Avalanche Photodetector. The solid-state equivalent of a PMT, usually restricted to operation in the red, near-infrared and infrared part of the spectrum. For photon-counting applications, they are operated in the so-called 'Geiger Mode'. The device is noisier than a PMT but has greater quantum efficiency. Maximum quantum efficiencies are about 8...
Australian Private Doctor [periodical, périodique]
Adult polycystic disease
Avalanche Photo Diode. A type of detector used in fibre optic receivers.
USN designation for Fast Destroyer Transport [US]