= Laser diode
A <laser diode> is an electrically injected <semiconductor laser>. Forward <biasing> supplies <electrons> and <electron holes> to an active region, where radiative recombination can amplify a compatible optical mode by <stimulated emission>.
Reflecting facets or other cavity structures provide feedback. Below the <laser threshold>, emission is dominated by spontaneous processes; above it, stimulated emission into resonator modes becomes important. A <light-emitting diode> can also use carrier recombination but does not require this feedback-and-gain threshold. Output power, emitted spectrum and terminal <current-voltage characteristic> together characterize the device more fully than brightness alone.
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