Lecture 8: Laser amplifiers
Lecture 8: Laser amplifiers
Lecture 8: Laser amplifiers
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Rate equations in the absence of amplifier radiation<br />
The rates of increase of the population densities of levels 2<br />
and 1 arising from pumping and decay are<br />
dN 2 /dt = R 2 –N 2 / 2<br />
dN 1 /dt = -R 1 –N 1 / 1 + N 2 / 21<br />
<br />
Steady-state population difference in the absence of amplifier<br />
radiation (dN 1 /dt = dN 2 /dt = 0)<br />
N 0 = N 2 –N 1 = R 2 2 (1- 1 / 21 ) + R 1 1<br />
<br />
A large gain coefficient requires a large population difference<br />
( 0 () = N 0 e ())<br />
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