Lecture 8: Laser amplifiers

Laser amplification vs. electronic amplifiers
Laser amplification differs in a number of respects from
electronic amplification.
Electronic amplifiers rely on devices in which small changes
in an injected electric current or applied voltage result in large
changes in the rate of flow of charge carriers (electrons and
holes in a semiconductor field-effect transistor). Tuned
electronic amplifiers make use of resonant circuits (e.g. a
capacitor and an inductor) to limit the gain of the amplifier to
the band of frequencies of interest.
In contrast, atomic, molecular, and solid-state laser amplifiers
rely on differences in their allowed energy levels to provide
the principal frequency selection. These entities act as
natural resonators that select the frequency of operation and
bandwidth of the device.
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