Phase control of group velocity via Fano-type interference in a triple semiconductor quantum well

We analyze the absorption-dispersive properties of a weak probe laser field based on the ISBT in a triple semiconductor quantum well (SQW) structure driven coherently by two control laser fields. It is shown that the system can produce anomalous and normal dispersion regions with negligible absorption by adjusting the intensities of the control fields and the Fano-type interference. More interestingly, the dispersion can be changed between normal and anomalous simply by adjusting the relative phase between two coherent control fields due to the existence of the Fano-type interference. Thus the relative phase can be regarded as a switch to manipulate light propagation with subluminal or superluminal. In addition, the temporal and spatial dynamics of the probe laser pulse with Gaussian-type envelope are analyzed.