Enhanced index and negative dispersion without absorption in semiconductor quantum wells

We investigate the dispersive and absorptive properties in a three-level ladder-type SQW system that both cascade transitions are driven by the same strong coherent field and are probed by the same weak probe field. It is found that the positive or negative refractive index with vanishing absorption can be also easily obtained in this solid-state system. Our scheme shows many intrinsic characteristics that other schemes do not have, which may provide some possibilities for the technological applications in solid-state optoelectronics.