Lasers

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Lasers

The light from lasers differs from ordinary light in several important aspects. Ordinary light
from a light bulb travels randomly in all directions (unless the bulb is equipped with an integral
reflector that directs the light). The light is thus incoherent. Even when incoherent light is
directed with a reflector, it still spreads rapidly.
The light from a laser is temporary and spatially coherent. This means that all of the
wave-fronts of light are lined up in time and space (see Diagrams). The waves of light go up and
down in sync, and travel in the same direction.
Coherent light spreads less than other types of light. For example the beam of a tightly focused
flashlight would spread between 2 degrees and 5 degrees over a 3 meter (10 ft) throw distance.
The sides of a laser beam are almost parallel but the light still spreads slightly. This spread is
called divergence and is measured in milliradians (mrad). If a laser has a specified divergence
of 5 mrad, then in the above example with a 3 meter throw (10 ft), a laser beam will spread only
about 3/20 of a degree.

This is a simplified explanation of the process of stimulated emission. If you are interested in
more detailed information about this subject, you should consult a science or physics book.
Let us take the HeNe laser as an example. If a glass tube were filled with a mixture of helium
and neon gas; and an electrical current were applied to the electrodes, the gas would emit light
energy. T...

Submitted by: digitalessays
Date Submitted: 08-11-98 5:00pm
Category: Social Issues
Words: 1112
Pages: 4.45