Unusual optical properties of aligned carbon nanotube mats in infrared energy region.

We studied the optical properties of aligned carbon nanotube mats for photonic device applications. We employed ab-initio density functional calculations in the linear combination of atomic orbital formalism. The calculated dielectric functions of the semiconducting carbon nanotube mats show a strong anisotropy when the electric field of the light is parallel or perpendicular to the tube axes. Especially, there are strong optical absorptions near the band edges in the infrared energy region, when the electric field of the light is parallel to the carbon nanotube axes. The unusual optical properties of the semiconducting carbon nanotube mats present a new opportunity for applications in electro-optical devices in the infrared energy region.