7 Semiconductor amplifiers (SOA) and Raman amplifiers
7.1 Semiconductor optical amplifiers

A Semiconductor optical amplifier (SOA) make use of a semiconductor as a gain medium and as such, are electrically pumped. They can be compared to laser diodes, with the caveat that the end mirrors are replaced with anti-reflection layers. The signal is amplified by stimulated emission in the electrically excited active layer.

Spectral characteristic of SOA.

The temperature displays a very strong linear effect on gain. Practical applications resulting from this are unclear due to the slow nature of temperature control. However, it can be seen at least that the temperature must be held steady in order to provide consistent amplification, and that minimal temperature results in maximal amplification.

Temperature dependence of gain in an SOA.

The classification of the linear and nonlinear regimes of the SOA is useful as it is generally undesirable to operate the amplifier in the nonlinear regime.

Linear and nonlinear regimes of an SOA.