightwave, Inc. and a thorough evaluation of our electronics' performance under various operating conditions, we demonstrate the effectiveness of this readout system in improving the performance of NFAD-based photon detectors. At the optimal bias for NFADs, our electronics were able to significantly reduce the afterpulsing probability by a factor of 200 for dead times ranging from 5 to 20µs following each detection event. This helps to keep the total DCRs at around 100 counts per second or less for a 20µs hold-off time. The versatility of our detection system makes NFADs a cost-effective alternative to more complex detectors, such as superconducting nanowire single-photon detectors, in the research of long-distance quantum communications and low-noise single photon detectors at telecommunication wavelengths.

CMOS Single-Photon Avalanche Diode Circuits for Probabilistic Computing.

Intrinsically random hardware devices are increasingly attracting attention for their potential use in probabilistic computing architectures. One such device is the single-photon avalanche diode (SPAD) and an associated functional unit, the variable-rate SPAD circuit (VRSC), recently proposed by us as a source of randomness for sampling and annealing Ising and Potts models. This work develops a more advanced understanding of these VRSCs by introducing several VRSC design options and studying their tradeoffs as implemented in a 65-nm CMOS process. Each VRSC is composed of a SPAD and a processing circuit. Combinations of three different SPAD designs and three different types of processing circuits were evaluated on several metrics such as area, speed, and variability. Measured results from the SPAD design space show that even extremely small SPADs are suitable for probabilistic computing purposes, and that high dark count rates are not detrimental either, so SPADs for probabilistic computing are actually easier to integrate in standard CMOS processes. Results from the circuit design space show that the time-to-analog-based designs introduced in this work can produce highly exponential and analytical transfer functions, but that the less analytically tractable output of the previously proposed filter-based designs can achieve less variability in a smaller footprint. Probabilistic bits (P-bits) composed of the fabricated VRSCs achieve bit flip rates of 50 MHz and allow at least one order of magnitude of control over their simulated annealing temperature.

Integration of vertically-aligned carbon nanotubes with superconducting nanowire single photon detectors

We report on initial fabrication efforts in the integration of superconducting nanowire single-photon detectors (SNSPDs) with vertically aligned carbon nanotubes (VACNTs) with the goal of creating a wideband single-photon detector. SNSPDs provide high detection efficiencies and low dark count rates, while the VACNTs are excellent broadband optical absorbers. Combining these technologies could potentially enable the development of highly sensitive and versatile optical sensors for a variety of applications, such as spectroscopy, optical communication, and imaging in light starved environments. We developed two fabrication processes for the integration of VACNTs on SNSPDs. The first involves capping the SNSPDs with a protective layer and growing the VACNTs directly above nanowires. Thermal and electrical characterizations of the devices demonstrated a degradation of the superconducting qualities of the SNSPDs. The second process involved suspending the SNSPDs on a thin membrane via a backside etch, where VACNTs were then grown on the backside of the membranes below the nanowires. The membrane style devices showed no degradation in the superconducting properties of the nanowires. Measurements of the membrane style devices before and after the VACNT growth display similar superconducting properties and photon count rates.

Study of Proton-Induced Defects in 40-nm CMOS SPADs

Defects induced by 62 MeV protons in SPADs are studied. A study of the Dark Count Rate (DCR) variation after irradiations for different biasing conditions underlines the predominance of field enhancement effects such as Poole-Frenkel effect and phonon-assisted-tunneling over band-to-band tunneling. Activation energy measurements below mid-gap value confirm the important contribution of these field effects. However, unexpected behaviors in these energies are seen: very low activation energies are extracted for SPADs with a DCR induced around 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> counts per second. We attribute them to the contribution of different groups of defects, with different energy level distribution. This analysis is completed with an annealing study between 100 °C and 300 °C. Results for high DCR SPADs correlate well with the presence of defect clusters. Moreover, histogram of the annealing temperature at which the DCR starts to drop displays two peaks at 170 °C and 250 °C. The first one is attributed to phosphorus vacancies and complex cluster of defects with an energy distribution inside the Si bandgap centered above mid-gap. The second one is attributed to clusters of divacancies that also anneal at temperatures around 250 °C.

Speeding axion haloscope experiments using heterodyne-variance-based detection with a power meter

We describe a new axion search method based on measuring the variance in the interference of the axion signal using injected photons with a power detector. The need for a linear amplifier is eliminated by putting a strong signal into the microwave cavity, to acquire not only the power excess but also measure the variance of the output power. The interference of the external photons with the axion to photon converted signal greatly enhances the variance at the particular axion frequency, providing evidence of its existence. This method has an advantage in that it can always obtain sensitivity near the quantum noise limit even for a power detector with high dark count rate. We describe the basic concept of this method both analytically and numerically, and we show experimental results using a simple demonstration circuit.

