All-optical modulation by plasmonic excitation of CdSe quantum dots

Photonics is a promising candidate technology for information processing, communication and data storage(1-3). Essential building blocks, such as logic elements and modulators, have been demonstrated(4-6). However, because of weak nonlinear light-matter interactions, these components typically require high power densities and large interaction volumes, limiting their application in dense chip-based integration. A solution may be found in surface plasmon polaritons (SPPs), guided electromagnetic waves that propagate with high field confinement along a metal-dielectric interface. We demonstrate an all-optical modulator in which efficient interaction between two light beams at different wavelengths is achieved by converting them into co-propagating SPPs interacting by means of a thin layer of CdSe quantum dots (QDs). The high SPP field confinement and high QD-absorption cross-section enable optical modulation at low power densities (similar to 10(2) W cm(-2)) in micrometre-scale planar devices.