Orientational Imaging of Subwavelength Au Particles with Higher Order Laser Modes

We present a new method for the imaging of single metallic nanoparticles that provides information about their shape and orientation. Using confocal microscopy in combination with higher order laser modes, scattering images of individual particles are recorded. Gold nanospheres and nonorods render characteristic patterns reflecting the different particle geometries. In the case of nanorods, the scattering patterns also reveal the orientation of the particles. This novel technique provides a promising tool for the visualization of nonbleaching labels in the biosciences. The optical properties of gold nanoparticles are influenced strongly by particle plasmons (PPs), that is, the collective oscillations of free electrons in the conduction band. A large number of theoretical and experimental studies were dedi-cated to the understanding of PP physics and revealed fascinating properties.1-4 For example, PPs in gold particles are linked to broad band photoluminescence2 and strong local field enhancement, making these nanostructures promising candidates for a variety of different applications.