Lecture 8: Laser amplifiers
Lecture 8: Laser amplifiers
Lecture 8: Laser amplifiers
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Amplified spontaneous emission<br />
<br />
<br />
<br />
The resonant medium that provides amplification via<br />
stimulated emission also generates spontaneous emission.<br />
The light arising from the spontaneous emission, which is<br />
independent of the input to the amplifier, represents a<br />
fundamental source of laser amplifier noise.<br />
Whereas the amplified signal has a specific frequency,<br />
direction, and polarization, the noise associated with<br />
amplified spontaneous emission (ASE) is broadband,<br />
multidirectional, and unpolarized.<br />
=> it is possible to filter out some of this noise by following the<br />
amplifier with a narrowband optical filter, a collection<br />
aperture, and a polarizer.<br />
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