Enhanced Cross-Phase Modulation via Phase Control in a Quantum dot Nanostructure

A four-level quantum dot （QD） nanostructure interacting with four fields （two weak near-infrared （NIR） pulses and two control fields） forms the well-known double-cascade configuration.We investigate the cross-phase modulation （XPM） between the two NIR pulses.The results show,in such a closed-loop scheme,that the XPM can be greatly enhanced,while the linear absorption and two-photon absorption （gain） can be efficiently depressed by tuning the relative phase among the applied fields.This protocol may have potential applications in NIR all-optical switch design and quantum information processing with the solid-state materials.