Lecture 8: Laser amplifiers
Lecture 8: Laser amplifiers
Lecture 8: Laser amplifiers
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Transition rates<br />
<br />
In thermal equilibrium, both the blackbody radiation spectral<br />
density and the atomic population density in each energy<br />
level should reach a steady state<br />
N 2<br />
(W 21<br />
()W sp<br />
()) N 1<br />
W 12<br />
()<br />
<br />
This is the principle of detailed balance in thermal<br />
equilibrium. The steady-state population distribution in<br />
thermal equilibrium:<br />
N 2<br />
N 1<br />
<br />
W 12<br />
()<br />
W 21<br />
()W sp<br />
() <br />
B 12<br />
u()<br />
B 21<br />
u() A 21<br />
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