Essay/Term paper: Lasers

Essay, term paper, research paper:  Information Technology

Lasers


The laser is a device that a beam of light that is both scientifically
and practically of great use because it is coherent light. The beam is produced
by a process known as stimulated emission, and the word "laser" is an acronym
for the phrase "light amplification by stimulated emission of radiation."

Light is just like radio waves in the way that it can also carry
information. The information is encoded in the beam as variations in the
frequency or shape of the light wave. The good part is that since light waves
have much higher frequencies they can also hold much more information.

Not only is the particle the smallest light unit but it is a particle as
well as a wave. In beams of light whether they are ordinary natural or
artificial the photon waves will not be traveling together because they are not
being emitted at exactly the same moment but instead at random short bursts.
Even if the light is of a single frequency that statement would also be true. A
laser is useful because it produces light that is not only of essentially a
single frequency but also coherent, with the light waves all moving along in
unison.

Lasers consist of several components. A few of the many things that the
so-called active medium might consist of are, atoms of a gas, molecules in a
liquid, and ions in a crystal. Another component consists of some method of
introducing energy into the active medium, such as a flash lamp for example.
Another component is the pair of mirrors on either side of the active medium
which consists of one that transmits some of the radiation that hits it. If the
active component in the laser is a gas laser than each atom is characterized by
a set of energy states, or energy levels, of which it may consist. An example
of the energy states could be pictured as a unevenly spaced ladder which the
higher rungs mean higher states of energy and the lower rungs mean lower states
of energy. If left disturbed for a long time the atom will reach its ground
state or lowest state of energy. According to quantum mechanics there is only
one light frequency that the atom will work with. There are three ways that the
atom can deal with the presence of light either it can absorb the light, or
spontaneous emission occurs, or stimulated emission occurs. This means that if
the atom is at its lowest state that it may absorb the light and jump to its
high state and emit extra light while doing so. The second thing it may do is
if it is at its highest state it can fall spontaneously to its lower state thus
emitting light. The third way is that the atom will jump from its upper state
to its lower state thus emitting extra light. Spontaneous emission is not
effected by light yet it is rather on a time scale characteristic of the states
involved. That is called the spontaneous lifetime. In stimulated emission the
frequency of the light is the same as the frequency of the light that stimulated
it.

Carbon-monoxide, color center, excimer, free-electron, gas-dynamic,
helium-cadmium, hydrogen-fluoride, deuterium-fluoride, iodine, Raman spin-flip,
and rare-gas halide lasers are just a few of the many types of lasers there are
out there in the world. The helium-neon laser is the most common and by far the
cheapest costing about $170. The diode laser is the smallest being packed in a
transistor like package. The dye laser are very good for their broad,
continuously variable wavelength capabilities.

The theory of stimulated emission was first proved by Albert Einstein in
1916, then population inverse was discussed by V. A. Fabrikant in 1940. This
led to the building of the first ammonia maser in 1954 by J. P. Gordon, H. J.
Zeiger, and Charles H. Townes. In July of 1960 Theodore H. Maiman announced the
generation of a pulse of coherent red light by means of a red crystal- the first
laser. In 1987 Gordon Gould won a patent he had been trying to get for three
years to build the first gas-discharged laser which he had conceived in 1957.
In that same patent the helium-neon was included.

Bibliography:

Bertolotti, M., Masers and lasers: An Historical Approach (1983);
Kasuya, T., and Tsukakoshi, M., Handbook of Laser Science and Technology (1988);
Meyers,Robert, ed., Encyclopedia of Lasers, 3d ed. (1989);
Steen, W. M., ed., Lasers in Manufacturing (1989);
Whimmery, J. R., ed., Lasers: Invention to Application (1987);
Young, M., Optics and Lasers, 3d rev. ed. (1986).