A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation"The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light which is coherent. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers and lidar (light detection and ranging). Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum Alternatively, temporal coherence can be used to produce ultrashort pulses of light with a broad spectrum but durations as short as a femtosecond.Ordinary light, such as coming from the sun, a light bulb, or a candle, is emitted in many directions away from the source. <br />There are many types of lasers:<br />solid state laser*<br />* gas laser<br /> liquid laser*<br /> *semiconductor lase<br />The applications of lasers include:<br />• Lasers in medicine<br />• Lasers in communications<br />• Lasers in industries<br />• Lasers in science and technology<br />• Lasers in military<br /><br />بواسطة م.م. أيلاف مهدي