Stratospheric aerosol lidar with a 300 µm diameter superconducting nanowire single-photon detector at 1064 nm.

Stratospheric aerosols play an important role in the atmospheric chemical and radiative balance. To detect the stratospheric aerosol layer, a 1064 nm lidar with high resolution and large dynamic range is developed using a superconducting nanowire single-photon detector (SNSPD). Measurements are typically performed at 1064 nm for its sensitivity to aerosol, whereas detectors are limited by low efficiency and high dark count rate (DCR). SNSPDs are characterized by high efficiency in the infrared wavelength domain, as well as low noise and dead time, which can significantly enhance the signal quality. However, it is still challenging to build an SNSPD with both large active area and high count rate. To improve the maximal count rate (MCR) so as to avoid saturation in the near range, a 16-pixel interleaved SNSPD array and a multichannel data acquisition system are developed. As a reference, a synchronous system working at 532 nm is applied. In a continuous comparison experiment, backscatter ratio profiles are retrieved with resolutions of 90 m/3 min, and the 1064 nm system shows better performance, which is sensitive to aerosols and immune to the contamination of the ozone absorption and density of molecule change in the lower stratosphere.

Feasibility of skewness-based characterization of SiPMs with unresolved spectra

Conventional methods of SiPM characterization are mostly based on a resolved spectrum of photoelectron or dark electron detection events which represents a random number of fired SiPM cells. However, such methods are not applicable for unresolved spectra caused, for example, by a low single electron response to noise ratio or a high dark count rate, for example of irradiated SiPMs. This challenge is anticipated in modern developments of radiation-intense facilities like CERN CMS and applications of large-area SiPMs and SiPM arrays with noisy readout like Cherenkov Telescope Array.The method of statistical moments is a well-known technique for the estimation of parameters of a random variable distribution using sample moments of raw data. The first two moments have already been used for estimation of the gain and the number of photoelectrons by the mean and the variance of detected charges relying on a priori knowledge of the Excess Noise Factor of the SiPM or PMT. The third moment or skewness of the measured charge can also be involved to estimate three main SiPM parameters including crosstalk.The skewness-based characterization presumes Generalized Poisson distribution of fired cells which was found to be in good agreement with many experiments. Initial theoretical and experimental evaluations of the skewness method have shown promising results. This study focuses on the feasibility of using such method to characterize the parameters of SiPM with unresolved charge-amplitude spectrum.

High-sensitivity low-noise photodetector using a large-area silicon photomultiplier.

The application of silicon photomultiplier (SiPM) technology for weak-light detection at a single photon level has expanded thanks to its better photon detection efficiency in comparison to a conventional photomultiplier tube (PMT). SiPMs with large detection area have recently become commercially available, enabling applications where the photon flux is low both temporarily and spatially. On the other hand, several drawbacks exist in the usage of SiPMs such as a higher dark count rate, many readout channels, slow response time, and optical crosstalk; therefore, users need to carefully consider the trade-offs. This work presents a SiPM-embedded compact large-area photon detection module. Various techniques are adopted to overcome the disadvantages of SiPMs so that it can be generally utilized as an upgrade from a PMT. A simple cooling component and recently developed optical crosstalk suppression method are adopted to reduce the noise which is more serious for larger-area SiPMs. A dedicated readout circuit increases the response frequency and reduces the number of readout channels. We favorably compare this design with a conventional PMT and obtain both higher photon detection efficiency and larger-area acceptance.

High photon detection efficiency InGaAs/InP single photon avalanche diode at 250 K

Planar semiconductor InGaAs/InP single photon avalanche diodes with high responsivity and low dark count rate are preferred single photon detectors in near-infrared communication. However, even with well-designed structures and well-controlled operational conditions, the performance of InGaAs/InP SPADs is limited by the inherent characteristics of avalanche process and the growth quality of InGaAs/InP materials. It is difficult to ensure high detection efficiency while the dark count rate is controlled within a certain range at present. In this paper, we fabricated a device with a thick InGaAs absorption region and an anti-reflection layer. The quantum efficiency of this device reaches 83.2%. We characterized the single-photon performance of the device by a quenching circuit consisting of parallel-balanced InGaAs/InP single photon detectors and single-period sinusoidal pulse gating. The spike pulse caused by the capacitance effect of the device is eliminated by using the characteristics of parallel balanced common mode signal elimination, and the detection of small avalanche pulse amplitude signal is realized. The maximum detection efficiency is 55.4% with a dark count rate of 43.8 kHz and a noise equivalent power of 6.96 × 10−17 W/Hz1/2 at 247 K. Compared with other reported detectors, this SPAD exhibits higher SPDE and lower noise-equivalent power at a higher cooling temperature.

