The Laser
Definition :
The term “Laser” means Light Amplification by the Stimulated Emission of Radiation. This device creates a uniform and coherent light (different from an ordinary light bulb).
The process is based on an optical amplification, by stimulating the emission of photons.
Many lasers are able to deliver a light where the beam is parallel and approaching a single wavelength and thus very pure.
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Who invented it ?
"The ideas that led to the invention of the laser were discovered by Albert Einstein in 1916. But it was not until 1953 that these ideas were put into use. The first laser was actually called a maser, because it used microwaves. (This is the same type of energy that is used in a microwave oven). Charles Townes and two of his students made the first maser, but it would only work for short amounts of time. Two scientists from the Soviet Union (Russia) named Nikolay Basov and Aleksandr Prokhorov figured out how to make the maser stay on. These three men won a Nobel Prize in 1964 for their discovery.The first idea for a laser came from Charles Townes and Arthur Schawlow. Gordon Gould worked on the idea and wrote them down in a paper in 1959. This paper was the first time the word laser was used.The first working laser was invented by Theodore Maiman and demonstrated on May 16, 1960."
http://en.wikibooks.org/wiki/Wikijunior:How_Things_Work/Laser
Definition :
A Laser is device that creates and amplifies electromagnetic radiation of a specific frequency through the process of stimulated emission. The radiation emitted by a laser consists of a coherent beam of photons, all in phase and having the same polarization. |
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inversionthen emission is continuously stimulated, and a stream of coherent photons develops. One of the mirrors is partially transparent, allowing the laser beam to exit from that end of the chamber |
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Schematic:
http://people.seas.harvard.edu/
How does it work ?
A laser is an optical oscillator, which is can be made out of a solid, liquid or gas. It contains two with mirrors at both ends: one is totally reflecting and the other only partially. To make it work, the material is excited or "pumped," with an energy source such as light or electricity.
When this energy source gives energy the electrons in the atoms, they become excited. But the interesting part is when a few of the electrons drop back to lower energy levels spontaneously, and then release a photon (or a quantum of light). The photons created stimulate other excited electrons and emit more and more photons. Then the light waves (photons), which passes through the laser medium, is reflected by the mirrors at both ends. It keeps the light back and forth creating a chain reaction. After that, the light beam goes out through the output.
Uses of Laser:
Gas Lasers
| Chemical Lasers
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Excimer Lasers
| Solid State Lasers
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Pointers
| Entertainment
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Applications of Laser :
The laser is part of our daily life. Many examples…
The laser pointer used in classrooms | The CD in a computer or in a hi-fi that are used to read |
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In industry, laser is often used for cutting and microscopic processing. | For military purposes, laser is used to intercept guided missiles. |
Lasers are used to measure distance. |
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