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Lecture 8: Laser amplifiers

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Gain coefficient<br />

<br />

<br />

The coefficient () represents the net gain in the photon-flux<br />

density per unit length of the medium.<br />

The photon-flux density therefore is given as<br />

( z)<br />

(0)exp[<br />

( ) z]<br />

<br />

The optical intensity I(z) = h(z)<br />

I( z)<br />

I(0)exp[<br />

( ) z]<br />

<br />

Thus, () also represents the gain in the intensity per unit<br />

length of the medium.<br />

79

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