ANALYTICAL MODEL OF A SEMICONDUCTOR OPTICAL AMPLIFIER

The spatial dependence of the material gain is introduced in the model of a semiconductor optical amplifier. Analytical expressions of the p rofiles of the carrier density, spontaneous emission, and amplified fi elds are obtained for amplifiers with arbitrary facet reflectivities. The nonuniformity of the carrier density is demonstrated in the case o f low facet reflectivities. The model predicts the output saturation p ower and gain ripple, with good agreement with experimental results in resonant and traveling-wave amplifiers. Very low-gain ripple measured in low facet reflectivities amplifiers is explained by the model. A c omparison with the uniform gain model shows that important deviations can occur in the case of low facet reflectivities. It is also shown th at with the currently achievable low facet reflectivities, the maximum available gain is limited by spontaneous emission.