VACUUM PHOTODIODES

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VACUUM PHOTODIODES 1- Definition . Vacuum photodiode is a photo detector that utilize the external photoelectric effect. . External photoelectric effect: Generation of free electrons when photons strike the surface of a metal. Electrons are emitted from the surface. . Photo detector is a device which absorbs light and converts the optical energy to

measurable electric current.

Circuit schematic of vacuum photodiode.

Principles of Photo-detection of vacuum photodiodes: Vacuum photodiodes work on the principle of conversion of photons to electrons. Electrons are freed from the surface of metal by the energy absorbed from an incident stream of photons. However, it may absorb photons only if the energy of

incident photons is above a certain minimum threshold. Principles and Operation mode of vacuum photodiodes : Vacuum photodiodes operate on the photoelectric effect: sufficiently energetic photons strike a metal plate, called the cathode, and eject electrons that are then collected at the anode as shown in the figure below. The resulting current is measured and gives an estimate of the incident photon flux.


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