Dendritic fluorene oligomers for nonlinear absorption in the visible range

We report here the nonlinear absorption proper-ties of dendritic molecules of oligofluorenes. Measurements were performed in chloroform between 450 and 650 nm for nanosecond time duration pulses. The nonlinear absorption is attributed to a three-photon absorption process involving first a two-photon absorption (TPA) step followed by an excited state absorption (ESA) process. The corresponding three-photon absorption coefficient alpha 3 presents at resonance high values (alpha 3 > 10000cm(3)/GW(2) for 2G1 the first dendrimer generation bearing a bifluorene at a concentration of 50 g/L). These values are strongly enhanced with respect to those obtained in the same conditions for analog linear oligofluorenes.