The current that flows through a photosensitive device, such as a photodiode, as the result of exposure to radiant power. Note 1: The photocurrent may occur as a result of the photoelectric, photoemissive, or photovoltaic effect. Note 2: The photocurrent may be enhanced by internal gain caused by interaction among ions and photons under the influence of applied fields, such as occurs in an avalanche photodiode (APD. )