High Resolution Optical Scans of Pixelated Silicon Avalanche Photodiodes

Pixelated avalanche photodiodes are increasingly used in applications where photomultiplier tubes have previously been employed. These pixelated avalanche photodiodes have 100's of pixels which each act as a single-photon detector. A high-resolution optical scanner has been constructed that can measure the uniformity of response of different pixels, the uniformity of response across individual pixels, and crosstalk between pixels on a single device. This scanner features a micron-sized photon beam and is able to position the photodiode with micron level precision. Initial measurements performed on a Hamamatsu multi-pixel photon counter (MPPC) will be presented.