The word laser is an
acronym for light amplification by
stimulated emission of radiation, although
common usage today is to use the word as a
noun -- laser -- rather than as an acronym
-- LASER.
A laser is a device that creates and
amplifies a narrow, intense beam of coherent
light.
Atoms emit radiation. We see it every day
when the "excited" neon atoms in a
neon sign emit light. Normally, they radiate
their light in random directions at random
times. The result is incoherent light -- a
technical term for what you would consider a
jumble of photons going in all directions.
The trick in generating coherent light --
of a single or just a few frequencies going
in one precise direction -- is to find the
right atoms with the right internal storage
mechanisms and create an environment in
which they can all cooperate -- to give up
their light at the right time and all in the
same direction.
Exciting atoms or molecules
In a laser, the atoms or molecules of a
crystal, such as ruby or garnet -- or of a
gas, liquid, or other substance -- are
excited in what is called the laser
cavity so that more of them are at
higher energy levels than are at lower
energy levels. Reflective surfaces at both
ends of the cavity permit energy to reflect
back and forth, building up in each passage.
(See figure below)
![[ animation showing
electrons reflecting off mirrors until the are excited enough to
exit as laser light ]](images/laser.gif)
In a ruby
laser, light from the flash lamp, in what is
called "optical pumping", excites
the molecules in the ruby rod, and they
bounce back and forth between two mirrors
until coherent light escapes from the
cavity.
If a photon whose frequency corresponds
to the energy difference between the excited
and ground states strikes an excited atom,
the atom is stimulated as it falls back to a
lower energy state to emit a second photon
of the same (or a proportional) frequency,
in phase with and in the same direction as
the bombarding photon.
This process is called stimulated
emission. The bombarding photon and the
emitted photon may then each strike other
excited atoms, stimulating further emission
of photons, all of the same frequency and
phase. This process produces a sudden burst
of coherent radiation as all the atoms
discharge in a rapid chain reaction.
Wide range of sizes and uses
First built in 1960, lasers now range in
size from semiconductor lasers as small as a
grain of salt to solid-state and gas lasers
as large as a storage building. The light
beam produced by most lasers is pencil-thin
and maintains its size and direction over
very large distances.
Lasers are widely used in industry for
cutting and boring metals and other
materials, in medicine for surgery, and in
communications, scientific research, and
holography. They are an integral part of
such familiar devices as bar-code scanners
used in supermarkets, scanners, laser
printers, and compact disk players.
Not sure of an application? We will be
happy to run a sample for you. Call today!
Altatech Laserworks
ph:
916.817.8334
or via e-mail:
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