Determination of the nonlinear refractive index of lyotropic mixtures with and without ferrofluid doping: a time-resolved Z-scan experiment in millisecond time scales

Z-scan experiments were carried out on micellar isotropic lyotropic mixtures with and without ferrofluid doping. Ferrofluid doping, even in small quantities, strongly modifies the sample absorption properties. A method to reduce the Z-scan data is proposed to calculate the nonlinear refractive index of high- and fast-absorber samples. The usual Z-scan data treatment procedure, with the usual transmittance normalization, gives the correct sign, order of magnitude, and linear behavior of n(2) with the ferrofluid grain concentration. However, the difference from the absolute values Of n(2) Calculated here and those obtained using the usual Z-scan data treatment procedure increases with the concentration of ferrofluid grains. The origin of this nonlinear optical response of the samples is assumed to be mainly from a thermal origin, in which the micelles are indirectly heated by contact with the ferrofluid grains. (c) 2006 Optical Society of America.