Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. It is a technique of producing intense beams of light, ultraviolet or infrared radiation of almost a single wavelength. The unique thing about laser radiation is that not only have they the same wavelength, but all waves travel in phase, like soldiers marching in step. This makes a laser beam so intensely energetic that it can drill a hole, even in diamond, instantly.
A laser works by first pumping energy, in the form of a flash of light, into a collection of atoms, and then forcing the excited atoms to lose energy in the form of light, which appears as a coherent beam. The principle is quite simple. When the atoms in the laser material, which may be a solid, liquid or gas, are excited to a higher state, they can be made to return to the ground state by absorbing radiation of a particular wavelength. In a laser this process goes on till the beam is powerful enough to pass through the half-silvered mirror. The first laser was built in 1960 by an American, Theodore H. Maiman. He used a rod of ruby crystal. The ends of the rod were polished flat and silvered, one end being half-silvered to allow the beam to come out. Now a variety of lasers have been made from solids like the ruby crystal and semi-conducting materials, liquids, and gases which produce beams of different colours having different energies.
