Photon-counting arrays for spatially varying low-light-level signals

The capability of combining single photon counting with information on the spatial distribution of incoming photons is of great interest to many scientific disciplines such as astronomy and spectroscopy, where an accurate assessment of this information can be critical to the success of an experiment. Photomultiplier arrays and scintillators are usually used in these applications. However these electromechanical solutions need to be operated at high voltages (approximately kV), they tend to be very fragile, bulky and extremely expensive. A solution to this problem which utilizes silicon integrated circuit technology would alleviate a lot of these undesirable effects and would be low cost, small area and more robust. This makes the concept of a solid state photon counting array very attractive for a large number of applications. To date this has not been achieved because of the difficulties involved in integrating high voltage optical detectors into an integrated circuit. This paper shows how this can be achieved and indicates areas of future research which will enable the possibility of large area and high pixel count spatially resolved photon counting devices.