Before we can learn about the laser we need to know a little bit about
light (since that is what a laser is made of). Light from our sun, or from an
electric bulb, is called white light. It is really a mixture of all the different
colours of light. The colours range from violet, indigo, and blue, to green,
yellow, orange, and red. These make up the visible part of the
electromagnetic spectrum. Light is made up of particles, called PHOTONS,
which travel in waves. The difference in the colour depends on the
wavelength of the light. Violet light has the shortest wavelength while red has
the longest. There are other parts of the electromagnetic spectrum which
includes infra-red, radar, television radio and micro- waves (past red on the
spectrum), and on the other end of the spectrum are the other invisible
radiations, ultra- violet, X rays, micro waves and gamma rays.
wavelength of the light is important to the subject of the laser. A laser is made
up of COHERENT light, a special kind of light in which the wavelengths of
the light are all the same length, and the crests of these waves are all lined up,
or in PHASE. The word Laser is an acronym for Light Amplification by
Stimulated Emission of Radiation. What does that mean? Basically a laser is a
device which produces and then amplifies light waves and concentrates them
into an intense penetrating beam.
The principles of the laser (and it's cousin the maser) were established
long before these devices were successfully developed. In 1916 Albert
Einstein proposed stimulated emission, and other fundamental ideas were
discussed by V.A. Fabrikant in 1940. These ideas, followed by decades of
intensive development of microwave technology set the stage for the first...