Efficient weak-light amplification through phase control in a quantum well waveguide with electron spin coherence

We propose and analyze a new scheme to realize efficient weak-light amplification via phase control in a GaAs quantum well (QW) waveguide when driven coherently by two orthogonally polarized optical fields (a σ-polarized probe field and a π-polarized control field). It is shown that the amplification and absorption properties of the system are very sensitive to the relative phase between these driving fields. By choosing the relative phase appropriately, the enhanced amplification of the weak σ-polarized radiated field can be achieved in such a QW waveguide. We support our results by numerical calculation and analytical explanation. These theoretical investigations may find applications in devising the QW waveguide amplifier at room temperature.