LASER stands for Light Amplification by Stimulation Emission of Radiation. It is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. They emit the light coherently. There are two coherent namely: spatial coherence and temporal coherence. Spatial coherence allows the laser to be focused to tight spot. In temporal coherence allows laser to have a very narrow spectrum.
Lasers are used in common devices such as DVD players, laser printers and bar code scanners. In medical used for surgery and various skin treatments. In industry used for welding and cutting the materials. In military and law enforcement to measure the range, speed and to marking the targets. They are also used in scientific research.