Laser - Background And History, How It Works, Stimulated Emission, Oscillation, Solid State Lasers, Gas Lasers - Applications
light source found conventional
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.
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In the 1950s, there was a push by scientists to develop sources of coherent electromagnetic radiation at wavelengths shorter than vacuum tubes could provide. Charles Townes and co-workers at Columbia University, New York, developed the ammonia maser (microwave amplification by stimulated emission of radiation) in 1954, a device which produced coherent microwaves. In 1958, Townes and Art Schawlow p…
Stimulated emission is a process similar to absorption, but operates in the opposite direction. In absorption, an incoming photon is absorbed by an atom, leaving the atom in an excited state and annihilating the photon in the process. In stimulated emission, an incoming photon stimulates an excited atom to give up its stored energy in the form of a photon that is identical in wavelength, direction…
Stimulated emission alone is not sufficient to produce laser output. The emission from the atoms occurs in all directions; to produce the highly directional output that makes the laser such a useful tool, the light must be trapped in an optical cavity that provides feedback, i.e., forces the light to travel in a desired direction. An optical cavity is free conduction band electrons recombine with …
Although the first laser demonstrated was a solid state ruby laser, for many years the most common commercial systems were gas lasers such as helium neon lasers and argon ion lasers, or lasers based on organic dyes. Helium neon lasers were frequently limited in output power, argon ion lasers required expensive, sophisticated power supplies and cooling sources, and the dyes used in dye lasers were …
A pulsed infrared laser beam traveling down a single strand of optical fiber can carry thousands of times the information which can be carried by an electrical signal over copper wire. Not only can a single optical signal travel more rapidly than an electrical signal, but optical signals of different wavelengths, or colors, can travel down a fiber simultaneously, and without interfering. This tech…
Since a laser beam can be focused down to a very small spot of light which can be absorbed very well at the surface of a material (be it metal, plastic, textile, etc.), the material can reach very high temperatures up to 9,032°F (5,000°C) and melt or even vaporize. In factories, laser systems are used to measure parts, inspect them for quality, and label, cut, weld, or resurface mate…
Lasers have a variety of applications in the field of medicine. Using laser beams whose wavelength is absorbed strongly, surgeons can cut and remove tissue with great precision by vaporizing it, with little damage to the surrounding tissue. The systems are used in minimally-invasive surgical techniques such as angioplasty (removing plaque from artery walls) and lithotripsy (the destruction of kidn…
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