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We present the design and simulations of a singlephoton sensitive imager based on Single Photon Avalanche Diodes (SPADs) with an innovative pixel architecture that includes 4 separate SPADs with independent active time-gating and quenching circuit, a shared Time-to-Digital Converter (TDC) with 50 ps resolution, 4 independent photon counters, and multiple operation modes. The TDC is driven by smart arbitration logic, which preserves spatial information among the 4 detectors; furthermore, an alternative operation mode exploits photoncoincidence on multiple detectors to reduce the effect of high background levels, e.g. in LIDAR applications with strong ambient light.Key features are the ability to operate in simultaneous photon counting and timing modes for capturing 2D and 3D images of the scene in a single shot (frame), the option of a counting-only mode, reducing power consumption and increasing achievable framerate when timing information is not needed, and the ability to individually shut down noisy detectors or to enable just some regions of interests.

Speckle contrast optical spectroscopy (SCOS) measures absolute blood flow in deep tissue, by taking advantage of multi-distance (previously reported in the literature) or multiexposure (reported here) approach. This method promises to use inexpensive detectors to obtain good signal-to-noise ratio, but it has not yet been implemented in a suitable manner for a mass production. Here we present a new, compact, low power consumption, 32 by 2 single photon avalanche diode (SPAD) array that has no readout noise, low dead time and has high sensitivity in low light conditions, such as in vivo measurements. To demonstrate the capability to measure blood flow in deep tissue, healthy volunteers were measured, showing no significant differences from the diffuse correlation spectroscopy. In the future, this array can be miniaturized to a low-cost, robust, battery operated wireless device paving the way for measuring blood flow in a wide-range of applications from sport injury recovery and training to, on-field concussion detection to wearables.

Proportional electroluminescence (EL) in noble gases is used in two-phase detectors for dark matter searches to record (in the gas phase) the ionization signal induced by particle scattering in the liquid phase. The “standard” EL mechanism is considered to be due to noble gas excimer emission in the vacuum ultraviolet (VUV). In addition, there are two alternative mechanisms, producing light in the visible and near infrared (NIR) ranges. The first is due to bremsstrahlung of electrons scattered on neutral atoms (“neutral bremsstrahlung”, NBrS). The second, responsible for electron avalanche scintillation in the NIR at higher electric fields, is due to transitions between excited atomic states. In this work, we have for the first time demonstrated two alternative techniques of the optical readout of two-phase argon detectors, in the visible and NIR range, using a silicon photomultiplier matrix and electroluminescence due to either neutral bremsstrahlung or avalanche scintillation. The amplitude yield and position resolution were measured for these readout techniques, which allowed to assess the detection threshold for electron and nuclear recoils in two-phase argon detectors for dark matter searches. To the best of our knowledge, this is the first practical application of the NBrS effect in detection science.