A gas laser in which a very short electrical pulse excites a mixture containing a halogen such as fluorine and a rare gas such as argon or krypton. It produces a brief, intense pulse of ultraviolet light. The output of an excimer laser is used for writing patterns on semiconductor chips, because the short wavelength can write very fine lines. In fiber optics, it is used to write fiber Bragg gratings. See
ultraviolet light.