The laser is a device that generates "well-organized", or coherent light. The mechanism relies on a process known as stimulated emission, and the word laser is derived from Light Amplification by Stimulated Emission of Radiation. The maser uses the same principle to generate or amplify electromagnetic radiation in the longer wave length microwave region.Characteristic Light is a wave and as such can be characterized by its frequency or wavelength. Ordinary light is incoherent, but laser light is coherent, that is all of it has the same wavelength and phase. Information can be carried by electromagnetic radiation. Light, with a higher frequency than radio waves or microwaves, has a greater information carrying capacity. All beams of radiation spread out as they travel (unless they are confined within a pipe or an optical fiber); however, this spreading can be minimized for coherent radiation.
Light has a shorter wavelength than radio waves or microwaves and therefore spreads less and can be usefully transmitted over longer distances. In addition, coherent light can be focus into a smaller point than can incoherent radiation. Pulsed lasers offer the possibility of power multiplication: energy can be stored relatively slowly (in the inverted population); and then some fraction can be retrieved in a very brief laser pulse, thus, the power (the rate at which energy is provided) can be much higher than that of the original energy source. Concentration of even modest amount of energy in a very small area can produce intense heating.
