Abstract:
Laser stands for Light Amplification by Stimulated Emission of Radiation, was discovered in
1960. Laser light beam is different from normal light beam because of its high temporal and
narrow spectral bandwidth. Here amplification of light is achieved by a laser active medium
(gain medium). This medium is obtained by stimulated emission of photons from a lower
energy state to a higher energy state previously populated by a pump source. In order to start
the lasing active in the medium it must be in no thermal energy distribution known as
population inversion.
