An intrinsic characteristic of carbon nanotubes (CNTs), which are allotropes of carbon, is one-dimensional anisotropy. It is derived from the peculiar geometrical shape of the molecules and is manifested in their electrical, thermal, mechanical, and optical properties. Here, we report an optical polarizer that makes effective use of such anisotropy of CNTs. The polarizer we fabricated is made of uniaxially aligned CNTs embedded in a polymer film. Thanks to the $\pi$ plasmon-originated broad absorption spectrum and strong optical anisotropy of single-wall CNTs (SWCNTs), the film exhibits a degree of polarization of $\sim 90\%$ with keeping flat transmittance through the spectral region from 350 to 800 nm. In order to efficiently obtain well-aligned CNTs, we used SWCNTs shortened into a length of less than 200 nm. We also observed enhancement of the degree of polarization at the wavelengths of Van Hove singularities.

• Received 13 February 2008

DOI:https://doi.org/10.1103/PhysRevB.77.153407