Slow light using semiconductor quantum dots

A variable semiconductor optical buffer based on the electromagnetically induced transparency in a quantum dot waveguide is theoretically investigated with feasible parameters for applications to a 40 Gbps optical network. We show the refractive index and absorption spectra of the quantum dot waveguide at various pump levels, which exhibit an optimal pump power for maximum slow-down factor, in agreement with the previous experimental observation using a Pr-doped solid. The group velocity slow-down factor is theoretically analysed as a function of the pump intensity at different broadened linewidths. Inhomogeneous broadening in self-assembled quantum dots degrades the slowdown factor. In order to reduce the inhomogeneous broadening effects, we propose to use a resonant microcavity structure with quantum dots embedded in the active layer to enhance the slow-down factor.