Hi,
There is another technologies for photon counting technologies:
Channel Photomultipliers (CPMs) – A CPM is actually an advanced monolithic version of the traditional
glass photomultiplier tube (PMT), which can also be used to count photons. Photons entering the CPM
produce electrons that are accelerated toward an anode through a multi-curved, semi-conductive vacuum
channel. As the electrons hit the channel walls, secondary electrons are produced, which, in turn, produce
still more. This creates an avalanche effect much like the APD.
Also, Charged Coupled Devices (CCDs) – A CCD is an array of ordinary (non-avalanche) photodiodes that
feeds information to a set of read-out electronics. Unlike other detectors, where each photon directly
generates a single count of electrons almost instantaneously, the electrons produced in a CCD first charge
a capacitor. Users can then read out the intensity of light, which is proportional to the amount of charge.
Although CCDs are not specifically designed for photon counting, they can perform this function when
thermo-electrically cooled to reduce dark current and noise.
Thanks