A laser is a device that amplifies or strengthens light. A laser produces a thin, intense beam of light that can burn a hole in a diamond or carry the signals of many different television pictures at the same time. The word laser stands for light amplification by stimulated emission f radiation.

Light is a form of energy that is released from individual atoms or molecules in a substance. The amount of energy in an atom depends on the motion of the electrons that orbit the atom’s nucleus. When an atom absorbs energy, its energy level increases, and the atom is said to be excited. An excited atom can return to its normal energy level by releasing its excess energy in the form of light. This release of energy is called spontaneous emission.

Excited atoms can be made to release light systematically. This kind of release, called stimulated emission, is the main process that takes place in a laser. Stimulated emission occurs when the energy released from one atom interacts with another atom that is still excited. The interaction triggers the excited atom into releasing its own extra energy as light. The light, thus produced, is called laser light. Laser light travels in narrow beam and is source of intense heat.

The basic parts of laser include a power source and alight-amplifying substance. The power source provides the energy that causes atoms to become excited.

NOTE : There are three major kinds of lasers, based on their light-amplifying substance :

(1) solid lasers,

(2) gas lasers, and

(3) liquid lasers.