What happens when you shine a laser on a light-emitting diode

Driven by voltage, the doped p–n-transition allows for recombination of an electron with a hole. Due to the drop of the electron from a higher energy level to a lower one, radiation is generated in the form of an emitted photon. The laser diode chip is the small black chip at the front; a photodiode at the back is used to control output power. All of these everyday devices are powered by a beautiful and bizarre principle of physics: how atoms. There are several variations of construction used for laser diodes, each aimed at achieving the maximum efficiency for converting electric current into laser light. It works on the same basic principle as an LED, but with an internal structure that for...