Slow light in quantum dot vertical cavity semiconductor optical amplifiers

Slow light in the Technologically important devices InGaAs/GaAs quantum dot (QD) Vertical Cavity Semiconductor Optical Amplifiers (QD-VCSOAs) is studied. The presented work benefits from the possibility offered by QD-VCSOA structures for operation exclusively at the amplifying regime without reaching threshold unlike Quantum Well (QW) VCSOAs. The mathematical formulation of the main slow down metric based on gain dispersion is presented. The effects of various functional (current, input signal) and structural (inhomogeneity, cavity length, density of dots etc) properties on the optical delay properties of the QD-VCSOA are identified and relevant design strategies are outlined. The numerical investigation concludes that considerably higher Group Delays can be achieved in QD-VCSOAs compared to QW-VCSOAs by means of static (i.e. structural design) and dynamic (i.e. injection current) properties. The results highlight the flexibility (tunability) offered by the QDs in tailoring SL properties of the VCSOA.