Lecture 8: Laser amplifiers

Gain bandwidth
The dependence of the gain coefficient () on the frequency
of the incident light is contained in its proportionality to the
lineshape function g().
The latter is a function of width centered about the atomic
resonance frequency 0 = (E 2 –E 1 )/h.
The laser amplifier is therefore a resonant device, with a
resonance frequency and bandwidth determined by the
lineshape function of the atomic transition.
This is because stimulated emission and absorption are
governed by the atomic transition.
The linewidth in frequency (Hz) and in wavelength
(nm) are related by
= |(c/)| = (c/ 2 ) = ( 2 /c)
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