Theory of optical scattering by achiral carbon nanotubes and their potential as optical nanoantennas

The Leontovich-Levin equation for optical scattering by an achiral carbon nanotube (CNT) of finite length is formulated, based on a quantum-mechanical microscopic model of the conductivity. Both approximate analytical and numerical solutions of the Leontovich-Levin equation yield a comparable surface current density distribution and scattering pattern. Applications over a wide frequency range from the terahertz to the ultraviolet are possible. The CNT polarizability in the low-frequency range and the scattering pattern in the range of optical interband transitions as well as in the vicinity of plasmon resonance are calculated. Geometric resonances of strongly retarded surface waves emerge and can be used for the qualitative interpretation of experimentally observed features in the optical response characteristics of CNT-based composite mediums. The potential of isolated CNTs as optical nanoantennas of both the receiving and transmitting types is established.