Architecture optimization of SPAD integrated in 28 nm FD-SOI CMOS technology to reduce the DCR

This article presents a study of Single Photon Avalanche Diodes (SPAD) implemented in 28 nm Fully Depleted Silicon-On-Insulator (FD-SOI) CMOS technology based on transient TCAD simulations and Dark Count Rate (DCR) measurements. The integration of SPAD in this technology is currently being studied. This work allows for a better understanding of the mechanism behind the quite high DCR measured at relative low excess bias voltages with the initial FD-SOI SPAD design (≈500 Hz/µm2 at 5% excess bias voltage). In this study, a TCAD transient simulation methodology is introduced to better understand SPAD behavior during the avalanche process. TCAD simulations revealed that Shallow Trench Isolation (STI) structures within the active area have a negative effect on avalanche quenching, because of slower carrier evacuation with possible occurrence of secondary avalanches in series. Based on this analysis and on previous optimization works, we propose a new architecture of the FD-SOI SPAD combining several modifications to achieve a lower DCR (≈20 Hz/µm2 at 5% excess bias voltage measured with passive quenching).

Simultaneous resolution of photon numbers and positions with series-connected superconducting nanowires

In this Letter, we report on a device with which to resolve photon numbers and positions simultaneously, using single-channel readout from superconducting nanowire single-photon detectors (SNSPDs). The nanowires in the SNSPDs are connected in series with parallel resistors for producing response pulses with different amplitudes, whose values obey a distribution of 1:2:4:,..,2n-1. In single-photon detection, a saturated counting rate is obtained at a low dark count rate (&amp;lt;10 cps). Furthermore, we observed 16 output modes corresponding one-to-one with 16 states (15 photon responses + 1 state without photons) in multiphoton mode. This structure not only inherits the advantages of high quantum efficiency and low dark count rate of traditional SNSPD, but also realizes the resolution of photon position and number simultaneously without complicated optical system. Thus, this proposal offers a promising platform for realizing scalable and practical quantum information chips.

Characterization of new silicon photomultipliers with low dark noise at low temperature

Silicon photomultipliers (SiPMs) have low radioactivity, compact geometry, low operation voltage, and reasonable photo-detection efficiency for vacuum ultraviolet light (VUV). Therefore it has the potential to replace photomultiplier tubes (PMTs) for future dark matter experiments with liquid xenon (LXe). However, SiPMs have nearly two orders of magnitude higher dark count rate (DCR) compared to that of PMTs at the LXe temperature (∼165 K). This type of high DCR mainly originates from the carriers that are generated by the band-to-band tunneling effect.To suppress the tunneling effect, Hamamatsu Photonics K.K. have developed a new SiPM with lowered electric field strength. We have characterized its performance in a temperature range of 153 K to 298 K. We demonstrated that the newly developed SiPMs have 6–60 times lower DCR at low temperatures than that of the conventional SiPMs.

Theoretical Prediction of High-Performance Room-Temperature InGaAs/Si Single-Photon Avalanche Diode Fabricated by Semiconductor Interlayer Bonding

Single-photon avalanche diode (SPAD) is an ultrasensitive device for the detection of weak signals. Epitaxial InP-based devices exhibit poor avalanche characteristics and poor compatibility with Si complementary metal oxide semiconductor (CMOS) circuit, and epitaxial Si-based devices show high dark count rate (DCR) and limited detection wavelength. Here we first show a new generation of InGaAs-on-Si SPADs, achieved by semiconductor interlayer bonding, for the detection of 1550-nm infrared signals theoretically. This wafer-bonded InGaAs/Si SPAD has enabled a significant step-change in performance. The dark current of this SPAD is four orders of magnitude lower than that of the epitaxial ones (300 K). High gain-bandwidth-product of 254 and 353 GHz is achieved at the gain of ~ 24 and ~ 36, respectively, for the wafer-bonded SPAD with polycrystalline Si bonding layer at InGaAs/Si bonded interface. In comparison with epitaxial SPADs, the wafer-bonded ones exhibit low DCR ( ~ 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> Hz at 10% V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">br</sub> ), high single photon detection efficiency ( ~ 24% at 10% V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">br</sub> ), and high pulse repetition rate (1 GHz at 5% V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">br</sub> ) at 300 K. These results indicate that utilizing the wafer-bonded platform, the route toward high-performance InGaAs-on-Si SPAD arrays for use in future eye-safe laser radar (LIDAR) and quantum communication at room temperature (RT) is expected to be achieved.

