The term 'laser' is actually the acronym derived from Light Amplification by Stimulated Emission of Radiation. However, these days instead of using it in its acronym form, it has been turned into a noun. A laser is an apparatus that produces an intense, narrow beam of light, that is coherent and monochromatic. The light produced from it, therefore, is quite different from the usual light that we are familiar with. Properties of Laser Light

• The light from a laser is monochromatic, which means that it is of a particular wavelength, or of a single color.
• The beam is coherent, which means that each photon is in synchrony with the other photons, or the patterns of their waves are aligned with each other, thus increasing the intensity of the light emitted.
• It is also highly directional, which means that the light emitted is very tight, concentrated, and intense. In contrast, the light from a flashlight or a light bulb, for example, is comparatively diffuse and weak, since the light emitted is scattered in many directions.

Stimulated emission is required in order to create the above three properties, which cannot be done with an ordinary light bulb, wherein the photons from atoms are released randomly. Whereas, when stimulated emission is accomplished, the photons are emitted in an organized manner. Four Basic Components An active medium - This can be solid crystals, gases, glasses, dyed liquids, or semiconductors. The active medium consists of atoms, the electrons of which may be stimulated to a higher level of energy, when energy from an external source is applied. A mechanism for stimulation - This is used to provide energy to the active medium. The stimulating mechanism can be either chemical, electrical, optical, or a combination of any of these. A mirror that is highly reflective - Essentially reflecting 100 percent of the light from the laser. A partially transparent mirror - Which allows a part of the light to be transmitted through it. Creation of a Laser Light Stimulation is provided to the active medium, which is contained in a resonating optical cavity, via any source of energy, such as another laser, or a current of electricity. This energy is absorbed by the medium, with the particles contained in it becoming 'excited'. On achieving a certain threshold, further stimulated emission results when light shines through the active medium, or instead of absorption, energy is released. The resonating active cavity, which is a chamber of a specific size, is equipped with a semi-transparent mirror at one end, and a fully reflective mirror at the other. These mirrors cause the light that is contained inside the chamber to bounce back and forth via the active medium, gaining increased amounts of energy each time it bounces and passes across to the other end. When there is a leveling of this effect, the active medium becomes saturated, creating the laser light, which gets emitted through the semi-transparent mirror. Uses Initially, when it was first invented, nobody knew for what practical purpose the laser could be used, and it was regarded as just an interesting curiosity created by science. However, today, it is used in various fields, and its usefulness is continuing to grow. For example, it is used in the retrieval and storage of data; in the medical field; taking measurements; communications; industrial cutting and welding; monitoring pollution; displays and holography; surveying; and research in nuclear fusion.