Optical dichroism of lithographically designed silver nanoparticle films.

Films of identically shaped, elongated, and parallel-oriented metal nanoparticles arranged in a regular pattern upon a transparent substrate were produced by use of electron-beam lithography. Because of the strong difference in the particles' polarizability components, the optical extinction spectra show strong dichroism. Moreover, one can shift the spectral position of the extinction maximum in a wide range from 480 to 600 nm by variation of the particles' aspect ratio. This result suggests that designed metal particle films can be used as artificial optical thin-film media.