Pulse-gated mode of commercial superconducting nanowire single photon detectors* *Project supported by the National Natural Science Foundation of China (Grant No. 61605248) and the National Basic Research Program of China (Grant No. 2013CB338002).

High detection efficiency and low intrinsic dark count rate are two advantages of superconducting nanowire single photon detectors (SNSPDs). However, the stray photons penetrated into the fiber would cause the extrinsic dark count rate, owing to the free running mode of SNSPDs. In order to improve the performance of SNSPDs in realistic scenarios, stray photons should be investigated and suppression methods should be adopted. In this study, we demonstrate the pulse-gated mode, with 500 kHz gating frequency, of a commercial SNSPD system for suppressing the response of stray photons about three orders of magnitude than its free-running counterpart on the extreme test conditions. When we push the gating frequency to 8 MHz, the dark count rate still keeps under 4% of free-running mode. In experiments, the intrinsic dark count rate is also suppressed to 4.56 × 10−2 counts per second with system detection efficiency of 76.4372%. Furthermore, the time-correlated single-photon counting analysis also approves the validity of our mode in suppressing the responses of stray photons.

In-silico generation of random bit streams

Silicon PhotoMultipliers (SiPM) are rapidly approaching a significant maturity stage, making them a well recognised platform for the development of evolutionary and novel solutions in a wide range of applications for research and industry. However, they are still affected by stochastic terms, notably a high Dark Count Rate (DCR), limiting their use when single photo-electron pulses convey the required information, for instance in chemiluminescence or fluorescence analysis of biological samples. In such applications, randomness of the spontaneous generation of carriers triggering the avalanche and the rate of occurrences is significantly decreasing the sensitivity of the system against solutions based, for instance, on traditional photo-multiplier tubes.However, unpredictability of the “dark” pulses has a potential value in domains connected to encryption and, in general terms, cybersecurity. ”Random Power” is a project approved within the ATTRACT call for proposals (https://attract-eu.com), having as a main goal the generation of random bit streams by properly analysing the time sequence of the Dark Pulses. The principle has been proven using laboratory equipment and its value assessed applying the National Institute of Standard and Technology (NIST) protocols, complemented by other test suites. The advantages against competing techniques have been thoroughly analysed and the development of a dedicated board, integrating the system in a low cost, low power, scalable design is on-going.The principle, protected by a patent application entered its international phase by the time of writing (application no.102018000009064, deposited at the Office of the Minister of Economic Development, as required by the Italian law; international PCT extension no.PCT/IB2019/058340 deposited in October 2019) will be described, together with the results obtained so far, the current development stage including an FPGA embedded Time-To-Digital Converter (TDC) and future perspectives.

Experimental method to monitor temperature stability of SiPMs operating in conditions of extremely high dark count rate

The use of Silicon Photomultipliers (SiPMs) in high radiation environments (e.g. detectors at collider experiments) or in outdoor conditions (e.g. LIDAR applications), requires to deal with a high level of dark count noise. An undesired effect emerging under these conditions is the self-heating of the SiPM due to a large power dissipation that causes variations of the breakdown voltage and thus affects operating parameters such as gain and PDE. A method to evaluate the heat dissipation properties of different SiPM packages and the temperature stability of SiPMs during operation under extremely high dark count rates (larger than 30 GHz) is presented in this paper. Starting from a condition in which the SiPM is at thermal equilibrium with the environment, a change in the current measured under intense illumination with a LED can be attributed to a temperature variation of the SiPM due to self-heating. Under certain assumptions, a quantitative estimate of the local change of temperature can be obtained if certain parameters of the SiPM are known: gain, photon detection efficiency, equivalent charge factor and drift of the SiPM breakdown voltage with temperature. The method is applied to evaluate the thermal conductivity of different SiPM package configurations, which is a key requirement for reliable operation in conditions of extremely high dark count rate. Among the SiPM package configurations tested, the one consisting of a ceramic substrate coupled to a copper heat sink provided the best performance in terms of good heat dissipation with less than 0.5 °C temperature variation for 100 mW dissipated power.

Digitized waveform signal processing for fast timing: an application to SiPM timing in the presence of dark count noise

In this paper we illustrate techniques for digitized waveform signal processing of fast timing detectors. In the example discussed here, timing analysis of SiPM signals in the presence of high Dark Count Rates, a large data set of digitized waveforms is used to develop an optimal strategy relevant to the electronics front end design.