We have all at some point in our lives used or seen someone use a laser.

They are used in compact disc players for stereos or computers, laser surgery,
laser printers, holography, cutting and borring metals, communication, bar-code
scanners, etc. Over the past three decades’ lasers have become a tool used
daily by many people and they have become very useful in scientific research.

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As you can see lasers are a very useful and important tool which is why I have
chosen this topic to write about.


The term laser is an acronym. It stands for “light amplification by
stimulated emission of radiation”. They produce a narrow, intense beam of
coherent light.


In a laser the atoms or molecules of a crystal, like ruby or garnet-or
of a gas, liquid, or other substance-are excited so that more of them are at
higher energy levels than are at lower energy levels. 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 frequency, in phase
with and in the same direction as the bombarding photon. This process is
called stimulated emission. The bombarding photon of the emitted photon may
then 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. The
light beam produces is usually pencil thin and maintains its size and direction
over very long distances.


Lasers vary greatly in the way they look and what they are used for.

Some lasers are as large as buildings while others can be the size of a grain
of salt.


There are many parts to lasers. I will now explain what they are and
their uses.


1) Pumping systems:
The pumping system is used to transmit energy to the atoms or molecules
of the medium used in the laser.


a. optical pumping systems uses photons provided by a source such as a Xenon
gas flash lamp or another laser to transfer energy to the lasing material. The
optical source must provide photons which correspond to the allowed transition
levels of the lasing material.


b. collision pumping relies on the transfer of energy to the lasing material by
collision with the atoms or molecules of the lasing material. Again, energies
which correspond to the allowed transition must be provided. This
often done by electrical discharge in a pure gas – or gas mixture – in a tube.


c. chemical pumping systems use the binding energy released in chemical
reactions to raise the lasing material to the metastable state.


2) Optical Cavity:
An optical cavity is required to provide the amplification desired in the
laser and to select the photons which are traveling in the desired direction.

As the first atom or molecule in the metastable state of the inverted
population decays it triggers (by stimulated emission) the decay of another
atom or molecule in the metastable state.


3) Laser Media:
Lasers are usually classified by the lasing material used by the laser. There
are four types which are solid state, dye, gas and semiconductor.


a. solid state lasers employ a lasing material distributed in a soloid matrix
sytem. Accessory devices which may be internal or external may be used to
convert the output .


b. gas lasers use a gas or a mixture of gas within a tube. The most common gas
laser uses a mixture of helium and neon with a pimary output of 632.8 nm which
is a red visible colour.


c. dye lasers use a laser medium that is ususally a complex organic dye in a
liquid solution or suspension. The most striking feature of these lasers is
their “tunability”. Proper choice of the dye and it’s concentration allows
production of laser light over a broad range of wavelength in or near the
visible spectrum.


d. semiconductor lasers are not to be confused with solid state lasers.

Semiconductor devices consist of two layers of semiconductor material sandwiched
together.


Laser Applications
Laser Surgery
The small, intense, bright beam of light can be focused with lenses to provide
a point of energy intense enough to burn through living flesh.


Laser Welding, Cutting & Blasting
Once again the laser’s intense energy when focused make it ideal for providing
concentrated welding and cutting.


Laser Shows
The intense color of laser light has opened up a whole new world for laser
artists to weave a new kind of art using different coloured lenses, mirrors and
crystals.


Power Generation
Laser-powered fusion holds hope of generating tremendous amounts of electricity
through the use of lasers.


Information Technology
Using fiber optic bundles to carry them, modulated laser beams can transfer
huge amounts of information(internet). Lasers in compact disc players read tiny
reflections on CD’s and laser discs to play back audio and video. Someday your
house could be fitted with fiber optics to carry cable tv and phone service.


Category: Science