Photon counting is the technique of choice for attaining the ultimate sensitivity in optical signal measurements. Started and developed with photomultiplier tubes, it received new impulse from the introduction of microelectronic detectors, called Single-Photon avalanche Diodes SPAD. They combine typical advantages of microelectronics (small size, high reliability, ruggedness and suitability to integrated systems) with improved basic performance (high photon detection efficiency, low dark-counting rate, picosecond photon-timing and high counting-rate capability). The seminar will outline the evolution of SPAD devices and associated electronics and will illustrate some examples of recent applications, such as: analysis of DNA and proteins; single molecule spectroscopy; adaptive optics in modern telescopes; non-invasive testing of ULSI circuits.

Sergio Cova is Full Professor of Electronics since 1977 at Politecnico di Milano, Italy, where he had received a doctor degree in Nuclear Engineering in 1962. Life Fellow of the IEEE. He has given contributions to research and development of detectors for optical and ionizing radiations, of microelectronic devices and circuits, of electronic and optoelectronic measurement instrumentation systems. In this frame he carried out also interdisciplinary work in collaboration with researchers in physics, astronomy, biochemistry and molecular biology. He pioneered the development of silicon Single-Photon Avalanche Diodes (SPAD) and the extension of photon counting techniques to the infrared spectral range with devices in germanium and III-V semiconductors. He invented the Active-Quenching Circuit (AQC) that opened the way to the application of SPADs and developed it up to monolithic integrated form. He is author of over 180 papers in international journals and conferences and of 5 international patents (USA and EU). In 2005 he established with other colleagues the university spin-off company MPD Micro-Photon-Devices.