Absorption spectra of a quantum dot – Metallic nanoparticle composite under the bistable condition.

The interplay between the optical nonlinearity of semiconductor quantum dots (SQD) and positive feedback from metallic nanoparticles (MNP) may result in optical bistability. Here, we present a theoretical study of the absorption spectrums of a nanocomposite comprising an SQD and an MNP in an optical bistability condition. The SQD is modeled as a two-level system and treated quantum mechanically using density matrix formalism, while the MNP is treated classically in the framework of the Maxwell equation. In the linear regime, the results show that the absorption spectrum of the system revealed a discontinuity, depending on which branch the bistable characteristic of the system resides. In the strong field regime, the absorption spectrum manifests a Fano shape. This finding implies that optical bistability in the system can be identified from its effects on the absorption spectrum. [ABSTRACT FROM AUTHOR]