Answer:
Laser stands for: light amplification by stimulated emission of radiation, and is the process by which light energy is converted into a narrow, extremely intense beam of monochromatic radiation capable of delivering large amounts of power. All lasers possess a lasing cavity comprised of two mirrors placed in parallel, one of which is partially reflective. Between the mirrors is a lasing medium (gas, solid or liquid). An external power source provides energy to the lasing cavity that starts the light amplification process by “pumping” the laser medium into an excited state. From this higher energy level, it may return to its resting state (spontaneous emission) or, if struck by a photon, release two photons of the same energy and wavelength in phase with each other (stimulated emission). Some of these photons strike other excited atoms. Those photons not parallel to the long axis of the cavity are lost as heat. The small percentage that are given off parallel to the long axis form an energy wave which strikes the mirrors and reflects back and forth, continuing the process. Unlike ordinary light, laser light is collimated, monochromatic (uniform wavelength), coherent (in phase) and unidirectional. Light striking the skin surface may be reflected, transmitted to deeper tissues, scattered or absorbed. The laser effect occurs when absorbed light is converted to heat, resulting in coagulation of the targeted tissue.