Tunable narrow-band plasmonic resonances in electromagnetically-induced-transparency media

The spectral response of a plasmonic nanostructure may heavily depend on the refractive index of its surroundings. The key idea of this paper is to control this response by coherent optical means, i.e. with an optically controlled electromagnetically-induced-transparency medium. In such environment, an external laser provides a knob to shift the position of plasmonic resonances without the need to change the geometry of the nanostructure. Additionally, the setup can be exploited to excite narrow-band surface plasmon polaritons.