A device that generates a monochromatic and coherent beam of light. The acronym “laser” stands for “light amplification by stimulated emission of radiation”. It is based on an optical medium illuminated by a flash lamp. This causes the excitation of electrons in the optical medium. The de-excitation releases photons of the identical wavelength. The wave of photons bounces off mirrors at the ends of the optical medium and stimulates other electrons to de-excite as they pass through. A beam of monochromatic, coherent radiation is produced. Lasers have an extremely wide range of applications: surgery, laser-cutting, inertial confinement fusion, or a bar scanner in a grocery store.
Laser principle. The flashlamp provides energy to electrons and excites them. When de-excited, the electrons release photons of the same wavelength. As the wave of light bounces back and forth off the mirrors at the ends of the laser, it stimulates the de-excitation of more and more electrons, releasing more and more photons of the same wavelength. Eventually, a beam of coherent, monochromatic light is produced. (Source: © designua / stock.adobe.com)