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OCR for page 133
Gl
*Bandwidth The difference between the frequency limits of a
band containing the useful frequency components of a signal.
Coherent light—Radiant electromagnetic energy of the same,
or almost the same, wavelength, and with definite phase
relationships between different points in the field.
*Continuous wave laser A laser in which the beam of coherent
light is generated continuously, as required for communica-
tion and certain other applications.
Dispersion In laser telecommunication, the spreading or
broadening of light pulses as they pass through an optical
fiber. Dispersion limits the rate at which light carrier pulses
can be transmitted and decoded without error.
*Electro-optics—The study of the influence of an electric field
on optical phenomena. See optoelectronics.
*Excimer laser- A laser containing a noble gas, such as helium
or neon, which is based on a transition between an excited
state in which a metastable bond exists between two gas atoms
and a rapidly dissociating ground state.
*Gas laser- A laser in which the active medium is a discharge in
a gas contained in a glass or quartz tube with a Brewster-angle
window at each end; the gas can be excited by a high-frequency
oscillator or direct-current flow between electrodes inside the
tube; the function of the discharge is to pump the medium, to
. . . .
O stain popu. .atlon inversion.
*SOURCE: McGraw-Hill Dictionary of Scientific & Technical Terms, 3rd ea.,
1984. New York: McGraw-Hill. Reprinted with permission.
_~
133
OCR for page 134
1 34 GLOSSARY
1
*Hydrogen maser -A maser in which hydrogen gas is the basis
for providing an output signal with a high degree of stability
and spectral purity.
*Klystron An evacuated electron-beam tube in which an initial
velocity imparted to electrons in the beam results subse-
quently in density modulation of the beam; used as an
amplifier or oscillator for microwave radiation.
Laser A device that uses the maser principle of amplification of
electromagnetic waves by stimulated emission of radiation and
operates in the ultraviolet, optical, or infrared region of the
spectrum. Derived from light amplification by stimulated
. . ~ . . .
emlsslon ot raulatlon.
*Laser spectroscopy—A branch of spectroscopy in which a laser
is used as an intense, monochromatic light source.
Maser An acronym formed from microwave amplification by
stimulated emission of radiation.
Molecular beam epitaxy A technique for growing single crys-
tals of compound semiconductor thin films through the mol-
ecule-by-molecule deposition of material from a molecular
beam. The structure of the film is determined by the crystal
structure and orientation of the underlying substrate.
Neodymium-g~ass laser A laser that produces intense light
pulses in the near-infrared portion of the spectrum, specifi-
cally with a wavelength of about 1 Em.
*Optical fiber—A long, thin thread of fused silica, or other
transparent material, used to transmit light. Also known as a
light guide.
*Optoelectronics The branch of electronics that deals with solid-
state and other electronic devices for generating, modulating,
transmitting, and sensing electromagnetic radiation in the ultra-
violet, visible-light, and infrared portions of the spectrum.
*Quantum electronics The branch of electronics associated
with the various energy states of matter, motions within atoms or
groups of atoms, and various phenomena in crystals. Practical
applications include the atomic hydrogen maser and the cesium
atomic-beam resonator.
*Ruby laser An optically pumped solid-state laser using a ruby
crystal (A1203) doped with chromium (Cr+3) impurities. Laser
emission occurs in the red part of the optical spectrum.
Semiconductor laser—A laser in which stimulated emission of
coherent light occurs in a semiconductor when excited by
carrier injection, electron-beam excitation, impact ionization,
optical excitation, or other means. The most common form is
the diode laser, in which electrons and holes are driven into a
pn junction and combine there.
Representative terms from entire chapter:
molecular beam
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