Gain without population inversion and superluminal propagation in the metal nanoparticles-graphene nanodisks-quantum dots hybrid systems.

Nanoplasmonic hybrid systems are novel materials due to their optical properties that can be manipulated by sub-wavelength structures of these materials paving the way for interesting optical phenomena such as superluminal propagation. We study the optical properties of metal nanoparticle-graphene nanodisks-quantum dots hybrid system using density matrix approach. The quantum dot is modeled as a three level lambda type configuration interacting with a weak probe field and strong control field. We realize that due to the surface plasmon effects, we can control the optical properties of the quantum dot including absorption, dispersion and group index by the geometrical features of these components in addition to the parameters of the interacting fields. A controllable switching between subliminal and superluminal propagation is observed at certain parametric conditions leading to interesting potential applications such as signal processing and optoelectronic devices.