Room-temperature slow light with semiconductor quantum-dot devices

We demonstrate room-temperature slow light that is electrically and optically controllable by using a quantum-dot (QD) semiconductor optical amplifier (SOA) at zero and low bias below the transparency current. The absorption spectrum of the QD SOA exhibits a spectral dip with a corresponding group-index dispersion and group delay owing to coherent population oscillation caused by the interaction of pump and probe laser light near resonance of the first heavy-hole-conduction-state transition. At an optical pump power of approximately 0.3 mW inside the single-mode waveguide without current injection, a group-index change of 3.0 with a bandwidth of 2 GHz was measured. This group-index change can be controlled by injection of electrical current and by changing the optical pump power.