Lase

Lase is a verb meaning to emit light produced by a laser, i.e., to undergo lasing. Lasing is the process by which light is amplified by stimulated emission of radiation in a gain medium, yielding light that is coherent, monochromatic, and highly directional.

In a typical laser, energy is supplied to a gain medium (which may be solid, liquid, or gas) by optical, electrical, or chemical pumping, creating a population inversion. Photons within the medium stimulate excited particles to emit additional photons with the same phase and frequency. The optical cavity, formed by mirrors or through feedback mechanisms, provides amplification and spectral selectivity. When the optical gain exceeds losses, the device begins to lase and emits a beam of coherent light.

The term 'lase' and the noun 'lasing' arose from the development of the first lasers in the 1960s. In common usage the verb is primarily found in technical contexts; to lase describes the act of emitting laser light rather than the static state.

Lasing underpins a wide range of technologies. Applications include materials processing (cutting, welding), medicine and surgery, telecommunications and data transmission, sensing and spectroscopy, and scientific instrumentation.