High Sensitivity Photodetector for Photon-Counting Applications

In the last years, there has been a large development of low-light applications, and many of them are based on photon counting using single-photon detectors (SPDs). These are very sensitive detectors typically with an internal gain. The first candidate SPD was the photomultiplier tube (PMT), reaching a very high gain (~106), but there have been a large development of many other solutions, like solid-state solutions. Among them, single-photon avalanche diodes (SPADs) have been used in spectroscopy, florescence imaging, etc., particularly for their good detection efficiency and time resolution (tens of picoseconds). SPADs have been developed in silicon and III–V materials, for the NIR wavelength range. SPADs can be used as single high-performance pixels, or in arrays. SPAD arrays have imaging capabilities, with high sensitivity. Another kind of array is the silicon photomultiplier (SiPM), where all the pixels are connected to a common anode and a common cathode. SiPMs are used in nuclear medicine, physics experiments, quantum-physics experiments, light detection and ranging (LIDAR), etc., due to their high detection efficiency combined with large sensitive areas, and high dynamic range. SiPMs with many small cells present several advantages and nowadays the SPAD pitch can be reduced down to 5 μm

Super-Resolution Quantum Imaging at the Heisenberg Limit

Quantum imaging exploits the spatial correlations between photons to image object features with a higher resolution than a corresponding classical light source could achieve. Using a quantum correlated $N$-photon state, the method of optical centroid measurement (OCM) was shown to exhibit a resolution enhancement by improving the classical Rayleigh limit by a factor of $1/N$. In this work, the theory of OCM is formulated within the framework of an imaging formalism and is implemented in an exemplary experiment by means of a conventional entangled photon pair source. The expected resolution enhancement of a factor of two is demonstrated. The here presented experiment allows for single-shot operation without scanning or iteration to reproduce the object in the image plane. Thereby, photon detection is performed with a newly developed integrated time-resolving detector array. Multi-photon interference effects responsible for the observed resolution enhancement are discussed and possible alternative implementation possibilities for higher photon number are proposed

Characterization-Based Modeling of Retriggering and Afterpulsing for Passively Quenched CMOS SPADs

The current trend in the design of systems based on CMOS SPADs is to adopt smaller technological nodes, allowing the co-integration of additional electronics for the implementation of complex digital systems on chip. Due to their simplicity, a way to reduce the area occupied by the integrated electronics is the use of passive quenching circuits (PQCs) instead of active (AQCs) or mixed (MQCs) ones. However, the recharge phase in PQCs is slower, so the device can be retriggered before this phase ends. This paper studies the phenomena of afterpulsing and retriggering, depending on the characteristics of the SPADs and the working conditions. In order to do that, a test chip containing SPADs of different size has been characterized in several operating environments. A mathematical model has been proposed for fitting afterpulsing phenomenon. It is shown that retriggering can be also described in terms of this model, suggesting that it is linked to carriers trapped in the shallow levels of the semiconductor and that should be taken into account when considering the total amount of afterpulsing events.Junta de Andalucía TIC 233

Characterization of space-momentum entangled photon with a time resolving CMOS SPAD array

Single photon avalanche diode arrays can provide both the spatial and temporal information of each detected photon. We present here the characterization of entangled light with a sensor specifically designed for quantum imaging applications. The sensors is time-tagging each detection events at the pixel level with sub-nanosecond accuracy, within frames of 50 ns. The spatial correlations between any number of detections in a defined temporal window can thus be directly extracted from the data. We show the ability of the sensor to characterize space-momentum entangled photon pairs emitted by spontaneous parametric downconversion. Their entanglement is demonstrated by violating an EPR-type inequality.Comment: 15 pages, 12 figure

Multivariate prediction of Saliva Precipitation Index for relating selected chemical parameters of red wines to the sensory perception of astringency

Astringency is an essential sensory attribute of red wine closely related to the saliva precipitation upon contact with the wine. In this study a data matrix of 52 physico-chemical parameters was used to predict the Saliva Precipitation Index (SPI) in 110 Italian mono-varietal red wines using partial least squares regression (PLSr) with variable selection by Variable Importance for Projection (VIP) and the significance of regression coefficients. The final PLSr model, evaluated using a test data set, had 3 components and yielded an R2test of 0.630 and an RMSEtest of 0.994, with 19 independent variables whose regression coefficients were all significant at p < 0.05. Variables selected in the final model according to the decreasing magnitude of their absolute regression coefficient include the following: Procyanidin B1, Epicatechin terminal unit, Total aldehydes, Protein content, Vanillin assay, 520 nm, Polysaccharide content, Epigallocatechin PHL, Tartaric acid, Volatile acidity, Titratable acidity, Catechin terminal unit, Proanthocyanidin assay, pH, Tannin-Fe/Anthocyanin, Buffer capacity, Epigallocatechin PHL gallate, Catechin + epicatechin PHL, and Tannin-Fe. These results can be used to better understand the physico-chemical relationship underlying astringency in red win

Single-Photon Avalanche Diode-Based Detection and Imaging: Bringing the Photodiode Out of Its Comfort Zone

Our society is becoming more and more reliant on images, and we are getting used to having a visual representation of everything. However, our eyes are, in some ways, quite limited; they can see "just" colors and their intensity. What could we see if we were able to capture every piece of information that a single photon carries? Being able to measure, for example, the position, direction, wavelength, polarization, and time of arrival of every photon would give us the basis for having an almost fully complete understanding of the scene. Even though not all of these quantities need to be measured together, single-photon sensing can enable more and new dimensions to be added to the information space that we are gathering during an image acquisition

A 64×64-pixel digital silicon photomultiplier direct ToF sensor with 100Mphotons/s/pixel background rejection and imaging/altimeter mode with 0.14% precision up to 6km for spacecraft navigation and landing

Recent technology surveys identified flash light detection and ranging technology as the best choice for the navigation and landing of spacecrafts in extraplanetary missions, working from single-point altimeter to range-imaging camera mode. Among all available technologies for a 2D array of direct time-of-flight (DTOF) pixels, CMOS single-photon avalanche diodes (SPADs) represent the ideal candidate due to their rugged design and electronics integration. However, state-of-the-art SPAD imagers are not designed for operation over a wide variety of scenarios, including variable background light, very long to short range, or fast relative movement

A 64 x 64-Pixels Digital Silicon Photomultiplier Direct TOF Sensor With 100-MPhotons/s/pixel Background Rejection and Imaging/Altimeter Mode With 0.14% Precision Up To 6 km for Spacecraft Navigation and Landing

This paper describes a 64×64-pixel 3-D imager based on single-photon avalanche diodes (SPADs) for long-range applications, such as spacecraft navigation and landing. Each 60-μm pixel includes eight SPADs combined as a digital silicon photomultiplier, a triggering logic for photons temporal correlation, a 250-ps 16-b time-to-digital converter, and an intensity counter, with an overall 26.5% fill factor. The sensor provides time-of-flight and intensity information even with a background intensity up to 100 MPhotons/s/pixel. The sensor can work in imaging (short range, 3-D image) and altimeter (long range, single point) modes, achieving up to 300-m and 6-km maximum distance with <;0.2-m and <;0.5-m precision, respectively, consuming less than 100 mW