An acronym of Light Amplification by Stimulated Emission of Radiation. A laser is a cavity that has mirrors at the ends and is filled with lasable material such as crystal, glass, liquid, gas, or dye. These materials must have atoms, ions, or molecules capable of being excited to a metastable state by light, electric discharge, or other stimulus. The transition from this metastable state back to the normal ground state is accompanied by the emission of photons which form a coherent beam.

Laser Hardening

Laser-beam traversal of metal to harden quenching process producing the maximum hardness for most metals.

Laser Oscillation

The buildup of the coherent wave between laser cavity end mirrors. In CW mode, the wave bounding back and forth between mirrors transmits a fraction of its energy on each trip; in pulsed operation, emission happens instantaneously.

Laser Rod

A solid-state, rod-shaped lasing medium in which ion excitation is caused by a source of intense light, such as a flashlamp. Various materials are used for the rod, the earliest of which was synthetic ruby crystal.

Laser Safety Officer

Abbreviated LSO.   One who possess the authority and responsibility to monitor and to enforce the control of laser hazards and to effect the knowledgeable evaluation and control of laser hazards in order to establish a laser or laser system’s safe use.

Leading Edge Spike

The initial pulse in a series of pulsed laser emissions, often useful in starting a reaction at the target surface. The trailing edge of the laser power is used to maintain the reaction after the initial burst of energy.


The range of electromagnetic radiation frequencies detected by the eye, or the wavelength range from about 400 to 750 nanometers. It is sometimes extended to include photovoltaic effects and radiation beyond visible limits.


Commonly called illumination; the luminous or visible flux per unit area on a receiving surface at any given point.