Plasmonic control of nonlinear absorption in metallic nanocomposites

Recent advances in nanofabrication techniques have led to a rising interest in the optoelectronic properties of nanocomposite systems. These system are formed by combining quantum emitters with plasmonic nanoparticles. Typically, these types of nanocomposites employ the strong local electromagnetic field produced by localized surface plasmons in metallic nanoparticles to enhance and/or control optical processes in nearby molecules or semiconductor nanoparticles. Strong local fields generated by localized surface plasmons are particularly attractive in the study of nonlinear optical processes. In this talk nonlinear absorption in a quantum dot–graphene nanoflake nanocomposite system will be discussed. An external laser field is applied to the nanocomposite to simultaneously observe two-photon processes in the quantum dot and excite localized surface plasmons in the graphene nanodisk. It is found that the strong local field of the graphene plasmons can enhance and control nonlinear optical processes in the quantum dot. Specifically, we show that the two-photon absorption coefficient in the quantum dot can be switched between single- and double-peaked spectra by modifying the graphene–quantum dot separation. Two-photon processes in the quantum dot can also be switched on or off by slightly changing the gate voltage applied to the graphene. Our findings indicate that this system can be used for nonlinear optical applications such as all-optical switching, biosensing and signal processing.