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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).
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).
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