A laser is constructed from an energy source, a gain medium, and two mirrors.
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Some of the most common sources of energy for a laser, called the pump source, are flash lamps, arc lamps, and external lasers, but microwaves, radiofrequency radiation, the sun, electric glow discharge (a type of plasma), electron beams, the supersonic flow of gases such as CO2, chemical reactions, and nuclear fission have also been used.
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There are thousands of different gain media, which is also known as laser media. Liquids such as organic chemical solvents combined with chemical dyes, gases such as carbon dioxide, argon, krypton, and mixtures of helium-neon, and solids such as crystals and glasses with added impurities, are some examples.
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The optical resonator, also called the optical cavity, in its simplest form is made of two parallel mirrors surrounding the gain medium. One is a high reflector and one is a partial reflector.
When light is spontaneously emitted from the medium, it is reflected by the mirrors back into the medium and then amplified by stimulated emission. Stimulated emission is when an atom interacts with a wave of a certain electromagnetic frequency, drops to a lower energy level, and emits a photon.
The emitted photons are what you see as a beam of light.
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In 1960, lasers were called a "solution looking for a problem". Nowadays, they have widespread uses in electronics, information technology, science, medicine, industry, law enforcement, military, and entertainment.
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Sources:
http://en.wikipedia.org/wiki/Laser
http://en.wikipedia.org/wiki/Laser_construction
http://en.wikipedia.org/wiki/Laser_pumping
http://en.wikipedia.org/wiki/Electric_glow_discharge
http://en.wikipedia.org/wiki/Stimulated_emission
http://science.howstuffworks.com/laser.htm
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How do you see the future of lasers? Do you think they'll continue being important in technology, or that they'll become obsolete with another discovery?
Also, while it's not particularly earth-shattering, I rewrote the "About This Blog" page. I felt like it needed a serious change . . . and if you're interested, you can go HERE to read the new one.
-----The Golden Eagle
