1. UCM-ELEC group Members involved in the work described here
Overall dedication: 1 FTE
Pedro Antoranz,
Dr. Engineer
Jose Miguel Miranda,
Professor
Julio Quesada,
Electronic Engineer
Jose Manuel Yebras,
Dr. Engineer

2. Pulse Shortening for large area devices
Hamamatsu
S C, 3x3 mm
Yebras J.M., Antoranz P., Miranda J.M., "Strategies for shortening the output pulse of Silicon Photomultipliers", Optical Engineering, vol. 51 (7), no (2012). doi:  /1.OE
Good afternoon. We have worked with silicon photomultipliers of Hamamatsu. On the one hand, we have tried to obtain a cheap characterization for them by using incoherent light sources. On the other hand, we have tried to enhance the Single Photon Counting pattern provided by the device ant its capability to work at high frequency. As you can see here, photopulse shortening has helped a lot to enhance the counting pattern when devices of large area are used. These devices provide poor results when they work alone. However, with shortening, more peaks, narrower and more intense are obtained. However, this strategy does not improve the intrinsic speed of the detector.
Yebras J.M., Antoranz P., Miranda J.M., “Single Photon Counting with Silicon Photomultipliers, shortening systems and incoherent illumination”, J. Europ. Opt. Soc. Rap. Public., vol. 7, no (2012). doi:  /jeos
Yebras J.M., “Use of Silicon Photomultipliers for high speed and low light intensity measurements”, PhD thesis,

3. Active quenching aiming to enhance SiPM frequency response
For improving the device speed several schemes for active quenching have been tested. Here you can see a circuit in which an important reduction of parasitic pulses is obtained. At bottom left you can see how the cathode voltage is fastly restored to the value that provides high gain and sensitivity. To the right you can see the enhancement obtained in photopulse amplitude when active quenching is used. And at top right you find that a good frequency response is extended up to tens of mega-hertzs.

4. SiPM characterization at different temperatures
1 pe charge for SiPM S C.
Dependence of breakdown voltage with temperature.
PDE dependence with bias voltage and temperature
Crosstalk dependence with bias voltage and temperature
Also, we have worked in silicon photomultiplier characterization. We have investigated the evolution of several parameters, like gain, photodetection efficiency, darkcounts, crosstalk and afterpulsing, as a function of the bias voltage and the temperature. These results have provided a way to estimate the elements in the equivalent circuit for the detector and a good agreement between simulations and experimental results were obtained. In this slide you can see some of our results. Photodetection efficiency and gain are directly proportional to overvoltage and inversely proportional to the temperature. Unfortunately, crosstalk and afterpulsing probability show the same dependencies. Finally, we have observed that single photon counting patterns for large area devices show much lower dependence with temperature variations when photopulse shortening is used. Thank you.
BOD150 for tests in the range [-10ºC, 70ºC]