Single-photon avalanche diodes for short-wave infrared detection

Single-photon detection is an exciting and rapidly advancing field with numerous emerging applications areas. There is a demand for highly efficient low noise single-photon detectors. 1310 and 1550 nm are particularly desirable detection wavelengths for use in time-of-flight imaging, light detection and ranging in automobiles, and low loss optical fibre transmission in quantum key distribution networks. Silicon based single-photon detectors dominate in the visible and near-infrared spectral ranges, but this report investigates the design and characterisation of planar Germanium-on-Silicon Single-Photon Avalanche Diodes (SPADs) as an efficient short-wave infrared detector. A single-photon detection efficiency of up to 30 % at a temperature of 125 K was achieved at a wavelength of 1310 nm, with dark count rates in the order of a few thousand counts per second, a low noise equivalent power of 4 x10 -17 WHz-1/2 and timing jitter as low as 126 ps at 150 K. These results represent the highest sensitivity and lowest jitter Ge-on-Si SPAD detectors demonstrated. These planar geometry Ge-on-Si SPADs show potential for operation at Peltier cooled temperatures and easy integration into readily available Si SPAD circuitry as well as high efficiency single-photon detection. Further investigation was performed into altering the thickness of the germanium absorption layer within the Ge-on-Si devices and the results showed potential to improve the single-photon detection efficiency with a refined fabrication process by growing thicker Ge layers to increase the absorption of SWIR photons. A selection of avalanche photodiodes fabricated in the alternative material system of InGaAsSb/GaSb and AlGaAsSb/GaSb were also investigated for operation in the short-wave infrared region

Geiger Mode Ge-on-Si Single-Photon Avalanche Diode Detectors

High efficiency single photon avalanche detectors (SPADs) based on the Ge-on-Si material system are a promising emerging technology for high sensitivity optical detection in the short-wave infrared region. Here we demonstrate record single photon detection efficiencies of 38% at 1310nm with an operating temperature of 125K. This was achieved using a novel planar geometry which allowed us to achieve an NEPs of 3×10 −16 WHz −1/2 and reduced afterpulsing when compared to InGaAs/InP based SPADs operated in nominally identical conditions

Ge-on-Si Single Photon Avalanche Diode Detectors for LIDAR in the Short Wave Infrared

Ge-on-Si single photon avalanche diodes are used to demonstrate LIDAR in laboratory conditions. Modelling demonstrates that eye-safe kilometre range-finding is achievable at 1450nm wavelength. Afterpulsing is found to be considerably lower than commercial InGaAs/InP devices

Does Choose & Book fail to deliver the expected choice to patients? A survey of patients' experience of outpatient appointment booking

Provisional abstract: Background: Choose and Book is a central part of the UK Government patient choice agenda that seeks to provide patients with a choice over the time, date and place of their first outpatient appointment. This is done through the use of a computerised booking system. After a 2004 pilot study, Choose and Book was formally launched in January 2006. This is the first study of patient experience of Choose and Book since then. Methods: A questionnaire survey of reported experience of choice over the time, data and place of appointment, carried out in a National Health Service hospital in London. 104 patients at their first outpatient appointment completed the questionnaire, consisting of a consecutive series of patients referred through Choose and Book and a sample referred through the conventional booking system. Results: Among the Choose and Book patients, 66% (31/47; 95% CI 52 to 78%) reported not being given a choice of appointment date, 66% (31/47; 95% CI 52 to 78%) reported not being given a choice of appointment time, 86% (37/43; 95% CI 74 to 94%) reported being given a choice of fewer than four hospitals in total and 32% (15/47; 95% CI 20 to 46%) reported not being given any choice of hospital. Conclusions: In this study, patients did not experience the degree of choice that Choose and Book was designed to deliver

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Planar Geometry Ge-on-Si SPAD Detectors for the Short-wave Infrared

We present innovative planar geometry Ge-on-Si single-photon avalanche diode (SPAD) detectors. These devices provide picosecond timing resolution for applications operating in the short-wave infrared wavelength region such as quantum communication technologies and three-dimensional imaging. This new planar design successfully reduces the undesirable contribution of surface defects to the dark current. This has allowed for the use of large excess biases, resulting in a single-photon detection efficiency of 38% when operated at 125 K using 1310 nm wavelength illumination. A record low noise equivalent power of 2 × 10-16 WHz-1/2 was achieved, more than a fifty-fold improvement compared to the previous best Ge-on-Si mesa geometry SPADs when operated under similar conditions. These Ge-on-Si SPAD detectors have operated in the range of 77 K to 175 K, and we will discuss ways in which the operating temperature can be raised to that consistent with Peltier cooling. We will present analysis of Ge-on-Si SPADs, which has revealed much reduced afterpulsing compared with SPAD detectors in other material systems. Laboratory trials have demonstrated these Ge-on-Si SPAD devices in short-range LIDAR and depth profiling measurements. Estimations of the performance of these detectors in longer range measurements will be presented. We will discuss the potential for the development of high efficiency arrays of Ge-on-Si SPADs for the use in eye-safe automotive LIDAR and quantum technology applications

Ge-on-Si Single-Photon Avalanche Diode Detectors with Low Noise Equivalent Power in the Short-Wave Infrared

Single-Photon Avalanche Diode (SPAD) detectors are of significant interest for a range of applications [1] , in particular for quantum technologies (e.g. quantum-key distribution, quantum information processing), and light detection and ranging (LIDAR) for defence, terrain mapping, and autonomous vehicles. These applications either require, or benefit from, operation at wavelengths in the short-wave infrared (SWIR). Previous SWIR single-photon LIDAR has typically used InGaAs/InP SPAD detector technology, which has relatively low efficiency and suffers from afterpulsing. Previously, a pseudo-planar design for a Ge-on-Si SPAD was demonstrated [2] , yielding a huge improvement in performance for Ge-on-Si SPADs at 1310 nm and demonstrating the potential for Si foundry compatible SWIR SPADs. Furthermore, reduced afterpulsing was demonstrated compared to a commercial InGaAs/InP device when measured in nominally identical conditions. Here we present a further step change in performance, with reduced dark count rate (DCR), record low noise-equivalent-power (NEP) and low jitter by scaling the technology and developing 26 µm diameter pixels [3]

Effect of Antiplatelet Therapy on Survival and Organ Support–Free Days in Critically Ill Patients With COVID-19

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