A device which operates under the processes of absorption and stimulated emission and by the condition that gain exceeds loss in order to sustain amplification. The term laser is the acronym for Light Amplification by the Stimulated Emission of Radiation.
The standard components of a laser include: 1.) a lasing material known as the gain medium. 2.) a pump source. 3.) laser cavity
To achieve lasing, the atoms of a material such as crystal, glass, liquid, dye or gas are excited by the pump source to a semistable state. The pump source is conventionally another light source (i.e. a laser diode or flash lamp) or an electric discharge. The light emitted by an atom as it drops back to the ground state interacts with nearby excited atoms to release identical pairs of photons in the process called stimulated emission. This process is duplicated as the photons bounce back and forth in the cavity from mirrors or other reflective cavity structures which then further amplify the light emission, producing beams of light at specific frequencies; traditionally, lasers comprise cavities in which a pair of mirrors (one highly reflective and one partially reflective) bounce light between them for amplification.
Lasers are used in a wide range of applications and industries including manufacturing, consumer electronics, medicine, sensing, aesthetics, basic scientific research, entertainment and more.