When most
people see a laser beam they are amazed by its
unique physical properties. Laser light is so unique
from other light because it is coherent; unlike
ordinary light, which travels in all directions, laser
light travels in a straight beam. The word laser is
an acronym for Light Amplification by Stimulated
Emission of Radiation. The history of the laser is
very interesting. Lasers have changed immensely
since they were first invented. Before the laser was
invented, Charles Townes developed the maser in
1954. The maser has basically the same principles
as the laser, but it involves microwaves instead of
light. The maser lead Theodore Maximan to
assemble the first working laser in 1960; he did
this by applying the masers qualities to light. This
first solid-state laser was a ruby crystal laser. A
year after the first solid-state laser was invented,
the first gas laser was constructed by Ali Javan,
W. R. Bennett, and D. R. Herriot. This was a
helium-neon laser. The helium-neon laser is the
most common laser found today. Many other
types of lasers have been invented since then: the
semiconductor laser (1962), the chemical laser
(1964), the liquid laser (1966), and the free
electron laser (1977). All lasers work basically on
the same principles. First the atoms in the
substance used are pumped. For example, the
helium and neon would be pumped in a
helium-neon laser. This is where the electrons of
the atoms jump to higher orbitals, which have
more energy. The substance can be pumped by
using flashlamps, other lasers, atomic explosions,
electric discharges, solar energy, and etc... When
the atoms are pumped, they perform stimulated
emission. This is where the electrons are
stimulated by photons to release coherent photons
of a single frequency and color. After the pumping
process, the oscillation process takes place. In this
process energy is amplified to make it stronger
and more useful. This is done by bouncing the
photons between two mirrors until they reach a
certain intensity. The two mirrors are one of 100
percent efficiency and one of a lesser efficiency.
When the photons reach the certain intensity, they
leave the mirror of lesser efficiency in a coherent
beam. There are basically four main types of
lasers: solid-state, gas, liquid, and semi-conductor.
Solid-state lasers are made from a crystalline
material such as ruby. The crystals have impurities
in them that can be stimulated to release radiation
in a coherent fashion. These impurities are needed
to make the laser last for long periods of time. If
the crystals do not have impurities, then they can
have some added; this is called "doping." The
crystals in solid state lasers are usually pumped by
using flashlamps. Gas laser beams are much more
coherent than the beams of solid-state lasers. Gas
lasers are lasers that contain a tube of gas or a
mixture of gasses. The most common gas laser is
the helium-neon laser. Unlike solid-state lasers,
gas lasers are pumped by using electrical
discharges. Liquid lasers are usually filled with an
organic dye substance. These lasers allow
measurements to be taken on a scale never
thought possible. They can do this because they
can be flashed in pulses lasting only billionths of a
second. Liquid lasers are pumped in a very unique
way; they are pumped by using other lasers. The
ruby laser is the most commonly used for this
process. The semiconductor laser is the most
advanced of the four main types of lasers. These
lasers are able to be made smaller than any other
type of laser. This is because the semiconducting
substance used can be smaller than a grain of salt.
The most common semiconductor used in these
lasers is gallium arsenide. This type of laser is the
kind that is used for fiber optic communications.
Because there are so many types of lasers, they
can be used to do a variety of things. One thing
they can be used for is the measurement of
distance and motion. Lasers are great for this
because their frequencies are very sensitive to
motion; they can sense even the smallest of
movements. Lasers can be used for measurement
by comparing their wavelengths with a specific unit
of measurement. There are devices that can
measure the number of wavelengths in a desired
area, so they can be converted into a different unit.
Lasers are great for the measurement of optical
components such as lenses and prisms. Lasers are
also used a lot in industry. Cutting is one of the
applications of lasers in industry. Laser beams can
be focused into a very small spot that is of high
power. The laser can then be used to cut materials
that are to small, hard, or thick to be cut in any
other way; the cuts are also very accurate. Laser
are also used in industry during constructions and
land surveys.