Glossary

Wavelength ( of a light wave ): distance between two consecutive identical states of the electric ( or magnetic ) field
Photodetector: device sensitive to light and converting the absorbed photons into a signal, in most cases into an electrical signal
Bandwidth: width ( expressed in frequency or wavelength unit ) of the spectrum in which a phenomenon is supposed to happen
Shot noise: electronic noise caused by the random motion fluctuations of charge carriers (electrons) in a conductor; in a photodetector, the shot noise is partly intrinsic and partly coming from the photon noise