Laser

The laser is a device that uses the principle of stimulated emission to produce light. The qualities of the light generated by a laser are significantly different from that generated by a conventional source such as an incandescent light bulb or fluorescent light tube. These major differences include: divergence: the laser generally emits a pencil thin beam of light whose divergent angle is closely related to the wavelength and limiting aperture size. bandwidth: the light emitted by the laser generally consists of a very narrow range of wavelengths, or color. intensity: the output from a laser is typically orders of magnitude higher in intensity (measured in watts per square meter) than a conventional light source. coherence; the output from a laser is generally coherent; that is, the peaks and troughs of the lightwaves all correspond, allowing the light to form clear interference patterns.

When it was first invented, the laser was called "a solution looking for a problem" because few good applications could be found for it. This is no longer the case, and the laser has found its way into many uses in every day life. The major application areas for the laser are in communications, materials processing, optical data storage, surgery, defense, and scientific research.