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Lecture 8: Laser amplifiers

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Four-level pumping<br />

<br />

The population difference can be written in the general form<br />

N<br />

N0<br />

1 <br />

s W i<br />

N 0<br />

spN a<br />

W<br />

1 sp<br />

W<br />

s<br />

<br />

sp<br />

1 sp<br />

W<br />

96<br />

96

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