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. The 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 maser (a laser made up of micro-waves), and this in turn helped to produce more advances in this area of science. These efforts cumulated in July 1960 when Theodore H. Maiman announced the generation of a pulse of coherent red...
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