A Light Amplification by Simulated Emission of Radiation (LASER) is a device used to concentrate light into a narrow beam. The light emitted by these devices is thin and coherent. Laser light is different from the light that normally radiates from atoms. Atoms typically radiate light randomly, resulting in light that is refereed to as incoherent. Basically, this means atoms radiate jumbles of photons that go in numerous directions. Coherent light behaves quite differently, going in one clearly defined direction.
To create coherent light for a laser, the right atoms must be used in the right kind of environment to allow the atoms to emit light at a particular time and in a precise direction. Atoms or molecules of gases, liquids, crystals, or other materials are used to make lasers. These atoms are excited within a cavity, putting most of them at higher energy levels, while reflective surfaces in the cavity reflect energy and enable it to build up. Through a process called stimulated emission, photons with matching frequencies and phases are emitted. Finally, a fast, chain reaction occurs, discharging atoms and leading to the production of coherent light.
The laser made its debut in 1960. Now, it is available in many different sizes, ranging from those about the size of a grain of sand to those as big as some buildings. Despite such variations, most lasers produce light beams that are very thin and capable of maintaining size and course, even when traveling over great distances.
Lasers are used for an amazing variety of things. They have many important applications in modern medicine, including Laser-Assisted in Situ Keratomileusis (LASIK) eye surgery. They are also important in many manufacturing and construction processes, as well as military and scientific applications. Many people have turned to laser printers to make printing professional-looking documents easier. Likewise, lasers are important components of Compact Disc (CD) and Digital Video Disc (DVD) players.