Manipulating Nanoscale Interactions in a Polymer Nanocomposite for Chiral Control of Linear and Nonlinear Optical Functions

摘要

Chiral photonics is an emerging direction that offers the potential to control both linear and nonlinear optical functions for applications ranging from optical switching, to negative- and near-zero refractive index metamaterials, to chiral bioimaging. However, realization of such applications requires materials with optical chirality at visible wavelengths that is orders of magnitude larger than that of naturally-occurring materials. We report the design, synthesis and supramolecular organization of a nanocomposite of quantum dots in a chiral polymer, in which resonant coupling between the excitonic manifolds of the polymer and quantum dots significantly amplify the chiral response. Specifically, we report gigantic enhancement of optical activity of chiral poly(fluorene-alt-benzodithiazole) via doping with CdTe/ZnS core-shell quantum dots. Excitonic coupling between the helical polymeric strands and single quantum dots as well as the coupling between helically arranged quantum dots was responsible for the observed gigantic enhancement. These nanocomposites also have an exceptionally large value of the effective nonlinear refractive index for right-circularly polarized light, 2.4 × 10~(-3) cm~2 GW~(-1).