Technical Center



Technical Center: Laser Glossary of Terms



Lambertian Surface

An ideal diffuse surface whose emitted or reflected radiance (brightness) is dependent on the viewing angle.


An acronym for light amplification by stimulated emission of radiation. A laser is a cavity, with mirrors at the ends, filled with material such as crystal, glass, liquid, gas or dye. A device which produces an intense beam of light with the unique properties of coherence, collimation and monochromaticity.

Laser Accessories

The hardware and options available for lasers, such as secondary gases, Brewster windows, Q-switches, and electronic shutters.

Laser Controlled Area

(See Controlled Area.)

Laser Device

Either a laser or a laser system.

Laser Medium (Active Medium)

Material used to emit the laser light and for which the laser is named.

Laser Oscillation

The buildup of the coherent wave between laser cavity end mirrors producing standing waves.

Laser Product

A legal term in the U.S. See 21 CFR 1040.10, a laser or laser system or any other product that incorporates or is intended to incorporate a laser or a laser system.

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 (LSO)

One who has authority to monitor and enforce measures to the control of laser hazards and effect the knowledgeable evaluation and control of laser hazards.

Laser System

An assembly of electrical, mechanical, and optical components which includes a laser. Under the Federal Standard, a laser in combination with its power supply (energy source).

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.


A curved piece of optically transparent material which depending on its shape is used to either converge or diverge light.


The range of electromagnetic radiation frequencies detected by the eye, or the wavelength range from about 400 to 760 nanometers. The term is sometimes used loosely to include radiation beyond visible limits.

Light Regulation

A form of power regulation in which output power is monitored and maintained at a constant level by controlling discharge current.

Limiting Angular

Subtense The apparent visual angle which divides intrabeam viewing from extended-source viewing.

Limiting Aperture

The maximum circular area over which radiance and radiant exposure can be averaged when determining safety hazards.

Limiting Exposure Duration

An exposure duration which is specifically limited by the design or intended use(s).

Longitudinal or Axial Mode

Determines the wavelength bandwidth produced by a given laser system controlled by the distance between the two mirrors of the laser cavity. Individual longitudinal modes are produced by standing waves within a laser cavity.

Lossy Medium

A medium which absorbs or scatters radiation passing through it.


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