THEORETICAL-STUDY OF 3RD-ORDER NONLINEAR-OPTICAL RESPONSE OF SEMICONDUCTOR CARBON NANOTUBES

We present a theoretical study of the nonlinear-optical properties of single-shell semiconductor carbon nanotubes (CNs) within a simple mode l based on the two-band approximation of their electronic structure. B y use of the Genkin-Mednis approach, we have calculated the nonlinear- optical spectra of the susceptibility of chi((3))(omega) for the follo wing third-order polarization effects: the third harmonic generation, the intensity-dependent index of refraction, the two-photon absorption and the DC Kerr effect. It is found that in off-resonant conditions t he susceptibility chi((3))(0) shows a four-power dependence on the tub ule radius and can reach values typical of bulk III-V semiconductor co mpounds with the strongest nonlinear optical properties. The optical s pectra of chi((3))(omega) under the three-photon resonance regime have revealed considerable enhancement of the radiation power generated at a third-harmonic frequency. Our results show that in CNs the nonlinea r index of refraction as large as 2 x 10(-8) cm(2) W-1 can be achieved in a region where the two-photon absorption is small. The change of t he refractive index of CNs of the order of 10(-11)E(0)(2) (V-2 cm(-2)) was found to be induced by a uniform static electric field E-0 applie d along the CNs axis. It is concluded that carbon nanotubes present a considerable interest in view of their possible utilization in a varie ty of nonlinear optical devices. (C) 1998 Elsevier Science B.V. All ri ghts reserved.