LightEmitting

Lightemitting refers to the emission of light by a material as energy is released in the form of photons. It covers a range of processes in which electrons or excitations return to lower energy states, including spontaneous emission, stimulated emission, and electroluminescence. Light emission can be triggered by electrical, optical, chemical, or thermal stimulation, and is studied under the broader field of luminescence.

Spontaneous emission occurs when excited atoms or molecules decay naturally, emitting photons with characteristic wavelengths. Stimulated emission, in contrast, happens when an incoming photon induces an excited system to emit a second photon in phase with the first, a principle used in lasers and laser-related technologies. Electroluminescence is light produced by the passage of electric current through a material, a mechanism central to most modern lighting and display devices.

Common lightemitting materials include semiconductors used in light-emitting diodes (LEDs) and laser diodes, organic materials in organic light-emitting diodes (OLEDs), inorganic or organic phosphors for fluorescence, and scintillators used in radiation detection. Chemiluminescent and bioluminescent systems generate light through chemical reactions and are notable for low heat production and specialized applications.

Applications of lightemitting phenomena span general illumination, displays (television, smartphones, signage), signaling, medical imaging, optical sensing, and scientific instrumentation. Measurement of lightemitting performance involves quantities such as luminous flux, luminance, spectral power distribution, and efficiency metrics like luminous efficacy and external quantum efficiency.

See also luminescence, phosphor, LED, OLED, laser diode, and photoluminescence.