Concentration and wavelength dependence of the effective third-order susceptibility and optical limiting of C60in toluene solution

Publisher Website
Google Scholar
Abstract
The optical limiting action of C60 in toluene solution is mainly due to reverse saturable absorption (RSA). It is shown that the formalism describing nonlinear optical response due to instantaneous two-photon absorption can be used in the case of sequential two-photon absorption, yielding effective values of the relevant parameters of optical nonlinearity due to RSA. The effective two-photon absorption parameter beta eff and the effective nonlinear refractive index parameter gamma eff', which are related respectively to the imaginary and real parts of the effective third-order susceptibility chi eff(3) were measured by the z-scan technique as a function of fullerene concentration and of incident laser intensity and wavelength over the 420-640 nm region. The concentration dependence of these parameters indicates that the solution is optically thin as far as the ground state of C60 is concerned, whereas the wavelength dependence confirms the applicability of the formalism used in the sequential two-photon absorption model. Comparisons are made with other z-scan results on C60.