gain-assisted magneto-optical rotation in a four-level quantum system near a plasmonic nanostructure

We propose and theoretically demonstrate a mechanism to achieve a gain-assisted magneto optical rotation (mor) of a linearly polarized probe beam in a double v–type closed-loop atomic system. the quantum system is considered to be placed in the proximity of a plasmonic nanostructure which can produce quantum interference between decay channels of the quantum system. we also apply a linearly polarized control beam and a microwave beam to the system. it is shown that manipulating the intensity of the microwave beam and relative phase of the applied beams results in well-optimizing optical properties of the system where by proper choice of these parameters the atomic medium becomes birefringent gain media. induced birefringence can be reinforced by increasing the intensity of the magnetic field and quantum interference coefficient. it is found, compared with the absence of the plasmonic nanostructure, the presence of the plasmonic nanostructure causes the gain-assisted mor to occur at much smaller magnetic field. hence, we propose that such a gain-assisted mor can have potential application in detecting quantum interference effect.