L

Lambertian surface

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

Laser

An acronymn for light amplification by stimulated emission of radiation. A cavity with mirrors at the ends, filled with material such as crystal, glass, liquid, gas, or dye. A device that produces an intense beam of light with the unique properties of coherency, collimation, and mono-chromaticity.

Laser medium

Also known as active medium. Material used to emit 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 affect the knowledgeable evaluation and control of laser hazards.

Laser system

An assembly of electrical, mechanical, and optical components that 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.

Lens

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

LIDAR

An acronymn for light detection and ranging that describes a remote sensing technique that uses a laser beam to probe the characteristics of a surface target.

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 that 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 that is specifically limited by the design or intended use(s).

Linear polarization

With respect to radiation, a light beam in which the polarization direction is fixed.

Longitudinal mode

Also referred to as 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 that absorbs or scatters radiation passing through it.