Excimer laser

An excimer laser produces ultraviolet pulses from short-lived excited molecular complexes, typically formed from a noble gas and a halogen. Its gain medium emits light when those complexes decay into repulsive ground states.

Excimer: An excited molecular complex that is stable only in an excited electronic state and dissociates after returning to its ground state. The laser’s gain medium consists of these short-lived complexes.
Photolithography: A patterning process that uses light to transfer circuit designs onto a photosensitive surface. Excimer wavelengths define fine features in semiconductor fabrication.
Noble gas: An element in group 18 of the periodic table, characterized by a filled outer electron shell. Noble-gas atoms form the excited complexes in common excimer laser mixtures.
Nd:YAG laser: A solid-state laser that uses neodymium-doped yttrium aluminum garnet as its gain medium. Unlike an excimer laser, it generates light from an excited solid crystal.
Population inversion: A condition in which more particles occupy an excited state than a lower-energy state capable of absorbing the same radiation. Excimer formation creates the excited-state population needed for optical gain.
LASIK: A refractive eye surgery that reshapes the cornea with a laser to correct vision. Excimer lasers remove corneal tissue with controlled ultraviolet pulses.
Halogen: An element in group 17 of the periodic table, including fluorine and chlorine. A halogen partner helps form the emitting molecular complex.
Carbon dioxide laser: A gas laser that emits primarily infrared radiation from carbon dioxide molecules. Its infrared output and thermal cutting behavior differ from excimer ultraviolet ablation.
Stimulated emission: The process by which an incident photon prompts an excited atom or molecule to emit a matching photon. It amplifies ultraviolet light as excimer molecules decay.
Photorefractive keratectomy: A refractive surgery that reshapes the corneal surface after removing its outer epithelial layer. It uses excimer ablation without creating a corneal flap.

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