Surface plasmon assisted superluminal light propagation in a quantum dot–metallic nanoparticle hybrid system

We study the optical properties of a coupled quantum dot (QD)–metallic nanoparticle (MNP) hybrid system via a quantum mechanical density matrix method. The QD system is considered as a three-level V-type configuration and is interacted with a weak probe light and a strong coupling light. The QD is placed near the MNP system and therefore the transition is interacted with a probe laser located near to the frequency of the MNP. We realize that due to the radius of the MNP and surface plasmon effects, the distance between the QD and MNP can optimize the absorption, dispersion, and group index of the hybrid system. We find that the probe amplification without population inversion can be obtained with a suitable distance between the QD and MNP. Moreover, a tunable superluminal light propagation is obtained for some parametric conditions of the hybrid system. (paper)