Electric Vector

The electric field associated with a light wave which has both direction and amplitude.

Electromagnetic Radiation

The propagation of varying electric and magnetic fields through space at the velocity of light.

Electromagnetic Spectrum

The range of frequencies and wavelengths emitted by atomic systems. The total spectrum includes radio waves as well as short cosmic rays. Frequencies cover a range from 1 Hz to perhaps as high as 10²⁰ Hz.

Electromagnetic Wave

A disturbance which propagates outward from an electric charge that oscillates or is accelerated. Includes radio waves; X rays; gamma rays; and infrared, ultraviolet, and visible light.

Electron

Negatively charged particle of an atom.

Embedded Laser

A laser with an assigned class number higher than the inherent capability of the laser system in which it is incorporated, where the system's lower classification is appropriate to the engineering features limiting accessible emission.

Emission

Act of giving off radiant energy by an atom or molecule.

Emissivity

The ratio of the radiant energy emitted by any source to that emitted by a blackbody at the same temperature.

Enclosed Laser Device

Any laser or laser system located within an enclosure which does not permit hazardous optical radiation emission from the enclosure. The laser inside is termed an "embedded laser."

Energy (Q)

The capacity for doing work. Energy is commonly used to express the output from pulsed lasers and it is generally measured in Joules (J). The product of power (watts) and duration (seconds). One watt second = one Joule.

Energy Source

High voltage electricity, radio waves, flashes of light, or another laser used to excite the laser medium.

Enhanced Pulsing

Electronic modulation of a laser beam to produce high peak power at the initial stage of the pulse. This allows rapid vaporization of the material without heating the surrounding area. Such pulses are many times the peak power of the CW mode (also called "Superpulse").

Excimer

A gas mixture used as the active medium in a family of lasers emitting ultraviolet light.

Excitation

Energizing a material into a state of population inversion.

Excited State

Atom with an electron in a higher energy level than it normally occupies.

Extended Source

An extended source of radiation can be resolved into a geometrical image in contrast with a point source of radiation, which cannot be resolved into a geometrical image. A light source whose diameter subtends a relatively large angle from an observer.