Optical properties of elongated noble metal nanoparticles

The importance of anisotropy in the optical response of metal nanoparticles of different end shapes is studied theoretically. The number, behavior, and localization of the plasmon modes in terms of the shape and elongation is revised in detail for silver, gold, and copper nanoparticles. It is found that the position of longitudinal and transversal modes depends not only on the aspect ratio but also on the nanoparticle end shape. Besides, the relation between nanoparticles' anisotropy and optical macroscopic birefringence is also analyzed for different shapes and materials.