Determination of Third-Order Optical Nonlinearity of Triphenylamine from Femtosecond Degenerate Four-Wave Mixing in Solutions
Anna Samoc, MArek Samoc and BArry Luther-Davies
A positive real part and a sizeable imaginary part of the third-order nonlinear susceptibility χ(3)(−ω;ω,ω−ω) were determined in triphenylamine solutions in chloroform at an off-resonant wavelength of 800 nm with femtosecond pulses (FWHM 140 fs). The values and the sign of the components of the complex second hyperpolarizability on the order of γ ~ 10-35 esu were determined from analysis of a quadratic dependence of the degenerate four wave mixing (DFWM) signal on triphenylamine concentration, studied in the range 0 – 30 wt %. The analysis took into account changes of the linear refractive index and density of solutions with the solute concentration. The γ data were used to derive the nonlinear refractive index n2, χ(3), and the two-photon absorption cross-section σ2 of triphenylamine at 800 nm.