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 radiowaves as well as short cosmic
rays. Wavelengths 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 systems
lower classification is appropriate to the engineering features limiting accessible
EMERGENT BEAM DIAMETER Diameter of the laser beam at the exit aperture of the
system in centimeters (cm) defined at e(-1) or e(-2) irradiance points.
EMISSION Act of giving off radiant energy by an atom or molecule.
EMISSIVITY The ratio of the radiant energy emitted by a any source to that
emitted by a blackbody at the same temperature.
EMITTANCE The rate at which emission occurs.
ENCLOSED LASER DEVICE Any laser or laser system located within an enclosure
whichdoes not permit hazardous optical radiation emission from the enclosure.
The laser inside is termed an "embedded laser."
ENERGY The product of power (watts) and duration (seconds). One watt second
= one Joule.
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, radiowaves, 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").
ETALON A Fabry-Perot interferometer with a fixed air gap separation. Such a
device also serves as a basic laser resonant cavity.
EXCIMER "EXCITED DIMER." 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
EXEMPTED LASER PRODUCT In the U.S., a laser device exempted by the U.S. Food
and Drug Administration from all or some of the requirements of 21 CFR 1040.
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.