Two-dimensional two-photon absorptions and third-order nonlinear optical properties of Ih fullerenes and fullerene onions

Abstract

The third order static and dynamic nonlinear optical (NLO) responses of I_h symmetry fullerenes (C₆₀, C₂₄₀, and C₅₄₀) and fullerene onions (C₆₀@C₂₄₀ and C₆₀@C₂₄₀@C₅₄₀) are predicted using the ZINDO method and the sum-over-states model. The static second hyperpolarizability of I_h symmetry fullerenes increases exponentially with fullerene size [from 10.00 × 10⁻³⁴ esu in C₆₀ to 3266.74 × 10⁻³⁴ esu ≈ γ₀(C₆₀) × 9^2.63 in C₅₄₀]. The external fields of strong third order NLO responses of I_h symmetry fullerenes change from ultra-violet (C₆₀) to the visible region (C₅₄₀) as the fullerene size increases. The outer layer fullerene in the fullerene onions has dominant contributions to the third order NLO properties of the fullerene onions, and the inter-shell charge-transfer excitations have conspicuous contributions to the third order NLO properties. The two-dimensional two-photon absorption spectra of C₆₀ and C₂₄₀ show that those fullerenes have strong two-photon absorptions in the visible region with short wavelength and in the ultra-violet region.