Phase-dependent electromagnetically induced grating in a four-level quantum system near a plasmonic nanostructure

A quantum optical model involving a plasmonic nanostructure (PN) is proposed for controlling the diffraction efficiency of an electromagnetically induced grating in a four-level quantum system. By tuning the distance between the PN and the four-level quantum system, diffraction efficiency can be adjusted and energy can be transferred from zero order to higher orders. Moreover, due to the presence of the PN, the medium becomes phase-dependent and therefore, phase control of grating can be possible by changing the relative phase of the applied fields.