Abstract
The word LASER is an acronym for Light Amplification by Stimulated Emission of Radiation. The principle of stimulated emission of radiation is not a new one for it was first described by Albert Einstein in 1917 in his publication The Quantum Theory of Radiation. However, it was not until 1954 that Gordon et al, described how stimulated emission of radiation could be achieved in the microwave range of the spectrum. This was known as the MASER (Microwave Amplification by Stimulated Emission of Radiation). In 1958 Schawlow and Townes extended the principle of the maser into the optical frequency range and in 1960 Maiman created the first working ruby laser. In 1961 Bennett et al, produced the first gas laser, the helium-neon (He-Ne) laser and also in the same year the neodymium-yttrium-aluminium-garnet (Nd-YAG) laser was developed.
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