Photon counting imaging in the infrared with e-APD arrays

Since the first photon counting systems in the visible, developped by Boksenberg and his collabortors in 1972, many groups around the world improved photon counting techniques. In the 2000's in the visible, EMCCDSs (electron multiplying charge coupled devices) allowed to replace the classical image intensifier photon counting systems by solid state devices and improved a lot the QE. But EMCCDs suffer from several issues, and the most important of them is the excess noise factor which prevents to know what is the exact incoming number pf photons in the case of multiple photons per pixel. In the infrared there was no equivalent to EMCCDs up to the development of e-APD sensors and cameras made with HgCdTe material (electron initiated avalanche photo diode). We will present the concepts of photon counting in the infrared with such devices and the main properties and advantages of infrared e-APDs compared to their visible counterpart, EMCCDs and the possibility to detect the photon energy (color) with such devices.