Quantum Dot Versus Quantum Well Semiconductor Optical Amplifiers for Subpicosecond Pulse Amplification

The performance of quantum well and quantum dot semiconductor optical amplifiers was theoretically investigated. The effects on subpicosecond pulse propagation due to gain and refractive index dispersion, calculated using a microscopic polarization equation and a reduced wave equation in the linear regime including the background refractive index dispersion, were used in the comparison. In particular, the spectral shift and phase modulation imposed on the pulse were compared. It is shown that quantum dot amplifiers suffer comparable spectral shifts to the quantum well amplifier, strong linear frequency chirp and large pulse broadening. In quantum dot amplifiers with small inhomogeneous broadening, similar pulse break-up is shown as that calculated for the quantum well amplifier. In quantum dot amplifiers with large inhomogeneous broadening, the background refractive index dispersion makes the linear frequency chirp the dominant feature. In the light of our calculations, the advantages and disadvantages of quantum dot and quantum well amplifiers are discussed.