lecture33 - 33 Lasers Stimulated Emission Gain Inversion...

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33. Lasers Stimulated Emission Gain Inversion The Laser Two-level, three-level, and four-level systems
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Stimulated emission leads to a chain reaction and laser emission. Excited medium If a medium has many excited molecules, one photon can become many. This is the essence of the laser. The factor by which an input beam is amplified by a medium is called the gain and is represented by G .
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