Fluorescence-detected three-dimensional linear dichroism: A method to determine absorption anisotropy in single sub-wavelength size nanoparticles

We introduce theoretically and demonstrate experimentally a method for the determination of three-dimensional absorption anisotropy (three-dimensional linear dichroism) of single luminescent nanoparticles. The anisotropy is measured by monitoring polarization-modulated fluorescence intensity excited alternately by epi-illumination and by total internal reflection. As an example of the application of the method, three-dimensional linear dichroism measured on single light-harvesting systems of photosynthetic bacteria is presented.