Polarimetry-based analysis of dipolar transitions of single colloidal CdSe/CdS dot-in-rods

We use polarization resolved micro-photoluminescence to analyze the dipolar nature of single core/shell cadmium selenide/cadmium sulfide (CdSe/CdS) dot-in-rods. Polarization analysis, anisotropy measurements on more than 400 nanoparticles, and defocused imaging suggest that these nanoparticles behave as linear dipoles. The same methods were also used to determine the three-dimensional orientation of the emission dipole, which proved to be consistent with the hypothesis of a linear dipole tilted with respect to the rod axis. Moreover, we observe that for high-energy pumping, the excitation transition of the dot-in-rod cannot be approximated by a single linear dipole, contrary to the emission transition. (paper)